Polyethers millable polyurethanes

BASIC VULCANIZATION RECIPE FOR A POLYETHER MILLABLE POLYURETHANE... 

Examples of vulcanizable elastomers include natural rubber (NR), styrene butadiene rubber (SBR), butadiene rubber (BR), ethylene-propylene-diene monomer-rubber (EPDM), butyl rubber (HR), polychloroprene or neoprene (CR), epichlorohydrin rubber (ECO), polyacrylate rubber (ACM), millable polyurethane rubber, silicone rubber, and flu-oroelastomers. Examples of thermoplastic elastomers include thermoplastic polyurethane elastomers, styrenic thermoplastic elastomers, polyolefin-based thermoplastic elastomers, thermoplastic polyether-ester (copolyester) elastomers, and thermoplastic elastomers based on polyamides. 

To produce the millable polyurethane elastomers, one can bring diisocyanate molecules into reaction with oligomeric hydroxyl-terminated polyesters or polyethers and lower-molecular-weight diols (e.g., 1,4-butanediol). The ester-derived elastomers are designated AU, while the ether-derived materials are designated EU. An illustrative chemical structure is given here, where toluene diisocyanate was used ... 

Millable polyurethane elastomers are elastomers to which the conventional techniques of mill compounding and vulcanization can be applied. In this approach, stable (hydroxyl-terminated) polymers are prepared by the reaction of linear polyesters (commonly adipates) or polyethers (commonly poly(oxytetramethylene) glycol) with diisOcyanates. These polymers are rubber-like gums which may be compounded on two-roll mills with other ingredients. Vulcanization may be effected by several types of reagents, but isocyanates, sulphur systems and peroxides are the most widely used. 

A drawback to the cast elastomers is limited shelf-life and a need to store them in the absence of moisture. As a result, millable elastomers were developed. These are produced by first forming hydroxy-terminated linear polyurethanes through reactions of linear aliphatic polyesters or polyethers with diisocyanates. The prepolymers are rubber-like gums that can be compounded on rubber mills with other ingredients and crosslinked. Crosslinking is accomplished by adding either more diisocyanates, or sulfur, or peroxides. Diisocyanates dimers that dissociate at about 150 °C are often used ... 

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