The properties and uses of many polymers can be modified by varying their formulation and by the use of additives. Additives often contain different chemical elements from the original polymer materials and need to be distributed evenly throughout the polymer to work effectively.
Examples of additives for plastics and where SEM-EDS has a potential role:
|Plasticiser||Esters of benzene-1,2-dicarboxylic acid||Acts as a lubricant for polymer chains.Large amounts give a flexible product, low quantities produce a rigid one.|
|Stabiliser||Lead carbonate (<1%), lead phosphate or, for non-toxic requirements, mixtures of metal octadecanoates and epoxidized oil||Prevents decomposition of polymer. Without a stabiliser, poly(chloroethene), for example, decomposes on heating to give a brittle product and hydrogen chloride. Some plastics become coloured (yellowing) when exposed to long periods of sunlight.|
|Extender||Chlorinated hydrocarbons||Extends the effect of the plasticiser, but generally cannot plasticise alone. They are cheaper than plasticisers, so help reduce costs.|
|Fillers||Chalk, glass fibre||Tailor the plastic for special requirements, or make it cheaper.|
|Miscellaneous||Flame retardants, UV stabilisers, antistatics, processing aids, pigments||Impart specially required properties to the plastic for the manufacturing process or for end-use.|