Film blowing of linear low-density polyethylene blended with a novel hyperbranched polymer processing aid

The use of hyperbranched polymer (HBP) as a processing aid for linear low-d ensity polyethylene (LLDPE) in the tubular film blowing process was investi gated. Through the addition of HBP, sharkskin was successfully eliminated w ithout significantly changing the overall physical properties of LLDPE film s. Also, there was a minimum of 40% enhancement in processing rate with add ition of 0.5 wt% HBP. The study showed that HBP and LLDPE are immiscible, a nd HBP has a tendency to migrate to the surface, subsequently, it seems to form a lubricating layer between the metal surfaces and the bulk material. This phase separation between HBP and LLDPE results in an HBP-rich surface, which has a high potential to create unique surface properties tailored to various applications. Rheological analysis indicated that excessive slip w as present in HBP/LLDPE suggesting that the onset of slip is not the cause of sharkskin. On the contrary, it may be partially responsible for the elim ination of sharkskin. (C) 2000 Elsevier Science Ltd. All rights reserved.