Investigation of thermoplastic elastomer (TPE) foaming process using blowing agent by rheological and morphological methods

Abstract

The effects of a chemical blowing agent (CBA) or an encapsulated physical blowing agent (PBA) on morphological development in ethylene octene copolymer (EOC) matrix using dicumyl peroxide (DCP) as a curing agent were investigated by rheological, mechanical, and morphological methods. Temperature ramp tests were carried out to understand curing and foaming processes. Curing temperature (Tcure) was determined as the crossover temperature where storage modulus G′ coincided with loss modulus G′′ in the rheological point of view. For the CBA, Tcure increased with increasing CBA concentration, whereas for the PBA, Tcure decreased with increasing PBA concentration. Other critical temperatures T1st, T2nd by foaming process were determined using the axial normal force. With these critical temperatures (Tcure, T1st, T2nd), curing and foaming mechanisms can be estimated. Simultaneously, volume expansions of samples were observed with camera. Morphology and mechanical analysis were conducted on fully cured and foamed ECP (is defined as EOC with DCP) with blowing agent. ECP with the CBA exhibited an irregular open‐cell structure, whereas when produced using the PBA, it formed a regular closed‐cell structure. Specific tensile strength tended to increase with increasing PBA concentration but as blowing agent concentration increased elongation at break decreased. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47358.

Microcellular foam of styrene–isobutylene–styrene copolymer withN2using polypropylene as a crystallization nucleating and shrinkage reducing agent

“…Foaming is a promising method to expand the application of TPE. TPE foams have been used in various fields such as sportswear, automobile parts, packing materials, and medical equipment 4,5 . Chemical foaming has been a central technique for elastomeric foams 6 .…”