Structure and properties of sewing thread made of modified polyphenylene sulfide and polytetrafluoroethylene

Abstract

The structure and properties of sewing thread made of modified polyphenylene sulfide and polytetrafluoroethylene (MPPS/PTFE) have important influence on its application in high temperature filter bag, which were characterized thoroughly by scanning electron microscopy (SEM), fourier transform infrared (FTIR) spectroscopy, thermogravimetry (TG) and differential scanning calorimetry (DSC). SEM shows that there were a lot of hairiness on the surface of MPPS/PTFE sewing thread, which were good for plugging pinholes in the filter bag. The mechanical properties of MPPS/PTFE sewing thread was worse than that of PTFE and MPPS sewing thread, but the flexibility of MPPS/PTFE sewing thread was improved by the addition of MPPS fibers. From the TG analysis, the thermal stability of MPPS/PTFE sewing thread was worse than that of PTFE sewing thread, but better than that of MPPS sewing thread, in which the initial thermal decomposition temperature was 527.6 °C, and the carbon residue rate was 30.8% in the nitrogen atmosphere at 800 °C. From the DSC analysis, the number of melting times has greater influence on melting temperature of MPPS/PTFE sewing thread than that of PTFE and MPPS sewing thread, and the melting temperature from the second melting was 23 °C smaller for PTFE fibers and about 22 °C smaller for MPPS fibers than that from the first melting, respectively. There were more irregular areas inside MPPS/PTFE sewing thread after the first melting, so the melting enthalpy of MPPS/PTFE sewing thread was became small. Meanwhile, the heating rate for the second melting has a little effect on melting temperature and melting enthalpy of MPPS/PTFE sewing thread. Therefore, the heating rate of 20 °C min-1 for the second melting was recommended in terms of cost.