On the determination of polymer crystallinity for a thermoplastic PPS composite by thermal analysis

Changes in the crystallinity of thermoplastics result in significant changes in the mechanical behaviour of composites containing them, particularly those that are matrix dominant such as buckling, compression or creep. For this reason, the ability to characterize precisely the polymer crystallinity in thermoplastic composites becomes an important requirement. Owing to the heterogeneous nature of the composite, determination of the crystallinity becomes more complicated. This paper discusses the use of two thermal techniques, namely differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA), and analyses the modifications necessary for precise application on a polyphenylene sulphide thermoplastic composite. The results indicate that while the DSC method was more consistent, it suffers from an inherent recrystallization error, so that it became significantly inaccurate at low crystallinity. The DMA method suffered less recrystallization effect, but it can only analyse matrix material with which a complete amorphous structure can be obtained, and is also less consistent.