Crosslinked elastomeric polyurethane

F. G. Hutchinson, Elastomer Production, U.S. Pat. 3,868,431 (1975). SINs based on crosslinked elastomeric polyurethane and ethylenically unsaturated monomers, i.e., MMA + DEGDM. Reinforced elastomers. 

A curable epoxy resin containing a crosslinked elastomeric latex " yields a special type of sequential IPN. The elastomers mentioned include SBR, EPR, NBR, silicone rubber, and PEA. Hawkins " described an epoxy/polyurethane semi-SIN, and Mendoyanis " revealed an epoxy/liquid rubber SIN. The liquid rubbers were based on polysulfide rubber or polyethylene. The final products could be extended to 400% at... 

The finite size effects in the contact between a spherical lens of polyurethane and a soft flat sheet of crosslinked polyfdimethyl siloxane) (PDMS) has been addressed by Falsafi et al. [37]. They showed that for deformations corresponding to contact diameters larger than the sheet thickness, the compliance of the system was affected by the glass substrate supporting the soft sheet. In order to minimize the finite size effects in the adhesion measurement of small elastomeric lenses, Falsafi et al. [38] and Deruelle et al. [39] used relatively thick elastic sheets to support their samples. 

When a thermoplastic polyurethane elastomer is heated above the melting point of its hard blocks, the chains can flow and the polymer can be molded to a new shape. When the polymer cools, new hard blocks form, recreating the physical crosslinks. We take advantage of these properties to mold elastomeric items that do not need to be cured like conventional rubbers. Scrap moldings, sprues, etc. can be recycled directly back to the extruder, which increases the efficiency of this process. In contrast, chemically crosslinked elastomers, which are thermosetting polymers, cannot be reprocessed after they have been cured. 

Polyurethane multiblock copolymers of the type described by Eqs. 2-197 and 2-198 constitute an important segment of the commercial polyurethane market. The annual global production is about 250 million pounds. These polyurethanes are referred to as thermoplastic polyurethanes (TPUs) (trade names Estane, Texin). They are among a broader group of elastomeric block copolymers referred to as thermoplastic elastomers (TPEs). Crosslinking is a requirement to obtain the resilience associated with a rubber. The presence of a crosslinked network prevents polymer chains from irreversibly slipping past one another on deformation and allows for rapid and complete recovery from deformation. 

Elastomeric, lignin-derived polyurethanes can be produced from a three-component system, in which a polyether diol (like PEG) is used as soft segment, provided that the crosslink density is held at a low level and that the soft segment content is high enough to keep T below room temperature. 

Thermoplastic elastomers, e.g., polyurethane elastomers, have an entirely different structure that is heterogenic. They have an elastomeric matrix and phase-separated hard blocks, which act as embedded physical crosslinking sites. The hard blocks can be softened at elevated temperatures to obtain a single-phase melt that is easily processed. Upon cooling, the two-phase nature is recovered and the material becomes a solid again. 

If physical crosslinks are used in an IPN system, then we would have a thermoplastic IPN. Up to this time, few IPNs or SINs have been made where both components are elastomeric. One of these rare works involves the crosslinking of cis-l,4-polyisoprene (Elastollan) in thermoplastic polyurethanes (Morthane). ... 

If the diol chain extender is used in exact molar proportion to the unreacted isocyanate, then a linear polyurethane elastomer is obtained. The resulting thermoplastic elastomer may be extruded or injection-moulded, and the properties arise from the ability of the hard and soft segments to form semi-crystalline domains that act as virtual crosslinks in the polymer and give it elastomeric properties, as shown in Figure 1.17. 

Polyurethane elastomers derive their elastomeric properties from phase separation of the hard and soft copolymer segments, such that the hard (urethane) segment domains serve as crosslinks between the amorphous soft segment domains, which are usually polyesters or polyethers. We are interested in the systems in which the hard segments are prepared from diphenyl-methane 4,4 -diisocyanate (MDI) with a linear diol as the chain extender ... 

Uses Intermediate solvent humectant coating resin raw material in paints crosslinking agent in polyurethane elastomers polyurethane chain extender intermediate for plasticizers, pharmaceuticals mfg. of tetrahydrofuran, terephthalate plastics elastomeric fabric coatings in food-pkg. adhesives Regulatory FDA 21CFR 175.105... 

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