An Investigation of the Flammability, Morphology and Torque Rheology of Poly(Vinyl Chloride) with Silanes and Cu2+ Modified Montmorillonites

Abstract

Silane-modified montmorillonites(MMTs) and Cu2+-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 Cu2+ were intercalated into the interlayers, and that the silane-modified MMTs and Cu2+-silane modified MMTs were exfoliated and dispersed in PVC by the melt-intercalation method. A small amount of Cu2+ 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). Cu2+-silane modified MMTs presented a better smoke suppressant effect than Na+-MMTs and silane modified MMTs, and the smoke-reducing efficiency of Cu2+-silane modified MMTs reached 44% although the Cu2+-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 Cu2+-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.