Polyurethane Rubber, toughened

Kumar G., Neelakantan N.R., and Subramanian N., Mechanical behaviour of polyacetal and thermoplastic polyurethane elastomer toughened polyacetal, Polym. Plastics TechnoL Eng., 32, 33, 1993. Newmann W. et al.. Preprints, 4th Rubber Technology Conference, London, May 22-25, 1962. Farrissey W.J. and Shah T.M., Handbook of Thermoplastic Elastomers (Walker B.M. and Rader C.P., eds.). Van Nostrand Reinhold, New York, 1988. 

Hydroxy-functionalized liquid rubbers can be prepared from myrcene that are suitable for polyurethane elastomer formation, and as rubber toughening agents ... 

Fig. 13.8 The T-peel resistance as a function of the crosshead speed for nitrile rubber/phenolic polyurethane liquid rubber blend toughened epoxy (upper curve) and conventional nitrile rubber-toughened epoxy structural adhesives (lower curve).

Urethanes have also been used to toughen vinyl-terminated acrylic adhesives for improved impact resistance. Thus rubber-toughened urethane acrylates [79,80], water-dispersible urethane acrylates [81], and high-temperature-performance urethane-acrylate structural adhesives have been reported [82]. Polyurethanes terminated with acrylic functionality are also used for anaerobic or radiation-cured adhesives with improved toughness [83]. 

A surface activated rubber particle, Vistamer, was recently introduced as a low-cost toughener for epoxy and polyurethane adhesives. The source of the rubber is reprocessed... 

In contrast, Li and Shimizu [103] ascribed the toughening behavior of the PLA-based blends to debonding at the rubber/matrix interface during deformation, which released the hydrostatic stress and facilitated the occurrence of shear yielding. When the hydrostatic stress is released within a PLA/polyurethane elastomer (PU) blend, debonding is easily induced at the interface between the (PU) domains and PLA matrix. This results in voids around the rubber, which allows shear yielding and improved the toughness of the materials, as shown by... 

Impact Modifiers. Notched impact strength and ductility can be improved with the incorporation of impact modifiers, which can also lower the brittle-ductile transition temperature and give much improved low temperature toughness. Impact modifiers are rubbers (often olefin copolymers) that are either modified or contain functional groups to make them more compatible with the nylon matrix. Dispersion of the rubber into small (micrometer size) particles is important in order to obtain effective toughening (19). Impact modifiers can be combined with other additives, such as glass fiber and minerals, in order to obtain a particular balance of stiffness and toughness. Modified acrylics, silicones, and polyurethanes have also been proposed as impact modifiers. 

Toughening of anaerobics by using urethane methacrylate monomers or by incorporating rubbers has been moderately successful, to create (although expensive) structural adhesives. However, in contrast to other tough adhesives such as reactive acrylics and polyurethanes, they remain relatively brittle materials. 

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