Liquid Rubber Toughening

In this method, a liqnid rnbber is blended with a thermoset resin before curing [108-200]. Various liquid rubbers used for toughening thermoset resins are presented Table 4.1. The toughening effect of a particular modifier is largely dependent on the 

Name of liquid rubber Abbreviation/source/reference 

Carboxyl-terminated copolymer of butadiene and acrylonitrile CTBN, Goodrich company 

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Zen Zeng, Y.-B., Zhang, M.-Z., Penc, W.-Z., Yu, Q. Microstructure, mechanical properties, and fracture behavior of liquid rubber toughened thermosets. J. Appl. Polym. Sci. 42 (1991) 1905-1910. 

Keywords unsaturated polyester, vinyl ester, impact modifiers, liquid rubbers, toughening, microstructure, cure, cavitation. 

Several such failure mechanisms may take place simultaneously in a toughened resin, depending on the type of particles, whether liquid rubber or rigid particles, and the matrix material. Each of these mechanisms contributes to the energy absorption of the whole structure. 

Thermosets are generally used in advanced composites due to their excellent thermal and dimensional stability, high modulus, and good mechanical properties. Because thermoset resins are inherently brittle, however, some applications require improved fracture resistance. Toughening of thermosets has been achieved through various methods, such as incorporation of reactive liquid rubber [1-9], elastomer [10], or rigid thermoplastics [11-25], and IPN formation with ductile component [26]. 

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

Pearson and Lee (1991) examined the effects of particle-size and particle-distribution effects on rubber-toughened epoxy resins. They examined a variety of CTBN liquid rubbers and a methacrylated butadiene styrene core-shell particle in a DGEBA-piperidine system. They found that the toughening mechanism for small particles was internal cavitation of the... 

Compatibilized, Segmented Liquid Rubbers as Epoxy-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).

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