Re-use After Modification

Similar to the method described rmder direct re-use, in which PET-flakes are added during the esterification process, PET-pol5oner is broken down into low-molecular, low-viscous fractions. Such method could already be viewed as a method of re-use after modification. Because the intermediate products are not separated at any moment of the process, the degree of purity of PET-scrap must be high. 

Glycolysis can be considered as a method for direct re-use, whereas methanolysis and hydrolysis are mainly taken into consideration for monomer recovery, as discussed below. 

The low-molecular weight depolymerizates can be introduced directly into a polymerization system,preferentially after filtration. In this method, particular care has to be taken in order to avoid glycol ether formation, which may lead to PET of inferior properties. The glycol5dic degradation can also be pushed to further completion, leading to DGT-recovery, rather than to direct re-use. 

Although this method for producing unsaturated resin, e.g., for use in regular castings or in fiber-reinforced laminates, has been thoroughly studied by PET-film manufacturers, it is believed that the method is not currently used in production.  

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