Rubber toughening, technology

A blend was prepared by dissolving a rubber material in styrene and polymerizing the system. The blend contains not only rubber and polystyrene (PS), but also a graft polymer because of the attachment of short polystyrene side chains to the rubber molecules. The toughness of this material was markedly improved compared to that of the unmodified PS. A technology based on bulk polymerization [26] has been widely used the concentrated emulsion polymerization method employed by us, however, allows one to obtain rubber toughened latexes. 

P. Somdee, Natural rubber toughened polylactic acid, PhD thesis, Sur-anaree University of Technology, 2009. 

The rubber phase can be grafted to the polymer phase. The rubber toughened nylons are a spectacular example of this technology. A variation consists of polymers grafted to elastomers to provide a three dimensional interface. The rubber phase can be encapsulated inside of a particle rich in the matrix resin. 

Rubber toughened polymers have been and will continue to be a major area of polymer blend technology. Examples of these studies and the diversity of systems investigated are tabulated in Table 6.1 to demonstrate the depth of literature investigations. Additional examples are discussed in Chapter 4. 

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. 

As technology advances, materials have been developed which evade the above classification. Mixtures of thermoplastics and thermosetting resins have been developed in which the thermoplastics material acts as a toughening agent for the thermosetting resin. Alloys or blends of two or more thermoplastics, or of plastics and rubbers, are becoming commonplace. 

Historically, a number of different impact-modification technologies have been used. These include various maleated oleflnic rubber such as EB, EP, and so on SBS bromi-nated isobutylene-para-methyl styrene elastomers produced by Exxon and many others. Dow s metallocene-based ethylene-a-olefln elastomers were found to be very effective as well. The rheology of toughened nylon 6,6 is usually directly related to the maleic anhydride graft level of the impact modifier. Rubber particle size averages of greater than 0.25 pm and less than 0.5 pm are required to achieve the required balance of mechanical performance. Optimum particle size varies with the percentage of rubber. 

Commercially available liquid rubber (CTBN, ATBN)-toughened epoxy often shows outstanding fracture properties, and the technology is exploited in engineering adhesives [58]. However, because the butadiene component of the elastomer contains unsaturation, it would appear to be a site for premature thermal and/or oxidative instability, and such modified resins are not suitable for application at high temperature. One would imagine that excessive crosslinking could take place with time which would detract from otherwise desirable improvements accomplished with these structures. Second, there is some limitation in its use due to a possibility of the... 

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