Syntheses and evaluation of novel biodegradable amino acid based anhydride polymer resins and composites

A novel synthetic biodegradable oligomer based upon methacrylated aminocaproyl maleamic acid (MACMA), was synthesized and characterized. Injectable and in situ crosslinkable polymer networks were formulated by copolymerization of MACMA with triethyleneglycol dimethacrylate (TEGDMA). In addition, composites composed of MACMA, TEGDMA and beta-tricalcium phosphate (β-TCP) were prepared. The networks and composites were initiated by photo- and redox-polymerization, respectively. The initial compressive (CS) and diametral tensile strengths (DTS) of these materials were determined and used to evaluate the effects of MACMA/TEGDMA ratios on the degradation behavior of the materials. The neat resin networks exhibited initial CS values ranging from 6.7 to 284.2 MPa and the composites demonstrated initial DTS values ranging from 2.8 to 20.8 MPa and CS values ranging from 19.1 to 119.5 MPa. During the course of degradation the polymer neat resins lost 51%, 69% and 61% of their initial CS after 3 weeks for the MACMA/TEGDMA ratios at 25/75, 50/50 and 75/25, respectively. The resin with the MACMA/TEGDMA ratio of 75/25 completely degraded after 6 months. The composite with the MACMA/TEGDMA ratio of 25/75 exhibited a significant increase in CS after an initial decrease for 7 days and then lost 57% of its initial CS after 3 months. The composite composed of poly(MACMA) homopolymer showed a complete degradation after 21 days.     

NOVEL TRIMETHACRYLATES: SYNTHESIS,CHARACTERIZATION, AND EVALUATION OF NEW MONOMERS FOR IMPROVED DENTAL RESTORATIVES

ABSTRACT

Two novel trimethacrylates, i.e., 1,1,1-tri-[4-(methacryloxyethoxy)-phenyl] ethane (TMPE) and 1,1,1-tri-[4-(2-methyl-2-methacryloxyethoxy)-phenyl]ethane (TMMPE), have been synthesized by reacting methacryloyl chloride with the corresponding hydroxyl intermediates. Both trimethacrylate monomers, having a low viscosity of 11.5 and 13.1 Pa.S, respectively, were blended with TEGDMA at three different weight ratios, i.e., 90/10, 70/30, and 50/50. The mixtures were made visible light-curable (VLC) by the addition of camphorquinone (0.5 wt%) and N,N-dimethyl-aminoethyl methacrylate (1.0 wt%). In addition to evaluation as cured neat resins, VLC formulations with 70% by wt. of silanated microfiller were also prepared and evaluated. The control in both cases was a VLC formulation of BisGMA/TEGDMA (70/30 and 50/50 wt/wt). These new, formulated resins have both improved physical properties and higher double bond conversion than the BisGMA control, as well as decreased linear polymerization shrinkage (LPS). The neat resin having 70/30 (wt/wt) ratio of TMPE/TEGDMA (T7T3, Table 2) exhibited a compressive strength (CS) of 496 (±51) MPa compared to the 70/30 (wt/wt) ratio of BisGMA/-TEGDMA control having 425(±27) MPa. A filled resin having a 90/10 (wt/wt) ratio of TMPE/TEGDMA exhibited a flexural strength (FS) of 122.6(±23) MPa, compared with a similar filled BisGMA/TEGDMA (70/30, wt/wt) resin exhibiting 112.7(±19) MPa. These and other results suggest that these new trimethacrylates have potential application in formulating dental composites with improved performance.     

Syntheses and evaluation of biodegradable multifunctional polymer networks

The biodegradable, injectable and in situ crosslinkable polymer networks based upon di(propylene fumarate)-dimethacrylate (DPFDMA) and polycaprolactone trimethacrylate (PCLTMA), were prepared and characterized. The polymer networks were initiated by photopolymerization. The initial compressive (CS) and diametral tensile strengths (DTS) of the networks materials were determined and used to evaluate the effects of PCLTMA/DPFDMA ratios on the degradation behavior. The networks exhibited initial DTS values ranging from 2.5 to 9.3 MPa and CS values ranging from 1.8 to 146.0 MPa. The increase of PCLTMA in the formulation led to an increase in viscosity and DTS. The degree of conversions and polymerization shrinkage of the resins ranged from 60% to 72% and 5.1% to 6.4%, respectively. After 6 month, PCL300TMA/DPFDMA resins at a ratio of 100/0, 75/25 and 25/75 lost 70%, 87% and 46% of their initial CS, respectively, while PCL900TMA/DPFDMA and PCL300TMA/PCL900TMA resins at 75/25 lost 100% and 83% of their initial CS, respectively.     

Preparation and Evaluation of Visible Light-Cured Multi-Methacrylates for Dental Composites

Abstract

To explore new VLC oligomers exhibiting low shrinkage, low water sorption, and improved mechanical properties, a family of multi-methacrylates, based on poly(isopropylidenediphenol) resin (BPA), was synthesized, characterized, and evaluated. The BPA resin, having an average of eight phenolic hydroxyl groups per molecule, was treated with ethylene carbonate and the resultant product esterified at four different grafted levels, using methacryloyl chloride. Structures of these EEBPA oligomers, were confirmed by FT-IR and ¹³C NMR. The EEBPA oligomer/TEGDMA (50/50, w/w) blends were combined with 0.5 wt% camphoroquinone(CQ) and 1.0 wt% N,N-dimethylaminoethyl methacrylate (DMAEM). The control was BisGMA/TEGDMA (50/50, w/w) blends having the same levels of CQ/DMAEM. Differential photocalorimetry (DPC) and differential scanning calorimetry (DSC) showed the multi-methacrylate/TEGDMA (neat resin) blends have polymerization characteristics comparable to the BisGMA/TEGDMA control. These multi-functional oligomers have lower polymerization shrinkage and lower uptake of water and other liquids. In addition, two experimental oligomers EEBPA #2 and #3 have higher compressive strength than the BisGMA and comparable diametral tensile strength to the BisGMA control. These results suggest that the new type of multi-functional methacrylate oligomers (EEBPA) have potential application in formulating dental composites with improved properties.     

METHACRYLOYL DERIVITIZED HYPERBRANCHED POLYESTER. 2. PHOTO-POLYMERIZATION AND PROPERTIES FOR DENTAL RESIN SYSTEMS

The purpose of this research is to demonstrate the usefulness of the synthesized hyperbranched multi-methacrylates (H-MMAs) in dental applications. We synthesized three hyperbranched multi-methacrylate oligomers and evaluated them as modifiers for use in the dental resin system: bisphenol A glycidyl dimethacrylate (BisGMA)/tri(ethylene glycol) dimethacrylate (TEGDMA). Their photo-polymerization activities, viscosity, mechanical properties, such as compression, diametral tensile, and flexural strength, were evaluated. H-MMAs (10%) modified dental resins have lower polymerization shrinkage and about 15% increase in mechanical strength compared to the Bis-BisGMA control. For example, H30-MMA has compressive, diametral tensile, and flexural strength of 576, 47, and 85 MPa, compared with the BisGMA control having 497, 43, and 77 MPa. In addition, hyperbranched polymer modified resins have higher glass transition temperature (T_g) and lower thermal expansion coefficient (α) than the control. This research is significant both for increasing our knowledge about hyperbranched multi-functional polymers as well as leading to new dental resin systems with better performance.     

Synthesis of oligomeric urethane dimethacrylates with carboxylic groups and their testing in dental composites

Carboxyl urethane dimethacrylate oligomers with poly(ethylene oxide) sequences in the structure were synthesized and examined in photopolymerizable resins that could better adhere to various kinds of materials, including tooth substrates. Aspects of the morphogenesis of dental composites formed through a photochemically initiated radical copolymerization of the carboxylic derivatives, in addition to other partners encountered frequently in such materials, were studied comparatively with the corresponding urethane dimethacrylate monomer. The effect of a small quantity of a carboxylic macromer (ca. 10%) on the formation of a network with a non‐carboxyl urethane dimethacrylate oligomer (90%) as a potential substitute for diglycidyl methacrylate of bisphenol A and a filler (1/1 70% Aerosil/glass) was visualized by fluorescence spectroscopy with a pyrene methanol probe. The results showed the following: (1) the degree of conversion in the formulations into which carboxyl urethane dimethacrylate was incorporated decreased with increasing poly(ethylene oxide) chain length, (2) the formation of excimers was inhibited in the derived composites, and (3) an important quenching of the monomer fluorescence emission with the UV–vis irradiation time was observed in the formulation containing a filler (Aerosil+Zr/Sr glass). Preliminary testing of the resin composites suggested that all urethane oligomers containing carboxylic acid could lead to dental materials with reduced polymerization shrinkage and good mechanical properties. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1956–1967, 2007     

Synthesis and properties of liquid crystalline urethane methacrylates for dental composite applications

Three novel liquid crystalline methacrylates have been synthesized and characterized to be tested as comonomers in light‐curing dental resin‐based composites. The selected formulations consist of an alkylammonium or cholesteryl urethane methacrylate and 2,2‐bis[4‐(2‐hydroxy‐3‐methacryloyloxypropyl)phenyl]propane (BisGMA) or a BisGMA derivate modified with urethane methacrylate groups, further diluted with triethyleneglycol dimethacrylate (TEGDMA) and reinforced with 70% filler (zirconium silicate nanopowder, silanized filler). This study addresses the relationships between the LC monomer structure, photopolymerization rates (by differential scanning photo calorimetry), and specific properties of the dental resin composites (volumetric shrinkage, water sorption, water solubility, and hydrophobicity). The investigation of LC properties by differential scanning calorimetry and polarizing microscopy indicated that the LC mesophase is stable to room temperature (cationic monomers) or at 40 °C (cholesteryl methacrylate). It was found that the polymerization rate for LC urethane methacrylates used in combination with BisGMA/TEGDMA (0.122–0.136 s^?1) is higher than that of the mesogenic monomers alone (0.085–0.107 s^?1). The structures of the urethane monomers and, consequently, the viscosity of the comonomer mixture influence both the rate and the degree of conversion (44.8–67.5 %) of the photopolymerization process. Polymerization shrinkage measured by pycnometry showed lower values for LC monomers (3.25–3.43 vol %) comparatively with the monomer mixture (5.19–6.65 vol %). Preliminarily, the effect of ammonium groups from two resin composites incorporating alkylammonium structures (4.5 wt %) was tested on Streptococcus mutans, and distinct zone of inhibition was observed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis, formulation and evaluation of novel zinc-calcium phosphate-based adhesive resin composite cement

Three novel adhesive oligomers having carboxylic acid and methacrylate groups were synthesized, characterized and used to formulate composite bone cements with newly synthesized zinc-calcium-silicate phosphate. The optimal formulation was determined based on types of oligomer, oligomer/diluent ratio, initiator concentration, and filler level using compressive strength (CS) and curing time (CT) as screening tools. Shrinkage, exotherm and aging of the formed composite cements were also evaluated. Results show that the experimental cement was 186% higher in CS, 16% higher in diametral tensile strength, similar in flexural strength, 56% less in exotherm and 64% less in shrinkage, as compared to conventional polymethylmethacrylate cement. The optimal concentrations for initiators were found to be 1.5% (by weight) for both benzoyl peroxide and N,N^′-dimethyl-p-toluidine. With increasing initiator concentration, diluent content and zinc oxide content in the cement formulation, CS of the cement increased but curing time decreased. Shrinkage and exotherm of the cement decreased with increasing filler level. CS was not proportional to an increase of filler level and CT increased with an increase of filler level. During aging, the cement showed an increase of strength over 24 h and then no change for over nine months. It appears that this novel cement may be a potential candidate for orthopedic restoration if its biological performance is good and the formulation is optimized.     

Alkoxysilane functionalized polycaprolactone/polysiloxane modified epoxy resin through sol-gel process

Incorporating elastic polysiloxane and/or an inorganic silica network in epoxy resin could result in the enhancement of physico-chemical properties due to the existence of Si-O bonds. To improve the compatibility between polysiloxane and epoxy matrices and intensively strengthen the properties of the modified system, here polysiloxane was introduced into epoxy resin through compatibilizing epoxy-immiscible polysiloxane with epoxy-miscible polycaprolactone segments via a sol-gel process. To fulfill the process, a blend containing alkoxysilane-functionalized polycaprolactone/polydimethylsiloxane (PCS-2Si) was firstly synthesized using direct nucleophilic addition between -OH groups of polydiol and -NCO of a silane. And then a series of modified epoxy resins were prepared in different epoxy/PCS-2Si weight ratios. All the modified composites were characterized by conventional methods, and their morphological, thermal degradation and surface properties were studied. The results showed that increasing the PCS-2Si content caused the changes of miscibility between epoxy and polysiloxane. Also, the thermal stability of the modified composites was greatly improved. As for the temperature value at 5% weight loss, it reached to 308.5 °C for the composite containing 50-60% (wt%) PCS-2Si, over 150 °C higher than that for neat amine-cured epoxy resin. Similarly, the modified composites showed good hydrophobicity. The improvement of these properties came from the improved interaction between PCS-2Si and epoxy, the forming of Si-O-Si network and the enrichment of siloxane chains on the surface of films. Therefore, it is believed that this modified epoxy appears promising as new high performance and highly functional materials.     

The Curing Efficiency and Mechanical Properties of Light-Activated Acrylic Resin

The aim of this investigation was to determine degree of conversion, and flexural and compressive strength of photocurable acrylic resin. The acrylic resins based on bis-phenol A glycidyl dimethacrylate (BisGMA) and triethylene glycol dimethacrylate (TEGDMA) were formulated and then irradiated with red light to form a solid crosslinked polymer. Various post curing conditions were studied to investigate their effects on curing efficiency. Degree of conversion was analyzed by means of Fourier Transform Infrared Spectroscopy (FTIR) to monitor the quantity of remaining acrylic double bond in the cured resin. Three-point bending and compressive strength were tested using Universal Testing Machine (UTM) to evaluate the mechanical performance. Our investigation demonstrated that the formulated acrylic resins were possibly polymerized under irradiation with red light and degree of conversion and mechanical properties were closely correlated.     

Chemical and Mechanical Characterization of Licorice Root and Palm Leaf Waste Incorporated into Poly(urethane-acrylate) (PUA)

A poly(urethane-acrylate) polymer (PUA) was synthesized, and a sufficiently high molecular weight starting from urethane-acrylate oligomer (UAO) was obtained. PUA was then loaded with two types of powdered ligno-cellulosic waste, namely from licorice root and palm leaf, in amounts of 1, 5 and 10%, and the obtained composites were chemically and mechanically characterized. FTIR analysis of final PUA synthesized used for the composite production confirmed the new bonds formed during the polymerization process. The degradation temperatures of the two types of waste used were in line with what observed in most common natural fibers with an onset at 270 °C for licorice waste, and at 290 °C for palm leaf one. The former was more abundant in cellulose (44% vs. 12% lignin), whilst the latter was richer in lignin (30% vs. 26% cellulose). In the composites, only a limited reduction of degradation temperature was observed for palm leaf waste addition and some dispersion issues are observed for licorice root, leading to fluctuating results. Tensile performance of the composites indicates some reduction with respect to the pure polymer in terms of tensile strength, though stabilizing between data with 5 and 10% filler. In contrast, Shore A hardness of both composites slightly increases with higher filler content, while in stiffness-driven applications licorice-based composites showed potential due to an increase up to 50% compared to neat PUA. In general terms, the fracture surfaces tend to become rougher with filler introduction, which indicates the need for optimizing interfacial adhesion.     

SWELLING AND WETTABILITY OF LIGHT-CURED METHACRYLATE-BASED DENTAL RESINS PREPARED FROM CHOLIC ACID

2 '-methacryloxy-3α, 7α 12α- trimethacryloyl cholic acid ethyl ester (CAGE4MA) has been prepared from cholic acid. Photo-polymeric resins were prepared from CAGE4MA. 2,2-bis[4-(2-hydroxy-3-methacrylyloxypropoxy)phenyl]propane (bis-GMA) was used for comparison, triethyleneglycol dimethacrylate (TEGDMA) was used as diluent. The polymerization was initiated by camphoroquinone (CQ)/N, N-dimethylaminoethyl methacrylate (DMAEMA) system. The conversion of CAGE4MA was 39% when the reaction time is 60s, which is lower than bis-GMA and TEGDMA.The swelling value of CAGE4MA resin was 0.41% in distilled water, which is much lower than those of bis-GMA resin (2.04%) and TEGDMA resin (4.77%) under the same conditions. Copolymers from CAGE4MA and TEGDMA have been prepared. With the increase of TEGDMA in mixture, the degree of conversion of CA GE4MA and swelling value increased. The swelling values of photocured resins in 0. 1mol/L HCl were also measured.     

含磷有机硅杂化环氧树脂固化体系性能研究

通过磷酸与γ-环氧丙氧基三甲氧基硅烷反应得到含磷有机硅氧烷,并加入到环氧树脂/4,4'-二氨基二苯基甲烷体系中混合,通过溶胶-凝胶的方法制备了含磷有机硅杂化环氧树脂固化物.对固化体系进行了玻璃化转变温度、热失重、阻燃、拉伸强度、冲击强度测试分析.结果表明,该固化体系的阻燃性得到提高,极限氧指数在25.8～29.3,玻璃化转变温度得到提高,在161～179℃;虽然初始分解温度比纯环氧树脂固化物低,但800℃残炭率可以达到26.5%,提高了36%;拉伸强度得到提高,在71～94 MPa,冲击强度可以达到14.36 kJ/m2,提高了14%.该固化体系具有较好的阻燃性能和热性能,同时具有较好的力学性能.     

Characterization of dimethacrylate polymeric networks: a study of the crosslinked structure formed by monomers used in dental composites

The resin phase of dental composites is mainly composed of combinations of dimethacrylate comonomers, with final polymeric network structure defined by monomer type/reactivity and degree of conversion. This fundamental study evaluates how increasing concentrations of the flexible triethylene glycol dimethacrylate (TEGDMA) influences void formation in bisphenol A diglycidyl dimethacrylate (BisGMA) co-polymerizations and correlates this aspect of network structure with reaction kinetic parameters and macroscopic volumetric shrinkage. Photopolymerization kinetics was followed in real-time by a near-infrared (NIR) spectroscopic technique, viscosity was assessed with a viscometer, volumetric shrinkage was followed with a linometer, free volume formation was determined by positron annihilation lifetime spectroscopy (PALS) and the sol–gel composition was determined by extraction with dichloromethane followed by ¹H NMR analysis. Results show that, as expected, volumetric shrinkage increases with TEGDMA concentration and monomer conversion. Extraction/¹H NMR studies show increasing participation of the more flexible TEGDMA towards the limiting stages of conversion/crosslinking development. As the conversion progresses, either based on longer irradiation times or greater TEGDMA concentrations, the network becomes more dense, which is evidenced by the decrease in free volume and weight loss after extraction in these situations. For the same composition (BisGMA/TEGDMA 60–40 mol%) light-cured for increasing periods of time (from 10 to 600 s), free volume decreased and volumetric shrinkage increased, in a linear relationship with conversion. However, the correlation between free volume and macroscopic volumetric shrinkage was shown to be rather complex for variable compositions exposed for the same time (600 s). The addition of TEGDMA decreases free-volume up to 40 mol% (due to increased conversion), but above that concentration, in spite of the increase in conversion/crosslinking, free volume pore size increases due to the high concentration of the more flexible monomer. In those cases, the increase in volumetric shrinkage was due to higher functional group concentration, in spite of the greater free volume. Therefore, through the application of the PALS model, this study elucidates the network formation in dimethacrylates commonly used in dental materials.     

Synthesis,characterization and polymerization characteristics of new dimethacrylates,derived from 3,3,5‐trimethylcyclohexan‐1‐one–phenol adducts,as monomers for dental composites

The object of this study was to synthesize, characterize and evaluate several new dimethacrylate monomers, in order to discover new compositions for possible formulation of improved dental restoratives. Dimethacrylates derived from the 3,3,5‐trimethylcyclohexan‐1‐one–phenol reaction products were prepared and characterized by Fourier transform infrared and nuclear magnetic resonance. Thermal‐ and photopolymerization characteristics of these experimental monomers, in blends with triethyleneglycol dimethacrylate (TEGDMA), were evaluated by differential scanning calorimetry and differential photocalorimetry. An additional dimethacrylate derived from the 3,3,5‐trimethylcyclohexanone–phenol adduct, supplied by Bayer AG, was also evaluated during the study. A control for comparison consisted of a 2,2‐bis[4‐(2‐hydroxy‐3‐methacryloyloxy‐propyl) phenyl]propane (BisGMA) blend with TEGDMA. It was found that the polymerization behavior and properties of the visible light‐cured neat resins were dependent on their chemical structures. The experimental resins exhibited comparable curing characteristics, lower water sorption, higher wet glass transition temperature, and other improved properties, compared with the polymerized BisGMA/TEGDMA control. The more rigid and hydrophobic nature of the experimental resins, accomplished by incorporation of the bulky trimethyl‐substituted cyclohexyl moiety in the novel dimethacrylates, was considered to be the major factor contributing to the improved properties. These new dimethacrylates, for formulating thermosets with lower water sorption and higher glass transition temperature, may offer a path to improving composites for a variety of applications, including such things as dental restoratives and bone cements. Copyright © 1999 John Wiley & Sons, Ltd.     

Characterization of the physical–mechanical properties of dental resin composites reinforced with novel micro-nano hybrid silica particles: An optimization study

Abstract

In the study, dental composites of color A2 using Bis-GMA/UDMA/TEGDMA resins (ratios 70/10/20), and silica filler (70%wt, 75%wt, and 80%wt) which is a hybrid of two silica types in nano and micro dimensions were made using two different photoinitiators namely BAPO and camphorquinone. The optimum photoinitiator was selected based on the mechanical tests results after which the composites were subjected to the following tests: FTIR to evaluate polymerization degree, microhardness test, UTM, and SEM micrographs were taken to analyze the surface fracture of samples. The results of photoinitiator selection (flexural strength test) is 36.54?MPa, 37.62?MPa, and 75.08?MPa for BAPO?+?camphorquinone, camphorquinone, and BAPO respectively. The results show that the BAPO photoinitiator exhibits better results over camphorquinone and also BAPO/camphorquinone initiator systems. Then after choosing the photoinitiator system composites with different filler contents show higher mechanical strength than existing dental composites. The results of the mechanical tests for the composites with different filler contents synthesized after initiator system selection were significantly higher than the values specified in ISO 4049:2009 (102?MPa over 80?MPa). FTIR results indicate that the degree of conversion in these composite is 25.41%, 37.68, and 40.94% for composites with different filler amounts.     

Synthesis,characterization and evaluation of new fluorene‐based dimethacrylates for formulating dental composites

This study focused on the preparation and evaluation of several new fluorene‐based dimethacrylates, as possible intermediates to formulate improved dental composites. As the first step towards modification of the composite formulation, the new monomers and unfilled resin matrix were prepared. The formulated and visible light‐cured materials were found to be more hydrophobic, along with having higher wet (water saturated) glass transition temperatures (T_g) than the commonly used matrix resins based on 2,2‐bis(4(2‐hydroxy‐3‐methacryloxy‐propyloxy))‐phenylpropane (Bis GMA). In addition, the new matrix resins exhibited greater compressive strength, along with greater resistant to creep and fracture. Finally, the results suggested a correlation may exist between creep and the homologous temperature (T/T_g) of the light‐cured neat resins, where the T/T_g may be used to compare the mechanical properties of different materials at various temperature. Copyright © 1999 John Wiley & Sons, Ltd.     

Thermal stability of styrene–(ethylene butylene)–styrene-based elastomer composites modified by liquid crystalline polymer, clay, and carbon nanotube

The thermal decomposition behaviors of styrene?C(ethylene butylene)?Cstyrene (SEBS) thermoplastic elastomer filled with liquid crystalline polymer (LCP), organomontmorillonite (OMMT), and carbon nanotube (CNT) as a heat stabilizing filler, were comparatively investigated using nonisothermal- and isothermal-thermogravimetric analyses in air. The isoconversional method was employed to evaluate the kinetic parameters (E _a, lnA, and n) under dynamic heating. For neat samples, OMMT and CNT exhibited their respective lowest and highest thermal stabilities as revealed from the lowest and the highest T _onset values, respectively. The decomposition rates of the composites containing OMMT at the temperature >250?°C were higher than those containing CNT and LCP, respectively, whereas the elastomer matrix degraded with the highest rate. The obtained TG profiles and calculated kinetic parameters indicated that the incorporation of LCP, OMMT, and CNT into elastomer matrix improved the thermal stability. Especially, the CNT- and OMMT-containing composites significantly improved the thermal stability compared with the neat matrix polymer. Simultaneously recorded DSC thermograms revealed that the degradation processes for the neat polymers and their composites were exothermic in air. From the simultaneously recorded DSC data, the enthalpy of thermal decomposition for each composite system was found to be lower than that of the neat matrix and mostly decreasing with increasing filler loading. The isothermal decomposition stabilities of the neat SEBS and its composites containing the different fillers were in agreement with those of the nonisothermal investigation.     

Effect of the Poly(Methyl Methacrylate) Molecular Weight on the Mechanical Properties BisGMA/TEGDMA Semi-interpenetrating Polymer Networks

Abstract

The effect of poly(methyl methacrylate) [PMMA], with different molecular weights on the mechanical properties of a polymerized BisGMA/TEGDMA base monomer resin was investigated. With the aid of acetone solvent, PMMA could be readily dissolved in BisGMA/TEGDMA mixtures. The addition of PMMA can significantly improve the compressive strengths and decrease the Knoop hardness values of the BisGMA/TEGDMA/PMMA semi-IPNs. The thermal expansion coefficients rapidly increased before T_g, and decreased after T _g. The observed properties could be attributed to the effect of the molecular weight of the PMMA on the phase structures of the semi-IPNs.     

Properties of composites based on the epoxy aliphatic resin DEG-1

This paper presents the results of research on creating composites using the DEG-1 water-soluble epoxy resin cured by polyethylenepolyamine. It was shown that the obtained composites, in which quartz sand or Portland cement were used as the filler, have high damping properties, rigidity, and bending compressive strengths.