Rubber flex resistance tests

Neoprene is the generic name for polychloroprene rubber. It has been produced commercially since 1931 and had rapid and wide acceptance because it is much superior to natural rubber for heat and oil resistance. Heat resistance is far better than NR, BR or SBR. but less than EPDM. When heated in the absence of air, neoprene withstands degradation better than other elastomers which are normally considered more heat resistant, and retains its properties fifteen times longer than in the presence of air. Compression set at higher temperature is better than natural rubber and 100°C is typically the test temperature rather than 70°C. Abrasion resistance is not as good as natural rubber but generally better than most heat resistant and oil resistant rubbers. This is also true for tear strength and flex resistance. 

In dynamic testing of ozone resistance, a fabric-backed vulcanized rubber specimen is continuously flexed in the ozone chamber over a roller. The fabric backing is in the form of a belt. Any protective chemical films (e.g., certain waxes and antiozonants) that might build up on the surface of the specimen in static testing are quickly broken by the continuous flexing. ASTM test method D 1149 covers static testing and D 3395 covers dynamic testing in a controlled ozone atmospheres. 

The slow-bend brittle point test does not have the same practical significance as the BeU Telephone Laboratories brittle point test because most rubber articles which are exposed to low temperatures in service are required to withstand fairly rapid flexing. If the slow-bend brittle point test were used as a criterion of the cold resistance of these rubber articles, it might qualify the rubbers for a lower temperature than they could safely withstand in service (Morris et al. 1944). 

Hardness/Flexural Strength - The analogous resistance to elastomer chain deformation accounts for the increase in rubber hardness obtained in proportion to filler loading, surface area, structure activity/surface treatment, and structural anisometry. Hardness is typically measured as resistance to surface indentation under specific conditions, so the force is supplied as a point of compression rather than an area of tension. Similar filler particle dynamics apply, nevertheless. Flexural strength is likewise related as a measure of a sample s resistance to deformation (flex) imder a compressive force. With a force supplied to an end-supported test sample, the upper surface is under compression and the lower surface is in tension... 

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