Phase Transformation in Poly(1-butene) upon Drawing

Abstract

Isotactic poly(1-butene) (PB-1) films, consisting either of crystal form III (solution-grown crystal mat) or I‘ (melt-crystallized film under a high pressure), were drawn uniaxially by tensile draw and solid-state coextrusion in the range of room temperature to 80 °C, below their melting temperatures (Tm = 90−100 °C). The phase transformations induced by draw were characterized by WAXD and DSC. The results are discussed in terms of the effect of drawing variables on the deformation mechanism of PB-1. Tensile draw, which proceeded with a clear neck, was variable and affected by the initial crystal forms and draw temperatures. Upon the tensile draw of form I‘ films, oriented unstable form II crystals were formed independently of draw temperatures. They spontaneously transformed into the stable form I, as reported. When the form III mat was tensile drawn at 80 °C, near its Tm, oriented form II crystals were obtained, whereas the draw at a lower temperature of 70 °C produced oriented form I‘ crystals. Crystal...