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3D‐printed PLA/PMMA polymer composites: A consolidated feasible characteristic investigation for dental applications
Abstract
This research article focused on the blending of poly(lactic acid)/poly(methyl methacrylate) (PLA/PMMA) polymer materials to overcome PLA's inherent weaknesses, such as low glass transition temperature, brittleness, and lack of melt strength. Consolidated feasible characteristic investigations, such as mechanical, thermal, and aging behavior, were carried out for PLA/PMMA blended polymer materials. Initially, the miscibility of PLA/PMMA blend filaments was prepared at various blend ratios (91/9, 82/18, and 73/27) and samples were printed by fused deposition modeling (FDM). Differential scanning calorimetry (DSC) and Fourier infrared spectroscopy (FTIR) analysis have been utilized to evaluate the glass transition temperature (Tg) and intermolecular interaction, respectively, on blended polymer materials. Experimental tensile, compression, and flexural strength testing were performed on neat polymers and blended polymer composites. Compared to neat PLA materials, blended composites had 13.24% and 19.07% higher flexural and compression strengths. Besides, the interfacial interaction of neat and blended polymers has been done using dynamic mechanical analysis (DMA). Furthermore, Tg, storage modulus, and aging behavior of blended polymer materials have significantly improved over neat PLA materials. Altogether, the development of PMMA/PLA blends as sustainable biomaterials for dental applications aligns with environmental concerns and the need for biocompatible materials in dentistry.
Highlights
Blending of PLA and PMMA helps mitigate the inherent constraints of PLA.
Blended composites exhibited greater compressive and flexural strengths.
Better glass transition temperature and intermolecular interaction.
Excellent thermal stability and water aging imply viable dental biomaterials.
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Poly(lactic acid) (PLA) is gaining popularity in manufacturing due to environmental concerns. When comparing to poly(methyl methacrylate) (PMMA), PLA exhibits low melting and glass transition temperature (Tg). To enhance the properties of these polymers, a PMMA/PLA blend has been introduced. This study aimed to investigate the optimal ratio of PMMA/PLA blends for potential dental applications based on their mechanical properties, physical properties, and biocompatibility. The PMMA/PLA blends were manufactured by melting and mixing using twin screw extruder and prepared into thermoplastic polymer beads. The specimens of neat PMMA (M100), three different ratios of PMMA/PLA blends (M75, M50, and M25), and neat PLA (M0) were fabricated with injection molding technique. The neat polymers and polymer blends were investigated in terms of flexural properties, Tg, miscibility, residual monomer, water sorption, water solubility, degradation, and biocompatibility. The data was statistically analyzed. The results indicated that Tg of PMMA/PLA blends was increased with increasing PMMA content. PMMA/PLA blends were miscible in all composition ratios. The flexural properties of polymer blends were superior to those of neat PMMA and neat PLA. The biocompatibility was not different among different composition ratios. Additionally, the other parameters of PMMA/PLA blends were improved as the PMMA ratio decreased. Thus, the optimum ratio of PMMA/PLA blends have the potential to serve as novel sustainable biomaterial for extensive dental applications.
Poly(lactic acid) (PLA) is gaining popularity in manufacturing due to environmental concerns. When comparing to poly(methyl methacrylate) (PMMA), PLA exhibits low thermal properties. To enhance the properties of these polymers, a PMMA/PLA blend has been introduced. This study aimed to investigate the optimal ratio of PMMA/PLA blends for potential dental applications based on their mechanical properties, physical properties, and biocompatibility. The PMMA/PLA blends were manufactured by melting and mixing using twin screw extruder and prepared into thermoplastic polymer beads. The specimens of neat PMMA (M100), three different ratios of PMMA/PLA blends (M75, M50, and M25), and neat PLA (M0) were fabricated with injection molding technique. The neat polymers and polymer blends were investigated in terms of flexural properties, glass transition temperature (T g ), miscibility, residual monomer, water sorption, water solubility, degradation, and biocompatibility. The data was statistically analyzed. The results indicated that T g of PMMA/PLA blends improved with increasing PMMA content. PMMA/PLA blends were miscible in all composition ratios. The flexural properties of polymer blends were superior to those of neat PMMA and neat PLA. The biocompatibility was not different among different composition ratios. Additionally, the other parameters of PMMA/PLA blends were improved as the PMMA ratio decreased. Thus, the optimum ratio of PMMA/PLA blends have the potential to serve as novel sustainable biopolymer for extensive dental applications.
Functional cellular structures with controllable mechanical and morphological properties are of great interest for applications including tissue engineering, energy storage, and aerospace. Additive manufacturing (AM), also referred to as 3D printing, has enabled the potential for fabrication of functional porous scaffolds (i.e., meta-biomaterials) with controlled geometrical, morphological, and mechanical properties. Understanding the biomechanical behavior of 3D printed porous scaffolds under physiologically relevant loading and environmental conditions is crucial in accurately predicting the in vivo performance. This study was aimed to investigate the environmental dependency of the mechanical responses of 3D printed porous scaffolds of poly(methyl methacrylate) (PMMA) Class IIa biomaterial that was based on triply periodic minimal surfaces – TPMS (i.e., Primitive and Schoen-IWP). The 3D printed scaffolds (n = 5/study group) were tested under compressive loading in both ambient and fluidic (distilled water with pH = 7.4) environments according to ASTM D1621 standards. Outcomes of this study showed that compressive properties of the developed scaffolds are significantly lower in the fluidic condition than the ambient environment for the same topological and morphological group (p≤0.023). Additionally, compressive properties and flexural stiffness of the studied scaffolds were within the range of trabecular bone's properties, for both topological classes. Relationships between predicted mechanical responses and morphological properties (i.e., porosity) were evaluated for each topological class. Quantitative correlation analysis indicated that mechanical behavior of the developed 3D printed scaffolds can be controlled based on both topology and morphology.
There is a growing demand for customised, biocompatible, and sterilisable components in the medical business. 3D Printing is a disruptive technology for healthcare and provides significant research and development avenues. Simple 3D printing service gives patients low-cost individualised prostheses, implants, and gadgets, enabling surgeons to operate more effectively with customised equipment and models; and assisting medical device manufacturers in developing new and faster goods. 3D printed tissue pieces can overcome various challenges and may eventually allow medication companies to streamline research and development. In the long run, it may also assist in lowering prices and making medicines more accessible and effective for everybody. There is a growing corpus of research on the advantages of employing 3D printed anatomic models in teaching and training. The capacity to 3D printing individual anatomical diseases for practical learning is one of the fundamental contrasts between utilising 3D and regular anatomical models. 3D printing is very appealing for producing patient-specific implants. This literature review-based paper explores the role of 3D printing and 3D bioprinting in healthcare. It briefs the need and progressive steps for implementing 3D printing in healthcare and presented various facilities and enablers of 3D printing for the healthcare sector. Finally, this paper identifies and discusses the significant applications of 3D printing for healthcare research and development. 3D printing services can be deployed to easily construct complex geometries in plastic or metal with good precision. This results in improved prototypes, lower costs, and lower part processing times. They can now physically create with natural materials, previously unattainable with prior technologies. Every hospital should have 3D printers in the future, allowing new organs/parts to be developed in-house.
Presently, society needs an eco-friendlier alternative for non-biodegradable polymers, nonetheless, synthetic polymers have established the market because of cost and easy to manufacture. To address the challenge of reducing the lifetime of degradation of these polymers, the scope of blending natural biopolymers is effective. This paper focuses on confirming the effectiveness of biodegradation in the molecular level of polymer blends between synthetic polymers and biopolymers. The synthetic polymers such as poly (methyl methacrylate) (PMMA) and poly (vinyl chloride) (PVC) were blended with varying compositions of biodegradable cellulose acetate butyrate (CAB). Using dimethylformamide (DMF) the films of PMMA/CAB, PVC/CAB blends were prepared by the solution casting method. Four different methods for studying biodegradability of these blends, namely soil burial test, enzymatic degradation, activated sludge degradation followed by microbial degradation were performed. The confirmation of degradation was done by NMR, FTIR, and Gel Permeation Chromatography (GPC) studies. Moreover, degradation analyses were determined by the weight loss method. Sufficient biodegradability was shown with an increase in CAB content in the blend. This work provides an approach for bringing about the degradation of synthetic polymers without much compromise on their properties. Also, the type of microorganisms that effectively degrades these polymer bends can be known.
Objective Polylactic acid (PLA) is one of the most widely used materials in three-dimensional (3D) printing technology due to its multiple advantages such as biocompatibility and biodegradable. However, there is still a lack of study on 3D printing PLA for use as a denture base material. The goal of this study was to compare 3D printing PLA to traditional poly(methyl methacrylate) (PMMA) as a denture basis.
Materials and Methods The PMMA (M) and PLA (L) specimens were fabricated by compression molding, and fuse deposition modeling technique, respectively. Each specimen group was divided into three different temperature groups of 25°C (25), 37°C (37), and 55°C (55). The glass transition temperature (Tg) of raw materials and specimen was investigated using differential scanning calorimetry. The heat deflection temperature (HDT) of each material was also observed.
Statistical Analysis The data of flexural strength and flexural modulus were analyzed with two-way analysis of variance, and Tukey honestly significant difference. The Tg and HDT data, on the other hand, were descriptively analyzed.
Results The results showed that PLA had lower flexural strength than PMMA in all temperature conditions, while the PMMA 25°C (M25) and PMMA 37°C (M37) obtained the highest mean values. PLA 25°C (L25) and PLA 37°C (L37) had significant higher flexural modulus than the other groups. However, the flexural properties of L55 could not be observed, which may be explained by Tg and HDT of PLA.
Conclusion PLA only meets the flexural modulus requirement, although it was greater than flexural modulus of PMMA. On the other hand, PMMA can meet both good flexural strength and modulus requirement. However, increase in temperature could reduce flexural strength and flexural modulus of PMMA and PLA.
Fused deposition modelling (FDM) additive manufacturing is a technology that works horizontally and vertically in which an extrusion nozzle moves on a building platform. Knowing the mechanical properties of the parts manufactured by the FDM method is very important forthe parts to work efficiently in places of usage. Additive manufacturing with the FDM method is widespread due to its advantages such as easy-to-use features, low cost, flexibility in material options, and less processing after printing. Two different polymer materials (PLA and ABS), tensile, compression test and 3 point bending tests, a total of 36 test specimens were printed on the FDM type printer. The samples obtained were subjected to mechanical tests to determine their mechanical properties. As a result of the study, the effect of the samples' mechanical properties produced by the PLA and ABS-based FDM method was examined and compared with the literature. The results showed that the mechanical properties of PLA and ABS material are highly dependent onthe filling density. While the mechanical properties were improved by the increase in filling density rate, the print speed has been decreased. The research findings obtained are of a nature that will guide the optimization of the FDM method's parts in terms of mechanical properties.
Polylactide (PLA) is one of the most important bioplastics worldwide and thus represents a good potential substitute for bead foams made of the fossil-based Polystyrene (PS). However, foaming of PLA comes with a few challenges. One disadvantage of commercially available PLA is its low melt strength and elongation properties, which play an important role in foaming. As a polyester, PLA is also very sensitive to thermal and hydrolytic degradation. Possibilities to overcome these disadvantages can be found in literature, but improving the properties for foaming of PLA as well as the degradation behavior during foaming have not been investigated yet. In this study, reactive extrusion on a twin-screw extruder is used to modify PLA in order to increase the melt strength and to protect it against thermal degradation and hydrolysis. PLA foams are produced in an already known process from the literature and the influence of the modifiers on the properties is estimated. The results show that it is possible to enhance the foaming properties of PLA and to protect it against hydrolysis at the same time.
Over recent years, enthusiasm towards the manufacturing of biopolymers has attracted considerable attention due to the rising concern about depleting resources and worsening pollution. Among the biopolymers available in the world, polylactic acid (PLA) is one of the highest biopolymers produced globally and thus, making it suitable for product commercialisation. Therefore, the effectiveness of natural fibre reinforced PLA composite as an alternative material to substitute the non-renewable petroleum-based materials has been examined by researchers. The type of fibre used in fibre/matrix adhesion is very important because it influences the biocomposites’ mechanical properties. Besides that, an outline of the present circumstance of natural fibre-reinforced PLA 3D printing, as well as its functions in 4D printing for applications of stimuli-responsive polymers were also discussed. This research paper aims to present the development and conducted studies on PLA-based natural fibre bio-composites over the last decade. This work reviews recent PLA-derived bio-composite research related to PLA synthesis and biodegradation, its properties, processes, challenges and prospects.
Over millions of years of evolution, nature has created organisms with overwhelming performances due to their unique materials and structures, providing us with valuable inspirations for the development of next-generation biomedical devices. As a promising new technology, 3D printing enables the fabrication of multiscale, multi-material, and multi-functional three-dimensional (3D) biomimetic materials and structures with high precision and great flexibility. The manufacturing challenges of biomedical devices with advanced biomimetic materials and structures for various applications were overcome with the flourishing development of 3D printing technologies. In this paper, the state-of-the-art additive manufacturing of biomimetic materials and structures in the field of biomedical engineering were overviewed. Various kinds of biomedical applications, including implants, lab-on-chip, medicine, microvascular network, and artificial organs and tissues, were respectively discussed. The technical challenges and limitations of biomimetic additive manufacturing in biomedical applications were further investigated, and the potential solutions and intriguing future technological developments of biomimetic 3D printing of biomedical devices were highlighted.
A wide range of polymers are commonly used for various applications in prosthodontics. Polymethyl methacrylate (PMMA) is commonly used for prosthetic dental applications, including the fabrication of artificial teeth, denture bases, dentures, obturators, orthodontic retainers, temporary or provisional crowns, and for the repair of dental prostheses. Additional dental applications of PMMA include occlusal splints, printed or milled casts, dies for treatment planning, and the embedding of tooth specimens for research purposes. The unique properties of PMMA, such as its low density, aesthetics, cost-effectiveness, ease of manipulation, and tailorable physical and mechanical properties, make it a suitable and popular biomaterial for these dental applications. To further improve the properties (thermal properties, water sorption, solubility, impact strength, flexural strength) of PMMA, several chemical modifications and mechanical reinforcement techniques using various types of fibers, nanoparticles, and nanotubes have been reported recently. The present article comprehensively reviews various aspects and properties of PMMA biomaterials, mainly for prosthodontic applications. In addition, recent updates and modifications to enhance the physical and mechanical properties of PMMA are also discussed.
Objective Different polymerization and reinforcement techniques have been tested to enhance the mechanical characteristics of denture base acrylic resins. The goal of the present study was to evaluate the influence of autoclave polymerization techniques with glass fiber reinforcement on the flexural strength and elastic modulus of polymethyl methacrylate denture base resins.
Materials and Methods Ninety specimens were fabricated from heat-polymerized acrylic resin and randomly distributed depending on the polymerization technique into three groups (n = 30): water bath polymerization, short-cycle autoclave polymerization, and long-cycle autoclave polymerization. Each group was further divided into three subgroups (n = 10) based on the concentration of glass fiber 0, 2.5, and 5wt%. The flexural strength and elastic modulus were investigated using a universal testing machine. One-way ANOVA and Tukey’s post hoc test were performed to analyze the results (α = 0.05).
Results The flexural strength and elastic modulus values were significantly higher in 5wt% glass fiber reinforced long-cycle autoclave group in comparison with the other test groups (p < 0.05).
Conclusions The long-cycle autoclave polymerization technique with the glass fiber reinforcement significantly increased the flexural strength and elastic modulus of the denture base resin material.
Additive manufacturing (AM) has emerged over the past four decades as a cost-effective, on-demand modality for fabrication of geometrically complex objects. The ability to design and print virtually any object shape using a diverse array of materials, such as metals, polymers, ceramics and bioinks, has allowed for the adoption of this technology for biomedical applications in both research and clinical settings. Current advancements in tissue engineering and regeneration, therapeutic delivery, medical device fabrication and operative management planning ensure that AM will continue to play an increasingly important role in the future of healthcare. In this review, we outline current biomedical applications of common AM techniques and materials.
Background/purpose:
Clinically, PMMA resin is extensively used for fabricating provisional FPDs. However, fracture often occurs due to the unsatisfactory mechanical strength, especially within connectors of long-span provisional FPDs. The purpose of this study is to evaluate the fracture load of fiber-reinforced provisional FPDs with various pontic span lengths, and to identify the most suitable span length for fiber-reinforced long-span provisional FPDs.
Materials and methods:
Fifty-six provisional FPDs with various pontic span lengths were fabricated. Seven samples from each group were reinforced with glass fibers. Unreinforced counterparts served as control. The samples were fixed on the abutments after thermocycling and then received a fatigue test. Subsequently, they were mechanically loaded until fracture, and the initial fracture load and fracture patterns were recorded. Statistical analysis, including two-sample t-test, one-way, two-way ANOVA, Tukey-Kramer HSD post hoc analysis and χ2 test were used to evaluate mechanical performance.
Results:
The mean fracture load of FPDs with 14 mm pontic span length is significantly higher than the other lengths. The fracture load of each reinforced group is significantly higher than each counterpart control. There is no interaction between two variables, pontic span and fiber reinforcement. With fiber reinforcement, the fracture patterns were altered from catastrophic fracture to bent or partial fracture. But, the fracture patterns were not affected by pontic span.
Conclusion:
The fracture load of acrylic FPDs decreases significantly when pontic span length is greater than 17 mm. Adding glass fibers into long-span provisional FPDs can significantly improve the fracture resistance and fracture patterns.
The current paper investigates the influence of poly(methyl methacrylate-coethyl acrylate) (PMMA-co-EA) content on the flow, mechanical, thermal and morphological properties of poly(lactic acid) (PLA). Mechanical test results indicated that the blends were softer and tougher due to the decreased tensile and flexural strengths and the increased elongation at break and impact
resistance. With the presence of PMMA-co-EA, regions of amorphous were found to increase together with the decreased degree of crystallinity at all blend compositions. Rheological properties indicated that molten PLA/PMMA-co-EA blends were more viscous in both under shear and applied load, which suitable
for the blow molding process. At 10 wt%, the increased shear viscosity and decreased melt flow index (MFI) were around 240 and 63% respectively. PMMA-co-EA provided good bottle blown product at 10 wt%. Less than this concentration, some flaws were clearly observed.
Poly methyl methacrylate (PMMA), are widely used as a prosthodontic denture base, the denture base materials should exhibit good mechanical properties and dimensional stability in moist environment. In the present research, efforts were made to develop the properties of PMMA resin that used for upper and lower prosthesis complete denture, by addition four different types of nanoparticles, which are fly ash, fly dust, zirconia and aluminum that added with different ratios of volume fractions of (1%, 2% and 3%) to poly methyl methacrylate (PMMA), cold cured resin (castavaria) is the new fluid resin (pour type) as a matrix. In this work, the Nano composite and hybrid Nano composite for prosthetic dentures specimens, preparation was done by using (Hand Lay-Up) method as six groups which includes: the first three groups consists of PMMA resin reinforced by fly ash , fly dust and ZrO2 nanoparticles respectively, the second three groups consists of three types of hybrid Nano composites, which includes ((PMMA:X% fly ash)+ (1%Al + 3% ZrO2)), ((PMMA:X% fly dust)+ (1%Al + 3% ZrO2)) and ((PMMA:X%nZrO2)+(1%fly ash+3%fly dust)) respectively. As well as, the effect of water absorption was taking into consideration in this study. The compression test results show that the values of the compressive strength with and without the effect of water absorption increased with the addition of Nano powders (fly ash, fly dust, zirconia, and aluminum). Also, the results showed that the maximum values of compressive strength reach to 286.25MPa for (PMMA: 2%nZrO2) Nano composite. Whereas the maximum values of compressive strength for hybrid Nano composite reach to 270MPa for ((PMMA: 2%fly ash) + (1%Al + 3% ZrO2)) hybrid Nano composite. Moreover, the results showed that the maximum value of compressive strength under the effect of water absorption reach to 335MPa in the Nano composite material (PMMA+2% fly dust), whereas the maximum value of compressive strength under the effect of water absorption for hybrid Nano composite reach to 632MPa for ((PMMA: 2% fly dust) + (1%Al + 3% ZrO2)) hybrid Nano composite. 4566 INTRODUCTION he most popular material has been used for the construction of dentures for many decades is the poly methyl methacrylate acrylic resin (PMMA) and it has many advantages such as accurate fit, stability in the oral environment, inexpensive equipment's, clinical manipulation and easy laboratory and good aesthetics [1]. This material is still not enough to achieve the ideal mechanical requirements for dental applications although it is the most commonly used in dentistry for fabrication of denture bases. This problem was attributed mainly to its low plaque accumulation and low fracture resistance [2 and 3]. It was found that nearly 70% of dentures had broken within the first 3 years of their delivery in a survey to compare ten types of denture base resins. In a study [4] evaluating the denture fracture, it was reported that 29% of the repairs were because of midline fractures which were more commonly seen in the upper dentures and the rest were other types of fracture and 33% of the repairs were due to de bonded/detached teeth. Composites are multiphase materials that are chemically dissimilar and artificially made and separated by distinct interface [5]. Polymer composite materials reinforced with particles (ceramic, metal particles) can be used for various engineering applications to provide unique mechanical and physical properties with a low specific weight. In order to achieve better mechanical strength, it is usually reinforced with fillers. These fillers can be chosen as particles such as ceramic powders or fibers (aramid, carbon and glass). Ceramic particles with Small size are known to enhance the tribological and mechanical properties of polymers [6]. Fly ash, an industrial waste, because it is a mixture of oxide ceramics, it can be used as a potential filler material in polymer matrix composites. It improves the mechanical and physical properties of the composites [7]. Some researches which are accomplished in this field it's:-Schajpal, V. K and Sood, S. B., added powders such as silver, copper and aluminum with (99.9 %) purity into PMMA acrylic resin denture base material in different volume fraction of (5%, 10%, 15%, 20% and 25%) with average particle size of (10 µm). The addition of these metal fillers showed a decrease in the tensile strength and an increase in the compressive strength as the percentage of metal fillers increases. With the addition of these metal fillers, thermal conductivity increased progressively but did not proportionally as the metal fillers volume fraction increased [8]. Z. A. Mohd Ishak, et al, studied the effect of water absorption and Simulated Body Fluid (SBF) on the flexural properties of PMMA/HA composites for an immersion duration of 2 months. Silane coupling agent [3-methacryloxypropyltrimethoxy silane [(γ-MPS)] was used in order to enhance the interfacial interaction between the PMMA and HA. It was found that flexural strength of the PMMA/HA composites after water absorption and Simulated Body Fluid (SBF) absorption was decreased due to the plasticizing effect of water molecules [9]. Chow Wen Shyang, investigated the effect of the addition of hydroxyapatite (HA) particles on the flexural properties of a heat polymerizing PMMA resin denture base. The results showed that the flexural strength, flexural strain and flexural modulus were decreased with the addition of hydroxyapatite (HA) particles [10]. Hanan Abdul, et al., studied the effect of the addition of Siwak powder in three different concentrations (3%, 5% and 7%) by weight with average particle size of 75 micro meters on the Certain Mechanical Properties of Acrylic Resin The results showed that the addition of Siwak powder with (3% and 5%) by weight to the Acrylic Resin did not greatly affect the compressive strength, tensile strength and impact strength of the Acrylic Resin in comparison to the control group, while the addition of (7 %) Siwak powder to the Acrylic Resin revealed a significant decrease in the compressive strength, tensile strength and impact strength [11]. The one recent study mentioned elsewhere, which involved the numerical study by the tensile properties analysis of the prosthetic dentures which prepared from the same of composite material maintained in the reference above, and the numerical analysis results of the finite element method shown the some agreement with the experimental results [12].
Blends were prepared from poly(lactic acid) (PLA) and three thermoplastics, polystyrene (PS), polycarbonate (PC) and poly(methyl methacrylate) (PMMA). Rheological and mechanical properties, structure and component interac- tions were determined by various methods. The results showed that the structure and properties of the blends cover a rela- tively wide range. All three blends have heterogeneous structure, but the size of the dispersed particles differs by an order of magnitude indicating dissimilar interactions for the corresponding pairs. Properties change accordingly, the blend con- taining the smallest dispersed particles has the largest tensile strength, while PLA/PS blends with the coarsest structure have the smallest. The latter blends are also very brittle. Component interactions were estimated by four different methods, the determination of the size of the dispersed particles, the calculation of the Flory-Huggins interaction parameter from sol- vent absorption, from solubility parameters, and by the quantitative evaluation of the composition dependence of tensile strength. All approaches led to the same result indicating strong interaction for the PLA/PMMA pair and weak for PLA and PS. A general correlation was established between interactions and the mechanical properties of the blends.
Poly(lactic acid) (PLA) is known to be a useful material in substituting the conventional petroleum-based polymer used in packaging, due to its biodegradability and high mechanical strength. Despite the excellent properties of PLA, low flexibility has limited the application of this material. Thus, epoxidized palm olein (EPO) was incorporated into PLA at different loadings (1, 2, 3, 4 and 5 wt%) through the melt blending technique and the product was characterized. The addition of EPO resulted in a decrease in glass transition temperature and an increase of elongation-at-break, which indicates an increase in the PLA chain mobility. PLA/EPO blends also exhibited higher thermal stability than neat PLA. Further, the PLA/1 wt% EPO blend showed enhancement in the tensile, flexural and impact properties. This is due to improved interaction in the blend producing good compatible morphologies, which can be revealed by Scanning Electron Microscopy (SEM) analysis. Therefore, PLA can be efficiently plasticized by EPO and the feasibility of its use as flexible film for food packaging should be considered.
Progressive research on polymer composites is encouraged in this current era in order to create a new functional structured material for various integrated engineering applications. The present investigation entails developing a novel Structurally alternate-layered Material (SAM) with a common Polylactic Acid (PLA) and Carbon Fiber Reinforced Polymer (CFRP) via their successive alternate layer deposition using the non-toxic and high printing speed capacity 3D printing approach - Filament Freedom Fabrication (FFF) with raster angle of 0°. Extensive experimental studies on mechanical behavior and microscopic observation of SAM are carried out. Furthermore, SAM is subjected to numerical simulation via ABACUS on mechanical testing for identifying its tensile and compression behaviour. The resulting data are compared to those of PLA and CFRP. The results obtained from both the numerical and experimental methodologies are congruent, indicating that the mechanical behaviour of SAM is superior to PLA and marginally comparable to CFRP. Overall, the newly synthesized SAM is advantageous and could be potentially considered as a mechanically stabled, cost-effective and feasible alternative polymer composite material for any integrated engineering applications.
Fused deposition modeling (FDM) is a prominent technique in additive manufacturing (AM), widely employed for the construction of intricate prototypes through successive layer-by-layer deposition. Among the thermoplastic matrices used, polylactic acid (PLA) stands out as an environmentally friendly and hydrophobic polymer derived from organic sources. PLA boasts properties like biocompatibility, biodegradability, and high strength, making it a favored choice in diverse industries, including medical, food packaging, and textiles. The incorporation of wood flour into the thermoplastic matrix, referred to as Wood-PLA, has demonstrated increased material strength, leading to its adoption in sectors like automobile and aircraft interiors, fencing, flooring, musical equipment, and various other consumer goods. Additionally, the introduction of multi-material, an innovative material with varying multi-phase properties across different structural regions, has found application in a wide array of industries, including biomedical, energy storage, optoelectronics, aerospace, automobile, and defense. This study aims to investigate the impact of different build orientations (0˚, 45˚, and 90˚) on the mechanical properties of Wood-PLA, pure PLA, and multi-layered material (MLM) fabricated through FDM. Finite element analysis of tensile and compressive test has performed using ABAQUS software and compared with experimental outcomes. Additionally, fracture morphology are examined to gain insights into the modes of failure during fracture. Results reveal significant variations in the mechanical properties of Wood-PLA, PLA and MLM, depending on the build orientation. Furthermore, the examination of fracture morphology provides valuable insights into the failure mechanisms in these materials. Hence this study contributes to the growing body of research on advanced materials and additive manufacturing techniques, paving the way for improved material selection and design considerations.
The goal of this study is to provide first-hand knowledge to the industrial community on the mechanical properties of structurally graded materials (polylactic acid/ceramic-reinforced polylactic acid) wall fabricated through fused filament fabrication. Structurally graded materials are inhomogeneous materials that consist of two or more materials to produce a final structure with distinctive material properties. Because of their specific gradient, structurally graded materials are commonly used in various applications such as aerospace, medicine, optoelectronics, biotechnology, etc. These applications have certain requirements and significant properties such as thermo-mechanical resistance and chemical stability. Filaments of polylactic acid were deposited over ceramic-reinforced polylactic acid to fabricate structurally graded material walls. Coupon studies revealed that structurally graded materials exhibited mechanical properties (tensile strength: 19.1 ± 0.3 MPa, flexural strength: 100.1 ± 0.23 MPa, compressive strength: 64.6 ± 2.35 MPa, impact energy: 1.32 ± 0.038 J, and hardness: 81.5 Shore-D) that are better than polylactic acid. It is revealed that structurally graded materials possess better mechanical properties than polylactic acid and exhibit behavior similar to ceramic-reinforced polylactic acid. Fracture morphology indicates the occurrence of brittle fracture in tensile sample.
Statement of problem:
Biomaterials, including polymethyl methacrylate (PMMA) and bisacrylate, have been widely used as conventional interim materials and may exhibit cytotoxicity or systemic toxicity.
Purpose:
This study was designed to compare the mechanical properties of polylactic acid (PLA) as an alternative to conventional dental polymers for computer-aided design and manufacturing (CAD/CAM).
Material and methods:
Four groups (n = 20 per group) of CAD/CAM polymers were assessed. Specimens of PLA (PLA Mill) and PMMA (PMMA Mill) for subtractive manufacturing, PLA for fused deposition modeling (PLA FDM), and bisphenol for additive manufacturing by stereolithography (Bisphenol SLA) were fabricated into 2-mm-wide, 2-mm-thick and 25-mm-long specimens using a milling machine, an FDM printer, and an SLA printer, respectively.The flexural strength (FS) and elastic modulus (EM) were calculated. The surface roughness and Shore D hardness were analyzed with a 3D optical surface roughness analyzer and a Shore durometer, respectively.
Results:
PLA Mill showed the lowest FS (64.9 ± 8.28), followed by PLA FDM (104.27 ± 4.42 MPa), PMMA Mill (139.2 ± 20.95 MPa), and Bisphenol SLA (171.56 ± 15.38 MPa), with statistically significant differences. PLA FDM showed the highest EM, followed by PLA Mill, Bisphenol SLA, and PMMA Mill. Significant differences were observed not only between PMMA Mill and Bisphenol SLA but also between PLA FDM and PLA Mill. The lowest Shore D hardness was observed for PLA FDM, followed by PLA Mill, PMMA Mill, and Bisphenol SLA, which showed the highest value among the 4 groups, with significance. The highest values for the surface roughness parameters were observed for PLA Mill, and the lowest were observed for Bisphenol SLA.
Conclusions:
Among the tested CAD/CAM polymers, Bisphenol SLA was the most durable material, and the mechanical properties of PLA FDM were within the clinically acceptable range.
Poly(methyl methacrylate) (PMMA) was incorporated as compatibilizer in immiscible poly(vinylidene fluoride) (PVDF)/poly(lactic acid) (PLA) blends at different ratios. Scanning electron microscopy results revealed that, after adding PMMA, the phase morphology of PVDF/PLA blends evidently changed and the boundary became diffused, indicating improved interaction between PVDF and PLA. The sea-island biphasic morphology of PVDF/PLA (1:1) blend transferred to pseudo co-continuous morphology with the incorporation of PMMA. Differential scanning calorimetry and polarized light microscopy results showed that the presence of pre-crystallized PVDF facilitated the crystallization of PLA on cooling from the melt, but the molten PLA slightly retarded the crystallization of PVDF. With the inclusion of PMMA in the blends, PVDF crystal growth was further inhibited due to its miscibility with PMMA, and its crystallinity was also decreased. The elongation at break (ductility) of PLA and PVDF/PLA blends increased drastically by up to 27.8 and 11.1 times respectively, after formation of ternary PVDF/PLA/PMMA blends. Dynamic mechanical analysis results showed that the individual glass transition temperatures of PVDF and PLA in the blends shifted to higher temperatures after adding PMMA. PMMA showed more affinity to PVDF than to PLA. Rheological property measurements confirmed the increase in complex viscosity and storage modulus of the blends with increasing PMMA loading.
Polymer blends have been intensively studied because of their theoretical and practical importance in different variety application field. In the present work, the development on hybrid gel polymer based poly(methylmethacrylate) (PMMA) blended with biodegradable polymer namely poly(lactic acid) (PLA) as a host polymer in polymer electrolytes application have been successfully prepared. The effect of PLA in PMMA as hybrid polymer was investigated for their structural properties via fourier transform infrared (FTIR), x-ray diffraction (XRD) and differential scanning calorimetry (DSC). FTIR analysis shown that the interaction between PMMA and PLA has occurred via dipole-dipole forces. XRD analysis revealed the increment of amorphous phase when PLA was added into PMMA. Decreased in Tg value upon addition of PLA into PMMA indicate that the flexibility of the polymer backbone, thus enhanced the amorphous behaviour of hybrid gel polymer. These findings shown that the present hybrid polymer shown favourable properties to be used as host polymer for polymer electrolytes application.
The incorporation of PMMA into phosphorus-containing flame retarded PLA was assessed as a possible strategy to reduce the sensitivity of the material to ageing in water at 70 °C. PLA and PMMA are miscible and the unique glass transition temperature can be easily controlled by a proper amount of PMMA according to Gordon-Taylor equation. Water penetration as well as phosphorus release was reduced when incorporated PMMA amount increased. Consequently, the ability to form char and the fire performances measured in cone calorimeter were further preserved. Nevertheless, an efficient protective effect was only observed when PMMA incorporation allows the glass transition temperature in the blend to increase above the ageing temperature. This is achieved for a weight ratio PMMA/PLA no lower than 1.
Poly(methyl methacrylate) (PMMA) is widely used worldwide for artificial teeth and the fabrication of denture bases. Compared to metallic denture base materials, PMMA exhibits beneficial properties, such as aesthetic value, lighter weight, ease of manipulation, and cost-effectiveness. On the other hand, prostheses based on PMMA are susceptible to fracture due to poor mechanical properties (flexural and impact strengths) and tend to degrade over time due to water sorption. To improve the mechanical attributes of the PMMA resins for dental applications, various techniques have been investigated and varying results have been obtained. One method is to fabricate PMMA based biocomposites (e.g., polyamides, epoxy resins) or adding a rubber based copolymer (e.g., butadiene styrene) to PMMA to enhance its impact strength. Alternative methods include the use of metal wires or different types of fibers to strengthen PMMA based dentures. However, metal incorporation negatively affects the aesthetics, and tends to generate stress concentration zones which weaken the dentures instead of strengthening them.
The addition of carbon/graphite fibers (CFs) into PMMA resins has been shown to substantially enhance the flexural and impact strengths of acrylic resin-based dentures. However, their gray color negatively affects their esthetic value. Therefore, they are not commonly used as a means of reinforcing dentures. Ultra-high molecular weight polyethylene (UHMWPE) fibers have a naturally white appearance and they have been shown to strengthen PMMA based dentures by increasing the impact strength and Young’s modulus. However, in order to create a bond between the fibers and PMMA resin, these fibers need to undergo special pretreatment (e.g., plasma treatment) before they can be used. Despite substantially enhancing the tensile strength and toughness of PMMA based dentures, aramid fibers (AFs) are not commonly used for denture reinforcement as they possess a yellow color and are difficult to incorporate into PMMA resins.
Encouraging results have been achieved by the incorporation of glass fibers (GFs) into PMMA resins for denture strengthening. The beneficial effect of the addition of GFs on the mechanical properties of acrylic resins has been documented in several research studies. GFs possess excellent esthetics, in addition to having excellent mechanical properties. As a result, they are currently the prime focus of research aimed at reinforcing acrylic dentures. Additionally, GFs easily bond with PMMA resins after treatment with a suitable silane coupling agent, such as trimethoxysilylpropylmethacrylate silane.
Apart from the obvious benefits of fiber reinforcement on PMMA dentures, their clinical use is still limited due to their high cost and the difficult technique necessary for their incorporation into PMMA, especially when short and randomly oriented GFs are used which tend to “clump” within the denture and negatively affect the strength of the prosthesis. This issue can be overcome by using woven or multidirectional fibers in the form of a mesh or network. The aim of this chapter is to highlight the benefits of PMMA and the advancements in PMMA based materials for dental application.
Three flame-retarded systems based on PLA, PMMA and PLA/PMMA blend have undergone hydrothermal ageing. The miscibility of the blend as well as the crystallization behaviour of PLA were studied by DSC. The impact of ageing in terms of weight variations, melt viscosity, molecular weight distribution, morphology, and thermal degradation was investigated. Results showed that crystallization of PLA and significant hydrolysis phenomenon occurred during ageing. Flame retardant content determined by EDX and ICP revealed a loss of phosphorus during ageing, especially for flame-retarded PLA (91 wt% phosphorus loss after ageing). Incorporation of 50 wt% PMMA moderated the negative impacts observed. Fire properties evaluated using cone calorimeter revealed almost no impact of ageing on flame-retarded PMMA, contrary to flame-retarded PLA (increase of pHRR from 291 to 487 kW/m²). Flame-retarded blend shows intermediate properties. It revealed the positive effect of incorporation of PMMA in PLA, by limiting the water diffusion and by reducing the loss of phosphorus.
The inherent shortcomings of polylactide (PLA) including brittleness, low glass transition temperature, and melt strength during processing were addressed through a facile melt blending of PLA with polybutadiene-g-poly(styrene-co-acrylonitrile) (PB-g-SAN) core–shell impact modifier and poly(methyl methacrylate) (PMMA). Highly tough PLA-based ternary blends with drastically enhanced glass transition temperature (≈ 21 °C) and melt strength were successfully prepared. The effect of PMMA content (ranging from 0 to 30 wt %) on the phase miscibility, morphology, mechanical properties, thermal behavior, rheological properties, and toughening mechanisms of PLA/PB-g-SAN/PMMA blends with 30% PB-g-SAN was systematically investigated. It was found that PMMA can effectively tune the interfacial interactions, phase morphology and performance of incompatible PLA/PB-g-SAN blend owing to its partial miscibility with PLA matrix and miscibility with SAN shell of PB-g-SAN, as evidenced by DMTA analysis. Increase in PMMA content promoted the phase adhesion and dispersion state of PB-g-SAN terpolymer in the blends and highly toughened blends were achieved which showed incomplete break of impact specimen. The significant effect of phase morphology on imparting tremendous improvement in impact toughness was clarified. The maximum impact strength (about 500 J/m), elongation-at-break and glass transition were obtained for ternary blend with 25% PMMA. The PLA crystallinity was gradually suppressed in ternary blends upon progressive increase in PMMA content. Rheological studies showed solid-like behavior with enhanced viscosities for ternary blends. Micromechanical deformations and toughening mechanisms were studied by post-mortem fractography. Massive matrix shear yielding was found as the main source of energy dissipation triggered by suitable interfacial adhesion and microvoid formation.
The effect of UV light on polylactide/poly(methyl methacrylate) (PLA/PMMA) blends produced by melt-extrusion with a special emphasis on the peculiar influence of PLA stereocomplexes on the photochemical behavior of the blends is the focus of this paper. Stereocomplexable PLA have been prepared by melt-blending of high-molecular-weight poly(l-lactide) (PLLA), poly(d-lactide) (PDLA) and PMMA. The photochemical behavior of resulting PLA/PMMA blends was studied by irradiation under photooxidative conditions (λ > 300 nm, temperature of 70 °C and in the presence of oxygen). The chemical modifications induced by UV light irradiation were analyzed using infrared spectroscopy (IR) and size exclusion chromatography (SEC). Morphological changes were studied by differential scanning calorimetry (DSC) and atomic force microscopy (AFM). It was shown that PDLA and PMMA don't affect the rate of photooxidation of PLLA. However, PLA stereocomplexes have a strong impact on the morphology of the blends during photochemical ageing.
This study examines the rheological, mechanical and thermal behavior of Poly(lactic acid)/Poly(methyl methacrylate) (PLA/PMMA) blends and takes a look at the phase structure evolution during their melt processing. Semi-crystalline or amorphous PLA grades were combined with PMMA of different molecular weight to prepare the blends. The rheological properties and phase structure was first assessed using small-amplitude oscillatory shear experiments. The blends were injection molded into bars and characterized in terms of their tensile properties and of their dynamic mechanical behavior. Differential scanning calorimetry was also used to study the miscibility and crystallization behavior of prepared blends. Tensile properties of the blends nearly followed a linear mixing rule with no detrimental effect that could have been associated with an uncompatibilized interface. However, dynamic mechanical analysis and calorimetric experiments showed that some phase separation was present in the molded parts. Nevertheless, a single Tg was found if sufficient time was given in quiescent conditions to achieve miscibility. The Gordon-Taylor equation was used to assess the polymer interactions, suggesting that miscibility is the thermodynamically stable state. The ability of PLA to crystallize was strongly restricted by the presence of PMMA and little or no crystallinity development was possible in the blends with more than 30% of PMMA. Results showed an interesting potential of these blends from an application point of view, whether they are phase separated or not.
Poly(lactic acid)/poly(methyl methacrylate) (PLA/PMMA) blends were prepared by melt compounding technique. The miscibility of PLA/PMMA blends at various blending ratios (i.e. 80/20, 60/40, 40/60, and 20/80) was investigated using a dynamic mechanical analyzer (DMA) and solvent uptake experiment. The solvent uptake experiment was conducted to estimate the interaction of PLA/PMMA blends based on the calculation of Flory–Huggins interaction parameter (χ12). DMA results revealed that only single glass transition temperature (Tg) existed along the PLA/PMMA blends. Smallest χ12 (i.e. −0.03) was found on the PLA/PMMA20 blend, suggesting interaction between PLA and PMMA at this composition. The incorporation of PMMA slightly improved the UV protection properties of the PLA/PMMA blend, while maintaining their optical transparency.
Recent advances in 3D printing technologies have led to a rapid expansion of applications from the creation of anatomical training models for complex surgical procedures to the printing of tissue engineering constructs. In addition to achieving the macroscale geometry of organs and tissues, a print layer thickness as small as 20 µm allows for reproduction of the microarchitectures of bone and other tissues. Techniques with even higher precision are currently being investigated to enable reproduction of smaller tissue features such as hepatic lobules. Current research in tissue engineering focuses on the development of compatible methods (printers) and materials (bioinks) that are capable of producing biomimetic scaffolds. In this review, an overview of current 3D printing techniques used in tissue engineering is provided with an emphasis on the printing mechanism and the resultant scaffold characteristics. Current practical challenges and technical limitations are emphasized and future trends of bioprinting are discussed.
In order to improve the toughness of poly(lactic acid) (PLA), the incorporation of natural rubber (NR), which has a high elasticity and flexibility, can be used. However, the phase incompatibility between PLA and NR can cause poor mechanical properties of the final product in the absence of a compatibilizer because of their different polarities. In this research, epoxidized NR (ENR) and poly(methyl methacrylate) (PMMA) were used as co-compatibilizers for linking PLA/NR blends (PLA 100: NR 15 parts by weight per hundred parts of resin (phr)). Therefore, the aim of this research was to study the effect of the ENR/PMMA co-compatibilizer contents on the mechanical, thermal and morphological properties of the 100:15 phr PLA/NR blend. With 3 phr of ENR and 1 phr of PMMA, the elongation at break and impact strength of the 100:15 phr PLA/NR blend was significantly improved up to 1,813% and 362%, respectively. The thermal stability of the PLA/NR blend was also increased when using the co-compatibilizers. Interestingly, the PLA/NR blend containing the co-compatibilizer showed a high ultimate tensile strength after thermal aging at 100 °C for 1 h with good mechanical properties. However, the percentage of crystallinity and glass transition temperature were decreased by the added co-compatibilizer. Finally, a good compatibility between the PLA and NR matrices could be clearly observed by scanning electron microscopy in the presence of the co-compatibilizer.
In this paper, we report a simple approach for the fabrication of bone-like composite materials (BCMs) by blending chitosan (CTS), a natural polysaccharide, nano-hydroxyapatite as bone mineral, and polymethylmethacrylate-co-polyhydroxyethylmethacrylate (PMMA-co-PHEMA) as bone cement. Fourier transform infrared spectroscopy and X-ray diffraction (XRD) studies were performed to determine the components of composites. Scanning electron microscopy study of composites revealed a well-dispersed flake-like structure with increasing content of PMMA-co-PHEMA. The water-uptake ability of the BCMs was also found to increase with increasing the PMMA-co-PHEMA content. Study of mechanical properties revealed that the Young's modulus and stiffness increased significantly after the addition of PMMA-co-PHEMA in BCMs compared with CTS–HAP blend. © 2013 Wiley Periodicals, Inc. Adv Polym Technol 2014, 33, 21391; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21391
The miscibility of polylactic acid (PLA) and atactic poly(methyl methacrylate) (PMMA) blends is investigated as a function of composition. The blends quenched from the melt show the presence of a single glass transition temperature dependent on the composition. The equilibrium melting temperature is determined using the Hoffman-Weeks method and a depression is observed with increasing content of the PMMA component. The PLA spherulite growth rate and the overall isothermal crystallization rates decrease with increasing the amount of the amorphous component. The increase of the long period value as a function of the PMMA content in the blend is due to the segregation of PMMA component in the amorphous PLA interlamellar regions. The Lauritzen-Hoffman secondary nucleation theory analysis shows that the segregation of the PMMA in the interlamellar region induces an increase in the surface entropy of folding. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014
The reactive block copolymers were introduced as chain extenders to eliminate thermo-hydrolysis, transesterification or depolymerization of polylactic acid (PLA) during the thermal processing. A novel modified living anionic polymerization was employed to conquer the tough conditions of traditional anionic polymerization to synthesis the reactive block copolymers. In the first step, polystyrene capped with thiol end-group which can act as initiators for mercaptan/ε-caprolactam living polymerization was synthesized by anionic polymerization at room temperature. Then, the reactive block copolymers poly(styrene-b-methyl methacrylate-b-glycidyl methacrylate) (PS-b-PMMA-b-PGMA, PSMG) and poly(styrene-b-glycidyl methacrylate) (PS-b-PGMA, PSG), were synthesized via the mercaptan/ε-caprolactam living polymerization as proposed by our previous studied. FT-IR, 1H NMR, DSC, and POM analyses were used to confirm the structure, characteristics and thermal behavior of the PSMG, PSG and the processed PLAs. Analysis of the processed PLAs showed that their crystallization behaviors were strongly influenced by the segment content of the chain extenders, PSMG and PSG. The GMA segment contains epoxide moieties, which can increase the molecular weight and melt strength of PLA, while the MMA and styrene segments enhance miscibility with PLA and act as nucleating agents to promote crystallization, respectively. Compared to PSMG, PSG did not show a good reactivity and nucleation ability in PLA melt-blending because of lacking MMA segments. This result reveals the MMA segments are the key structure of the chain extender and the optimum ratio of styrene to MMA is at 1.0–1.2. The crystallinity of PLA could increase from 12.29% to 47.54% when these chain extenders, PSMG, were added in PLA melt-blending. By controlling the structure and segment length of PSMG via a novel modified living anionic polymerization route, we can obtain a quickly crystallinization and good mechanical properties of PLA resins.
Effects of thermal aging on electric properties of polymethyl methacrylate (PMMA) polymer are reported in this paper. PMMA samples are submitted to successive heat-cooling cycles (Tmax=45°C and Tmin=20°C) in the ambient air. Different complementary techniques are thus employed to investigate structural modifications, conduction processes and dielectric relaxations. These are the Fourier Transform Infra Red (FTIR) spectroscopy, impedance spectroscopy and current–voltage technique. Results are discussed in terms of FTIR bands intensities, relaxation frequencies and electrical conductivity. We demonstrated that thermal aging favors oxidation phenomenon. This causes an increase of free radicals leading to space charge amount increasing. PMMA polymer presents therefore a less insulating character.
Low molecular weight poly(lactic acid) was synthesized by direct polycondensation of lactic acid. The oligomers were characterized by viscometry, light scattering, and gel permeation chromatography (GPC). The swelling behaviour of tablets made of the above polymer immersed in buffer solutions at 37°C was studied. In the same experiments, the hydrolytic stability of d,l-PLA was assessed by measuring the weight loss after drying the tablets. In order to inhibit any degradation due to bacteria, formaldehyde was added in the solution as biostatic factor. The effect of an incorporated drug on the swelling behaviour of d,l-PLA tablets was also considered. It was found that the incorporation of drug in d,l-PLA tablets increases their swelling index, probably due to the creation of additional porosity in the specimens or other interaction between drug and polymeric matrix.
Poly(L-lactide) (PLLA) films having different crystallinities (Xc's) and crystalline thicknesses (Lc's) were prepared by annealing at different temperatures (Ta's) from the melt and their high-temperature hydrolysis was investigated at 97°C in phosphate-buffered solution. The changes in remaining weight, molecular weight distribution, and surface morphology of the PLLA films during hydrolysis revealed that their hydrolysis at the high temperature in phosphate-buffered solution proceeds homogeneously along the film cross-section mainly via the bulk erosion mechanism and that the hydrolysis takes place predominantly and randomly at the chains in the amorphous region. The remaining weight was higher for the PLLA films having high initial Xc when compared at the same hydrolysis time above 30 h. However, the difference in the hydrolysis rate between the initially amorphous and crystallized PLLA films at 97°C was smaller than that at 37°C, due to rapid crystallization of the initially amorphous PLLA film by exposure to crystallizable high temperature in phosphate-buffered solution. The hydrolysis constant (k) values of the films at 97°C for the period of 0–8 h, 0.059–0.085 h–1 (1.4–2.0 d–1), were three orders of magnitude higher than those at 37°C for the period of 0–12 months, 2.2–3.4×10–3 d–1. The melting temperature (Tm) and Xc of the PLLA films decreased and increased, respectively, monotonously with hydrolysis time, excluding the initial increase in Tm for the PLLA films prepared at Ta = 100, 120, and 140°C in the first 8, 16, and 16 h, respectively. A specific peak that appeared at a low molecular weight around 1×104 in the GPC spectra was ascribed to the component of one fold in the crystalline region. The relationship between Tm and Lc was found to be Tm (K) = 467·[1–1.61/Lc (nm)] for the PLLA films hydrolyzed at 97°C for 40 h.
This paper reports which are the possibilities of quantification by time of flight secondary ion mass spectrometry (ToF-SIMS) for some polymer blends. In order to assess the composition of the mixtures, we studied first different poly(l-lactide)/polymethylmethacrylate (PLA/PMMA) blends by X-ray photoelectron spectroscopy (XPS), this technique being quantitative. By XPS fitting of the C 1s level, we found a very good agreement of the measured concentrations with the initial compositions. Concerning ToF-SIMS data treatment, we used principal component analysis (PCA) on negative spectra allowing to discriminate one polymer from the other one. By partial least square regression (PLS), we found also a good agreement between the ToF-SIMS predicted and initial compositions. This shows that ToF-SIMS, in a similar way to XPS, can lead to quantitative results. In addition, the observed agreement between XPS (60–100 Å depth analyzed) and ToF-SIMS (10 Å depth analyzed) measurements show that there is no segregation of one of the two polymers onto the surface.
A thick film of aniline-formaldehyde copolymer and PMMA is synthesized via dispersion of aniline-formaldehyde copolymer powder as filler particles in PMMA with two different concentrations. Variation of the complex elastic modulus and mechanical loss factor (tanδ) with temperature is studied. It is observed that the complex elastic modulus decreases with temperature owing to thermal expansion of films. On the other hand, tanδ increases up to a characteristic temperature beyond which it shows a decreasing trend toward melting. Transition temperature T
g of sample S1 (pure PMMA) is found to be 80°C. In sample S2 (1 wt % aniline formaldehyde copolymer), the peak of tanδ at a lower temperature (66°C) corresponds to glass transition temperature T
g of the PMMA matrix, while the peak of tanδ at a higher temperature (107.8°C) corresponds to T
g of a polymer chain restricted by filler particles of aniline-formaldehyde copolymer. A further increase (10 wt % aniline-formaldehyde copolymer) in the concentration of filler particles of aniline-formaldehyde copolymer results in a more compact structure and a shift of T
g to a higher temperature, 122.2°C. This shift in the glass transition temperature of thick films of aniline-formaldehyde copolymer and PMMA is dependent upon the concentration of filler particles in the sample.
Methyl methacrylate (MMA), a monomer of acrylic resin, has a wide variety of dental, medical and industrial applications. Concerns have been raised regarding its potential toxicity in dental use, both for the patient and also in the workplace. Dental patients are also exposed to MMA leached from some dental appliances and the effects, at least in vitro, appear toxic to cells and may cause local mucosal irritation or even an allergic reaction. When exposed to MMA in the dental clinic, dentists and other dental staff appear to occasionally suffer hypersensitivity, asthmatic reactions, local neurological symptoms, irritant and local dermatological reactions. The integrity of latex gloves may also be compromised after exposure to MMA during dental procedures. MMA is not thought to be carcinogenic to humans under normal conditions of use. Techniques should be employed to reduce patients' exposure to MMA during dental procedures in order to reduce the risks of possible complications. Dental staff should avoid direct contact with MMA and room ventilation should be optimised.
The first use of polymethyl methacrylate (PMMA) as a dental device was for the fabrication of complete denture bases. Its qualities of biocompatibility, reliability, relative ease of manipulation, and low toxicity were soon seized upon and incorporated by many different medical specialties. PMMA has been used for (a) bone cements; (b) contact and intraocular lens; (c) screw fixation in bone; (d) filler for bone cavities and skull defects; and (e) vertebrae stabilization in osteoporotic patients. The many uses of PMMA in the field of medicine will be the focus of this review, with particular attention paid to assessing its physical properties, advantages, disadvantages, and complications. Although numerous new alloplastic materials show promise, the versatility and reliability of PMMA cause it to remain a popular and frequently used material.
A review of three-dimensional printing in tissue engineering
- N A Sears
- D R Seshadri
- P S Dhavalikar
- E Cosgriff-Hernandez
Sears NA, Seshadri DR, Dhavalikar PS, Cosgriff-Hernandez E. A
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- M K Subramaniyan
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- V Elumalai
Subramaniyan MK, Thanigainathan S, Elumalai V. Proc Inst
Mech Eng E. 2023. doi:10.1177/09544089231205791