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Cure Reaction (cure + reaction)
Selected AbstractsSynthesis, characterization, and cure reaction of methacrylate-based multifunctional monomers for dental compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Mousa Ghaemy Abstract The synthesis of 2,2-bis[(4-(2-hydroxy-3-methacryloxyethoxy)phenyl]propane (BHEP) and (1-methacryloxy-3-ethoxymethacryloxy-2-hydroxy)propane (MEHP) for use as the monomer phase in dental composites are reported. The monomers were prepared by the reaction of 2-hydroxyethyl methacrylate (HEMA) with diglycidyl-ether of bisphenol A (DGEBA) and with glycidyl methacrylate (GMA), respectively. The progress of the reaction was followed by measuring the disappearance of the epoxide group peak using FTIR and the structure of the monomers was characterized by 1H-NMR. BHEP and MEHP have lower viscosity because of the presence of long aliphatic spacer on both sides of the aromatic ring in BHEP and the absence of aromatic rings and the presence of only one hydroxyl group in each molecule of MEHP. Thermal curing of the monomers was conducted in a DSC using benzoyl peroxide as an initiator. Photopolymerization of the monomers was also conducted with the visible light using camphorquinone and N,N -dimethylaminoethyl methacrylate as the photoinitiating system. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Nonisothermal cure kinetics of DGEBA with novel aromatic diamineJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2007M. Ghaemy Abstract The effect of the molar ratio of diglycidyl ether of a bisphenol-A based epoxy (DGEBA) and synthesized 4-phenyl-2,6-bis(4-aminophenyl)pyridine (PAP) as curing agent during nonisothermal cure reaction by the Kissinger, Ozawa, and isoconversional equations was studied. The cure mechanism was studied by FTIR analysis. Kinetic analysis of the curing reaction of DGEBA at two different concentrations (42 and 32 phr) of the curing agent was studied by using DSC analysis. With an increasing PAP content, the pre-exponential factor increased by increasing collision probability between epoxide and primary or secondary amine groups in noncataltyic or catalytic modes. The activation energy also increased because of the increasing content of crosslink density. The activation energies obtained from three equations were in good agreement. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3076,3083, 2007. [source] Kinetics and thermodynamics of isothermal curing reaction of epoxy-4, 4,-diaminoazobenzene reinforced with nanosilica and nanoclay particlesPOLYMER COMPOSITES, Issue 8 2010M. Barghamadi The kinetics of the cure reaction for a system of bisphenol-A epoxy resin (DGEBA), with 4, 4,-diaminoazobenzene (DAAB), reinforced with nanosilica (NS), and nanoclay (NC) by means of isothermal technique of differential scanning calorimetry were studied. The Kamal autocatalytic-like kinetic model was used to estimate the reaction orders (m, n), rate constants (k1, k2), and also active energies (Ea) and pre-exponential factors (A) of the curing reaction. However, the existence of NS and NC with hydroxyl groups in the structure improves the cure reaction and influence the rate of reaction and therefore kinetics parameters. The Ea of cure reaction of DGEBA/DAAB system showed a decrease when nanoparticles were present and therefore the rate of the reaction was increased. Using the rate constants from the kinetic analysis and transition state theory, thermodynamic parameters such as enthalpy (,H#), entropy (,S#), and Gibbs free energy (,G#) changes were also calculated. The thermodynamic functions were shown to be very sensitive parameters for evaluation of the cure reaction. POLYM. COMPOS., 31:1442,1448, 2010. © 2009 Society of Plastics Engineers [source] Kaolin,epoxy-based nanocomposites: A complementary study of the epoxy curing by FTIR and fluorescencePOLYMER COMPOSITES, Issue 5 2010P.D. Castrillo This work is focused on the study of the effect exerted by the presence of kaolin on the cure reaction of an epoxy-based polymer, discussing the influence of different kaolin pretreatments. During the last few years, the interest on polymer matrix nanocomposite materials has sharply increased because generally they show improved properties when compared with those of the neat polymer (without filler). Among this sort of materials, polymer clay nanocomposites have been widely studied. However, there are not many works about kaolin-based composites. Although several techniques have been used to monitor the cure process in epoxy-based composites such as Fourier transform infrared spectroscopy (FTIR) or differential scanning calorimetry, only the use of the fluorescent response from a fluorophore seems to be adequate to monitor the reaction exactly at the interfaces at a molecular scale. In this work, FTIR and fluorimetry were used to monitor the cure reaction of the different composite systems at different curing temperatures. The analysis of FTIR experiments revealed that the presence of the reinforcement clay affects the extent of the cure reaction depending on the nature of its surface. On the other hand, the use of a fluorescent molecule chemically bonded to the reinforcement allows studying the curing exactly at the interface. Finally, with the collected data, a kinetic analysis was done and the results obtained were compared in terms of the technique used and the information source (interface or bulk). At the interface, the activation energy for the epoxy reaction is lower than that carried out in the bulk indicating that the reaction at the interface proceeds via a particular mechanism for which the reaction is favored. It seems that a higher amount of hydroxyl groups is capable of catalyzing the cure reaction. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source] Cure kinetics and conductivity of rigid rod epoxy with polyaniline as a curing agentPOLYMER COMPOSITES, Issue 10 2009Tiezhu Fu The samples of rigid rod epoxy resin (4,4,-diglycidyl (3,3,,5,5,-tetramethylbiphenyl) epoxy resin (TMBP)) with different weight contents of polyaniline (PANI) as a curing agent were prepared. The kinetics of curing reaction between TMBP and PANI was analyzed by dynamic differential scanning calorimetry in the temperature range of 25,300°C. The results showed that the heat of cure reaction of TMBP/PANI sample with 10 wt% PANI was larger than those of others. The active energies with different curing conversions of TMBP/PANI sample with 10 wt% PANI were calculated by iso-conversional method using the Coats-Redfern approximation. The results showed that the activation energy was dependent on the degree of conversion. The morphology of the cured samples was detected by scanning electron microscopy measurements. The relationship between morphology and conductivity of cured samples was researched. The conductivities increased from 2.7 × 10,4 to 9.5 × 10,4 S/cm with the increase of PANI from 5 to 20 wt% in cured samples. The thermal stabilities of cured TMBP/PANI samples were examined by thermogravimetric analysis. The results showed that the cured TMBP/PANI can be promising to use as a conducting adhesive. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Influence of epoxy sizing of carbon-fiber on the properties of carbon fiber/cyanate ester compositesPOLYMER COMPOSITES, Issue 5 2006Penggang Ren The high modulus carbon fiber (M40J) sized by epoxy resin E51 and E20 reinforced bisphenol A dicyanate (2,2,-bis(4-cyanatophenyl) isopropylidene resin composite was prepared in order to investigate the influence of epoxy sizing of the fiber on the properties of the composite. Differential scanning calorimetry (DSC) and fourier transforms infrared (FTIR) analysis showed that epoxy resin have catalytic effect on cure reaction of cyanate ester. Mechanical properties of the composite revealed that M40J fiber sized by epoxy resin could improve the flexural strength and interlaminar shear strength of M40J/bisphenol A dicyanate composites. The micro-morphology of the composite fractures was studied by means of scanning electron microscopy (SEM). Reduced flaws were observed in the M40J-bisphenol A dicyanate interface when the sized fiber was used. Water absorption of the composites was also investigated. It was found that the water absorption descended at the initial boiling stage (12 h). POLYM. COMPOS, 27: 591,598, 2006. © 2006 Society of Plastics Engineers [source] Chemorheological analysis of an epoxy-novolac molding compoundPOLYMER ENGINEERING & SCIENCE, Issue 2 2000T. H. Hsieh The chemorheological behavior of an epoxy-novolac molding compound was studied by a combination of differential scanning calorimetry and dynamic rheological measurements. Based on a modified version of Kamal and Sourour's kinetic expression, a procedure aiming at the phenomenological description of cure kinetics was developed. In combination with our kinetic study, an empirical Arrhenius-type expression was adopted for the description of the dependence of complex viscosity on temperature, frequency, and conversion by allowing the pre-exponential factor and the flow activation energy to be frequency- and conversion-dependent. At low conversions (, < ,0.05), the system behaves approximately as a thermoplastic material; at higher conversions, the rheological behavior of the system was dominated by the extent of cure reaction. [source] Studies on thermal and morphological properties of 1,1-bis(3-methyl-4-cyanatophenyl)cyclohexane-epoxy-bismaleimide matricesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 8 2003K. Dinakaran Abstract A new cyanate ester monomer, 1,1-bis(3-methyl-4-cyanatophenyl)cyclohexane has been synthesized and characterized. Epoxy modified with 4, 8 and 12% (by weight) of cyanate ester were made using epoxy resin and 1,1-bis(3-methyl-4-cyanatophenyl)cyclohexane and cured by using diaminodiphenylmethane. The cyanate ester modified epoxy matrix systems were further modified with 4, 8 and 12% (by weight) of bismaleimide (N,N,-bismaleimido-4,4,-diphenylmethane). The formation of oxazolidinone and isocyanurate during cure reaction of epoxy and cyanate ester blend was confirmed by IR spectral studies. Bismaleimide-cyanate ester-epoxy matrices were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and heat deflection temperature (HDT) analysis. Thermal studies indicate that the introduction of cyanate ester into epoxy resin improves the thermal degradation studies at the expense of glass transition temperature. Whereas the incorporation of bismaleimide into epoxy resin enhances the thermal properties according to its percentage content. However, the introduction of both cyanate ester and bismaleimide influences the thermal properties according to their percentage content. DSC thermogram of cyanate ester modified epoxy and bismaleimide modified epoxy show unimodel reaction exotherms. The thermal degradation temperature and heat distortion temperature of the cured bismaleimide modified epoxy and cyanate ester-epoxy systems increased with increasing bismaleimide content. The morphology of the bismaleimide modified epoxy and cyanate ester-epoxy systems were also studied by scanning electron microscopy. Copyright © 2003 John Wiley & Sons, Ltd. [source] | ||||||||||