Vinyl ester resins Toughening

The blending of DCPD resins has become an important practice. Typical blended resins include combinations of DCPD resins with isophthalic, orthoph-thalic or vinyl ester resins. Creating blends with higher-molecular-weight phthalic anhydride, isophthalic or vinyl ester resins can toughen neat DCPD resins, which are inherently brittle. In the case of vinyl ester and isophthalic and DCPD blends, a degree of improved chemical resistance and hydrolytic stability can be gained. 

In the same way, ABS acts as a toughener for vinyl ester resins (34). Assessment of the mechanical properties suggest that a chemical reaction may have occurred between the constituents of the blends. The blends are intended as a toughening agent for interlayer toughened vinyl ester/glass composite materials. 

Pha Pham, S., Burchill, P. J. Toughening of vinyl ester resins with modified polybutadienes. Polymer 36 (1995) 3279-3285. 

U11 Ullett, J. S., Chartoff, R. P. Toughening of xmsaturated polyester and vinyl ester resins with liquid rubbers. Polym. Eng. Sci. 35 (1995) 1086-1097. 

Rob Robinette, E. J., Ziaee, S., Palmese, G. R. Toughening of vinyl ester resin using butadiene-acrylonitrile rubber modifiers. Polymer 45 (2004) 6143-6154. 

The toughening effectiveness of impact modifiers of any kind in unsaturated polyester and vinyl ester resins will depend on the rate of impact or applied strain, atmospheric conditions (temperature, presence of solvents), and the toughness of the base resin. As the applied strain rate increases or the lest temperature decreases the effectiveness of the rubber additive may decrease. This is because the rubbery particles and the matrix resin b me more brittle under these conditions. As a result, when comparing toughness data from different sources, testing... 

Ullett, J.S. and Chartoff, R.P. (1995) Toughening of unsaturated polyester and vinyl ester resins with liquid rubbers. Poly. Engr. and Sci., 35,1086-1097. 

Three different matrix resins were used in this study a toughened vinyl ester, an untoughened vinyl ester, and an epoxy. Two different fiber layups were used designated by the letters L and P . The vinyl ester laminates were pultruded with the L lay-up while the epoxy laminate employed the P lay-up in order to prevent scaling problems in the epoxy resin system. 

Elastomer-modified epoxy resins are used in composites and structural adhesives, coatings, and electronic applications. Similar approach to toughen epoxy vinyl esters using other elastomeric materials has been reported (204). Other elastomer-modified epoxies include epoxy-terminated urethane prepolymers, epoxy-terminated polysulfide, epoxy-acrylated urethane, and epoxidized polybutadiene. Preformed dispersions of epoxy-insoluble elastomers have been developed and reported to achieve toughening without Tg reduction (205,206). 

Improved versions of the high performance resin systems continue to be developed (245,246). Toughening of epoxies and epoxy vinyl esters has emerged as an area for investigation (247). Lower styrene content vinyl esters have been developed to reduce worker exposure. Performance enhancements with epoxy and vinyl ester nanocomposites have been reported in the literature, but commercialization has not been yet realized. 

The polymers studied in this program were untoughened fabric filled, toughened isopolyesters and vinyl esters. All materials were neat resins vrithout any reinforcement. The ultimate tensile strengths and glass transition temperatures of the polymers used in this study ate summarized in Table 1. 

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