EFFECTS OF MIXING-RATIO AND MONOMER COMPOSITION ON MORPHOLOGY AND MECHANICAL-PROPERTIES OF SMI SAN BLENDS/

This article was concerned with the morphology and mechanical properti es of blends of poly(styrene-co-N-phenylmaleimide) (SMI) and poly( sty rene-co-acrylonitrile) (SAN) as functions of the mixing ratio of the b lends and the acrylonitrile content in SAN. Differential scanning calo rimetry (DSC) and. field-emission scanning transmission electron micro scopy (FE-STEM) were used for the morphology characterization, and ten sile strength and K-I (stress intensity factor in mode I), for the mec hanical property comparison. The miscibility of the polymers was clear ly distinguished using the number of glass transitions shown in the DS C thermograms. FE-STEM supports the DSC results, assisting in understa nding the blend morphology for the immiscible blends in terms of the s hape and size of the dispersed phase. The mechanical properties sugges t that the miscible blends are superior to the immiscible counterparts and illustrate how the acrylonitrile content in SAN and the molecular weights of SMI and SAN affect the toughness of the miscible blends. W e conclude from the study that the miscibility between SMI and SAN is an important factor for toughness enhancement of the blends. As a misc ible blend, the mechanical properties improve with increase of the acr ylonitrile content in SAN and the molecular weight of SMI and SAN. (C) 1998 John Wiley & Sons, Inc.