Thermal oxidation of metallocene ethylene-1-olefin copolymer films during one year oven aging

Abstract

Metallocene ethylene homopolymer, ethylene-1-hexene and ethylene-1-octadecene copolymer films were characterized and analysed during their aging in a forced draft oven at 60 degrees C and compared to commercial polymers (HDPE and LDPE). Each polymer is essentially different in its structure, and the variables used in the present Study are comonomer size and content in the main linear backbone polymer. The polymers were characterized initially using GPC, DSC, FTIR, and tensile tests. Later, at different time intervals, samples were removed from the oven and characterized using FTIR and GPC in order to detect changes in chemical structure, size, and molecular weight distribution due to thermo-oxidative aging. At the end of aging, films were subjected to tensile tests to quantify the effect of time on their useful life. As a qualitative reference parameter, the carbonyl index, the ratio of the infrared absorbance of the CO stretching band at 1715 cm(-1) and the absorbance of a reference band at 718 cm(-1), was determined. Kinetic thermo-oxidation is related to comonomer size and content in the main backbone polymer. As comonomeF size decreases or comonomer content increases, degradation rate increases. The scission factor (S) and carbonyl index (CI) graphs of each material show a slope increase which is related to the autocatalytic rate of oxidation.