Effect of alteration of antioxidant on the dielectric strength of biaxially-oriented polypropylene

The Weibull characteristic dielectric strength of biaxially oriented polypropylene (BOPP) was found to increase with appropriate UV exposure, accompanied by a reduction in the dispersion of the statistical distribution. UV absorption spectroscopy employed to demonstrate that the increase in dielectric strength was correlated with destruction of the antioxidant (Irganox 1010) to form 2,6-di-tert-butyl-1,4-benzoquinone (2,6-DTBBQ). Density functional theory computations (DFT) demonstrated that 2,6-DTBBQ is electronegative, i.e., accepts an electron readily, and introducing such a material into a polymer matrix generally increases its dielectric strength. Measurements of the BOPP mechanical properties as a function of UV exposure over the relevant range indicated that while statistically significant changes in stress at 1% offset and stress at break do occur, the changes are small and of no practical significance.