Solid-state polycondensation is an efficient way to increase the intrinsic viscosity of PET, which applies to PET bottle and industrial yarn production.
After extrusion, PET chips are amorphous. Therefore, prior to solid state polycondensation, crystallization plays an important part in the whole process. PET chips are heated evenly in the crystallizer in order to reduce their moisture content and increase their crystallinity, which ensures the quality of product.
The PET chips are transferred to a polycondensation reactor and kept in the reactor for a period of time, through which molecules are put together to re-form the polymer chains and molecular weight increases. So the intrinsic viscosity of chips can achieve the required level and the mechanical properties are also improved.
The longer the chain is, the higher the molecular weight is, and so is the IV. At the same time, the PET chips are decontaminated.