Properties of thermoplastic elastomeric polypropylene - Simulations of the effects of molecular weight and molecular weight distribution

摘要

The present investigation employs Monte Carlo techniques to model crystallization in stereoblock polypropylene. Of particular interest was determining how its properties might depend on the molecular weight and molecular weight distribution (polydispersity) of the chains. The simulations indicate that degrees of crystallinity and melting points should generally increase with increase in molecular weight and with decrease in polydispersity. The elongation modulus, based on the crystallites acting as temporary crosslinks in an elastomeric network, generally behaved similarly but were less sensitive to these variables. This decreased sensitivity is apparently due to the assumption that the elastic moduli depended only on the number density of the crystallites, without account for size effects, such as large crystallites, also functioning as filler particles.