Vulcanization tearing

There is a definite trend in the suppHer industry to develop multifimctional materials with value-added properties. One suppHer has introduced a modified hydrocarbon resin that softens, improves filler incorporation, improves mill banding, and increases tack in the green compound while imparting increased low strain (<100%) stiffness, significantly improving tear resistance in the vulcanized compound. 

NR adhesives perform adequately under peeling stresses. The peel strength can vary from a few N/m in PSA formulations to substrate tear in vulcanized compounds used in hose, belting and tire products. 

One-step vulcanization, wide range of curing conditions, high loading elasticity, snappiness, no deformation, weatherability. ozone resistance, heat resistance, tear resistance, coating performance, adhesive properties, skid resistance, abrasion resistance... 

Mooney viscometer is also used to measure the time it takes, from initial exposure of the compound to a particular temperature, to the time of onset of cure at that temperature [2]. This is known as the scorch time. Scorch time is an important parameter to the rubber processor, as a short time may lead to problems of premature vulcanization. As the test is taken past the onset of cure, the rotor tears the cured rubber, and therefore this device cannot be used to investigate rheological properties after the scorch time. 

ISO 34-1 2004 Rubber, vulcanized or thermoplastic - Determination of tear strength -Part 1 Trouser, angle and crescent test pieces... 

In all the above methods, it is necessary to cure specimens of test samples for each of a series of curing times and then perform the desired test on the vulcanizate. However, in the test for continuous measurement of vulcanization complete information could be obtained with saving in time. The mooney viscometer test approaches this objective. However a weakness of the mooney viscometer test is that the test is completed before a measurable modulus value after the scorch point has been obtained. This is because the test sample is destroyed after the induction period is passed due to tearing by continuous rotation of the rotor whether small or large. To overcome this deficiency and to provide a total cure curve for the entire vulcanization cycle, a series of instruments called cure meters was developed. In each of these instruments the stiffness or modulus of the compound was chosen as parameters for vulcanization continuously. The Vulkameter developed by Bayers, Germany was the first of the cure meters developed. 

The second class includes tests for ageing, oxygen and ozone attack, adhesion, resistance to wear and tear, fatigue, etc. This class also includes tests under simulated service conditions under laboratory environments and immersion in fluids. These two classes of tests are conducted on vulcanized rubber. 

This is due to over-vulcanization. The remedy is to reduce cure times and temperatures or modify the compound formulation to reduce the speed of cure. Tearing can also be due to method of removal of the product from the mould while it is in hot condition. Tearing can be eliminated by removing the products from the mould after sufficient cooling or by careful and slow removing. 

Reinforcement - The stiffening effect of solids, such as carbon black, on an unvulcanized elastomer mixture and the enhancement of the physical properties of the vulcanized compound, such as tensile, elongation, modulus, abrasion resistance, tear, etc. 

ASTM D624, 2000. Tear strength of conventional vulcanized rubber and thermoplastic elastomers. 

Rubber, vulcanized or thermoplastic Determination of tear strength... 

Part 1 Trouser, angle, and crescent test pieces Part 2 Small (delft) test pieces Standard test method for tear strength of conventional vulcanized rubber and thermoplastic elastomers Testing of rubber and elastomers Determination of the tear strength of elastomers Trouser test piece... 

An HAF carbon black, N347, was selected for use as the primary filler. This was primarily because HAF blacks gave satisfactory adhesion of vulcanized chlorobutyl rubbers to metal, and good tensile and tear properties. 

Ethylene and propylene monomers combine to form the saturated and stable backbone [4], This saturated backbone will provide excellent heat, oxidation, ozone, and weather aging because no reactive double bonds are in the backbone structure [4], The third monomer (ENB) is added in a controlled manner and provides a site for cross-linking via the double bond. The M in EPDM refers to a saturated backbone. By virtue of the ENB, various amounts of vulcanization can be obtained to acquire the durometer, tear strength and tensile and other properties needed for the sealing or isolation needs of the automobile part. 

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