Mechanical behavior rubber toughening

The fracture behavior of toughened polymers, containing rubber or inorganic fillers, may involve several mechanisms, as schematically illustrated in Fig. 8.1 (Garg and Mai, 1988a). These include ... 

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. 

As with tensile and impact behavior of rubber-toughened plastics, a major energy-absorbing mechanism appears to be crazing. Thus, at least qualitatively, low-frequency fatigue behavior of rubber-modified plastics appears to involve the same phenomena as are seen in tensile and impact loadings. 

Williams G, Watts DC (1970) Non-symmetrical dielectric relaxation behavior arising from a simple empirical decay function. Trans Faraday Soc 66 80-85 Williams ML, Landel RR, Ferry ID (1955) The temperature dependence of relaxation mechanisms in amorphous polymers and other glass-forming liquids. J Am Chem Soc 77 3701-3707 Wood LA (1958) Glass transition temperatures of copolymers. J Polym Sci 28 319-330 Wu SH (1985) Phase structure and adhesion in polymer blends a criterion for rubber toughening. Polymer 26 1855-1863... 

In the past, numerous studies of toughening mechanisms in rubber-modified polymers have been performed, mostiy via eiectron microscopy. Three main mechanisms can be distinguished that are strongiy reiated to the morphoiogy (disperse or network structures) and to the micromechanicai deformation behavior of the matrix [1, 2, 6] ... 

The improvement in toughness (impact strength) when EPR is added to PP matrix normally results in a reduction of its stiffness, which is usually related to a decrease in flexural modulus, yield stress, and an increase in the yield strain. A balance between toughness and stiffness is always required for optimum performance of the rubber-toughened polymer. The mechanical performance, shrinkage, and processing behavior of heterophasic polypropylene is influenced by rubber particle size, rubber composition, and rubber content. 

Elloappan, V., El-aasser, M.S., Klein, A., Daniels, E.S., Roberts, J.E., and Pearson, R.A. (1994) Effect of the core/shell latex particle interphase on the mechanical behavior of rubber-toughened poly (methyl methacrylate). J. Appl. 

Liquid reactive rubbers were also used for UP and vinyl ester formulations (Suspene et al., 1993 Siebert et al., 1996). Increases in fracture energy and fatigue- crack resistance were reported for some systems, although no significant improvements were observed for some other systems. These different behaviors are probably related to the heterogeneous structure of the matrix (Chapter 7). Toughening mechanisms in three-phase systems are not yet well established. 

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