Free Volume of cis-1,4 polyisoprene/polybutadiene blends

The number and radius of molecular order free space present in polybutadien e (PBD)/polyisoprene (PIP) blend were observed by positron life-time measur ement, and apparent free volume fraction was estimated. The changes in the number and radius of the free space were not represented to be a linear fun ction of blend composition. The apparent free volume fraction increased by mixing PBD with PIP and was approximated by a concave curve depicted agains t blend composition, even though the excess volume of mixing was proved to be negative. The change in the apparent free volume fraction was related to the variation of thermal expansion coefficient on blend composition.