ISOMER EFFECTS ON STRAIN RECOVERY PROPERTIES OF GLASSY POLYMER NETWORKS DETERMINED VIA DIGITAL IMAGE CORRELATION (DIC)

摘要

Digital image correlation (DIC) techniques were used to study the strain development of glassy polymer network isomers. The study of isomerism effects on mechanical performance within epoxy networks was investigated by the use of para- and meta-substituted triglycidyl aminophenol epoxies cured with 3,3'- or 4,4'-DDS. Isomerism greatly affected mechanical properties with meta-substitution leading to more rigid performance. Strain recovery experiments indicated that para-substitution leads to a higher level of energy storage through anelastic strain. This increased energy storage was attributed to increased sub-T_g cooperative molecular motion. The all para-substituted 44pAP network displayed the lowest modulus, lowest yield stress, and highest yield strain due to its ability to store energy through cooperative motions within the all para-substituted network. The all meta-substituted 33mAP network displayed more rigid behavior due to the lack of cooperativity within the network, which resulted in decreased energy storage and earlier yield.