Influence of Cu2+‐organic montmorillonites on thermal decomposition and smoke emission of poly(vinyl chloride) by cone calorimetric study

Cu²⁺‐Organic montmorillonites were prepared by modifying Na⁺ montmorillonite (Na⁺‐MMT) with silane coupling agents and cupric sulfate. PVC/organic montmorillonite composites were prepared by the melt intercalation method. Morphological structure of modified MMT and PVC/MMT was obtained by using XRD and SEM. The XRD results showed that silanes and Cu²⁺ were intercalated among interlayers and that modified MMT may have exfoliated dispersion in PVC. Effects of Cu²⁺‐organic montmorillonites on decomposition and smoke emission of poly(vinyl chloride) (PVC) in the flaming mode were investigated by using a cone calorimeter at an incident heat flux of 25 kW·m^?2. Cone experimental data demonstrated that the Cu²⁺‐organic montmorillonites prepared were new effective smoke suppressants. They clearly promoted an early HCl elimination, crosslinking reactions, and char residue formation, based upon the decomposition parameters of mass loss, mass loss rate, and time of initial decomposition (t_initial). Cu²⁺‐Organic montmorillonites decreased peak heat release rate, total heat release, peak smoke production rate, total smoke production, and smoke extinction area during the flaming process. The smoke‐reducing efficiency of Cu²⁺‐organic montmorillonites (Cu²⁺‐OMMTs) was the best. However, the content of cupric ion was only 0.6–0.8% in Cu²⁺‐OMMTs and 0.03–0.04% in PVC composites. They may make the smoke‐reducing efficiency reach 45–50%. This result further demonstrates that Cu²⁺ ion is a very effective smoke suppressant for PVC. J. VINYL ADDIT. TECHNOL., 13:31–39, 2007. © 2007 Society of Plastics Engineers.