Effects of Carbon Nanotubes on Processing Stability of Polyoxymethylene in Melt−Mixing Process

Carbon nanotubes (CNTs) filled polyoxymethylene (POM) composites were fabricated in order to form conducting pathways at a low CNT loading. It was found that addition of CNTs would lead to a drastic degradation of POM in the melt−mixing process. The effects of CNTs on the processing stability of POM were investigated by differential scanning calorimetry and thermogravimetric analysis. The results obtained show that the degradation behavior of POM is closely related to the surface chemical properties of CNTs. The presence of carboxylic acid groups on CNT surfaces catalyzes and accelerates the degradation of POM through acidolysis and hydrolysis, and results in a significant decrease in the processing stability of POM. However, graphitized CNT−POM mixtures show high processing stability due to the effective removal of functional groups on CNT surfaces during the graphitization process. Graphitized CNT/POM composites possess good electrical properties and a low percolation threshold of ca. 0.5 wt %, so they have a large potential to be applied as electronic components, self-controlled heaters, overcurrent protectors, and other functional devices.