Integration of Comonomers

The integration of comonomers results in polyoxymethylenes with good thermal stability and only slightly reduced mechanical properties. 

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Figure 5.259 shows the flat initial segments of the creep curve of polyethylenes of varying density and/or various degrees of crystallization. Although the curves slopes differ little from each other, they are less steep for lower densities. Similar behavior is found in all semi-crystalline plastics in which structural differences in the macromolecules in the form of branching cause relatively small differences in density, i.e., crystallinity, such as in polypropylene. Similar differences in polyethylene density are the result of integration of comonomers, such as propene-1, butene-1, hexene-1, or other a-olefins into the molecule chain [811]. 

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