Effects of Annealing Process on Crystallization and Low Temperature Resistance Properties of PP-R Composites

Abstract

The effects of the annealing process on the mechanical properties and crystallization behaviors of polypropylene random copolymer (PP-R) composites were investigated using differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). The experimental results indicated that the annealing process significantly influenced the comprehensive properties of PP-R composites. At temperatures below 23 °C, the impact strength of the PP-R composites annealed at 120 °C for 6 h was relatively high at 74.73 kJ/m², which was 16.8% higher than that of the samples annealed at 80 °C for 6 h. At low temperatures (-30-0 °C), the impact strength ranged from approximately 13.31 kJ/m² to 54.4 kJ/m². In addition, the annealing process conducted at 120 °C for 6 h improved the crystalline structure and low-temperature toughness of the PP-R composites and induced α-form to β-form crystal transformation. The work provides a possible method to reinforce and toughen the semicrystalline polymer at low temperatures (-30-0 °C) by annealing.

Keywords

polypropylene / crystallization / annealing process / low temperature toughness