Thermal stability and fire retardancy of polypropylene/sepiolite composite

Abstract

Polypropylene/sepiolite and PP/organo-sepiolite composites were prepared via melt extrusion, sepiolite was pre-modified with cetyltrimethyl ammonium bromide (CTAB). X-ray diffraction, transmission electron microscopy were used to characterize the morpohlogy of composites. Thermal stability and flame retardancy of the composites were evaluated by fhermogravimetric analysis(TGA), cone calorimetric analysis, limiting oxygen index(LOI) and the UL94 protocol. The peak heat release rate of PP/sepiolite and PP/organo-sepiolite composites, with 10% sepiolite loading, decreased by 54% and 66%, respectively. The other fire retardancy also improved by addition of sepiolite, fire performance index (FPI) of PP/sepiolite composite and PP/sepiolite composite increased by 41.7% from 0.014sm2/kW of PP to 0.024 sm2/kW, and that of PP/organo-sepiolite composite increased by 150% reached 0.035 sm2/kW. The smoke production rate (SPR) of PP/organo-sepiolite composite decreased by 40%, from 0.117m2/s of PP to 0.07m2/s of composite, while mass loss rate (MLR) decreased by 41%, from 0.45g/s of PP to 0.20g/s of composite. The limiting oxygen index of composite increased by 3, from 17.1(in PP) to 20.1. All of the composites could obtain an HB in the UL-94 horizontal burning test (UL-94HB) grade but were not classified in the vertical burning test (UL-94VB). © 2012 American Chemical Society.