Structure of Blown Films of Polyethylene/Polybutene-1 Blends

The structure of blown films of blends of low-density polyethylene (PE-LD) and isotactic polybutene-1 (iPB-1) with different content of iPB-1 was investigated using wide- and small-angle X-ray scattering (WAXS and SAXS), transmission electron microscopy (TEM), and polarizing optical microscopy (POM). TEM proves formation of a matrix-particle phase structure due to immiscibility of the blend components. Within the iPB1 particles, needle-like crystals with c-axis orientation were observed. The PE-LD matrix showed two populations of crystals. WAXS data indicate that the majority of crystals were oriented with the c-axis perpendicular to machine direction (MD), while SAXS data prove additional presence of stacks of lamellae, oriented parallel to MD. Quantitative birefringence measurements showed that the majority of molecule segments were oriented in the direction of the circumference of the film, confirming the WAXS data. The crystal orientation has direct impact on mechanical properties, which was demonstrated by measurement of the anisotropy of the modulus of elasticity. POLYM. ENG. SCI., 50:249-256, 2010. (C) 2009 Society of Plastics Engineers