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Curing Conditions (curing + condition)
Selected AbstractsCombined Effects of Hot Curing Conditions and Reaction Heat on Rubber Vulcanization Efficiency and Vulcanizate UniformityMACROMOLECULAR THEORY AND SIMULATIONS, Issue 4-5 2009Xiaoxia Wang Abstract A mathematical model of the chemical kinetics of silicone rubber vulcanization is developed, with the thermal effects being computed using the increment method, and the hot vulcanization process estimated with the finite element method. The results show that the reaction heat of rubber vulcanization is important for energy saving, and that a proper curing medium temperature is important when considering both vulcanization efficiency and vulcanizate uniformity. The results also indicate that increases in the forced convective heat transfer coefficient have no significant effect above a certain level. The validity of the numerical model is indirectly proven by comparison with existing data. [source] Curing mechanisms and kinetic analysis of DGEBA cured with a novel imidazole derivative curing agent using DSC techniquesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Li Liu Abstract A novel imidazole derivative, 2MI- g -CA, was obtained through the reaction of 2-methylimidazole (2MI) and cyanuric acid (CA) and characterized by means of elemental analysis, FTIR spectroscopy, 1H NMR spectroscopy, and mass spectrometric analysis. The curing mechanisms and kinetics of diglycidyl ether of bisphenol A (DGEBA) using 2MI and 2MI- g -CA as curing agents were studied with differential scanning calorimetry (DSC) under dynamic and isothermal conditions. Both dynamic and isothermal DSC thermograms of DGEBA/2MI system showed two distinct exothermic peaks, whereas those of DGEBA/2MI- g -CA system showed only one distinct exothermic peak. These results indicated that the two systems have different initiation curing mechanisms. The apparent activation energies (Ea) obtained from DSC scanning runs using the Kissinger and Ozawa methods were 79.0, 83.0 kJ/mol and 84.2, 88.8 kJ/mol for DGEBA/2MI and DGEBA/2MI- g -CA systems, respectively. These values suggested the novel curing agent 2MI- g -CA exhibited greater levels of latency during cure or increased the pot life of epoxy resin system. In addition, under the same curing condition, the Tg values of DGEBA/2MI- g -CA system were about 25°C higher than those of DGEBA/2MI system, exhibiting a better thermal stability. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Moisture curing kinetics of isocyanate ended urethane quasi-prepolymers monitored by IR spectroscopy and DSCJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008Ana Luísa Daniel-da-Silva Abstract The study of the kinetics of the curing of isocyanate quasi-prepolymers with water was performed by infrared spectroscopy and differential scanning calorimetry. The influence of the free isocyanate content, polyol functionality, and of the addition of an amine catalyst (2,2,-dimorpholinediethylether) in the reaction kinetics and morphology of the final poly(urethane urea) was analyzed. A second-order autocatalyzed model was successfully applied to reproduce the curing process under isothermal curing conditions, until gelation occurred. A kinetic model-free approach was used to find the dependence of the effective activation energy (Ea) with the extent of cure, when the reaction was performed under nonisothermal conditions. The dependence of Ea with the reaction progress was different depending on the initial composition of the quasi-prepolymer, which reveals the complexity of the curing process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source] Preparation and thermomechanical properties of epoxy resins modified by octafunctional cubic silsesquioxane epoxidesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2004Khine Yi Mya Abstract The thermomechanical properties of octafunctional cubic silsesquioxane-modified epoxy resins associated with dicycloaliphatic hardener (4,4,-dimethyldiaminodicyclo hexyl methane) were studied using thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. The structures of epoxy resin containing cubic silsesquioxane epoxides were characterized by Fourier transform infrared spectroscopy and wide-angle X-ray scattering techniques. In this work, octa(dimethylsiloxybutylepoxide) octasilsesquioxane (OB), and octa(glycidyldimethyl-siloxyepoxide) octasilsesquioxane (OG), were synthesized and used as additives to improve the properties of a commercial epoxy resin by exploring the effects of varying the ratio of OB or OG. The commercial Ciba epoxy resin (Araldite LY5210/HY2954) was used as a standard. It was found, by thermogravimetric analysis and dynamic mechanical analysis, that the highest thermal stability was observed at N = 0.5 (N = number of amine groups/number of epoxy rings). No glass transition temperature was observed by adding 20 mol % OB to the Ciba epoxy resin, indicating the reduction of chain motion in the presence of octafunctional cubic silsesquioxane epoxide. The storage modulus of the OB-modified epoxy resin also increased, especially at higher temperatures, compared with the Ciba epoxy resin under identical curing conditions. Fourier transform infrared data elucidated the preservation of cubic silsesquioxane structure after curing at high temperature. In contrast, the OG/Araldite LY5210/HY2954 systems gave poorer thermomechanical properties. The low viscosity of OB at room temperature (, 350 cPs) makes it suitable for composite processing and, when used in conjunction with the Ciba epoxy, lowers the viscosity of this system as well. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3490,3503, 2004 [source] New liquid-crystalline thermosets from liquid-crystalline bisazomethynic epoxy resins with naphthylene disruptors in the central coreJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2003P. Castell Abstract We synthesized novel epoxy-terminated monomers on the basis of imine groups with spacers of different lengths between mesogens and reactive groups and examined their mesogenic properties. Their reaction with primary aromatic diamines and tertiary amines was carried out to investigate the formation of liquid-crystalline thermosets. We explored how the curing conditions and the structures of the monomers and amines affected the formation of ordered networks. The special symmetry of a 1,5-disubstituted naphthalene unit in the central core led to nematic mesophases in the pure liquid-crystalline epoxy resins, and thermosets with locked nematic textures were obtained in all cases, regardless of the length of the spacer. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1536,1544, 2003 [source] UV curing kinetics and mechanism of a highly branched polycarbosilaneAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 1 2009Houbu Li Abstract The UV curing process in both air and nitrogen atmosphere for the highly branched polycarbosilane system was investigated by differential scanning photo calorimeter. The UV cured products were characterized by Fourier-transform infrared spectrometry (FTIR). By comparison with the FTIR results of the uncured liquid mixture and the cured samples, the possible cross-linking reactions were determined. The kinetics of the curing systems was studied. The rate constant k was calculated based on the experimental results. The activation energies in different curing conditions were obtained. According to these results, it was learned that the mechanism for the UV curing in nitrogen was controlled by the photolysis of photoinitiator. Comparably, the UV curing process in air was complicated. It was affected by not only the photolysis of photoinitiator, but also oxygen and tripropane glycol diacrylate. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||