Proprietes viscoelastiques de quelques polyolefines. Influence du nombre et de la taille des chaines laterales sur la relaxation β

The influence of branching in polyethylene and of the alkyl-group R in polyolefins -(CH₂-CHR)_x- has been shown. The source of the relaxation can be first attributed to restricted movements of units in branches and eventually to the adjacent moving methylene groups in the main amorphous chain, and then to a wide spread movement of amorphous chains caused by the R-groups. The vibration of R-groups of a definite length {(3 carbons)} bound to the crystalline regions but rejected in the amorphous phase is superimposed on the first type of movement.