An Investigation of the Flammability, Morphology and Torque Rheology of Poly(Vinyl Chloride) with Silanes and Cu ²⁺ Modified Montmorillonites

Silane-modified montmorillonites(MMTs) and Cu ²⁺ -silane modified MMTs have been prepared by treating Na ⁺ montmorillonites (Na ⁺ -MMTs) with silane coupling agents and copper (II) sulfate, and poly(vinyl chloride)(PVC)/modified MMT composites were prepared by using a twin-screw extruder. The microstructures of the modified MMTs and the composites were characterised by XRD and SEM. The results indicated that the silanes and Cu ²⁺ were intercalated into the interlayers, and that the silane-modified MMTs and Cu ²⁺ -silane modified MMTs were exfoliated and dispersed in PVC by the melt-intercalation method. A small amount of Cu ²⁺ was observed to shorten slightly the interlayer spacing of MMTs. The cone calorimetric data demonstrated that Na ⁺ -MMTs and modified MMTs changed the flammability behaviour of the composites; they effectively reduced the peak heat release rate (pk-HRR), peak smoke production rate (pk-SPR), total smoke production (TSP) and ignition time (IT). Cu ²⁺ -silane modified MMTs presented a better smoke suppressant effect than Na ⁺ -MMTs and silane modified MMTs, and the smoke-reducing efficiency of Cu ²⁺ -silane modified MMTs reached 44% although the Cu ²⁺ -silane modified MMTs contained only a small amount of copper (II) ion, 0.6~0.8%. The torque experiments indicated that silane modified MMTs improved the processability of the composites, while Cu ²⁺ -silane modified MMTs obviously increased the plasticising time of the composites. The tensile strength and flexural strength of the composites increased compared with PVC/Na ⁺ -MMTs composite.