EFFECT OF THE CHARACTERISTIC OF MATRIX ON DEFORMATION MECHANISM OF POLYMER BLENDS

Polymer blends composed of low-density polyethylene (LDPE) as a disper sed phase, polystyrene (PS) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) constituting a matrix phase and a small amount of block copolym er rene-block-ethylene-co-butene-block-styrene)(SEBS) as a compatilize r were studied for exploring deformation mechanism. The blend specimen s prepared via solution-melt procedure were observed by transmission e lectron microscopy (TEM) under in-situ stretching. For the blend with PS matrix, crazing initiated by the dispersed LDPE is the deformation mode while micro-shear yielding becomes dominate when a certain amount of PPO is incorporated. In the latter case, the LDPE particles within the deformation zones deform to ellipsoids indicative of the molecula r orientation in the microbands. The variation of the deformation mode can be attributed to the change of entanglement density of the matrix with changing composition of PS and PPO.