Double Functions of Chlorinated Carbon Nanotubes in Its Combination with Ni2O3 for Reducing Flammability of Polypropylene

Chlorinated carbon nanotubes (CNT-Cl) and its combination with Ni2O3 were used to prepare polypropylene (PP) composites via melt mixing The cone calorimetry and TGA results showed that both the flame retardancy and the thermal stability of the composites containing CNT-Cl were better than the samples containing unchlorinated CNTs NMR measurements confirmed that CNT-Cl could react with the double bond of degradation products at high temperature. Furthermore, the role of CNT-Cl in the combination between CNT-Cl and Ni2O3 was investigated by carbonization experiments and rheology measurements. The results demonstrated that CNT-Cl could significantly promote the carbonization of degradation products of PP catalyzed by nickel catalyst during combustion In contrast, the combination between unchlorinated CNTs and Ni2O3 could not promote the carbonization of degradation products of PP compared to the case containing Ni2O3 alone This was attributed to Cl radicals releasing from CNT-Cl, which worked as a catalyst to accelerate dehydrogenation-aromatization of degradation products of PP and promoted the carbonization of degradation products catalyzed by nickel catalyst