Polymerization or solidification stage

After mixing of several streams, the reactive mixture goes into a mold where polymerization or solidification takes place. The behavior of materials in a mold depends substantially on the chemical nature of the initial raw materials, on mixture viscosity, on shrinkage during polymerization and solidification, on adhesion to the mold walls, and on temperature. The main feature of free casting is that the mold is either unpressurized or the pressure is no higher than 0.5 MPa if a mold is 

To increase the production rate, the casting devices and the molds are grouped into one unit. Linear, vertical rotary, and multi-layer units are the most common.171 

A large exothermal effect resulting from chemical reactions is typical of these processes. When using oligomeric initial components, for example, formulations based on urethane prepolymers, epoxy resins, and lactams, self-heating may cause thermal decomposition. For this reason the correct choice of the initial solidification temperature is very important. 

In radical polymerization, particularly in the large-scale production of poly(methyl methacrylate), the monomer may boil hence the process should be carried out with continuous removal of reaction heat to eliminate overheating in the reactive volume. In this case, the choice of cooling method needs careful consideration.1 2 

Different devices are used to maintain the preset temperature in a mold cabinets, boilers, chambers, baths, infrared heaters, electromagnetic radiation, and so on. In a number of cases, solidification takes place owing to the heat output during the chemical reactions. 

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