Adaptation of polystyrene/multi-wall carbon nanotube composite properties in respect of its thermal stability

Abstract

Polystyrene (PS)/multi-wall carbon nanotube (MWCNT) nanocomposites were prepared by melt mixing and by coagulation of PS/MWCNT sonicated dispersion. Before mixing and coagulation particles of MWCNT were covered with PS nanospheres by microemulsion polymerization to increase their dispersibility and compatibility with the matrix. Microemulsion polymerization was carried out under sonication in the presence of surfactants and a cross-linking agent. The structure of modified MWCNT filler was revealed by SEM and TEM microscopy analyses. They show that PS is well grafted onto surface of MWCNT in form of ca 30 nm nanospheres or as ca 3-8 nm PS film layer. Significant changes in properties were recorded mainly for the coagulated sample. Although no shift of T-g was recorded for the melt mixed composite, the coagulated sample shows an increase by 9 degrees C. Also the reinforcing effect of MWCNT was more pronounced for the same method of preparation (further supported by the filler modification). The creep response of this material shifts to longer times not only in the T-g area, but also as low as 70 degrees C below it, which is perceived as an improvement of temperature stability (the same properties kept for a longer time). This was also proved by the increase of creep modulus, and consequently by the prolonged time needed to reach the same tensile creep compliance after aging.