Effect of alkyl quaternary ammonium on processing discoloration of melt-intercalated PVC-montmorillonite composites

Abstract

The effects of alkyl quaternary ammonium on the processing thermal stability of poly (vinyl chloride)/alkyl quaternary ammonium modified montmorillonite (PVC/OMMT) composites were investigated. PVC/sodium montmorillonite (MMT) composites were prepared for comparison. The intercalated PVC/OMMT composites exhibited a non-terminal rheological behavior, and showed better mechanical properties and higher thermal degradation stability than the PVC/MMT composites. However, under identical melt processing conditions, the PVC/OMMT composites were observed to discolor from light yellow to pink with increasing OMMT content, while the PVC and PVC/MMT composites kept good processing stability. It is suggested that the decomposition of alkyl quaternary ammonium modifier and the following catalytic effects on the dehydrochlorination of PVC were the main reasons for the discoloration of the PVC/OMMT composites. Discoloration of all the composites was investigated by UV–visible spectroscopy, yellowness index and haze measurement. All the composites were characterized and tested using wide angle X-ray diffraction, transmission electron microscopy, infrared spectroscopy, solution 1H nuclear magnetic resonance spectroscopy, tensile testing, notched Izod impact testing and thermogravimetric analysis as well as ARES rheometrics.