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The onset of thermal degradation dictates the maximum temperature at which a polymer can be used. It is an important limitation in how the polymer is manufactured and processed. For instance, polymers become less viscous at higher temperatures which makes injection moulding easier and faster, but thermal degradation places a ceiling temperature ...
As of 2017, over 100 million tonnes of polyethylene resins are being produced annually, accounting for 34% of the total plastics market. [8] [9] Many kinds of polyethylene are known, with most having the chemical formula (C 2 H 4) n. PE is usually a mixture of similar polymers of ethylene, with various values of n.
Polymer degradation is the reduction in the physical properties of a polymer, such as strength, caused by changes in its chemical composition.Polymers and particularly plastics are subject to degradation at all stages of their product life cycle, including during their initial processing, use, disposal into the environment and recycling. [1]
When concrete is subject to an excessive temperature increase during its setting and hardening as in massive concrete structures from where cement hydration heat cannot easily escape (semi-adiabatic conditions), the temperature gradients and the differential volume changes can also cause the formation of thermal cracks and fissures.
Thermosetting plastics are generally stronger than thermoplastic materials due to the three-dimensional network of bonds (crosslinking), and are also better suited to high-temperature applications up to the decomposition temperature since they keep their shape as strong covalent bonds between polymer chains cannot be broken easily. The higher ...
Polyethylene wax can be made by direct polymerization of ethylene under special conditions that control molecular weight and chain branching of the final polymer. Another method involves thermal and/or mechanical decomposition of high molecular weight polyethylene resin to create lower molecular weight fractions.
Another example of thermal decomposition is 2Pb(NO 3) 2 → 2PbO + O 2 + 4NO 2. Some oxides, especially of weakly electropositive metals decompose when heated to high enough temperature. A classical example is the decomposition of mercuric oxide to give oxygen and mercury metal.
Polymer concrete is a type of concrete that uses a polymer to replace lime-type cements as a binder. One specific type is epoxy granite , where the polymer used is exclusively epoxy . In some cases the polymer is used in addition to portland cement to form Polymer Cement Concrete (PCC) or Polymer Modified Concrete (PMC). [ 1 ]