Solid-state Polycondensation in PET Recycling

Similar to virgin PET, solid-state polycondensation (SSP) is the method of choice to increase the molecular weight in mechanical recycling processes. 

SSP of recycled PET (RPET) can be performed as either a continuous or a batch process. A continuous SSP offers a constant and overall higher productivity, as well as a more consistent product treatment, lower operating costs [117] and better process integration with a downstream manufacturing process. A batch SSP offers a larger degree of flexibility for small-scale operations with a large variation of raw material and final product specifications. 

Reclaimed PET material is either directly upgraded by solid-state poly condensation [118] or repelletized before SSP [119]. In either case, the energy consumption can be reduced by eliminating an additional drying step if the downstream 

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