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In this study, novel polyurethane/silica (PU/SiO2) hybrid materials, prepared without an external crosslinking agent, were developed via the chemical reaction between urethane groups of PU prepolymer and hydroxyl groups at the surfaces of silica. The added inorganic filler-silica thus played the dual roles not only inorganic chain extender but also...
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... groups on the silica were allowed to react with the terminal isocyanate groups of polyurethane prepolymer(pre-PU) to form the hybrid materials. Thus, the PU chains were chemically bonded to the silica particles to increase the crosslink density and reinforce the thermal and mechanical properties of the hybrid materials. The reaction is shown in Fig. ...
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... 28,29 Similar improvement in thermal stability is also reported by other literatures. [30][31][32] The optical microscopy images of bio-based PU foam incorporated with various fumed silica nanofillers are shown in Figure 4. With reference to the microscopy images, it can be observed the open-cell polyhedral foam structure formed across all samples. ...
Incorporating nano-sized fillers into bio-based polyurethane (PU) foams typically enhances their properties. In present investigation, palm oil-based PU foams are fabricated with varied loadings (0 to 5 wt%) of fumed nanosilica. The foams are then characterized for their fire-retardancy, thermal stability, foam morphology, and also mechanical properties. Marginal improvement in Limiting Oxygen Index (LOI) values, as well as failure to be rated under UL-94 Vertical Combustion Test indicate limited potential of fumed silica in improving flammability of organic polymeric foams; suggesting exorbitant amount is required for any distinguishable effect to manifest. Interestingly; results from Thermogravimetry Analysis (TGA) shows marked improvements in terms of char residue with more than seven-fold increase at 5 wt% filler loading, possibly owed to the inert filler nature of fumed nanosilica forming a char barrier and acting as fuel diluent. Filled PU foams displayed an increased open-cell content, likely because the filler functioned as a cell opener. Removing the influence of density, the normalized compressive properties showed notable improvement up until a certain loading, which could be credited to the increased stiffness imparted by the filler itself. The results portray the potential of fumed nanosilica as filler for bio-based PU foams, offering enhanced thermal stability and limited fire retardancy.
... Two types of TDI were mixed in the weight ratio of 80:20. APTES and PTMEG were dehydrated under vacuum drying at 80 • C for 12 h before use [26]. ...
... Surface modification of the GBs was achieved through a rapid reaction between the NCO group and OH group, which allowed the silanol group (Si-OH) to react with the terminal isocyanate groups (R-N=C=O) of the polyurethane prepolymer (pre-PU) ( Figure 1) [26]. Before synthesis, the GBs were first immersed in 1% (w/w) APTES in anhydrous toluene (99.8%, ...
... Thereafter, the GBs were washed with anhydrous toluene, deionized water, and ethanol (Samchun Chemicals). The pre-PU was prepared using the method described by Chen et al. [26]: 0.052 mol of the dehydrated PTMEG was added to a three-necked flask and stirred at 80 • C for 30 min. Then, 0.103 mol of TDI was added to the flask to react with the PTMEG. ...
Modern construction projects are often challenging, which has increased the demand for innovative materials that ensure improved safety, durability, and functionality. To explore the potential of enhancing soil material functionality, this study synthesized polyurethane on the surface of glass beads and evaluated their mechanical properties. The synthesis of polymer proceeded according to a predetermined procedure, where the polymerization was confirmed through analysis of chemical structure by Fourier transform infrared spectroscopy (FT-IR) and microstructure observation by a scanning electron microscope (SEM) after complete synthesis. The constrained modulus (M) and the maximum shear modulus (Gmax) of mixtures with synthesized materials were examined by using an oedometer cell equipped with bender elements under a zero lateral strain condition. Both M and Gmax decreased with an increase in the contents of polymerized particles due to a decrease in the number of interparticle contacts and contact stiffness induced by the surface modification. The adhesion property of the polymer induced a stress-dependent change in M but was observed to have little effect on Gmax. Compared to the behavior of the rubber-sand mixtures, polymerized particles show the advantage of a smaller reduction of M.
... This behavior confirmed that, PUmatrix incorporated with NS particles, formed a closed network structure due to formation of Si-O-Si linkage, which lead to less percolation of acid and alkali. Chen et al. have also reported similar findings.33 ...
The automobile paint industry normally consumes petro‐based feedstock as the raw material, which is non‐renewable and emits a higher amount of volatile organic compound, that pollutes the environment. This study focuses on the use of eco‐friendly castor oil (CO) as a substitute for petro‐based feedstocks; while synthesizing polyurethane (PU)‐based automobile clear coats. An acrylate‐PU/nano‐silica (NS) hybrid coating was developed, which was derived from CO‐based polyol. CO was modified by employing a process that includes epoxidation, followed by transesterification, and acrylation to synthesize the required polyols, which is used for acrylate‐PU paint synthesis via the in‐situ polymerization process. Triallyl isocyanurate (TI) modified NS particles were incorporated with the paint matrix by the ultrasonication method to enhance the paint properties. Experimental findings revealed that with the incorporation of NS particles, char residue, Young's modulus, abrasion resistance, and cross‐cut adhesion % increased by 71.31%, 42%, 0.28%, and 5% respectively. Also, glass transition temperature, pencil hardness, nanoindentation depth, water contact angle, and cross‐linking density were increased from −12.16°C, 2H, 3300 nm, 81.71°, and 0.90 mol/m3 to 1.65°C, 3H, 2000 nm, 92.26°, and 1.78 mol/m3 respectively. The UV‐visibility spectra, haze, transmittance, and gloss parameter showed the enhanced optical properties of the paint samples. PU/NS composite coating developed showed equivalent properties as that of the commercial clear coat.
... On the other hand, the diffraction peak of GOD was disappeared in the diffraction patterns of the EN-GOD3 and PU-EN-GOD1 hybrids showing that the d-spacing of GOD layers increases after addition to the polyurethane matrix. Such an increase could be related to the diffusion of polymer chains between the layers of GOD and finally its exfoliation [59,60]. The percentage of hard and soft segments and also BD for the samples were determined by using Eqs. ...
Thermal characteristics of epoxy-modified polyurethane and novolac resins composites were investigated by using graphene oxide (GO) functionalized with hyperbranched poly(amidoamine) (PAMAM) as the curing component (GOD). The dendritic hybrid curing agent of GOD was synthesized via a divergent method and used to cure epoxy-terminated polyurethane (EPU) and epoxidized novolac resin (ENR). After preparation of the first generation of PAMAM dendrimer by using amino-functionalized GO as the core, Fourier transform infrared spectra, X-ray diffraction (XRD), and thermogravimetric analysis (TGA) were used to prove the successful preparation method of GOD. TGA also showed that thermal characteristics of the hybrid EPU and ENR composites were determined by the amount of GOD and portion of the resins in the composites matrix. The hybrid composites with higher amounts of GOD and ENR matrix showed higher thermal stability and char residue. As example, the ENR-based hybrid composites with 3 wt% of GOD showed char residue of 57.2% at 600 °C and Tmax of 401.2 °C. In addition, morphological and structural study of the graphitic and hybrid samples was investigated by XRD and electron microscopies.
... The structure of the silicate backbone of C-S-H gels has been characterized by 29 Si NMR spectroscopy. The different types of Si sites in C-S-H gels and related structures are referred to as Q n sites [19,20], where n denotes the number of silicate tetrahedra connected to each silicon atom. For example, Q 1 represents the case in which only one silicon-oxygen tetrahedron is connected to the central silicon atom. ...
The adsorption behavior of water and ions at the surfaces of porous calcium-silicate-hydrate (C-S-H) gels affects the durability of concrete. This paper presents the results of molecular dynamics simulations performed using the Clay Force Field that were conducted to investigate the local structure, adsorption behavior, and dynamic properties of water and ions in the pores of C-S-H gels. A realistic C-S-H gel channel model was constructed and simulated with three mixed salt solutions (NaCl + Na2SO4, NaCl + Na2CO3, and Na2SO4 + Na2CO3) in the pores. The realistic C-S-H gel surface was found to be hydrophilic, causing water molecules to adopt an orderly arrangement near the substrate surface. This hydrophilicity is due to defective silicon chains in the substrate that provide large numbers of hydrogen bonding sites for surface water molecules. Additionally, calcium atoms near the surface attract water molecules to form hydration layers. The adsorption of cations near the substrate correlated negatively with the strengths of the ionic clusters formed by the dissolved anions and cations. As a result, the adsorption of sodium ion was strongest for the NaCl + Na2SO4 solution and weakest for the Na2SO4 + Na2CO3 solution. There were also clear differences in the adsorption behaviors of the anions. Chloride adsorption was mainly driven by ion pairing with calcium atoms near the surface, while sulfate adsorption was mainly due to ion pairing with surface-adsorbed sodium ions. Conversely, carbonate ions exhibited weaker surface adsorption because of their tendency to form ionic clusters in solution. These insights into the adsorption behaviors of common ions near a realistic C-S-H gel surface will be useful in future efforts to develop modified cement-based materials with improved properties.
... The effect was not manifested for the polymer of high innate strength-i.e., PUR based on polyol C (Figure 4). Strengthening effect of small additions of silica on the mechanical properties of polyurethanes remains in accordance with the results reported in recent literature [50,51]. ...
... The effect was not manifested for the polymer of high innate strengthi.e., PUR based on polyol C (Figure 4). Strengthening effect of small additions of silica on the mechanical properties of polyurethanes remains in accordance with the results reported in recent literature [50,51]. Figure S2). ...
The aim of the study was to evaluate the applicability and performance of polyglycerol- and sucrose-based polyols as components of a simplified formulation of polyurethane adhesives. Colloidal silica was used as a viscosity control and reinforcing agent. The adhesives were examined in terms of reactivity, thermal stability, viscosity, work of adhesion, wetting, surface energy, and bonding strength on wooden substrates. Silica was found to increase gelling time, but markedly improved bonding strength and adhesion with substrates. Bonded solid beech wood samples prepared at 80, 110, and 130 °C showed shear strengths between 7.1 MPa and 9.9 MPa with 100% wood failure. The renewable resource-based polyols were demonstrated to be useful in formulation of polyurethane adhesives for furniture industry-especially with silica as a filler.
... The IR peak centered at 448 and 1093 cm −1 can be assigned to the asymmetric stretching vibrations of Si−O−Si bonds. 20 The symmetric stretching vibrations of Si−O−Si species can explain the appearance of the bands at 792 and 1224 cm −1 . 21 In addition, the characteristic peak at 543 cm −1 could be attributed to the double six-membered ring, which is indicative of the existence of the micropore structure in HZSM-5, 8a while the band at 1632 cm −1 could be indexed to the vibrations of H 2 O on the sample surfaces. ...
In this study, a series of Mn-modified HZSM-5 samples were synthesized using the solid-state ion-exchange method, and the effects of the manganese loading amount, calcination temperature, reaction temperature, and gas components on mercury removal efficiency were systematically explored. Given that the mass ratio of HZSM-5 to KMnO4 and the calcination and reaction temperatures were set to 10:2.6 and 400 and 150 °C, Hg⁰ removal efficiency could reach a peak value of 96.4% when exposed to the flue gas containing 5% O2 and N2 as the balance. Among the various gas components, O2 and NO showed a positive impact on Hg⁰ removal; Hg⁰ removal efficiency could even reach ca. 100% when O2 and NO were simultaneously introduced. In contrast, the introduction of SO2 led to a decline of Hg⁰ removal efficiency by ca. 16%. In addition, Hg⁰ removal efficiency could still retain ca. 92% of that for the fresh sample after six regeneration and reuse cycles, which is indicative of a satisfactory stability and renewability. Finally, Mars–Maessen mechanisms dominated in the mercury chemical adsorption process.
... In this manner, the small bands centered at 873 and 1427 cm −1 suggest the presence of aragonite [24]. The mid-IR bands changed in frequency, which are related with silicate reactions after mud-acid interaction [25,26]. The bands at 3640 and 1086 cm −1 are not clearly observed after mud-acid interaction suggesting, respectively, partial reactions of leaching of CH and depolymerization with rearrange of silicates chains, leading to formation of new aluminosilicates [27]. ...
Inadequate zonal isolation in oil wells can provoke safety and environmental problems. New cement slurries can avoid such problems. In this work, novel cement slurries were prepared in the presence of seawater with in situ-formed epoxy resin–ethylenediamine. The new slurries were tested in relation to their mechanical properties and characterized by FTIR, XRD, TG/DTG, porosimetry by N2 adsorption-desorption and solid-state 29Si and 27Al NMR. Some kinetic features of long-term contact of the slurries with in situ-generated mud-acid were performed to evaluate the performances of the new slurries in routine acidizing procedures in oil well industry. The experimental kinetic data were well fitted to order-variable exponential kinetic model and a factorial design of four variables (24). In these studies, it was possible to evaluate in detail how some important experimental factors act on the quantities of acid that interact with the pastes, as well as to verify how these factors affect the speed with which the mud-acid interacts with the slurries. The results strongly suggest that the interactions occurred at epoxy/ethylenediamine cement slurry/mud-acid interfaces are due to surface reactions with preservation of the chemical structures of the cement slurries, even after long-term contact with mud-acid. The new cement slurry present good features to be used in environmental-friendly procedures in oil well field.
... 10 Chen et al. studied the effect of silica as an inorganic chain extender to improve the mechanical properties and thermal stability of PU, which had expanded the range of PU applications. 11 Meanwhile, polysilazane has large intermolecular force and high rigidity and stability due to a small angle of its Si-N-Si bond. 12 It can endow coatings with excellent properties such as heat resistance, weather ability, corrosion resistance, scratch, and contamination resistance when incorporated inside. ...
Due to their unique physicochemical properties, polysilazanes exhibit excellent performance when combined with some resin matrixes, which had drawn great research attention. In this article, polyurethane (PU) was firstly prepared by polytetrahydrofuran glycol, isophorone diisocyanate, and 1,4-butanediol as main materials. Then, the prepared PU was blended with polysilazane by mixing the two solutions together, which was cured to films via dip-coating method at room temperature. The structure, thermal stability, and surface properties of the composite coatings were investigated by Fourier-transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy. The results demonstrated that after modification with polysilazane, the heat resistance, hydrophobicity, and mechanical property of the PU coatings were improved. When the content of polysilazane was 6 wt%, the mechanical property of the composite films was optimized, with a maximum tensile strength of 25.7 MPa and elongation at break of 797%. Meanwhile, the water contact angle of the composite film was 107° and the water absorption reached a minimum of 2.1%, which showed improved hydrophobicity and water resistance.
... Thus, in the polyurethane dispersion, part of the PU chains is chemically bonded to the silica particles increasing the crosslink. This behavior is similar to the described in the literature by Chen et al. (2015). however, in the CP2 composite, is not observed the band located in 823 cm -1 (Si-Oh). ...
... Progressive changes in PU properties and increase in Tg values of composites can indicated that the filler particle affects the PU matrix properties. This effect can be due the chemical or physical interactions between filler and PU matrix; and effects derived from geometrical constrains of PU matrix, which is caused by the close proximity of the SiO 2 particles (Chen et al. 2015). In this work, it was possible to observe that the obtaining method of WPU/silica composites affect significantly the thermal and mainly weathering resistance these composites. ...
Waterborne polyurethanes (WPUs) are interesting materials for coatings when compared to solvent-based polyurethanes, once that reducing the concentration of volatile organic compounds that are harmful for human health and the environment. However, the WPU has low weathering resistance. In order to improve this behavior among others properties, inorganic fillers has been added in these systems. SiO2 particles from various sources, mainly, from agro-industrial waste, as rice husk has attracted the scientific and technological interest. In this study, the accelerated weathering essay was performed in waterborne polyurethane (WPU)/ silica (from rice husk ash) composites in order to evaluate the thermal and physical changes in these materials. These composites were prepared by two distinct methods: in situ polymerization and blending method. The highest resistance to thermal degradation and to accelerated weathering was reached with WPU/silica composites obtained by blending method due the interactions between SiO2 particles and the polymer matrices. Blending method for preparation WPU/silica composites proved to be a simpler and faster method, with no drawback for large scale application.
