Polyethylene oxide crystallinity extent

Consistent with the above observations is the recently proposed order of the intermolecular reaction rates in polyethylene oxide amorphous > interfacial > crystalline [Zhang et al., 1992]. The role of oxygen diffusion during the radiation-induced degradation was also brought out by the work of Burillo et al. [1992], who found that, because of the reduced diffusion of oxygen, the extent of oxidative reactions was lower in compressed PVC samples (P < 880 MPa) than in uncompressed ones. 

Branching can to some extent reduce the ability to crystallise. The frequent, but irregular, presence of side groups will interfere with the ability to pack. Branched polyethylenes, such as are made by high-pressure processes, are less crystalline and of lower density than less branched structures prepared using metal oxide catalysts. In extreme cases crystallisation could be almost completely inhibited. (Crystallisation in high-pressure polyethylenes is restricted more by the frequent short branches rather than by the occasional long branch.)... 

The extent of oxidative bond scissions in the insoluble R fractions (in analogy to polyethylene data (12)) may be concentrated in the noncrystalline isotactic PP chain segments (total initial crystallinity is about 50%, but increases presumably owing to secondary crystallization, particularly during thermooxidative degradation at 150°C). 

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