| Abstract: | Isotactic polypropylene and high density polyethylene are thermodynamically incompatible with one another yet it is possible to prepare physical blends of the two polymers and fabricate solid test specimens with a high degree of cohesion. This paper describes the preparation of such specimens and the investigation of their structure. Direct and indirect evidence builds up a model for the blends involving the degree of dispersion. The techniques include optical microscopy, density measurements and differential scanning calorimetry (DSC). Each blend, formed by deposition from solution, is a fine dispersion of the minor component in the major component. The degree of crystallinity of a blend is identical to that calculated from the crystallinities of the pure components in the appropriate ratio. During melting of the blends there is little interaction between the components but there are mutual effects during recrystallization. The α and β forms of polypropylene arise under appropriate conditions. |
