Photo-oxidative Degradation Behavior and Comprehensive Evaluation Model of LDPE Based on Improving Principal Components Analysis

Abstract

The artificial accelerated aging test of low density polyethylene (LDPE) was carried out for different time periods up to 64 days under UV environment to study the photo-oxidative degradation behavior and the rule. The influence on mechanical properties, chemical structure, thermal stability and melting property evolution of LDPE after photo-oxidation aging was studied by mechanics experiments, attenuated total reflection infrared spectroscopy (ATR-FTIR), thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC). Analytic hierarchy procedure (AHP) was used to determine the weighing values for assessment index of LDPE, and the photo-oxidative degradation comprehensive evaluation model of LDPE was established on the base of improving traditional principal components analysis (PCA). The results show with increasing aging time, the tensile strength, bending strength and impact strength of LDPE are declined by 39.7%, 32.3% and 96.4%, respectively. The concentration of carbonyl and hydroxyl groups are increased, the rupture of molecular chain is intensified. The initial thermal decomposition temperature and melting temperature peak value are declined and the LDPE surface microstructure is seriously damaged and the aging is severe. The comprehensive evaluation parameters exhibit changing trend in three stages. The evaluation results of improved PCA are more reasonable and all the above-mentioned shows that improved PCA is appropriate for the comprehensive evaluation of photo-oxidative degradation behavior of LDPE.

Keywords

• low density polyethylene
• photo-oxidative degradation
• principal components analysis (PCA)
• analytic hierarchy procedure (AHP)
• combined evaluating parameter