Crack propagation elastomers

E.H. Andrews, Crack propagation in a strain-crystallizing elastomer, J. Appl. Phys., 32, 542-548, 1961. 

Improve both impact strength and rigidity of thermoplastics by using up the energy of crack propagation. Elastomers are prototypical toughening additives. Examples of high-polymeric impact modifier/thermoplastic matrix systems are EVA, CPE and MBS in PVC, EP(D)M and SBS in PA, and acrylic rubbers in polyesters. 

Under some circumstances it is possible to observe very low 5 values for polymer solids, namely when the energy to fracture chemical bonds is provided by chemical reaction. An excellent example of this is the ozone cracking of unsaturated hydrocarbon elastomers where crack propagation occurs at threshold values of as low as 0.05 Jm Under such low stresses the toss function of Eq. (5) is effectively... 

To lower PA s sensitivity to crack propagation under impact conditions, the resins are blended with 10-25% of an elastomer or a polyolefin. The impact-modified PA s exhibit good processability. They are mostly formed by injection molding. Special compositions have been formulated for extrasion of tubings. 

Whereas the initiation of fracture appears to be a similar process for all elastomers, the propagation of a crack is widely different. Three basic patterns of crack propagation, or tearing, can be distinguished corresponding to three characteristic types of elastomeric compounds ... 

Tj N mm crack propagation value from R-curve of elastomers... 

Table 5.21 Crack initiation and crack propagation values of elastomers determined by using the MSM.

K12 Kliippel, M. The role of filler networking in fatigue crack propagation of elastomers under high-severity conditions. Macromol. Mater. Eng. 294 (2009) 130-140. 

Lor Lorenz, H., Steinhauser, D., Kliippel, M. Morphology and micro-mechanics of filled elastomer blends Impact on dynamic crack propagation. In Grellmann, W., Heinrich, G., Kaliske, M., Kliippel, M., Schneider, K., Vilgis, T. (eds.) Fracture mechanics and statistical mechanics of reinforced elastomeric blends. Lecture Notes in Applied and Computational Mechanics, Vol. 70, Springer, Berlin, 2013, 81-128. 

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