Reactive spray molding

Polyurethanes differ from most other polymers in that polymerization frequently takes place at the same time that we are molding or forming them into a usable shape. The three most common processes of this type are reactive foaming, reactive injection molding (RIM), and reactive spray coating. 

The diversity of release products and the wide range of release problems make classification difficult. One approach is by product form, with subdivisions such as emulsions, films, powders, reactive or inert sprays, reactive coatings, and so on. Another approach is by application, eg, metal casting, mbber processing, thermoplastic injection molding, and food preparation and packaging. 

Removal of the article from the mold is lengthy process because anti-adhesive lubricants have to be sprayed on the on a mold surface before every injection, in an operation that takes up to 25 - 30% of the full cycle. In reactive molding of polyurethane-based compounds, internal lubricants are used in combination with surface coatings. This allows us to remove articles from a mold many times with a single coating treatment. One of the compounds used as an internal lubricant is silicon-organic liquids. 

Two-component spray gun n. A spray head with fittings for attachment to two separate feed lines, each carrying one component of a reactive resin mixture, e.g., as in urethane foam-in-place molding or polyester gelcoating. 

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