Clean process technology impact analysis

In PVC technology certain polymeric additives can be considered as process aids. These polymers have a similar composition to those used as impact modifiers in PVC formulations but are more compatible and so are primarily included to ensure more uniform flow and hence improve surface finish. Such process aids include ABS, chlorinated polyethylene, MBS, EVA-PVC graft polymers and acrylate-methacrylate copolymers. As these are usually found in unplasticised PVC, direct analysis of the product by IR will usually indicate the presence of those that have a distinctive spectmm as no masking by plasticiser will take place. However, even rigid PVC can contain a small amount of phthalate and so it is advisable to carry out a solvent extraction to clean up the matrix first. Where the process aid (e.g., chlorinated polyethylene) has a relatively bland spectmm, a technique such as NMR will be required to both detect and quantify it. NMR will usually be required to quantify the other types as well, unless the spectrum is very distinctive and standards of known composition are available. 

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