Evaluation of aging behavior of polypropylene in natural environment by principal component analysis

To evaluate the aging behavior of polypropylene (PP) under an aggressive environment, principal component analysis (PCA) was used to establish a non-dimensional expression Z from a data set of multiple properties of PP. In this study, PP specimens were subjected to natural exposure under the tropical environment on Xisha islands in China for different time periods. Chromatic aberration, gloss, tensile strength, elongation at break, flexural strength and impact strength were tested to evaluate the aging behavior of the PP. Principal component analysis (PCA) was then used to find a specific property to represent all properties of PP. The combined evaluation parameter Z of PP degradation showed no change for the initial two months of exposure. After a sharp increase, the value of Z increased gradually and finally leveled off for the last two months. Based on the Z values, the effect of solar radiation intensity on the degradation of PP is discussed.