Chemical modification of polymer blends by reactive processing: In situ reactions of interlinking agents in PS/EPDM blends

摘要

Polystyrene(PS) and the ethylene-propylene-ethylidene norbornene terpolymer (EPDM) were melt-processed in the presence of multifunctional interlinking agents, divinylbenzene (DVB) and trimethylolpropane triacrylate (TRIS), in an internal mixer to promote functionalization of the :polymers and target in situ formation of the interpolymer product via coreaction of the functionalities. This approach leads to effective in situ compatibilization of the otherwise incompatible polymer components of the blends. The weight ratio of PS/EPDM and the concentration of the interlinking agents were kept constant at 70/30 and 5%, respectively. The effect of varying the concentration of the free-radical initiator (a peroxide) and the method of its addition during melt processing on the overall reaction outcome was also examined. Changes in torque during the melt-processing operation was monitored. Sequential extraction of the polymer blends was used to separate and characterize the insoluble fraction( interpolymer). Changes in the thermal behavior( shifts in glass transition temperatures) of both the polymer blends and their insoluble fractions was investigated together with an examination of the morphology and mechanical properties of the reactively processed blends. It was found that the use of mixed reactive interlinking agents in a one-step reactive blending process and the enhancement of PS reactivity via preinitiation before addition of the reactive agents :Led to an increase in the extent of the coupling reaction between the functionalized PS and EPDM. This results in the formation of an "across-phase" interpolymer with an optimum composition that is responsible for the significant changes observed in the morphology and associated improvements in the mechanical properties of the blend samples. (C) 1998 John Wiley & Sons, Inc. [References: 19]