Impact of branching on the UV degradation of metallocene LLDPE

Abstract

The effect of UV degradation on metallocene linear low density polyethylenes (LLDPEs) of different branching characteristics was studied. The samples were exposed to natural weather condition. The extent of the degradation on these LLDPEs was measured by Mechanical, FTIR and GPC testings. This paper addressed the structural modifications due to UV degradation of metallocene LLDPE (m-LLDPE). The results suggested that Z-N HDPE is very stable. Carbonyl absorbance and degradation of mechanical properties of m-LLDPEs increased with increasing branch content of the polymers. For short exposure times, the results suggested increase in the degree of cross-linking of m-PEs with the increase in BC leading to brittle behavior. However, at high exposure times chain scission dominates and it is branch content dependent. Most of the mechanical properties show a sharp rate of drop at branch contents less than 20 branches/1000 C followed by a slow drop rate. The results of the mechanical properties correlate very well with the carbonyl absorbance. GPC results confirmed that chain scission leading to a broader MWD is dominant at high exposure times and for LLDPEs with high branch contents. Branch type did not show any influence on mechanical properties.