Quantitative relationship between melting peak temperature and carbonyl index of polypropylene during UV aging based on date fitting

Abstract

In order to study the quantitative relationship of melting peak temperature (Tm) and structure parameter carbonyl index (CI) of polypropylene (PP) in the ultraviolet (UV) aging process, the Tm of PP change along with CI in UV aging process was fitted directly by using exponential decay function, and indirectly by using both polynomial and exponential decay function through taking aging time as intermediate variable. The results show that, both aging time and Tm decay exponentially with CI, and correlation coefficients of fitting curve obtained increase as the order of exponential decay functions increases. Compared with others, the fifth order polynomial is better in fitting the variation of Tm with aging time. The standard deviations of Tm between test value and calculated value obtained by formulas coming from direct and indirect fitting are 0.2024 and 0.1508 respectively, and the maximum relative errors are 0.20% and 0.16% respectively. The above solution shows that both formulas obtained by direct and indirect fitting can be used in quantitative analysis of Tm and CI, and the latter has a better fitting effect although its form is complex.