Polyurethane rubber-poly systems

By combining elastomeric and brittle glassy phases it is often possible to obtain improved properties over a range of temperature and frequency. However, relatively little attention has been given to fatigue in IPNs, and to energy absorption in polyurethane rubber/poly(methyl methacrylate) (PU/PMMA) systems. 

The development of plastics also reflects economic history. Restrictions on imported latex, wool, silk and other natural materials to Europe during the Second World War resulted in the rapid development of alternative synthetic plastics. Table 1 shows that between 1935 and 1945, many new polymers were introduced including polyethylene, polyamides, poly(methyl methacrylate), polyurethanes, poly(vinyl chloride) (PVC), silicones, epoxies, polytetrafluoro-ethylene and polystyrene. Polyethylene was incorporated into radar systems while PVC replaced the limited stocks of natural rubber as cable insulation. 

Whatever the nature of the elastomer used as matrix, i.e. polyurethane, poly(ethylene-vinylacetate) or styrene-butadiene rubber (SBR), it appears that the interfacial shear strength x of carbon fibre-elastomer composites is much higher than theoretically expected from equation (10). Figure 6 illustrates the variation of x versus W2 in comparison with the prediction from our model in the case of carbon fibre-SBR systems. Any other theoretical approach is able to explain these high values of x. 

Polyurethanes are also used in the construction of sport surfaces such as all-weather athletic areas, outdoor game areas, children s playgrounds, tennis courts, and multisport halls. The poly ether polyurethane systems, mainly based on PMDI, are applied by a pour-in-place method. Often additional rubber granules are added to the system. 

A Russian patent [179] claimed the application of this process to many polymers—poly(vinyl chloride), poly(vinylidene chloride), poly(methyl methacrylate), polystyrene, polymethacrylonitrile, fluoroethylene polymers, poly(vinyl acetate), polyamides, polyurethanes, polyesters, phenol-formaldehyde resins, and epoxy resins. The monomers used included acrylic and methacrylic acids, their esters, amides, vinyl acetate, and styrene. Attempts have also been made to apply this system to the preparation of block copolymers from natural rubber and vinyl monomers [180]. 

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. 

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