New evaluation method for the dispersion and morphology of composites and blends by thermal conductivity

Geometry, such as dispersion state of the filler, and morphology, such as continuity of the components, in polymeric composites and blends have been evaluated from their thermal conductivity. New theoretical equations for describing the thermal conductivity of two-phase materials in terms of the volume fractions and thermal conductivity of the constituting materials have been proposed and applied to the various heterogeneous materials. A new parameter in the equation represents the geometry and morphology of heterogeneous materials and is determined by fitting the calculated values to the experimental data. The determined parameter is utilized for the three dimensional evaluation of the heterogeneous materials.; A short carbon fiber filled polyethylene is investigated and the dispersion, orientation, and packing states of the carbon fiber are discussed from the thermal conductivity of the filled polymers. In spite of the thermal anisotropy of the carbon fiber, the new equation is applicable to this composite system. The upper limit of the thermal conductivity for this composite system is determined by the new equation. The analysis suggests that the loosest packing state of this composite system is three dimensional random packing. It is concluded that the short carbon fibers have some orientation in most samples.; Semicrystalline polymers are also investigated by applying the new equations. Semi-crystalline polymers are considered to be two-phase materials consisting of crystalline and amorphous phases. The continuous-discontinuous phase inversion of the crystalline phase is one of the important topics of the arguments.; The morphology of polyethylene(PE)/polystyrene(PS) blends is rigorously investigated. The crystallinity of the PE is evaluated as a function of the PS content. The new equations are successfully applied to the polymer blends and the three dimensional morphology of the PE/PS blends is evaluated. It is revealed that the new equations can determine the continuous-discontinuous phase inversion points of the blends.