Sulfonation of chlorinated polypropylene and its influence on the microstructure and the electric properties of polypropylene/chlorinated polypropylene/polyaniline composites

Abstract

Sulfonated CPP (CPP–SO3H) was prepared by modifying chlorinated polypropylene (CPP). The results of Fourier transform infrared spectroscopy (FTIR) illustrate that the sulfonic acid group (–SO3H) was successfully grafted onto CPP. Polypropylene (PP)/CPP–SO3H/polyaniline (PANI) and PP/CPP/PANI composites were prepared, and the microstructures and electric properties of the corresponding composites were carefully investigated by scanning electron microscopy (SEM), FTIR, ultraviolet (UV)-vis and wide-angle X-ray diffraction (WAXD). Compared with that of the PP/CPP/PANI composite, the volume resistivity of the PP/CPP–SO3H/PANI composites is lower. The UV-vis results show that PANI can be doped with CPP–SO3H and that the interactional strength between PANI and CPP–SO3H increases because of the introduction of –SO3H. The results of WAXD show that CPP–SO3H is more easily inserted into the interspaces of PANI-dodecylbenzene sulfonic acid and makes the layer distance increase compared with that of CPP. The addition of CPP–SO3H can improve the crystallinity of the composites. The results of SEM show that the introduction of –SO3H on CPP is favorable for dispersion of PANI in the PP/CPP–SO3H/PANI composites, and that it results in an increase in the area of the conducting components, an improvement in conductive properties and the compatibility of the PP/CPP–SO3H/PANI composites. The above results indicate that CPP–SO3H can act as PANI's doping agent and facilitate compatibility in PP/CPP–SO3H/PANI composites. This figure reveals the relationship between the area of the conducting parts and the volume resistivity changed with CPP–SO3H content. The PP/CPP–SO3H/PANI composites’ area of the conducting parts is much higher than the PP/CPP/PANI 0 composite’s area, and volume resistivity of the PP/CPP–SO3H/PANI composites is much lower than that of the PP/CPP/PANI 0 composite. These may elucidate that the introduction of the –SO3H on CPP can increase the area of the conducting parts of the composite, improve the compatibility between PP and PANI-DBSA and decrease volume resistivity of the composite.