Main Reactions in Extruders

Reactions involving polymers which have been performed in extruders can generally be divided into five categories [8], as indicated in Tab. 13.1. 

From a processing point of view, all reactions can be divided into two main groups single component and multi-component. 

Single-component reactions can occur throughout the bulk of the material. At the start of the reaction only one single component, monomer or prepolymer, is present or the components used are well miscible and premixed. For this group of reactions the temperature of the mixture plays an important role, as well as macro-mixing over the length of the extruder, which is related to the residence time distribution. Both parameters determine the progress of the reaction. 

Multi-component reactions, on the other hand, occur predominantly between immiscible components. Because the reaction proceeds mainly at the interface between the components, micro-mixing plays an important role. Normally, this type of reaction becomes diffusion-limited as the reaction progresses due to the build-up of reaction products at the interface between the components. To overcome this diffusion limitation, extensive micro-mixing is necessary. In addition to micro-mixing, these reactions are, of course, also influenced by temperature and macro-mixing. 

Step polymerization (condensation reactions) polyetheremide, polyesters, polyethylterephthalate (PET), polybutylterephtalate (PBT), polyamide 6.6, polyarylate, polyurethanes, polyamide 6 

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