The effect of certain processing variables on the form ii to form i phase transformation in polybutene‐1

Abstract

AbstractDensity and wide angle x‐ray scattering techniques were used to study the form II to form I phase transformation in polybutene‐1. The influence of deformation by cold rolling, orientation produced by melt processing (film blowing), and certain additives blended with the homopolymer on the phase transformation behavior were examined. A new technique based on a combination of wide angle X‐ray diffraction and density measurements was devised to determine the relative fractions of form I, form II, and amorphous phases present. Small reductions in thickness by cold rolling cause a rapid partial transformation to form I followed by further transformation at enhanced rates. The enhancement of crystal transformation by cold rolling is primarily the result of the stresses or strains applied rather than the orientation produced. The introduction of molecular orientation by melt processing also enhances the rate of the form II to form I phase transformation, but it is rather less effective than small amounts of cold rolling which themselves produce comparatively little change in molecular orientation. The mechanical blending of polypropylene with polybutene‐1 was found to accelerate the form II to form I phase transformation, while another additive (1‐naphtylacetamide) known to be a good nucleating agent for crystallization of polybutene‐1 did not increase the rate of phase transformation when added at concentration levels needed to nucleate crystallization from the melt.