Melt Strength Behavior of PE and its Relation to Bubble Stability in Film Blowing**

Abstract

Abstract Melt strength data are presented on the three major classes of commercial polyethylenes (LDPE, LLDPE and HDPE). The LDPE samples studied were polymerised by both tubular and autoclave reactor technology and the LLDPE samples were produced with different α-olefins as comonomer. Melt strength was assessed from uniaxial tensile experiments with a Rheotens apparatus. The melt strengths of both LLDPEs and HDPEs are much lower than those of LDPEs when compared at equal melt index or zero-shear viscosity level. Among the LDPEs the highest melt strength is observed for the LDPEs made by autoclave technology. The type of comonomer present in LLDPEs does not significantly affect its melt strength. The molecular factors controlling the melt strength of pure polyethylenes are discussed. A high melt strength is identified with a good bubble stability in the film blowing process.