Effects of wool fibre and other additives on the flammability and mechanical performance of polypropylene/kenaf composites

Influence of wool fibres (WF) in improving the flame retardant and mechanical properties of polypropylene/kenaf fibre/intumescent ammonium polyphosphate (PP/KF/APP) composites is described. Flammability of PP/KF/APP/WF composite was evaluated using cone calorimetry, UL 94-V vertical burning tests and thermo-gravimetric analysis, and compared to results of similar composites which contained an ultraviolet ray stabiliser and colourant combination (PP/KF/APP/UVC). Tensile, bending and impact test analyses were also conducted on both sets of composites. PP/KF/APP/WF system had stable residual char at elevated temperatures, significantly improving fire protection. High degree of cross-linked stable char formation and residual char in PP/KF/APP/WF composite provided sufficient evidence of synergistic effect of wool. WF increased the tensile modulus of the composite by approximately 16%, while UVC (together with APP) improved the composite's flexural stiffness by 21%.