Rubber-toughened resins

Figure 9. Effect of rubber content on toughness of rubber-toughened resins...

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. 

J. C. Hedrick, N. M. Patel, and J. E. McGrath, Toughening of Epoxy Resin Networks with Functionalized Engineering Thermoplastics, in Rubber Toughened Plastics, K. Riew (Ed.), American Chemical Society, Washington, DC, 1993. 

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. 

Swelling experiments showed that a lignin epoxide resin of 0.11 epoxy equivalents per lOOg formed a network polymer when cured with DETA, PA, or ATBN. Phase separation was observed in the rubber-toughened lignin epoxide network. Cured epoxides had lignin derivative contents of up to 95%. 

Ideally, rubber toughening should be accomplished without substantial sacrifices in modulus. For each modified resin, flexural and Young moduli and plane-strain fracture toughness were determined. Examination of various fracture surfaces by scanning electron microscopy showed the effects of modifier composition on the morphology of these multi-phase materials as well as the prominent features of the fracture process. 

Chorvath I et al. (2001) Silicone rubber-toughened thermoplastic resin composition. WO Patent 2001018 116... 

In many systems, such as epoxy resins, the rubber toughener may be soluble in the other phase, such as epoxy resin, so the phase separation must be achieved during cure. This is an example of phase separation during reactive processing. 

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... 

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. 

Some linear-elastic results were obtained for direct comparison with experimental values of mechanical properties available in the literature. The materials were rubber-toughened epoxy resin (5) and epoxy resin filled with glass beads (22). The material properties used for these analyses are shown in Table II. 

Rubber-Toughened Thermosetting Polymers in Structural Adhesives—Developments in Resins and Primers Kinloch, A. J., Ed. Applied Science Publishers London, 1980 Chapter 5, pp. 127-162. 

This study demonstrated that the final destination of the added core-shell rubber particles, in PC, PA, or both, in the PC-PA binary blend can be controlled by properly selecting the chemical structure of the shell in the core-shell rubber. The unreactive MBS rubber tends to reside in the PC phase and near the vicinity of the PC-PA interface. The reactive MBS-MA rubber can have a chemical reaction with PA end groups and can therefore be retained within the PA phase. High-molecular-weight bisphenol A epoxy resin has proved to be an efficient compatibilizer for PC-PA blends. Rubber-toughening of the PC-PA blend in which PC is the matrix is much more effective than with blends in which PA is the matrix. 

Pearson and Yee [171] provided further valuable insights. They showed that the GIc of their family of neat epoxies was very low and almost independent of Mc over the wide range that they examined. However, when these epoxies were used as matrix materials and 10% by volume of an elastomer was added as a filler, Gjc increased rapidly and almost linearly with increasing Mc. Consequently, while the unmodified epoxies were all very brittle, the rubber toughenability of these resins increased rapidly with decreasing crosslink density. 

Hence a low molecular weight, reactive elastomer is normally used for impact modification of thermosets. The low molecular weight of the mbbery prepolymer aids its easy dissolution or dispersability in the thermosetting resin. The reactive functionality couples the rubber covalentiy to the growing polymer network during the curing reaction. Hence the rubber toughened thermosets may also be considered as co-reacted thermosets and not true blends. 

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 ... 

Rubber-toughened epoxy resins have been characterized by their resin and rubber glass transition temperatures (57) using torsional braid analysis (TEA). These are reported in the literature as eTg and rTg, respectively. The Torsional Braid Analyzer has also been used to characterize ATBN-modifled coatings regarding transition temperatures. 

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