Physical aging of epoxy resin blended with a medium molecular weight poly(ether sulfone)

Abstract

The physical aging process of 4,49-diaminodiphenyl sulfone (DDS) cured diglycidyl ether bisphenol-A (DGEBA) blended with a medium molecular weight (i. e., M n = 10 600 and M w /M n = 2.3) poly(ether sulfone) (PES) was studied by DSC at four aging temperatures. The cured epoxy-rich phase is immiscible with the PES-rich phase, with their respective T g values being 29 8C apart. Hence, aging the network blend at a suitable temperature caused two well separated enthalpic relaxation processes due to physical aging of PES-rich and epoxy-rich phases. The experimental results indicated that the aging phenomena of the well separated phases in the network blend are similar to that of the corresponding neat polymers when the aging temperature T a is lower than T g by the same value.

Physical aging of epoxy polymers and their composites

“…As the aging time increases, it is clear that the endothermic peak temperature also increases, which is consistent with the trends shown in Figure 5. This trend has been observed in other studies as well 16–18, 82, 85, 87, 89, 92, 93. From Figure 17, it also appears that the endothermic peak temperature generally increases as the isothermal aging temperature increases.…”

“…This behavior is likely due to inability of the molecular network to relax for temperatures approaching T g . Similar trends were observed by Plazek and Frund93 and Fraga et al17…”

“…5). The shift in the endothermic peak temperature with aging time has been determined by several authors 15–18, 25, 72, 81, 82, 85, 87–89, 92, 93. A typical example of this type of data is shown in Figure 17 for a DGEBA/MTHPA epoxy system 15.…”

“…A large number of studies have been performed on the enthalpy relaxation of epoxies 14–18, 25, 43, 47, 52, 53, 56, 72, 77–79, 81–100. As shown in Figure 5, the enthalpy of a polymer decreases with aging time.…”

“…As physical aging progresses, T f decreases. If not measured directly from the specific volume versus temperature curves58 or DSC curves,18, 59, 75, 81, 85, 87–90, 92, 93 T f can be determined from the enthalpy relaxation using15, 17, 103 …”