Modified thermosets rubber

R. Siebert, "Rubber-Modified Thermoset Resins," in C. K. Riew and J. K. GiUham, eds., ACS Advances in Chemistry Series 208, American Chemical Society, Washington, D.C., 1983, p. 179 W. D. Bascom and D. L. Hunston, "Rubber Toughened Plastic," Adv. Chem. Ser. No. 222, American Chemical Society, Washington, D.C., 1989. 

Riew, C.K. and Gillham, J.K. Rubber Modified Thermoset Resins. Advances in Chemistry, 208, American Chemical Society, Washington, DC, 1984. 

Some of the conditions used in rubber test methods may need modifying for application to thermoplastic elastomers because of their intrinsic thermoplastic nature. If the temperatures generally used in ageing and compression set tests on thermosetting rubbers were applied to thermoplastic materials they could appear to perform extremely badly. Whether this was significant would depend on the service temperature. Data sheets need to be checked as those for thermoplastic elastomers may have used much lower temperatures that would be found for conventional rubbers, and it is only too easy to get a misleading impression of performance. 

Riew CK, Gillham JK (eds), Rubber-Modified Thermoset Resins, Adv. Chem. Sci., 208, ACS, Washington DC, 1984. 

DMTA is a very interesting tool for characterizing heterogeneous materials in which domains of distinct Tg values coexist. The most interesting cases involve modified thermosets of different types (see Chapter 8). Examples are the use of rubbers (e.g., liquid polybutadiene and random copolymers), or thermoplastics (e.g., polyethersulphone or polyetherimide in epoxy matrices or poly(vinyl acetate) in unsaturated polyesters), as impact modifier (epoxies), or low-profile additives (polyesters). The modifier-rich phase may be characterized by the presence of a new a peak (Fig. 11.10). But on occasions there may be superposition of peaks and the presence of the modifier cannot be easily detected by these techniques. If part of the added polymer is soluble in the thermoset matrix, its eventual plasticizing effect can be determined from the corresponding matrix Tg depletion, and the... 

The fracture modeling of rubber-modified thermosets was developed by Huang and Kinloch (1992a), Kinloch and Guild (1996), Huang et al. (1993b), and Yee et al. (2000). 

Following the requests to increase toughness by keeping a high Tg, for several applications (the aerospace industry in particular), high-Tg or semicrystalline thermoplastics (TP) can be used instead of rubbers to modify thermosetting polymers (Hedrick et al., 1985 Pearson, 1993 Hodgkin et al., 1998 Pascault and Williams, 2000). 

Core-shell rubber (CSR) particles are prepared by emulsion polymerization, and typically exhibit two or more alternating rubbery and glassy spherical layers (Lovell 1996 Chapter 8). These core-shell particles are widely used in thermoplastics, especially in acrylic materials (Lovell, 1996), and have also been used to modify thermosets, such as epoxies, cyanates, vinyl ester resins, etc. (Becu et al., 1995). 

Dusek, K. in Rubber-Modified Thermoset Resins, (eds.) Keith Riew, C., Gillham, J. K., Advances in Chemistry Series 208, 3, Am. Chem. Soc., Washington D.C. 1984... 

Much work has been reported on studying the structure of thermoset resins via SAXS, especially focussing on interpenetrating network polymers (IPNs), thermoset nanocomposites, rubber-modified thermosets and thermoset-thermoplastic blends. Most recently Guo et al, (2003) have examined the use of SAXS to monitor the nanostructure and crystalline phase structure of epoxy-poly(ethylene-ethylene oxide) thermoset-thermoplastic blends. This work proposes novel controlled crystallization due to nanoscale confinements. 

Riew, C. Gillham, J. (Eds.) (1984) Rubber Modified Thermosets, New York American Chemical Society/Wiley. 

He has edited or co-edited several volumes in the ACS Advances in Chemistiy Series Rubber-Modified Thermoset Resins, Volume 208 (1984) Rubber-Toughened Plastics, Volume 222 (1989) Toughened Plastics I Science and Engineering., Volume 233 (1993) and the current volume. 

The importance of the science and engineering of toughened plastics is reflected in the successful series of symposia held on the topic under the auspices of the American Chemical Society. The first, on Rubber-Modified Thermoset Resins, was held in Washington, DC, in 1983 the papers from that conference were published in 1984 as Volume 208 of the Advances in Chemistry Series. The theme of the 1988 symposium, Rubber-Toughened Plastics, was broadened to cover both thermosets and thermoplastics. The papers from that symposium, held in New Orleans, LA, were published in 1989 as Volume 222 of the Advances in Chemistry Series. In 1990 the symposium returned to Washington, DC, and was titled Toughened Plastics Science and Engineering. The papers were published in 1993 as Volume 233 of the Advances in Chemistry Series. 

Rubber toughened epoxy resins are the well known examples of impact modified thermosets utilizing reactive rubbery prepolymers. Epoxy resins can be toughened or flexibilized by any one of the following types of oligomeric reactive elastomers ... 

Various applications of the injection molding system have been developed outside the scope of the cure of rubbers, and a few examples are given, with the substitution of thermoset rubbers by thermoplastic elastomers a range of thermoplastic elastomer compounds were introduced and processed using reaction compounding technology. They are called reaction modified thermoplastic elastomers or ReMoTE [5]. 

Fig. 7. TTT diagram representing times for phase separation (doud point), gelation and vitrification for a castor-oil-modified epoxy system (4ho = 0.176) at different temperatures (Reprinted from Polymer International, 30, R.A. Ruseckaite, L. Hu, CC. Riccardi, R.JJ. Williams, Castor-oil-modified epoxy resins as model systems of rubber-modified thermosets. 2 Influence of cure conditions on morphologies generated, 287-295, Copyright (1993), with kind permission from the Society of Chemic Industry, London, UK)...

In order to obtain a -phase rich in modifier dispersed in the thermosetting polymer, the convenient condition (albeit not sufficient) is to select an initial modifier concentration, ( >mo < Mcrit- Usually this condition is fulfilled when using 15 wt% for a modifier with a number average molar mass, M < 5000 g mol (commercial rubbers used to modify thermosetting poly-... 

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