Equal Channel Angular Pressing The Structure And Properties Of Self-reinforced HDPE And PP

Polymer strength theory shows there is enormous difference between its theoretical strength and actual strength. It demonstrates there is much potentiality to enhance polymer actual strength. In addition, mechanical properties are enhanced by self-reinforced polymers. There is no interface problem between reinforcement and matrix. Self-reinforced polymers have superior applied properties than additive strengthened materials. Based on foregoing presupposition, this thesis applied equal channel angular pressing to the study of high density polyethylene and polypropylene to realize their self-reinforced effects.This question for study is to use equal channel angular pressing mould to squeeze the samples of two kinds of materials under but close to melting point temperature for three times and each time the samples are turned by 180°. Tensile test is exerted to compare quantitatively the difference of mechanic properties of each kind material among a variety of samples. Differential scanning calorimeter is applied to examine the difference of crystallinity among a variety of samples of each material. Oriented changes are analyzed among a variety of samples of each material by X-ray diffraction test. Through the above analyses, the following conclusions can be drawn:Tensile strength of high density polyethylene and polypropylene is raised by 5.18MPa and 6.32MPa respectively from original samples to the second-squeezed ones after equal channel angular pressing. The extensibility of high density polyethylene is reduced considerably. The tendency of crystallinity of two kinds of materials first drops then rises from original samples to the third-squeezed ones. The reason of the reduction of crystallinity is that the temperature is within the range of melting limits, which results in a little deficient crystals being melted. Later crystallinity is raised because of the enhancement of orientation. The tendency of...