Shear modification of low density polyethylene

✍ Scribed by J. W. Teh; Alfred Rudin; Henry P. Schreiber

• Publisher: John Wiley and Sons
• Year: 1985
• Tongue: English
• Weight: 651 KB
• Volume: 30
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.1985.070300402

✦ Synopsis

A single screw extruder was used to impose different shear histories on a low density polyethylene with broad molecular weight distribution and high molecular weight tail that had very little long chain branching. This polymer exhibits relatively high melt elasticity and the viscoelastic properties of its melt are strongly affected by preshearing. Such changes are accomplished without significant changes in molecular weight distribution or chemical structure. Measured viscous and elastic properties of the melt are different from pistondriven and screw extruder capillary rheometers. Shear modification effects in single screw extruders are enhanced by decreasing melt temperature, increased screw rotation speeds, and higher screw compression ratios. Melt elasticity can be cycled between high and relatively low values, for the particular polymer, by annealing or shearing the polymer melt.