Polymer features and properties

The chemical and physical constitution of polymer chains at the molecular level control their properties [49-52]. If a polymer chain is regular in its chemical structure and the stereochemical arrangements of the repeat units are also similar along the length of the chain then it might be possible for that polymer to form crystalline domains in the solid state. Unless there is regularity in the chain structure, it is not possible for the long polymer chains 

Polymeric materials can only function over a very limited temperature range. Organic material oxidizes and burns at about 250-300 °C in the presence of air. In order to retain any meaningful mechanical properties in organic polymers at temperatures of about 350 C it is necessary to produce polymers with highly aromatic chain structures as aromatic compounds withstand oxidation much more readily than aliphatic compounds since the protons on an aromatic ring are relatively inert. 

At very low temperatures, say — 60°C (but very much a function of molecular structure) most polymers become very brittle, lose their toughness and fracture readily. 

The influence of temperature on linear polymers can be summarized very 

Crystallizable polymers follow a different path on cooling. At high temperatures, crystalline polymers are also viscoelastic in character. On cooling a temperature is reached at which the polymer commences to crystallize. During crystallization, there is a significant increase in density as the chains pack more efficiently in the solid state. The crystallization temperature may be much lower than the polymer melting point since the melt is readily supercooled. After the bulk of the crystallization has taken place, the polymer is a solid 

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