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Synthesis, preparation and properties of novel high-performance allyl–maleimide resins
Abstract
Three novel allyl–maleimide monomers (i.e., A2B, AB and AB2) were designed, synthesized and thermally cured to yield a series of high-performance allyl–maleimide resins. All the monomers obtained are readily soluble in common organic solvents enabling an easy solution processing. The thermal properties of the three monomers were studied by the differential scanning calorimetry (DSC). A2B and AB showed fairly low melting temperature (Tm < 90 °C) and wide processing window ranging from 90 °C to 260 °C. The thermal stability of the cured allyl–maleimide resins (i.e., PA2B, PAB and PAB2) was studied by the thermogravimetric analysis (TGA). Dynamic mechanical analysis (DMA) was used to investigate the dynamic mechanical properties of the composites based on the cured allyl–maleimide resins. PA2B and PAB2 showed good glass transition temperatures (Tg > 270 °C) and their corresponding composites showed high bending modulus (E′ > 1900 MPa). Allyl-compound-modified BMI resins based on AB monomer were prepared. Rheometer revealed that the processability of the prepolymer (BR–AB-pre) was improved by the addition of AB monomer. The cured BMI resins (BR and BR–AB) showed good thermal stability (Td > 400 °C, both in nitrogen and in the air), high glass transition temperature (Tg > 320 °C), and good mechanical properties and low water uptake (<2.6%, 120 h).Graphical abstract
... The notion of self-healing-simply defined as the potential of a polymeric material to be mended after damage, through physical or chemical strategies [1]-was unconceivable a few decades ago for epoxy-and maleimide-based polymers [2][3][4][5]. These classes of polymers exhibit high performance characteristics, though they come along with an intrinsic brittleness. ...
... In the case of the DGEBA-allyl-Anth, there is a succession of small DTGA peaks/shoulders (200 • C, 245 • C, 275 • C). They were connected with the deprotection of the maleimide groups, followed by the -ene reaction with allyl groups (Wagner-Juaregg intermediate) and the subsequent Diels-Alder reaction that generates a cyclic network structure [4,49]. The cleavage of the ether-ether linkage and the decomposition of succinimide groups are reflected in the main degradation range (350-450 • C). ...
... 15, x FOR PEER REVIEW 7 of 15 structure[4,49]. The cleavage of the ether-ether linkage and the decomposition of succinimide groups are reflected in the main degradation range (350-450 °C). ...
The present work is focused on polyester resins obtained from the diglycidyl ether of bisphenol A and anthracene modified 5-maleimidoisophthalic acid. Because the maleimide-anthracene Diels–Alder (DA) adduct is stable at high temperatures, it is considered a good option for high performance polymers. However, the information related to the retroDA reaction for this type of adduct is sometimes incoherent. A detailed thermal study (conventional TGA, HiRes TGA, MTGA, DSC, MDSC) was performed in order to establish whether the rDA reaction can be revealed for this type of anthracene modified polyester resins. The TGA method confirmed the cleavage of the anthracene–maleimide DA adduct, while the DSC demonstrated the presence of anthracene in the system. At high temperatures, unprotected maleimide homopolymerizes and/or reacts with allyl groups according to the –ene reaction. Therefore, the thermal DA reaction is not displayed anymore upon the subsequent cooling, and the glass transition region is registered at a higher temperature range during the second heating. The use of sample-controlled thermal analysis (HiRes TGA) and MTGA improved the TGA result; however, it was not possible to separate the very complex degradation processes that are interconnected.
... The aviation industry is in search for high-temperature resistant matrices for high-performance composites, to meet the future demands of high speed and fuel efficiency. In this regard composites of Bismaleimides are getting attention due to their high temperature resistance, high dimensional stability, good resistance to chemicals and reasonable mechanical strength [6][7][8][9]. The processability of Bismaleimides is as easy as epoxy but its performance is much better than that of epoxy. ...
... Brittleness is one of the major concerns for Bismaleimides, which leading to low damage tolerance. Different strategies have been adopted to improve its toughness with minimum loss of the thermal properties [8][9][10][11]. ...
... They studied decomposition and formation of carbon deposit. Moreover, properties of imide polymers, such as solubility , dielectric and optical characteristics, crystallinity, thermal and mechanical resistances, can be modified by the use of substrates of different chemical structure or comonomers in their synthesis19202122 . Comonomer that reacts with imide contributes not only components of its structure but also its new properties to the copolymeric final product202122 . ...
... Moreover, properties of imide polymers, such as solubility , dielectric and optical characteristics, crystallinity, thermal and mechanical resistances, can be modified by the use of substrates of different chemical structure or comonomers in their synthesis19202122 . Comonomer that reacts with imide contributes not only components of its structure but also its new properties to the copolymeric final product202122 . ...
Thermogravimetry and differential scanning calorimetry were used for characterization of the thermal properties of new 4,4′-bismaleimidodiphenylmethane (BM) and divinylbenzene (DVB) porous copolymers and their carbonization products. Bead-shaped porous copolymers BM-DVB with the following monomer ratios 1:4, 1:1, 4:1 were synthesized using suspension copolymerization under the same conditions. Differences in the monomer ratio caused a different degree of cross-linking of the starting polymers. Before carbonization, the BM-DVB copolymers were pretreated using two methods. In one method, the starting material was stabilized in hot air (product was labeled PO-C800). In the other method, the copolymer was soaked in H3PO4 (product was named P800). Then, materials obtained by both methods were carbonized at 800 °C in an argon atmosphere. To characterize the heat resistance of the BM-DVB copolymers and their carbonized derivatives, their thermostabilities were evaluated. The data suggest the existence of a relationship between the composition and thermal stability of the copolymers and their carbonized derivatives. The most thermally resistant copolymer was that obtained with a 4:1 molar ratio of BM to DVB. Its thermal stability is caused by the high concentration of nitrogen atoms in the polymeric structure. 1:4 BM-DVB copolymer with a high degree of cross-linking was the least thermally stable, which might be caused by its microporous nature and small fraction of nitrogen. The derived carbons have very similar thermal properties, and an insignificant influence of the nature of the polymer precursor was observed. More important factors affecting thermal stability were the porosity and surface chemistry, which were created in the thermal pretreatment processes.
... Moreover, properties of imide polymers, such as solubility, dielectric and optical characteristics, crystallinity, thermal and mechanical resistances, can be modified by the use of substrates of different chemical structure or comonomers in their synthesis [19][20][21][22]. Comonomer that reacts with imide contributes not only components of its structure but also its new properties to the copolymeric final product [20][21][22] . ...
... Moreover, properties of imide polymers, such as solubility, dielectric and optical characteristics, crystallinity, thermal and mechanical resistances, can be modified by the use of substrates of different chemical structure or comonomers in their synthesis [19][20][21][22]. Comonomer that reacts with imide contributes not only components of its structure but also its new properties to the copolymeric final product [20][21][22] . ...
... Studies have been conducted to reduce its brittleness by modifying maleimide resin with an allyl compound. [8][9][10][11][12] The maleimide and allyl groups undergo the ene reaction, as shown in Fig. 1(a), and the Diels-Alder reaction, as shown in Fig. 1(b), to form the cross-linked product. According to Rozenberg tially. ...
Highly heat-resistant molding materials are required for manufacturing power modules. We investigated a sheet molding material where a blend of rigid and flexible maleimide resins (MA and MB, respectively) offer high heat resistance and toughness enhancement for wide-bandgap semiconductor packaging applications. We found that the MB formulation with 30% by weight of the maleimide resin enhanced toughness of the maleimide resin blend. This formulation passed -55/200°C package-level temperature cycle tests without compromising the heat resistance. We also found that the maleimide resin blend exhibited a strong adhesion strength to Cu foil (7.3 N·cm⁻¹). This performance maintained even after thermal storage at 200°C for 1,000 h. We think that the developed sheet molding material can be used for high-temperature-operating power modules manufactured with fan-out panel-level packaging.
... Bismaleimide (BMI) resin is known as the representative of thermally resistant thermosetting resins. It has excellent dielectric property of low dielectric loss and high volume resistance, and have been extensively used in electronics fields such as interconnects, circuit boards and adhesives for microelectronics applications [7,8]. However, like most other polymers, the dielectric property of BMI need to further improve, and the insufficient thermal and flame retardant property can't satisfy the requirement of the safe use of BMI resin as an electronic material. ...
A novel 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) functionalized hyperbranched polysiloxane (HBPEp-DOPO) with considerable epoxy groups was synthesized. The structure was characterized by Fourier transform infrared (FTIR) spectra and nuclear magnetic resonance (¹H-NMR). HBPEp-DOPO was then introduced into O,O’-diallylbisphenol A/4,4′-bismaleimidodiphenyl methane(DBMI) resin to develop modified composite with excellent dielectric and thermal properties as well as simultaneously improved comprehensive performance. The incorporation of HBPEp-DOPO not only remarkably increased the dielectric, mechanical, and thermal properties, but also obviously improved the flame retardancy. Compared with neat DBMI resin, HBPEp-DOPO/DBMI resins exhibited decreased dielectric loss with increasing the content of HBPEp-DOPO. Besides, adding 10 wt% HBPEp-DOPO could change the UL-94V of DBMI from V-2 to V-0. Moreover, HBPEp-DOPO/DBMI exhibited an improved mechanical property and thermal stability at a small addition amount. These attractive features allows the modified hyperbranched polysiloxane to have broad potential applications in cutting-edge industries, especially in electronic and electric insulating fields.
... [6][7][8] A bismaleimide/cyanate ester (BMI/BADCy) resin is selected as the model for modication owing to its widespread use in the electronics eld, such as circuit boards, interconnects, and adhesives for microelectronics applications (e.g., exible and rigid die attach adhesives). 9,10 However, there are also several problems with BMIs; high curing temperature and brittleness. ...
Functionalized benzoxazine with allyl groups has recently attracted a great deal of attention due to its polymerizable group. In order to improve the properties of 4,4′-bismaleimidodiphenyl methane (BMI)/cyanate ester (BADCy), benzoxazine (Boz) was added into the BMI/BADCy system in this paper. The effect of functionalized Boz with allyl groups on the dielectric, mechanical and thermal properties of BMI/BADCy composites was systematically investigated in detail using mechanical measurements, scanning electron microscopy (SEM), dynamic mechanical analysis (DMA) and thermo-gravimetric analysis (TGA). The results showed that the formation of Mannich bridge networks and an interpenetrating polymer network through the polymerization of Bz-allyl and BMI/BADCy increased the cross-linking densities and thermal stability. Allyl-based polymers also exhibited high glass transition temperatures, and higher char yields. The dielectric constant value and the dielectric loss factor of BBz2 reached minimum values of 3.17 and 0.083 at 106 Hz respectively. The mechanical properties (a high flexural modulus of 4.18 GPa and flexural strength of 120 MPa) of BBz2 were superior. Scanning electron microscopy analysis showed a distinct characteristic of ductile fractures for the blends.
... Limited studies have focussed on the synthesis of one-component Alder ene polymers. [9,10] Bindu et al. [11] have synthesized such polymers by co-reacting maleimidophenol with allyl phenol in the presence of formaldehyde while Zhenhua Luo [12] has synthesized allyl functional novolac and blended with maleimide to form the pre-polymer. ...
Novolac resins, bearing both allyl and maleimide groups in varying proportions and capable of self-curing via Alder ene reaction, were synthesized by anchoring maleimidobenzoyl groups onto allyl novolac resins. These systems are capable of self-curing at moderate temperature by undergoing two-step cure reaction, i.e. ene reaction (~60 °C) followed by Diels–Alder reaction (~180 °C) to form thermal stable resins. Anchoring of the allyl and the maleimide groups in the same molecule decreases the cure activation energy tremendously due to increased proximity of reactive species and favorable activation entropy factors. The increase in activation energy with conversion implied that the reaction migrates from chemically controlled zone to diffusion-controlled zone beyond ~50% conversions. The resins showed increasing thermal stability with enhanced maleimide content.
... Research has shifted, however, toward mixed end-group chemistries, that is, BMI-bisallylether-, BMI-CE-, BMI-benzoxazine-, BMI-benzocyclobutene-, and BMI-propargylbased systems. [18][19][20][21][22][23][24][25] The aim is to find high T g (> 250 °C) thermosets with low CTEs and improved mechanical properties over traditional BMIs and BNIs. Another area of interest is the use of BMIs as resin matrices for nanocomposite applications, where clay, ceramics, and carbon nanotubes are explored as the reinforcing phase. ...
The intent of this chapter is to provide the reader with a starting point on the chemistry, thermomechanical properties, and selection criteria of all-aromatic high-temperature thermosets. Both the reactive monomer and reactive oligomer approach as precursors toward high-temperature thermosets are discussed together with the 10 most commonly used reactive end-groups. Special emphasis has been placed on phenylethynyl-based systems because of the proven versatility of this end-group. Although relatively new, reactive all-aromatic thermotropic and lyotropic liquid crystal systems are included in this chapter as well because of their promising thermomechanical properties. © 2012 Elsevier B.V. All rights reserved.
... Polyimides have various applications, e.g., films, fibers, foams, porous membranes, composites, varnishes, adhesives, coatings, and others [9]. The properties of the obtained polyimide materials such as solubility, dielectric, and optical features, crystallinity, thermal and mechanical resistance can be modelled by the use of different monomers in their synthesis [10][11][12][13][14][15]. ...
The relations between chemical structures of BM-DVB copolymers obtained with various monomer molar ratios and their carbonization products were studied. Three porous copolymers 1:4, 1:1, and 4:1 of BM to DVB were the starting materials for preparation of active carbons. Two activation agents were employed: air and phosphoric acid. The carbonization process was performed in the same way in these two cases. To characterize the obtained materials FTIR spectroscopy, thermal and elemental analyses were applied. Porous structure parameters were obtained by means of nitrogen sorption. The results proved that differences in the molar ratio of monomers used in the syntheses of polymeric precursor play a key role for structure and properties of copolymers but have rather small influence on properties of the obtained carbons. Preliminary treatment is more effective during the activation process. The carbons obtained by activation with phosphoric acid are microporous and have well developed porous structures. The air activated carbons are mesoporous with specific surface areas similar to those of polymeric precursors.
... Polymers of N-substituted maleimides and their derivatives having a rigid imide ring in the backbone are known as high performance polymers. [1,2] Among them, bismaleimides (BMIs) have attracted much attention because of their high-temperature resistance, high glass-transition temperature, excellent chemical and corrosion resistance, and low cost. [3][4][5] In addition, they are suitable for solar energy applications due to the fact that they display absorption and emission spectrum in the visible region. ...
In the present study, maleimide-modified epoxide resin containing UV-curable hybrid coating materials were prepared and coated on polycarbonate substrates in order to improve their surface properties. UV-curable, bismaleimide-modified aliphatic epoxy resin was prepared from N-(p-carboxyphenyl) maleimide (p-CPMI) and cycloaliphatic epoxy (Cyracure-6107) resin. The structure of the bismaleimide modified aliphatic epoxy resin was analyzed by FTIR and the characteristic absorption band for maleimide ring was clearly observed at 3100 cm−1. Silica sol was prepared from tetraethylorthosilicate (TEOS) and methacryloxy propyl trimethoxysilane (MAPTMS) by sol–gel method. The coating formulations with different compositions were prepared from UV-curable bismaleimide-based epoxy oligomer and sol–gel mixture. The molecular structure of the hybrid coating material was analyzed by 29Si-CP/MAS NMR spectroscopy techniques. In the 29Si CP/MAS NMR spectrum of the hybrid coating, mainly two kinds of signals were observed at −68 and −110 ppm that correspond to T3 and Q4 peaks, respectively. This result shows that a fully condensed structure was obtained. The thermal and morphological properties of these coatings materials were investigated by using TGA and SEM techniques. Hardness and abrasion resistance properties of coating materials were examined and both were found to increase with sol–gel precursor content of the coating. The photopolymerization kinetics was investigated by using RT-IR. 70% conversion was attained with the addition of 15 wt% of BMI resin into the acrylate-based coating formulation. It was found that the UV-curable organic–inorganic hybrid coatings improved the surface properties of polycarbonate. Copyright © 2009 John Wiley & Sons, Ltd.
... In order to reach this goal, three kinds of bismaleimides in specifically given physical situations have been synthesized in one-pot route. Three aromatic bismaleimides (4,4′- bismaleimidodiphenyl methane (BMIDDM), 4,4′- bismaleimidodiphenylether (BMIDDE) and 4,4′- bismaleimidodiphenyl sulphone (BMIDDS)) having various bridging groups [24] may impart some special characteristics to the final products according to their donor and acceptor nature from the corresponding amine monomers (4,4′-diaminodiphenyl- methane (DDM), 4,4′-diaminodiphenylether (DDE) and 4,4′-diaminodiphenylsulphone (DDS)). Therefore, they were characterized by FTIR and NMR spectroscopy techniques. ...
T hree aromatic bismaleimide resins, 4,4′-bismaleimidodiphenyl methane (BMID-DM), 4,4′-bismaleimidodiphenylether (BMIDDE) and 4,4′-bismaleimidodiphenyl sulphone (BMIDDS) having various bridging groups from the corresponding amine monomers (4,4′-diaminodiphenylmethane (DDM), 4,4′-diaminodiphenylether (DDE) and 4,4′-diaminodiphenylsulphone (DDS)) were prepared. These resins were characterized by FTIR and NMR spectroscopy techniques. BMIDDM/BMIDDE and BMIDDM/BMIDDS mixtures at various concentrations were prepared to study the bismaleimide resin eutectic mixtures. Differential scanning calorimetry analysis was used to demonstrate the phase diagrams, the melting and solubility of each constituent of these binary systems (BMIDDM/BMIDDE and BMIDDM/BMIDDS) in different liquid and solid phases. Furthermore, in the present work the relationship between binary systems and the concept of a eutectic mixture with its extraordinary thermal properties is investigated. The eutectic melting point of the BMIDDM/BMIDDS system is considerable because of the much lower melting point of the above system compared to that of the synthesized monomer having the lowest melting point. It shows also a very easy way of using these materials in the molten state. The same DSC study on other mixtures, i.e., BMIDDM/BMIDDE and BMIDDE/BMIDDS is performed and the results are reported. The end results illustrate that by increasing the quantity of one monomer in the mixture, two melting points appear until they acquire the melting temperature of the eutectic composition (T e , a single and homogeneous peak). Impurities have similar effects on T o and T exo . The findings of this work can be applicable in the transportation industry, particularly in areas such as civil and military aircraft industry, aerospace, marine and automotive sectors.
The replacement of petroleum-based materials by renewable bio-based materials is an interesting topic of research for academic and industrial scientists. The approaches concerning development of biobased-polymers include utilization of sugars, polysaccharides, vegetable oils, lignin, furans and so on. These renewable resources can be turned into viable macromolecular materials via a series of chemical transformations and thus could be potentially useful candidates for the replacement of both thermoplastics and thermosetting materials.
The overall objective of the present thesis was to design and synthesize a series of difunctional monomers using cashew nut shell liquid (CNSL)- an agricultural waste product-as a starting material and utilization of these monomers for synthesis of high performance/ thermally stable polymers. Towards this end, a series of difunctional monomers, viz, aromatic diamine, diacid, diphenol and dinitrile containing pendent flexible pentadecyl chain was synthesized starting from CNSL. These difunctional monomers were utilized for the synthesis of high performance polymers such as aromatic polyesters, polyimides, polyhydrazides, poly(1,3,4-oxadiazole)s and poly(arylene ether)s. Additionally, cyanate ester, bismaleimide and epoxy resin containing pendent pentadecyl chains were synthesized using selected difunctional monomers derived from CNSL. The effect of pendent pentadecyl chains on properties of polymers was investigated.
Chapter 1 describes a literature review on recent advances in the field of polymers from renewable resource materials with particular emphasis on aromatic difunctional monomers and polymers derived from hemicellulose, lignin and CNSL. A comprehensive review of the literature on high performance polymers, viz., polyesters, polyimides, poly(1,3,4-oxadiazole)s and poly(arylene ether)s covering the aspects such as methods of synthesis, structure property relationship, etc., are also included.
Chapter 2 describes scope and objectives of the thesis
Chapter 3 describes synthesis of new difunctional monomers containing pendent pentadecyl chain using 3-pentadecyl phenol as a starting material which in turn is obtained from CNSL. The following difunctional monomers were synthesized:
1. 4-(4-Formylphenoxy)-2-pentadecylbenzaldehyde
2. 4-(4-Hydroxyphenoxy)-3-pentadecylphenol
3. 4-(4-(4-(4-Aminophenoxy)-2-pentadecylphenoxy)phenoxy)aniline
4. 4-(4-(4-(4-Carboxyphenoxy)-2-pentadecylphenoxy)phenoxy)benzoic acid
5. 4-(4-(4-(4-(Hydrazinocarbonyl)phenoxy)-2-pentadecylphenoxy)phenoxy)benzohydrazide
6. 3-Pentadecyl 4,4' biphenol
7. 2, 2-Pentadecyl-[1,1'-biphenyl]-4,4'-diol
8. 4,4’-Dibromo 3-pentadecyl biphenyl
9. 3-Pentadecyl-[1,1'-biphenyl]-4,4'-dicarboxylic acid, and
10. 3-Pentadecyl-[1,1'-biphenyl]-4,4'-dicarbohydrazide
The difunctional monomers and intermediates involved in their synthesis were characterized by FT-IR, 1H NMR, and 13C NMR spectroscopy.
Chapter 4 deals with synthesis and characterization of a series of aromatic (co)polyesters based on 4-(4-hydroxyphenoxy)-3-pentadecylphenol (HPPDP) and aromatic diacid chlorides. A series of copolyesters was synthesized from a mixture of HPPDP and bisphenol-A (BPA) with terephthalic acid chloride using phase-transfer catalysed interfacial polycondensation. Inherent viscosities of (co)polyesters were in the range 0.70-1.21 dL/g and number average molecular weights, measured by GPC in chloroform with polystyrene as a standard, were in the range 16,000-48,300. (Co)polyesters were soluble in chloroform, dichloromethane, pyridine and m-cresol at room temperature and could be cast into tough, transparent and flexible films from chloroform solutions. Polyesters containing pendent pentadecyl chains showed broad halo in the wide angle region (2θ = ~ 20°) which revealed their amorphous nature. T10 values for (co)polyesters were in the range 425-455 °C indicating their good thermal stability. A drop in Tg values (27-202 °C) and storage modulus (E’) of (co)polyesters was observed due to the presence of flexible pentadecyl chains which act as packing disruptive groups.
Chapter 5 describes synthesis and characterization of polyetherimides containing pendent pentadecyl chains and multiple ether linkages based on 4-(4-(4-(4-aminophenoxy)-2-pentadecylphenoxy) phenoxy)aniline and commercially available aromatic dianhydrides namely 3,3’,4,4’-oxydiphthalic anhydride (ODPA), 4,4’-(hexafluoro isopropylidene)diphthalic anhydride (6-FDA) and 3,3’,4,4’-biphenyl tetracarboxylic dianhydride (BPDA) using one-step solution polycondensation in m¬-cresol. Inherent viscosity of polyetherimides was in the range 0.66-0.70 dL/g, indicating formation of reasonably high molecular weight polymers. Polyetherimides were soluble in organic solvents such as chloroform, dichloromethane, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, pyridine, m-cresol and dimethyl sulfoxide. Polyetherimides could be cast into tough, transparent and flexible films from chloroform solution. The non-symmetrical structure of multiring diamine resulted into constitutional isomerism in polyetherimdes as evidenced from 1H NMR studies. X-Ray diffraction analysis showed that polyetherimides were amorphous in nature and a reflection in small angle region indicated layered packing of pentadecyl chains. Tg values of polyetherimides containing pendent pentadecyl chains were in the range 113-131 °C. Thus a significant drop in Tg was observed compared to analogous polyetherimides without pentadecyl chains. T10 values of polyetherimides were in the range 460-470 °C indicating their good thermal stability. The incorporation of pendent pentadecyl chains and flexible ether linkages increased gap between Tg and T10 values of polyetherimides and thus offered a wider processing window.
Chapter 6 embodies the synthesis and characterization of polyhydrazides and poly(1,3,4-oxadizole)s containing multiple ether linkages and pendent pentadecyl chains. The polyhydrazides were synthesized by polycondensation of 4-(4-(4-(4-(hydrazinocarbonyl)phenoxy)-2-pentadecylphenoxy)phenoxy)benzohydrazide (HPPPB) with aromatic diacid chlorides and were subsequently cyclized using POCl3 to the corresponding poly(1,3,4-oxadiazole)s. Inherent viscosities of polyhydrazides and poly(1,3,4-oxadiazole)s were in the range 0.65-0.72 dL/g and 0.54-0.62 dL/g, respectively. Polyhydrazides were soluble in polar aprotic solvents viz., N,N-dimethylformamide, N,N-dimethylacetamide, pyridine, dimethyl sulfoxide and m-cresol whereas poly(1,3,4-oxadiazole)s were soluble in common organic solvents, such as chloroform, dichloromethane, and tetrahydrofuran. X-Ray diffractograms of both polyhydrazides and poly(1,3,4-oxadiazole)s exhibited a broad halo at 2θ = 20° indicating amorphous nature and a reflection in small angle region (2θ = 2-3°), characteristic of layered packing of pentadecyl chains. The T10 values for poly(1,3,4-oxadiazole)s were in the range 425-440 °C indicating their good thermal stability. The T¬g values of polyhydrazides and poly(1,3,4-oxadiazole)s were in the range 92-103 °C and 175-192 °C, respectively. The lowering of Tg in polyhydrazides and poly(1,3,4-oxadiazole)s could be attributed to the presence of packing disruptive pendent flexible pentadecyl chains and flexiblizing ether linkages in the backbone. Poly(1,3,4-oxadiazole)s exhibited maximum UV-Vis absorption in the range 304-337 nm whereas maximum of fluorescence emission was in the range 380-394 nm in chloroform solution. The optical band (Eg) values for poly(1,3,4-oxadiazole)s were found to be in the range 3.33-3.65 eV indicating their potential application in opto-electronic devices
Chapter 7 provides study on synthesis and characterization of poly(arylene ether)s containing biphenylene linkages in the backbone and pendent pentadecyl chains obtained by polycondensation of 3-pentadecyl biphenol with commercially available aromatic dihalides by nucleophilic aromatic substitution reaction. Poly(arylene ether)s exhibited inherent viscosities in the range 0.50-0.81 dL/g indicating formation of reasonably high molecular weight polymers. The number average molecular weights (Mn¬) measured by GPC were in the range 2.2 x 104 - 8.3 x 104 with polydispersity of 2.2. 1H NMR studies of poly(arylene ether)s indicated the presence of constitutional isomerism which existed due to the non-symmetrical structure of 3-pentadecyl biphenol. Poly(arylene ether)s were soluble in common organic solvents such as dichloromethane, chloroform, and tetrahydrofuran. Tough, transparent and flexible films of poly(arylene ether)s could be cast from their chloroform solutions. X-Ray diffraction patterns showed halos over the range 2 =15-25° and broad reflections in the small-angle region at about 2θ ≈ 3° indicating amorphous nature and layered pentadecyl chain packing, respectively. Poly(arylene ether)s exhibited Tg in the range 35-60 °C which are lower than that of analogous poly(arylene ether)s without pentadecyl chains. The lowering of Tg could be attributed to packing disruptive effect of flexible pendent pentadecyl chains. The 10% decomposition temperatures (T10) of poly(arylene ether)s were in the range 410-455 °C, indicating their good thermal stability. The gas permeation study of poly(ether sulfone) containing pendent pentadecyl chains revealed moderate increase in permeability for helium, hydrogen and oxygen with lower permselectivity. However, there was large increase in permeability for carbon dioxide due to internal plasticizing effect of pentadecyl chains.
Chapter 8 is divided into three sections
Chapter 8a deals with synthesis, characterization and curing study of 4-cyanato-1-(4-cyanatophenoxy)-2-pentadecylbenzene (HPPDPCN), containing ether linkage and pendent pentadecyl chain. HPPDPCN was synthesized from 4-(4-hydroxyphenoxy)-3-pentadecylphenol by Grigat and Putter method and was characterized by FT-IR, 1H NMR and 13C NMR spectroscopy. The melting point of HPPDPCN was found to be 31 °C, which is lower than that of bisphenol-A based cyanate ester (BPACN, MP = 84 °C). The non-isothermal curing kinetics of HPPDPCN was studied by DSC and the activation energy of uncatalyzed curing was found to be 108.06 KJ/mol.
Chapter 8b deals with synthesis, characterization, curing kinetics and thermal properties of 4, 4’-bis-(4-maleimidophenoxy)-2-pentadecyl diphenyl ether (C15BMI). C15BMI was synthesized by the ring-opening addition reaction of 4-(4-(4-(4-aminophenoxy)-2-pentadecylphenoxy)phenoxy)aniline with maleic anhydride followed by cyclodehydration of N,N-bismaleamic acid using acetic anhydride and sodium acetate. The structure of C15BMI was confirmed by IR, 1H NMR and 13C NMR spectroscopy. The melting point of C15BMI was found to be 90 °C, which is lower than that of 4,4’-bis(maleimido)diphenylether (ODABMI, M.P., 183 °C). 4, 4’-Bis-(4-maleimidophenoxy)-2-pentadecyl diphenyl ether exhibited excellent solubility in common organic solvents such as chloroform, dichloromethane and tetrahydrofuran. Activation energy for curing of C15BMI was determined in non-isothermal curing mode using Coats-Redfern method and was found to be 75.32 KJ/mol. The T10 value of cured C15BMI resin was 430 °C indicating its good thermal stability.
Chapter 8c presents synthesis and characterization of diglycidyl ether of 4-(4-hydroxyphenoxy)-3-pentadecylphenol. 4-(4-Hydroxyphenoxy)-3-pentadecylphenol was reacted with epichlorohydrin in the presence of NaOH to obtain diglycidyl ether of 4-(4-hydroxyphenoxy)-3-pentadecylphenol which was characterized by IR, 1H NMR and 13C NMR spectroscopy.
Chapter 9 summarizes the results and outlines salient conclusions and future perspectives of research work carried out in the present thesis.
The current regulatory environment based on the ICH guidelines encourages a systematic and science-based approach in the pharmaceutical development, required by the “Quality by design” concept. This methodology implies that the quality of a product must be designed instead of assayed in the final dosage form. For this purpose, a deep knowledge of the factors affecting the quality of the product is needed to establish the design space. This design space is limited by critical points of the formulation whose knowledge is essential in order to develop a robust dosage form. This papers deals with the main critical points that must be taken into account in the design of solid dosage forms such as inert and hydrophilic matrices as well as controlled released systems based in new biopolymers. The influence of factors such as the particle size or the rheology of powders in these critical points has been analysed. Moreover, in silico simulation software has been employed to elucidate the release mechanism leading to unexpectedly low critical points in sustained release matrices prepared with two new polyurethanes.
The main objective of the present paper has been the development and study of two new biodegradable polyurethanes, PU(dithiodiethanol-DTDI) and PU[(ⁱPr)Man-DTDI], to be used as sustained matrix forming excipients. Furthermore, their capacity to act as excipient for colon drug delivery systems has been evaluated. Thus, SeDeM diagrams have been obtained to investigate their suitability to be processed through a direct compression process. Matrices containing 10–30% w/w of the polymers and theophylline anhydrous as model drug have been manufactured. Release studies have been carried out using a modified dissolution assay simulating pH and redox conditions for the gastro intestinal tract, including colon. Drug dissolution data have been analyzed according to the main kinetic models and their Excipient Efficiencies for prolonged release have been calculated. The principal parameters of the SeDeM Expert system, such as the parametric profile (mean radius) and the good compression index obtained for the polymers are above the values considered as adequate for direct compression even without addition of flow agents. The obtained values for Excipient Efficiency show good ability of the polymer to control the drug release. Finally, in the case of PU(dithiodiethanol-DTDI), a clear increase in the release rate has been observed when the formulation is subjected to colon simulating conditions.
A series of bismaleimide-triazine resins (EBT) were prepared from 2-(4′-maleimido)phenyl-2-(4′-maleimidophenoxyl)phenylbutane (EBA-BMI) and 2,2-bis(4-cyanatophenyl)propane (BADCy). The resins show attractive processability with good solubility in low boiling point solvents and wide processing temperature windows. Introduction of diallylbisphenol A (DBA) can decrease the curing temperature of EBT resins that the curing exothermic peak temperature shifted from 291 to 237 °C as the content of DBA increased from 0 to 20%. The curing condition influenced the thermal properties of the cured EBT resins. The glass transition temperature increased as the curing temperature and curing time increased. The cured EBT resins show high glass transition temperature up to 352 °C, high thermal stability with 5% weight loss temperature over 405 °C, low coefficient of thermal expansion about 45 to 52 ppm/°C, and high storage modulus up to 2.6 GPa at 250 °C. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44519.
A series of flame-retarded epoxy resins (EP) loaded with methyl MQ silicone resin and a novel hyperbranched polysiloxane (HPSi) acting as compatibilizer have been prepared. Compatibility of these EP composites was characterized by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results showed that HPSi significantly improved the compatibility of EP/MQ. The flame retardancy and thermal degradation behavior of these EP composites were investigated by limiting oxygen index (LOI), UL-94 vertical burning, themogravimetric analysis test (TG), FTIR and SEM. The results showed that the incorporation of MQ into EP can improve the thermal stability dramatically. It is observed that the LOI values of epoxy resins increased obviously (from 21% to 31%) with the MQ loading, which passed V-0 rating of UL-94. Specifically, its combustion residue at 700 °C was 14.5% weight, which exceed the value of neat EP resin (5.08% weight). Moreover, structural analysis of the remaining after vertical burning by FTIR spectra verified the formation of polyaromatic carbons. Additionally, morphology of the residue char showed the compact, smooth, and tight structure of EP composites systems. These outstanding integrated properties would make EP composites attractive for practical applications.
A novel allyl compound containing liquid crystalline structure, i.e., 4,4’-bis(4-allyloxy benzoic acid) phenyl ester (BAOBE), was synthesized. The chemical structure of BAOBE was characterized by Fourier transform infrared (FTIR) spectroscopy and 1H NMR spectra, and the liquid crystalline properties were confirmed by polarized optical microscopy (POM). Besides, a series of modified bismaleimide (BMI) resins were prepared based on N,N′-4,4′-bismaleimidodiphenylmethylene (BDM), BAOBE, and O,O’-diallyl bisphenol A (DABPA). The results of thermogravimetric analysis (TGA) indicate that the modified resins have excellent thermal stability with the highest temperatures for 5% weight loss above 438°C. The results of dynamic mechanical analysis (DMA) suggest that the glass transition temperature (Tg) of the modified resins are above 280°C. Besides, the introduction of BAOBE leads to a significant improvement in the flexural and impact properties of the modified BMI resins. Compared with the resin with only DABPA as a modifier, the highest flexural and impact strength can reach 156.2 MPa and 15.6 kJ/m2, increased by 19.2% and 90.2%, respectively.
Three novel bismaleimide monomers (MBA-BMI, EBA-BMI, and PBA-BMI) with unsymmetrical backbone and different pendant groups were synthesized using asymmetric diamine and maleic anhydride as the precursors. The prepared bismaleimide monomers show good solubility in common organic solvents such as acetone and tetrahydrofuran. The EBA-BMI melt treated at 180°C also shows low viscosity about 190–934 mPa s at the temperature range of 160–139°C below its melting point (166°C). In addition to the good processability, all three cured bismaleimides show high storage moduli at high temperatures (2.0 GPa at 400°C), high glass transition temperatures over 400°C, and good thermal stability with the 5% weight loss temperatures around 470°C under nitrogen atmosphere. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43491.
Multi-function and green are two keywords of developing new flame retarding thermosetting resins, however, to achieve this target is still a big challenging today. Herein, a new kind of flame retarding bismaleimide resins with simultaneously good processing characteristics, high toughness and outstanding thermal stability were prepared by copolymerizing 4,4’-bismaleimidodiphenylmethane (BDM) with allyl triphenylborate (ATPB). The structure and integrated performances of BDM/ATPB resins were systematically studied and compared with the BDM/o,o’-diallylbisphenol A resin (coded as BD) that is almost known to be the best modified bismaleimide resin available. Results show that BDM/ATPB resins are solids with low softening points; they can be dissolved in acetone and have wide processing window, completely overcoming the poor processing characteristics of BDM. The properties of the BDM/ATPB system are dependent on the molar ratio of imide and allyl groups, and BDM/ATPB3 resin of which the molar ratio of imide to allyl groups (1:0.85) is the same as that of BD resin not only has significantly improved flame retardancy, reflected by obviously longer time to ignition, 1.5-3.0 times higher fire performance index, and greatly decreased heat releases, but also has about 10 °C higher initial decomposition temperature in both air and nitrogen atmospheres as well as about 1.2-1.3 times higher impact and flexural strengths, clearly demonstrating that ATPB is a multi-functional and green modifier for bismaleimide. The origin behind these attractive results of BDM/ATPB resins was intensively discussed.
We investigated a novel artificial metamaterial that includes two plates of quartz glass dielectric material and a Ag microstructure sandwiched between the two plates. The Ag grid layer was designed and subsequently prepared by tape casting and screen printing. The transmission characteristics of this metamaterial were able to be controlled by adjusting the geometry parameters of the Ag grid such as the width of the strip and the size of the unit cell. Our work has demonstrated the possibility that the ceramic metamaterial can be used as a transmission material capable of work at high temperatures below the melting point of the metal.
The curing reaction of the bismaleimide resin system was analyzed by FT-IR spectroscopy and differential scanning calorimetry, and the curing reaction kinetics parameters were characterized. Otherwise the rheological behavior of the bismaleimide resin was studied through tracking the changes of the resin viscosity with reaction temperature and time by using a rotatory viscometer. The rheologic dynamic equation and dynamic index of the resin were also established under the condition of constant temperature.The result showed that the bismaleimide resin system was a typical thermosetting resin. This research will help to optimize the molding process parameters of the bismaleimide resin.
A series of flame-retarded epoxy resins (EPN) loaded with methyl phenyl silicone resin (Si603) and DOPO (9, 10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) have been prepared. The morphology of these EPN composites were characterized by differential scanning calorimentry (DSC). The mixed epoxy systems all exhibit single glass transition temperature which indicates a homogeneous morphology of these mixed epoxy systems. The thermal stability and flammability of these EPN composites were investigated with limiting oxygen index, UL 94 vertical burning, and themogravimetric analysis tests (TG). The results showed that the DOPO and Si603 system had excellent flame retardancy and antidripping properties for EPN. The TG curves suggested that there was a distinct synergistic effect of DOPO and Si603, and this effect greatly promoted the char formation of the EPN composites and hence improved the flame retardancy. Additionally, the structure and morphology of char residues were studied with Fourier transform infrared and scanning electron microscopy.
A novel polysiloxane (HPS) with epoxy and phenyl groups was synthesized by controlled hydrolysis and condensation of γ-(2,3-epoxypropoxy)propytrimethoxysilane (KH560) and diphenyl silanediol. Besides, HPS was used as the compatibilizer of the miscible diglycidyl ether of bisphenol A (DGEBA)/methyl phenyl silicone resin (Si603) blend. The structure and effect of HPS were characterized by Fourier transform infrared spectra, nuclear magnetic resonance (1H-NMR), differential scanning calorimetry, and scanning electron microscopy (SEM). The results showed that HPS could significantly improve the compatibility between epoxy resin (EP) and Si603 resin. In addition, the glass transition temperature (T
g) of the blend increases with increasing amount of Si603 from 129 to 151 °C. The thermal stability of blending system was studied by thermogravimetric analysis, derivative thermogravimetric analysis and SEM. The results showed that the incorporation of Si603 into DGEBA resin not only obviously increased the thermal resistance, but also remarkably improved the flame retardancy. The high limiting oxygen index of the HPS/EP/Si603/DDM system at 31 is considered as excellent flame retardancy in the epoxy system.
In the present paper we combine functionalization and biodegradation in the rational design of polymers that can be used as carrier systems for drug delivery in the colon. Functionalization of new polyurethanes (PUs) was achieved by thiol–ene coupling reactions, a simple and straightforward procedure included among the so-called click reactions, which are currently accepted as one of the most powerful tools in organic chemistry. Enhancement of the degradability of the new materials by the introduction of disulfide linkages into the polymer backbone has led to a new group of stimulus-responsive sugar-based polyurethanes able to be degraded by tripeptide glutathione under physiological conditions. Atomic Force Microscopy (AFM) on solid-supported multilayered dry polymer films—prepared by spin-coating from dimethylsulfoxide solutions—was used to study the morphology of the polymers and the degradation process in reductive environments. Matrix systems containing polymers selected according to their rheological properties were also investigated as modulated methotrexate-release systems.
Hyperbranched poly(aryl ether ketone)s with hydroxyl end groups (HBP-OH) and high degree of branching value (83%) were synthesized via an A2 + B3 approach. The polymerization conditions (e.g., polymerization temperature and time, monomer concentration, stoichiometric ratio of functional groups) were explored to avoid the gelation. Allyl-terminated hyperbranched PAEKs (HBP-AL) with low molecular weight (Mn = 3.4 × 103) and narrow polydispersity (PDI = 1.65) were obtained via the etherification of HBP-OH and it has been used for the modification of bismaleimide (BMI) resins. The prepolymers showed good processibilities with a viscosity below 0.6 Pa s at 110°C, though the viscosities slightly increased as the increase of HBP-AL contents. The cured BMI resins showed high glass transition temperatures (Tg > 320°C) and good thermal stabilities (Td > 400°C, both in nitrogen and air). It is inspiring to note that the incorporation of HBP-AL into BMI matrix results in a significant enhancement of toughness without any noticeable loss in modulus, processibility, and Tg. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers
New poly(1,2,3-triazole)s functionalized with allyl groups were prepared by the 1,3-cycloaddition reaction (click reaction) of azido-imides to bispropargyl monomers containing allyl groups. The copolymers of 4,4'-bismaleimidodiphenylmethane with allylated polytriazoles were prepared and their properties investigated. Modified bismaleimide resins had excellent processing compared with neat bismaleimides, especially improved olubility and faster thermal polymerization rate. In addition, the new cured systems had good thermal and dielectric properties (dielectric constant at 1 kHz ranged between 3.09 and 3.39, except the polymer with aliphatic segment instead of the imide group that had a higher constant, namely 4.6).
A novel fully end-capped hyperbranched polysiloxane (Am-HPSi) with large branching degree and amine-groups was successfully synthesized by a controlled hydrolysis of phenyltrimethoxysilane and γ-aminopropyl triethoxysilane, and its structure was characterized by nuclear magnetic resonance (1H-NMR and 29Si-NMR) and Fourier transform infrared (FTIR) spectra as well as gel permeation chromatography (GPC). In addition, Am-HPSi was used to develop a new modified bismaleimide resin with simultaneously improved flame retardancy and other typical properties. The incorporation of Am-HPSi to 4,4′-bismaleimidodiphenyl methane/2,2′-diallyl bisphenol A (BDM/DBA) resin not only obviously increases the thermal resistance, moisture resistance, impact strength, and dielectric properties, but also remarkably improves the flame retardancy. Specifically, the average heat release rate and total heat release of modified BDM/DBA resin with 10 wt% Am-HPSi are only 37 % and 23 % of that of neat BDM/DBA resin, respectively. A synergistic flame retarding mechanism is believed to be attributed to these results, which includes improving thermal stability, producing non-combustible gas, acting in the condensed phase, and providing a barrier for heat and mass transfer owing to the introduction of Am-HPSi to BDM/DBA resin. These attractive features of Am-HPSi/BDM/DBA resins suggest that the method proposed herein is a new approach to develop high performance resins for cutting-edge industries.
Carbon fiber–reinforced BMI composites have been subjected to combination accelerated aging comprising a hygrothermal process, a thermal-oxidative process, and a freezing process in order to simulate their responses under complicated service environments. This cyclical condition, including the freezing process, has not been investigated by other researchers so far. The effects of this combination accelerated aging on the mechanical properties have been characterized by FTIR, SEM/EDXA, XRD, and moisture-uptake determination. The results indicated that combination accelerated aging had great effects on the mechanical properties of the composite, the network structure of the BMI matrix, and the moisture uptake by the composite. After a third cycle of accelerated aging, moisture reached the center layer of the composite and as a result led to an obvious decrease in ILSS due to deterioration of the carbon fiber–BMI interface. Sufficient moisture absorption on the composite surface made the network structure of the BMI matrix more open, which facilitated stress relaxation and the creation of micro-cracks, with a consequent obvious decrease in flexural strength. With increasing number of combined-action accelerated aging cycles, ever more moisture was absorbed during each hygrothermal process due to the plasticizing effect of water, and micro-cracks propagated as a result of internal stresses caused by the hygrothermal process, the thermal-oxidative process, and the freezing process of each cycle. XRD analysis indicated that moisture penetrated through the amorphous region of the BMI matrix.
Three new polymerizable diols, based on mono-, di-, and tri-O-allyl-L-arabinitol derivatives, were prepared from L-arabinitol as versatile materials for the preparation of tailor-made polyurethanes with varied degrees of functionalization. Their allyl functional groups can take part in thiol-ene reactions, to obtain greatly diverse materials. This “click” reaction with 2-mercaptoethanol was firstly studied on the highly hindered sugar precursor 2,3,4-tri-O-allyl-1,5-di-O-trityl-L-arabinitol, to apply it later to macromolecules. A polyurethane with multiple pendant allyl groups was synthesized by polyaddition reaction of 2,3,4-tri-O-allyl-L-arabinitol with 1,6-hexamethylene diisocyanate, and then functionalized by thiol-ene reaction. The coupling reaction took place in every allyl group, as confirmed by standard techniques. The thermal stability of the novel polyurethanes was investigated by thermogravimetric analysis and differential scanning calorimetry (DSC). This strategy provides a simple and versatile platform for the design of new materials whose functionality can be easily modified. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
A novel kind of modified bismaleimide/cyanate ester (BCE) resins by copolymerizing with hyperbranched polysiloxane including high content of phenyl (HBPSi) was first reported. The effect of HBPSi on the curing mechanism, and that on the dielectric properties and flame retardancy of cured networks were systemically investigated. Results show that compared with BCE resin, HBPSi/BCE resin has obviously different cross-linked structure, and thus leading to simultaneously improved dielectric properties and flame retardancy. The reactions between HBPSi and the decomposition structure of BCE resin change the thermo-oxidative degradation mechanism of the first step in the thermo-oxidative degradation; in addition, the presence of HBPSi in BCE resin also significantly reduces the mass loss rate (MLR) and increases char yield at 800 °C under an air atmosphere. Therefore, the positive effect of HBPSi on improving the flame retardancy is attributed to the condensed phase mechanism. On the other hand, HBPSi/BCE resins exhibit improved dielectric properties (including decreased dielectric constant and loss) with increasing the content of HBPSi. More importantly, this investigation demonstrates that designing new polysiloxane with suitable chemical structure is important to develop high performance resins with attractive flame retardancy and dielectric properties.
In the field of high thermomechanical performance polymers, linear and thermosetting systems offer complementary properties.
Among the thermosetting materials, BMIs and BNIs have been extensively studied and are now commercially available. In this
chapter, firstly the main preparation and characterization methods are reviewed, and then the chemistry of the polymerization
processes is discussed for both families. For the BMIs, due to the electrophilic character of their double bond, different
polymerization pathways have been published, which is not the case for BNIs. Special attention has been paid to thermal polymerization
which has already been used in industrial achievements; however, on the other hand, the structure of these materials has been
considered for the purpose of establishing relationships between processability, stability and thermomechanical properties.
Bismaleimide (BMI) composites are used on some of the most important and complex, high performance applications ranging from military programs such as the Air Force's F-22 to Formula-1 race cars. BMI's most important attribute is the unique combination of high service temperature, good toughness and epoxy-like processing. BMI matrix composites provide the highest mechanical properties available through 350 °F/wet, exhibiting damage tolerance equivalent to the best epoxies. Certain BMIs are capable of extended service at 450 °F to 550 °F, approaching the performance of the condensation polyimide, PMR-15. BMIs are also versatile RTM resins. This paper will discuss the advantages of BMI composites. A detailed analysis of the current applications will illustrate how the advantages of BMIs were exploited and how to apply them to gain added value in your application.
This paper reviews the chemistry, properties, and applications of PMR polyimides, acetylene-terminated polyimides and bismaleimides. Thermosetting polyimides are being developed for use as matrix resins in structurally efficient advanced composites for aerospace and future non-aerospace applications. Their chemical structures can be altered to enhance toughness, processing ease, and temperature performance. However, it is very difficult to attain these three desired properties in one product. Bismaleimides are popular for use in the temperature range of 150-250°C because of their epoxy-like processing and polyimide-like temperature capability PMR polyimides are suitable for temperatures up to 371°C because of their outstanding thermo-oxidative stability. Acetylene-terminated Thermid materials are less favored because of the difficulty in processing; however, improvements in the processability are emerging.
Recent developments in the area of addition curable phenolic resins are reviewed. The article highlights the chemistry of addition-cure phenolic resins and discusses the different strategies involved in their molecular design. Structural modification through incorporation of thermally stable, addition curable groups on the novolac backbone is one strategy. The transformation of phenolic hydroxyl groups to addition curable functions forms an alternate approach. Cross-linking of novolac or its derivatives with a suitable curative also leads to addition-curable phenolic resin systems. This article examines the synthesis, characterization and curing of noted addition curable phenolic systems. Their thermal, physical and mechanical properties are discussed and the structure–property correlations examined. In selected cases, the adhesive properties of the systems have been examined. The review includes discussions on the properties of the composites in relevant cases. The systems discussed here include mainly allyl- and maleimide-functional phenolics, epoxy–phenolic, polybenzoxazine, bisoxazoline–phenolic, acetylene-functional and propargyl ether phenolics and phenolic-triazine. The relative advantages and demerits of these systems are discussed and their application potentials are considered.
Maleimide-terminated amorphous poly(arylene ether sulphones) and poly(arylene ether ketones) of controlled (2000–10000 or higher) were synthesized by nucleophilic aromatic substitution, step polymerization and bisphenol A phenolate with activated aromatic halides in the presence of m-aminophenol or 2,2′-(4-aminophenyl-4-hydroxyphenyl)propane. The amine-terminated oligomers of predictable molecular weight were then converted to maleimides. This ‘two-step’ method was accomplished by reacting the terminal amine with maleic anhydride in a co-solvent of pyrrolidone (). A second ‘one-step’ oligomer synthesis method employed either m-maleimidophenol or 2,2′-(4-maleimido-4′-hydroxyphenyl)propane as the ‘monofunctional’ end-capper. The oligomers were thermally crosslinked through a free-radical reaction of the maleimide end-groups. Curing at 250°C for 1 h produced networks which were 98% chloroform-insoluble. The influence of oligomer molecular weight on the thermal and mechanical properties of the solvent-resistant networks was investigated by differential scanning calorimetry, dynamic mechanical thermal analysis, flexural modulus and fracture toughness, KIC. Very substantial increases in toughness were observed relative to simple bismaleimides and were a function of the molecular weight between crosslinks () and the β-relaxation of the matrix.
In this article, a phosphorus containing bismaleimide (V) based on 2-(6-oxido-6H-dibenz 〈c,e〉 〈1,2〉 oxaphosphorin-6-yl)-1,4-dihydroxy phenylene (I) was synthesized and copolymerized with 4,4′-bismaleimidodiphenylmethane (BMDM) in various weight ratio (0–33phr). DSC scans show that the introduction of V into BMDM has increased the processing window for the resulted copoly(bismaleimide). DMA scans show these cured BMIs exhibit good modulus (∼2GPa) up to 400°C. There is no tangent peak for these cured BMIs implying that there is no relaxation below 400°C. TMA scans show introduction of V into BMDM increase the coefficient of thermal expansion (CTE). However, CTE of these cured BMIs are less than 50ppm, which is much less than common epoxy. There is no second transition during TMA heating scans up to 440°C, so Tgs of these cured BMIs are higher than 440°C, which is consistent with the DMA measurement. TGA heating scans also indicate that they have high thermal stability and their char yields increase with the content of V. Char yields at 800°C shift from 48 to 63 in nitrogen and from 0 to 18 in air when 25phr of V was introduced into BMDM. TGA isothermal experiments show that these cured BMIs are thermally more stable in air than in nitrogen below 450°C. Char yields also increase with the content of V.
Four kinds of polyetherimides with different diamines were prepared and used to improve the toughness of bismaleimide resins composed of bis(4-maleimidediphenyl)methane and o,o′-diallyl bisphenol A. Dynamic mechanical analysis and scanning electron microscopy were used to characterize the phase structure of the modified resins. The modified resins display different phase morphologies depending on the polyetherimide backbone structure. The results indicate that the degree of phase separation leads to different morphologies and toughening. The fracture energy (GIC) was increased by 300% with the PIM modified system.
N-(4-Hydroxyphenyl) maleimide was synthesized via two synthesizing procedures, and a new bismaleimide bearing polysiloxane (BPS) was prepared by reacting N-(4-hydroxyphenyl) maleimide with dichlorodimethyl silane at first, then the adduct was reacted with polysiloxane terminated by hydroxyl groups. The products were characterized by i.r., n.m.r. and elemental analysis, respectively. The molecular weight of BPS was determined by g.p.c. and its curing behaviour and cured resin thermal stability were investigated by d.s.c. and t.g.a. The toughening effect of BPS was investigated by introducing it into 4,4′-bismaleimido diphenylmethane (BMI) cured matrix. The results indicated that adding 20 wt% BPS into the BMI matrix could increase the impact strength 3.7 times as much as that of the pure BMI matrix. The toughening mechanism of the matrix was elucidated by the glass transition temperature, determined by d.s.c., and the fracture surface morphology was observed by s.e.m.
Curing bis(maleimide) (BMI) with diallylbisphenol A (DABPA) results in the formation of a high-performance thermoset resin. A variety of reactions in which maleimide units are converted to succinimide moieties have been proposed. In order to make spectral assignments for the fluorescence behavior observed during the cure of BMI/DABPA resin and to assess the likelihood that certain types of reactions take place during resin cure, several succinimide model compounds were synthesized from N-phenylmaleimide (NPM) and characterized. These model compounds gave fluorescence signals which were red-shifted by 40 nm or more from the emission maximum in DABPA resin, while no fluorescence was observed from the BMI. The BMI was found to quench the fluorescence from DABPA and a Stern−Volmer quenching constant was determined for this pair. Relative fluorescence quantum yields were determined for the model compounds. The DABPA resin component was found to have the highest quantum yield and is likely to be responsible for most of the fluorescence near 356 nm when the resin is excited near 280 nm. A succinimide derivative which arises from a Diels−Alder−Ene reaction sequence was found to have a higher quantum yield than other succinimides which were investigated. This type of structure might be responsible for most of the fluorescence observed in the long wavelength regions. Fluorescence peak shapes and peak positions were found to have a concentration dependence.
Curing bis(maleimide)/diallylbisphenol A (BMI/DABPA) results in the formation of a high-temperature thermoset resin. FT-IR, fluorescence, and UV-reflectance spectroscopy were used to investigate the cure behavior of this material under three different cure schedules. Fluorescence signals were quenched before curing due to the BMI component but increased and eventually leveled off as cure time increased. The largest fluorescence intensity increases occurred after 80% of the phenylmaleimide units were converted to phenylsuccinimide. Fluorescence signals were observed in both short-wavelength and long-wavelength regions. Model compound studies indicated that the phenolic portion of the BMI/DABPA resin has a higher quantum yield for fluorescence at a shorter wavelength than phenylsuccinimide derivatives. Therefore, fluorescence emission observed near 356 nm during curing is attributed to phenolic structures. FT-IR was used to quantify the extent of succinimide formation and to identify cross-linking processes which occurred during high temperature curing (250−260 °C). High-temperature curing processes were also identified by UV-reflection spectroscopy. Various reaction pathways are discussed in terms of their consistency with the spectroscopic data.
An investigation was carried out on the mechanism and kinetics of cure of a two-component bismaleimide formulation, composed of 4,4‘-methylenebis[maleimidobenzene] and 2,2‘-diallylbisphenol A. In-situ real time study of the progress of reaction was conducted in the temperature range from 140 to 250 °C using remote fiber optic near-infrared spectroscopy. The obtained signal was clean, free of noise, and remarkably reproducible. The principal reaction observed was an alternating copolymerization involving maleimide and allyl double bonds. Maleimide homopolymerization was detected only in the initial stages of reaction at temperatures above 200 °C. The extent of self-condensation (or etherification) of hydroxyl groups on the allyl component, which leads to cross-linking, was observed to vary with reaction temperature, suggesting a path to tailor-making networks with desired morphology and physical/mechanical properties.
Dithiols and diamines react with bismaleimides via a Michael type process to afford high-molecular-weight poly(imido sulfides) and poly(aspartimides), properties of which range from those of rubberlike elastomers to those of high-melting thermoplastics. This review presents a brief summary of the requirements for synthesis of these polymeric Michael adducts along with a discussion of structural effects on the thermal, morphological, and mechanical characteristics of the materials. Copolymeric poly(imido sulfides) as well as polymers from bis(dichloromaleimides) and bisphenols also are described.
Multifunctional compounds with pendent and terminal maleimide groups were prepared through the reaction of 4-maleimidobenzoic acid and 5-maleimidoisophthalic acid with diglycidyl ether of bisphenol A. The ratios of the pendent maleimide groups to the terminal maleimide groups in the obtained compounds were varied to tailor the chain length and properties of the maleimide compounds. The maleimide group ratios, determined from differential scanning calorimetry, showed good coincidence with the values calculated from the charged monomer amounts. The good solubility and low softening points of the maleimide compounds indicated their good processability. High glass-transition temperatures (220 °C) were observed for the cured resins because of the relatively high crosslinking density. The curing reaction, thermal stability, and degradation behavior of the resins were also studied with differential scanning calorimetry and thermogravimetric analysis. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3178–3188, 2004
The thermal reaction between N-phenylmaleimide and 2-allylphenol was taken as a model reaction in order to obtain information about chain extension and crosslinking mechanisms of the thermal curing of bismaleimides with diallylbisphenol A. Isolation (preparative HPLC) and characterization (1H and 13C NMR, FT-IR, HPLC/SM) of a monoadduct and two original triadducts (principally low molecular weight products of the reaction) and studies as a function of time (0–6h) of this thermally induced reaction (160–250°C) with equimolar quantites of N-phenylmaleimide and 2-allylphenol, as well as with an excess of N-phenylmaleimide, give direct evidence of the occurrence of an ene-reaction and further Diels-Alder and retro Diels-Alder reactions with rise in temperature.
While aromatic polyimides have found widespread use as high-performance polymers, the present work addressed the need for organosoluble pre-imidized materials through the use of a hyperbranching scheme. The AB 2 monomer, N-[3,5-bis(4-hydroxybenzoyl)benzene]-4-fluorophthalimide, was prepared from 4-fluoroisophthalic anhydride and 3,5-bis(4-hydroxybenzoyl)aniline. The latter was synthesized in three steps starting from commercially available 5-nitroisophthalic acid. The AB2 monomer was then polymerized via aromatic fluoride-displacement reaction to afford the corresponding hydroxyl-terminated hyperbranched polymer, HT-PAEKI, which was then functionalized with allyl and propargyl bromides as well as epichlorohydrin to afford allyl-terminated AT-PAEKI, propargyl-terminated PT-PAEKI, and epoxy (glycidyl)-terminated ET-PAEKI, in that order. All hyperbranched poly(ether-ketone-imide)s were soluble in common organic solvents. Intrinsic viscosities of HT-, AT-, PT-, and ET-PAEKI in NMP were 0.13, 0.08, 0.08, and 0.08 dL/g, in that order. AT-PAEKI displayed an exotherm due to Claisen rearrangement at 269 °C and allyl-based thermal-cure reaction at 343 °C. PT-PAEKI displayed only a single, strong exotherm at 278 °C. Because of hydrogen bonding, HT-PAEKI displayed T g of 224 °C while its derivatives exhibited lower Tg values ranging from 122 to 174 °C. Finally, AT-PAEKI was blended with a bisphenol A-based bis(maleimide) (BPA-BMI) in various weight ratios. The results from differential scanning calorimetric study indicated that the presence of AT-PAEKI (up to 32 wt %) significantly affect the glass transition temperatures and cure behavior of BPA-BMI. Dynamic mechanical analysis comparing cured BPA-BMI with the 5 wt % AT-PAEKI blend corroborates this increase in glass transition temperature.
A detailed investigation of the condensation of aromatic amines and maleimide compounds was conducted by the use of model compounds. Weak Brönsted acids were found to have a marked catalytic effect on the reaction. By using glacial acetic acid as the reaction medium, a number of model aspartimide compounds were prepared. Aromatic diamines and bismaleimide compounds were condensed to high polymers in cresol containing a small amount of a protonic acid catalyst. Polymers having a variety of novel backbone structures were prepared and their physical properties studied.
Three kinds of liquid crystalline aromatic azomethine modifiers were synthesized with high yield, and the modification of bismaleimide resin (BMI) with them was studied by scanning electron microscope, polarizing optical microscope, thermogravimetric analyzer, differential scanning calorimetry, and rheolometry. Blends cured at the temperature of liquid crystalline phase were found to have oriented liquid crystal-rich phase and improved mechanical properties. The addition of o,o′-diallyl bisphenol A in the blends of BMI decreases thermal properties but shows little effect on phase structures. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4366–4371, 2006
A thermosetting resin system for resin-transfer molding based on novolak and bismaleimide (BMI) was developed. The novolak resin was allylated and BMI was used as the curing agent, and allyl phenyl ether, as the diluent. The viscosity–temperature curve and the viscosity–time curve were used to characterize the processing property of the resin system. The resin system had a long pot life at the injection temperature. Based on the DSC data, a regime for the curing and postcuring cycles was established. The cured resin showed outstanding heat resistance and good flexural properties. Composites based on the resin system and woven glass fabric were fabricated using RTM technology. The composites showed very good flexural properties at room temperature and high retention rates at 200 and 300°C. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1651–1657, 2002
Two novel bismaleimide (BMI) monomers containing 1,3,4-oxadiazole, i.e., 5-tert-butyl-1,3-di[5-(4-maleimidophenyl)-1,3,4-oxadiazole-2-yl]benzene (Buoxd) and 4,4′-[5-(4-maleimidophenyl)-1,3,4-oxadiazole-2-yl]diphenyldimethylsilane (Sioxd), were designed, synthesized and copolymerized with 4,4′-bismaleimidodiphenylmethane (BMDM) to yield a new series of high-performance bismaleimide resins. Both monomers obtained are readily soluble in common organic solvents, such as dichloromethane and chloroform, enabling an easy solution processing. The thermal properties of the two monomers were carefully studied by the differential scanning calorimetry (DSC), optical microscopy and thermogravimetric analysis (TGA, simultaneous DSC). The BMI resins based on a mixture of Buoxd (or Sioxd) and BMDM in a weight ratio of 10% were prepared. DSC investigations showed that the thermal curing of the BMI resins could be accomplished at a lower temperature than the thermal curing temperatures of Buoxd and Sioxd, and the thermal processing window, i.e., the temperature range between the melting transition and thermal curing process, was over 26 °C. The thermal properties and thermal mechanical properties of the resulting BMI resins were investigated by DSC, thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). No glass transition temperature was found in the range of 50–350 °C, and very good thermal stability (Td > 490 °C in nitrogen) and high thermo-oxidative stability (Td > 460 °C in air) were revealed. Composites composed of the above BMI resins and glass cloth were also prepared, which showed high bending modulus (>1.6 GPa) at a very high temperature (e.g., 400 °C).
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