Tearing of rubbers

L. Mullins, Rupture of rubber. Part 9. Role of hysteresis in the tearing of rubber, Trans. Inst. Rubber Ind.,... 

Fig. 8.1. Toughening mechanisms in rubber-modified polymers (1) shear band formation near rubber particles (2) fracture of rubber particles after cavitation (3) stretching, (4) debonding and (5) tearing of rubber particles (6) transparticle fracture (7) debonding of hard particles (8) crack deflection by hard particles (9) voided/cavitated rubber particles (10) crazing (II) plastic zone at craze tip (12) diffuse shear yielding (13) shear band/craze interaction. After Garg and Mai (1988a).

Toughening mechanisms due to the elastomer spheres include shear-band formation, fracture of rubber particles, stretching, debonding and tearing of rubber particles, rubber cavitation, transparticle fi acture, crazing, formation of a plastic zone at the craze tip, diffuse shear-yielding, as well as shear band/craze interaction. 

Most fluid dynamics books publish data for linear roughness based on Moody s work. Such values are applicable to water. However, tests conduced on slurry pipelines can yield different values, due to the erosion of pipe, wear and tear of rubber linings, etc. 

Fig. 5.58 Pure shear test-piece used in the study of the tearing of rubbers, (a) Specimen before crack propagation (b) After crack propagation. (After Andrews, Chapter 9, in Polymer Science ed. Jenkins, North-Holland, 1972.)...

To make the flaw grow, say by 1 mm, we have to tear the rubber to create 1 mm of new crack surface, and this consumes energy the tear energy of the rubber per unit area X the area of surface torn. If the work done by the gas pressure inside the balloon, plus the release of elastic energy from the membrane itself, is less than this energy the tearing simply cannot take place - it would infringe the laws of thermodynamics. 

This behavior is similar to the cut growth and fatigue behavior of rubber compounds. The rate of the growth of a cut is a function of the tearing energy [38,39] which itself is proportional to the stored elastic energy density in the test piece. The exact value depends on the shape of the test piece. 

The tearing apart or breaking down of rubber compound on a cracker. 

Any substance used to prevent sticking of rubber to a mould surface, thus facilitating removal of the product without risk of tearing or splitting. The lubricant may be painted or sprayed on the mould surface or applied to the surface of the... 

Tearing out of small areas of rubber from the surface of a rubbered fabric, during the subsequent assembly of the uncured product. 

The injection-compression process is an important variation in which rubber is injected into a partly closed mould under low pressure used for moulding-on of rubber soles to footwear uppers. Rubber is injected into a gap between the shoe upper and the sole plate, which is held 3-4 mm wider than it would be in its final position. After injection at the first mould station of a multistation machine the sole plate is closed in the manner of compression moulding at the second mould station and rubber is pressed along the sole and over the toe cap. The importance of the process is that it becomes possible to mould without using normal high injection pressures which tear and distort canvas, leather or synthetic uppers. 

Loadman J (2005) Tears of the tree. The story of rubber - a modem marvel. Oxford University Press, Oxford... 

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