Polyurethanes(PU)
Otto Bayer, and co-workers, discovered and patented the chemistry of polyurethanes in 1937.
Polyurethane is an organic polymer that is formed by reacting a polyol with a diisocyanate and a catalyst. The polyol and diisocyanate are mixed in, which then react to form the polyurethane. Polyurethanes undergo a “cross-linking” chemical reaction to form a networked urethane connected chain.
RIM Polyurethanes cannot be heated and remolded or reshaped. Molding of consistent quality parts relies on precise ratio mixing, the ingredient chemicals and maintenance of the appropriate processing temperatures. When the diisocyanate and polyol react to form polyurethane the liquid mixture becomes increasingly viscous until forming a solid. The polyurethane molding reaction is exothermic (generates heat).
Polyurethane RIM is a closed-mold process that produces no styrene emissions. RIM materials offer the ability to produce high-quality parts with a wide range of physical properties.
Polyurethane RIM can be in-mold coated to provide a Class “A” final finish right out of the mold.
Polyurethane systems can be formulated with one or more additives:
- Blowing or foaming agents
- Colorants
- Flame retardants
- Heat stabilizers
- Ultraviolet stabilizers
- Reinforcing or cheapening fillers that improve dimensional stability and increase stiffness, as well as keep costs down on chemical materials
Courtesy of Bayer MaterialScience