Reactive Extrusion

Publisher Summary Reactive extrusion is an attractive route for polymer processing to carry out various reactions including polymerization, grafting, branching, and functionalization. Reactive extrusion polymerization involves polymerizing a liquid or solid monomer or prepolymer during the residence time in an extruder to form a high molecular weight melt. Low-cost production and processing methods for biodegradable plastics are of great importance because they enhance the commercial viability and cost-competitiveness of these materials. Reactive extrusion is an attractive route for the polymerization of cyclic ester monomers, without solvents, to produce high molecular weight biodegradable plastics. Extruders can be used for bulk polymerization of monomers, like methyl methacrylate, styrene, lactam, and lactide. From a mechanistic perspective, nearly all kinds of polymerization are performed in an extruder. These include radical polymerization, ionic polymerization, metathesis polymerization, and ring-opening polymerization. The techniques of characterization and experimental setup for reactive extrusion are described in the chapter. There are kinetic, heat transfer, and diffusion-related issues in a bulk polymerization process that make it difficult to develop and design processing methods that result in high molecular weight polymer at high throughputs with a high conversion of the monomer. However, extruders are ideal process vehicles for this purpose as they can be tailored to give various flow patterns, and residence time distributions and shear effects, each of which affect the polymerization and the polymer quality.