Effect of Low‐Density Polyethylene on the Processability of a Tubular‐Blown Polypropylene Film

ABSTRACT The effect of low‐density polyethylene (LDPE) on the processability of a tubular‐blown film of isotactic polypropylene (PP) was determined by evaluating its structure and mechanical properties. The LDPE addition provided strain hardening in transient elongational viscosity, and furthermore enhanced the flow‐induced crystallization of the PP. This phenomenon occurred even when the LDPE content was only 5%. Consequently, a bubble formed during film blowing was stabilized by the LDPE. This decreased the frost zone height, which provided a wide processing window. A PP/LDPE (95/5) film had marked chain orientation to the flow direction, which resulted in a high modulus in the machine direction. Furthermore, a PP/LDPE (85/15) film had a balanced tear strength, which was attributable to the isotropic orientation of PP chains in the film plane.