苯并噁嗪/环氧树脂/4,4′-二氨基二苯砜三元共混体系玻璃化转变温度的研究

采用动态热机械分析(DMA)研究了苯并噁嗪/环氧树脂/4,4′-二氨基二苯砜(DDS)三元共混体系玻璃化转变温度(Tg)与固化剂DDS含量的关系.随着DDS含量的增加,三元体系的交联密度呈现先增加后降低的变化趋势,介于聚苯并噁嗪和苯并噁嗪/环氧树脂体系之间;但是三元体系的Tg却逐渐降低,当DDS的含量超过20 mol%时,低于聚苯并噁嗪的Tg.差示扫描量热法(DSC)的结果表明,DDS对苯并噁嗪和环氧树脂都有很强的固化效果.通过测定体系的凝胶化时间,借助Arrhenius方程,判断三元体系的初始反应过程,推测了固化体系可能的网络化学结构.对各体系DMA曲线中损耗模量,储能模量和力学损耗因子的变化情况分析,结果表明体系最终Tg受氢键相互作用、交联密度和网络规整性以及链段的刚性等因素综合影响,其中氢键的类型和相互作用的强弱对Tg的影响最大.

GLASS TRANSITION TEMPERATURES OF POLYMER BLENDS BASED ON BENZOXAZINE/EPOXY RESIN/4,4′-DIAMINODIPHENYL SULFONE SYSTEMS

The glass transition temperatures ( r_gs) for a system of benzoxazine-epoxy, with 4, 4'-diaminodiphenyl sulfone (DDS) as a curing agent were investigated with dynamic mechanical analysis (DMA). With the increase of DDS, the crosslink density of the ternary system increases and then drops off as the content of DDS is more than 30 mol% , varying between that of polybenzoxazine and copolymer of benzoxazine-epoxy resin,but T_g monotonously decreases. When the content of DDS is more than 20 mol% ,T_g of the ternary system is lower than that of polybenzoxazine. Differential scanning calorimetry (DSC) curves show that benzoxazine and epoxy resin can be effectively cured by DDS, and the curing processing of the copolymer is improved with the addition of DDS. The initial reaction processes, and the possible structures of the ternary system cured were estimated through the Arrhenius equation. The storage modulus (E') , loss modulus (E") and loss tangent (tanδ) of each system obtained from DMA curves were studied, which show that T_g is affected by many factors, such as the interaction of hydrogen bond, crosslink density, regularity of the crosslink network and rigidity of the chain segment, among which the effect of hydrogen bond interaction on T_g is the strongest.