Chain Relaxation Time in ABS Polymer Melts.

Abstract

Nonlinear relaxation modulus G(t, γ) was examined for two types of ABS polymers, the ABS-T(1) system containing agglomerated network of rubber particles and the ABS-T(3) system in which the rubber particles were randomly dispersed. Both systems exhibited fast and slow relaxation processes, the former reflecting the relaxation of the SAN chains and the latter being attributed to motion of the network and/or dispersed rubber particles. The relaxation modulus of the chains, Gchain(t,γ), was evaluated by subtracting the modulus for the slow process from the G(t,γ) data. This Gchain(t,γ) exhibited the time-strain separable damping, and its longest relaxation time τg-SAN was attributed to the entanglement relaxation of the SAN chains grafted on the rubber particles. For the ABS-T(1) system, τg-SAN rapidly increased with the volume fraction of the gel components φgel (@ volume fraction of the particles) for small φgel (< 0.2) and then leveled off at larger φgel (≥ 0.2). This behavior was related to rapid increase and saturation of the entanglement density for the grafted SAN chains on full development of the tightly connected network occurring at small φgel. In contrast, the τg-SAN of the ABS-T(3) system increased gradually with φgel, reflecting gradual increase of the entanglement density for the SAN chains grafted on the randomly dispersed rubber particles. Thus, the difference in the dispersion state of the rubber particles in the ABS-T(1) and ABS-T(3) systems naturally resulted in the difference in the entanglement relaxation time of the grafted SAN chains.