Modified Rigid Urethane Foams

As opposed to flexible urethane foams, rigid urethane foams have a highly cross-linked chemical structure and a high percent of closed cells, e.g., over 90%. Rigid urethane foams can be classified as follows unmodified (or pure) rigid urethane foams and modified rigid urethane foams, which include isocyanurate-modified, epoxy-modified, amide-modified and oxazolidone-modified rigid urethane foams. 

These foams include isocyanurate-modified rigid urethane foams, isocyanurate-modified flexible urethane foams, urethane-oxazolidone foams, urethane-based IPN foams, and urethane-based hybrid foams. 

Preparation. The polyisocyanates utilized in rigid urethane foams include TDl-prepolymers, crude TDl (undistilled TDl), modified MDl... 

The frothing process is widely used in rigid urethane foam pour-in-place applications. The frothing process of urethane-modified isocyanurate foams has been used for the insulation of petrochemical plants, e.g., spherical tanks, reaction towers, etc. (79). An example of the frothing system is shown below (71). 

Sucrose and Modified Sucrose Polyols in Rigid Urethane Foam... 

Polyurethanes and Isocyanurate-Modified Polyurethanes. Phosphorus flame retardants, both additive and reactive, are used in large quantities in Polyurethanes. Rigid urethane foams employed in thermal insulation must adhere to stringent fire regulations. Flexible foams used in automotive seating must pass the MVSS-302 fire standard in furniture foam, they must pass the California state standard and other local fire codes. 

Urethane network polymers are also formed by trimerization of part of the isocyanate groups. This approach is used in the formation of rigid polyurethane-modified isocyanurate (PUIR) foams (3). 

The polyisocyanates which can be used for preparing isocyanate-based foams are mainly aromatic compounds and some aliphatic or aralkyl polyisocyanates. TDI (toluene diisocyanate) is widely used for flexible foams. Pure MDI (diphenylmethane diisocyanate) is used for elastomers and coatings. Modified TDI and modified MDI are used for high-resilience flexible foams. Polymeric isocyanates (polymeric MDI or oligomeric MDI) are mostly used for preparing rigid urethane and isocyanurate foams, and in part, for preparing flexible and semi-flexible foams. 

Matrix Plastic Foams. The matrix for plastic foams includes rigid polyurethane foam, urethane-modified isocyanurate foam, unsaturated polyester-polyurethane hybrid foam, and vinyl ester-polyurethane hybrid foam. 

Chem. Descrip. Tetrabromophthalatediol CAS 20566-35-2 EINECS/ELINCS 243-885-0 Uses Flame retardant for rigid urethane and urethane-modified isocyanurate foams for UL and factory mutual class 1 and 2 specs, slab stock, pour-in-place, and spray foams, urethane coatings and elastomers... 

Examples of the matrix resins employed for SRIM include rigid polyurethane (7,15, 16), or urethane-modified isocyanurate foam (9, 26, 35, 36). The matrix resins for foamed composites are required to have low viscosity and relatively slow cream time for better impregnation into fiber mat and fast-cure cycle time for higher j oductivity. 

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