Additives are often-ignored components of plastics.In discussions of the market success of polyvinyl chloride or polypropylene,for instance,only the polymers are usually mentioned,and little credit is given to the chemistries that enable these products to be as useful as they are.Sometimes there is good reason for this.Because certain types of additives haven't changed for decades,their growth often tracks the polymers that they are used with,and their presence is often forgotten.But in other cases,as when environmental and health concerns arise over their use,plastics additives take center stage until the industry finds a way either to replace the troublesome additives with newer varieties-often without government mandate-or,if possible,to prove its products are essentially harmless.
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