Influence of the dispersion of nanoclays on the cellular structure of foams based on polystyrene

Abstract

In the present work blends of polystyrene (PS) with sepiolites have been pro-duced using a melt extrusion process. The dispersion degree of the sepiolites inthe PS has been analyzed by dynamic shear rheology and X-ray micro-computed tom ography. Sepiolites treated with quaternary ammonium salts(O-QASEP) are better dispersed in the PS matrix than natural sepiolites(N-SEP) or sepiolites organo-modified with silane groups (O-SGSEP). A perco-lated network is obtained when using 6.0 wt% of O-QASEP, 8.0 wt% of N-SEPand 10.0 wt% of O-SGSEP. It has been shown that multiple extrusion processeshave a negative effect on the polymer architecture. They produce a reductionin the length of the polymeric chains, and they do not lead to a better disper-sion of the particles in the polymer matrix. Foams have been produced using agas dissolution foaming process, where a strong effect of the dispersion degreeon the cellular structure of the different foams was found. The effects on thecellular structure obtained by using different types of sepiolites, different con-tents of sepiolites and different extrusion conditions have been analyzed. Thefoams produced with the formulations containing O-QASEP present the lowestcell size and the most homogeneous cellular structures.