Macromolecular order in plastic kingdomA team of researchers at the Institute of Synthetic Polymer M
Macromolecular order in plastic kingdom
A team of researchers at the Institute of Synthetic Polymer Materials of the Russian Academy of Sciences, MIPT and elsewhere has determined how the regularity of polypropylene molecules and thermal treatment affect the mechanical properties of the end product. Their new insights make it possible to synthesize a material with predetermined properties such as elasticity or hardness. The paper detailing the study was published in Polymer.
In terms of production volume, polypropylene it is second only to polyethylene. By tweaking its molecular structure, polypropylene can be used to manufacture materials with a wide range of features, from elastic bands to high-impact plastic. However, the relationship between the polymer’s chemical structure and its mechanical properties is not fully understood.
What makes the properties of polymer materials so variable is their makeup. A polymer molecule is a long chain of repeating units of unequal length. If these molecules are jumbled up more or less at random in a material, it is said to be amorphous. Such polymers are soft. In other materials, the polymer chains form interconnections called crosslinks. This gives rise to regions of highly regular atomic structure (fig. 1), similar to that of crystals, hence the name crystallites. They hold the whole molecular network together, and the more crystallites there are in a material, the harder it is. To form crosslinks, molecular chains need to possess a certain structural regularity called isotacticity.
