Polyurethane Toughening

Yuan, Y., Ruckenstein, E., 1998. Polyurethane toughened polylactide. Polym. Bull. 40, 485-490. 

Pheno/Formaldehyde, Urea/Formal-dehyde, Resorcinol/Formaldehyde, Epoxide/Amine, Epoxide/Amide, Polyurethane, Toughened Acrylic, Polyester,... 

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. 

In such polyurethanes it is desirable to modify properties over a wide range of hardness and resilience the polyurethanes themselves are of inherent interest as toughening phases for brittle... 

In general, die position of thermal transitions markedly affects the mechanical behavior of polymeric coatings. IK and 2K polyurethanes based on the IPDI macromer behave as toughened plastics, since the ambient temperature T is... 

Novel, toughened one-component epoxy structural adhesives based on epoxy-terminated polyurethane prepolymer incorporating an oxolidone structure were developed to provide improved toughness, fracture resistance and adhesive properties with good chemical and moisture resistance.21 The hybrid resin cures with a standard latent curing agent/accelerator. 

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... 

Most conventional low-modulus adhesives and sealants, such as polysulfides, flexible epoxies, silicones, polyurethanes, and toughened acrylics, are flexible enough for use at intermediate low temperatures such as -40°C. Low-temperature properties of common structural adhesives used for applications down to -129°C are illustrated in Fig. 15.9, and the characteristics of these adhesives are summarized in Table 15.12. 

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

Going up somewhat in hard segment content to the 50-60% range affords ( at least in polyurethane or urea-urethane RIM) the elastomers and elastoplastics, or perhaps a better word than elastoplastics would be toughened plastics. 

Table VI contains the general properties for 50-60% HARD SEGMENT polymers. This table contains polymers which have been developed in the past such as the Polyurethanes in the 55 to 65 Shore D hardness (Fascia materials), as well as Poly(urea-urethanes) which are more recent developments. This hard segment range also covers 65 to 75D intermediate modulus materials which are in reality toughened plastics. The raw materials prices are for comparison purposes.

A further example of the new materials research being done on RIM processable polymers are the high modulus urethane -epoxy UN s, shown in Table IX (12). These materials are shown compared to a toughened plastic polyurethane 146,000 psi flexural modulus urethane naterial. The urethane-epoxy IEN s are based on two epoxies (Bisphnol A type and Novalak type). 

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).

A typical layered structure consists of two thin, glass-fibre-reinforced polymer skins bonded to a thick, lightweight honeycomb core (Fig. 4.5a). Such sandwich panels are used in railway carriages and aircraft there are similar structures inside many skins. Other examples are less obvious the space between the outer container and the toughened polystyrene liner of a refrigerator is filled with rigid polyurethane foam. 

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]. 

Polyurethane/epoxy-based polymer blends (so-called toughened epoxies)... 

Wan Wang, H.-H., Chen, J.-C. Toughening of epoxy resin by reacting with functional terminated-polyurethanes. J. Appl. Polym. Sci. 57 (1995) 671-677. 

Toughened acrylic adhesives are also classified as structural adhesives for limited exterior service environments, while polyurethane and polyesters (unsaturated) are considered as semi-structural adhesives for limited exterior service environments [3]. 

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