2. Materials and methods
2.1. Materials
PP (the content of cellulose, hemicellulose and lignin of PP in this study was 46.22%, 18.84% and 10.24% by dry weight, respectively) were collected from local market as solid waste. The collected materials were washed with distilled water for several times to remove all the dirt particles, and then dried in an oven at 60 °C to a constant weight. After that, yellow skin was removed and the remaining part of PP was ground into granules and screened. The screened materials with size between 0.25 and 1.00 mm were dried in an oven at 60 °C for 48 h, and then stored in a desiccator for further use.