Vulcanization Test

Vulkanisatjons-mittel, n. vulcanizing agent, -probe, /. vulcanizing test or sample, -ver-zdgerung, /. retardation vulcanization. 

Vulcanization tests are aimed at determining the behaviour of the compound during these three phases of vulcanization cycles. 

The classical means for following vulcanization by physical methods is to vulcanize a series of sheets for increasing time intervals and then measure the stress strain properties of each and plot the results as a function of vulcanization time. A modification of this test generally called a rapid modulus test is widely used in the industry as a production control test. A single sample taken from a production batch of compounded rubber is vulcanized at a high temperature and its tensile modulus is measured. Temperatures as high as 380°F are used to reduce the vulcanization test time to only a few minutes. Any modulus value deviating from a predetermined acceptance limit indicates that the batch is defective and is to be rejected. 

Wise R.W, Processing and Vulcanization Tests, Rubber Technology by Mourice Morton, 1973, Van Nostrand Reinhold Company. 

Method A is examination at 30x magnification with a binocular microscope and an optional camera. Illumination is at an oblique angle of 30° to accentuate the surface detail. The test piece is cut by a razor blade and vulcanized or unvulcanised material can be used. In the latter case, the sample is first compressed to minimize trapped air and the blade is heated. Warning is given that the result may not be the same as when using a vulcanized test piece. The result is compared to a set of standard photographs that are given in the standard. 

Rubber is a popular closure component, and additives such as vulcanizers, pigments (qv), or antioxidants may leach into the product. In cases where mbber closures are penetrated by needles in dosing, bits of the closure (coring) could enter the product. Thus, such closure components must be sufficiendy tested before use. 

There are many ways to measure these properties and some of them are proprietary. However, most laboratory tests are standardized by American Standard Testing Methods (ASTM). Many of them are interactive to various degrees. The rate and state of vulcanization is especially important to consider for components of heavier and thicker tines. The heat used to vulcanize the tine in a mold under pressure requites time to penetrate from both sides of the giant tine to the innermost portions. Securing a balanced state of cure, ie, the maximizing of physical properties in all the components, results in the innermost components having a faster rate of cure. The peripheral compounds should have a cure system which holds its physical properties well when overcured. 

Changes observed in the composition of the rubber/brass interphase correlated well with results of adhesion tests carried out on brass-plated steel wires embedded in blocks of rubber [46]. The force required to pull the wires out of the blocks decreased steadily as vulcanization temperature increased. This effect was especially pronounced when the specimens were aged at elevated temperature and humidity for several days before the wires were pulled out of the rubber blocks. 

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. 

Lord Kelvin s close associate, the expert experimentalist J. P. Joule, set about to test the former s theoretical relationship and in 1859 published an extensive paper on the thermoelastic properties of various solids—metals, woods of different kinds, and, most prominent of all, natural rubber. In the half century between Gough and Joule not only was a suitable theoretical formula made available through establishment of the second law of thermodynamics, but as a result of the discovery of vulcanization (Goodyear, 1839) Joule had at his disposal a more perfectly elastic substance, vulcanized rubber, and most of his experiments were carried out on samples which had been vulcanized. He confirmed Gough s first two observations but contested the third. On stretching vulcanized rubber to twice its initial length. Joule ob-... 

Fig. 7. Test specimens of vulcanized poly(HAMCL), based on tall oil fatty acids (TOFA)...

Scorch resistance, in vulcanization, 22 811 Scorch time, in vulcanization, 22 803 SCORE cleaning system, 24 22 Scotch-Marine boiler, 22 319 Scouring, 9 171, 183, 189, 192, 197 of fibers, 22 180 in wool processing, 26 384-385 Scoville Heat test, 23 159 Scrap... 

The pigments are also required to have a specific heat resistance. This is tested on five colorations with different pigment concentrations in the range 0.01 to 1% together with 10 times the amount of chalk. The colorations placed side by side are vulcanized hot for 15 minutes at 140°C and evaluated coloristically against the corresponding untreated comparison coloration. 

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