Second phase volume fraction and rubber particle size determinations in rubber-toughened polymers: A simple stereological approach and its application to the case of high impact polystyrene

Abstract

The determination of the volume fraction Φ and of the particle size distributionF(R) of the rubbery phase is necessary in many rubber-toughened polymers. High impact polystyrene is a good model system in which such a determination has to be performeda posteriori. The more commonly used procedures, i.e. phase-separation methods, analysis of micrographs and indirect mechanical measurements, all present drawbacks and difficulties. A simple stereological method, in which some of these difficulties are avoided, is proposed for the determination of Φ and of some features ofF(R) from the analysis of micrographs. The validity of the method is tested by means of a wide numerical simulation. The proposed method, together with a standard phase-separation procedure and with indirect, mechanical measurements, is tested experimentally on two series of high impact polystyrene and the collected data are compared and discussed. The results of this investigation suggest that approximate views relating elastic properties of rubber-toughened materials only to the rubber particle volume fraction, however this parameter has been measured, not considering the size, the morphology and/or the structure of the rubber particles, are possibly questionable.