The influence of long chain branches of LLDPE （LLDPE的长链分支的影响）.pdf

/10.1590/0104-1428.1732 The influence of long chain branches of LLDPE on processability and physical properties 1 1 2 Paula Cristina Dartora , Ruth Marlene Campomanes Santana * and Ana Cristina Fontes Moreira 1Department of Materials Engineering, Universidade Federal do Rio Grande do Sul – UFRGS, Porto Alegre, RS, Brazil 2Politecnic Institut, Universidade Estadual do Rio de Janeiro – UERJ, Nova Friburgo, RJ, Brazil *ruth.santana@ufrgs.br Abstract Two polyethylene-based on single-site metallocene catalyst (mLLDPE) were selected to characterize the effect of long chain branching (LCB) on blown film processability, optical and mechanical properties. 13C NMR and parallel plate rheology were used to identify LCB presence on LLDPEs. Blown films were produced from 100% LLDPEs using three different machine direction (MD) stretch ratios. When the same processing conditions for the two LLDPEs grades were used, better processability was observed for LLDPE with LCB. In relation to mechanical and physical properties, Elmendorf tear and optical properties were highly influenced by the presence of LCB. Tear resistance is affected by film orientation and is inversely proportional to the level of LCB in the polymer. It was observed a reduction of 50% in the MD tear strength when comparing with the polymer without LCB. However, haze decreases significantly with the presence of LCB, about 40%. Keywords: LLDPE, metallocene, long chain branching, NMR, rheology, mechanical properties. 1. Introduction Polyethylene is the most useful polyolefin in the world. There remain