Failure rubber

Adhesive Studies. The DHA-4VP copolymers had excellent properties as adhesion promoters for rubber-steel (brass-coated) composites (Table VII). The adhesion values of 44.8-47.6 lbs approach the limit of the test, i.e. rubber failure may occur at 45-50 lbs. The adhesion values listed in Table VII are the optima obtained in numerous tests in which pH, type of RF latex resin, curing temperatures, etc. were varied. Adhesion values ranged from the lower forties to the upper thirties, and coverages were in the 3+ range. 

There are two further constraints to be considered. These relate to the hardness or viscosity of the strip and to the stack height of the strip in its container Uncured rubber is thermoplastic and will flow under the pressure of its own weight. This flow behaviour can lead to strip adhesion problems on the lower levels of the stack. The effect is time and temperature related, and must be controlled through the size of container and accurate scheduling to avoid prolonged storage of the prepared rubber. Failure to control properly the stock presentation will provide the press operator with extra work separating strips, and cause component rejects. 

Excellent tack, good strength. Shear strength 30-180 Ib/in. peel strength 0.56 Ib/in. width. Surface can be tack-free to touch and yet bond to similarly coated surface Low cost, widely used. Peel strength higher than natural rubber failure occurs under relatively low constant loads... 

Adhesion. Commercially available one- or two-coat adhesive systems produce cohesive rubber failure in bonds between ethylene-acrylic elastomer and metal (16). Adhesion to nylon, polyester, or aramid fiber cord or fabric is greatest when the cord or fabric have been treated with carboxylated nitrile rubber latex. 

The fourth is rubber failure, where the strength of rubber is lessthan the bond strength. 

Rubber failure (R) is the type of failure to strive for. It indicates cohesive failure of the rubber. This means that the bond between the rubber and the adhesive is stronger than the tear strength of the rubber. 

Whatever the particular failure mode seen in a part, the goal of the process engineer is generally to work towards maximising the amount of rubber failure and minimise the amount of failure at the other interfaces. 

Rubber failure upon application of stress is delayed by i) viscoelastic energy dissipation and il) crystallization upon strain of the base polymer. A peculiar rubber failure, namely fatigue failure, is also affected by the same factors. The presence of carbon black or other reinforcing agents does not diminish the contribution of the base polymer on fatigue resistance. 

Rubber failure by application of stress has been studied extensively owing to its overwhelming scientific and practical interest. In particular, two mechanisms have been pul- forward as relevant in delaying rubber failure. The first mechanism is based on viscoelastic energy dissipation, which can be increased by increasing the glass transition of the base polymer, or by other routes such as the use of additives or controlled network imperfection. The second mechanism is... 

Limiting our analysis to the effect of the base polymer on rubber failure, the polymer structure could be tailored as a dissipative one by increasing Tg up to the maximum value acceptable for an elastomer or toward a strain crystallizable structure by increasing the microstructure regularity up to a point in which a rapid strain induced crystallization is achieved. 

A base polymer particularly interesting for studying the effect of the aforementioned mechanisms on rubber failure is polybutadiene. In fact, polybutadiene microstructure can be changed in an extremely wide range, by making use of the host of catalyst systems. developed by the ingenuity of chemists, just starting with the same monomer. 

Evaporation of Low cost, widely used peel strength higher than natu-solvent ral rubber failure occurs under relatively low con-... 

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