Thermal characterization of epoxy nanocomposites containing polyhedral oligomeric silsesquioxane: Glass transition temperature and chemical conversion

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• 作者：Puzhong Gu ; Guang Yang ; Sang Cheol Lee ; Jong Keun Lee
• 关键词：Epoxy ; Polyhedral oligomeric silsesquioxane (POSS) ; Glass transition temperature ; Chemical conversion ; Differential scanning calorimetry (DSC)
• 刊名：Fibers and Polymers
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：18
• 期：1
• 页码：131-139
• 全文大小：
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Polymer Sciences;
• 出版者：The Korean Fiber Society
• ISSN：1875-0052
• 卷排序：18

文摘

An epoxy resin (diglycidyl ether of bisphenol-A) was blended with different loadings of a glycidyl-polyhedral oligomeric silsesquioxane (POSS) and isothermally cured with an amine hardener at varying temperatures and times. The glass transition temperature (T_g) of the samples was measured at different chemical conversions (α) using differential scanning calorimetry (DSC). Time-temperature shifts were made for T_gvs. ln(time) data to be superposed at an arbitrary reference temperature in the kinetically controlled reaction regime, and these shift factors were used to obtain an Arrhenius activation energy. The influence of POSS on different reaction systems was investigated in terms of the T_g-α relationship, which was fitted with two models; DiBenedetto and Venditti/Gillham equations. It was found that POSS molecules played different roles at different stages of the curing process. At lower conversions, the inorganic cage of the incorporated POSS (up to 20 wt%) reduced the mobility of the molecular segments, giving rise to an increase in T_g. However, above the 20 wt% POSS, there was a depression of T_g, which may be associated with a plasticizing effect of organic substituents of the POSS molecules. Moreover, the effect of POSS on T_g became less pronounced when the conversion reached 0.8.