Rubber abrasion

Isoprene occurs in the environment as emissions from vegetation, particularly from deciduous forests, and as a by-product in the production of ethylene by naphtha cracking. In the United States, the total emission rate of isoprene from deciduous forests has been estimated at 4.9 tonnes per year, with greatest emissions in the summer. The global annual emission of isoprene in 1988 was estimated to be 285 000 thousand tonnes. Isoprene is produced endogenously in humans. It has also been found in tobacco smoke, gasoline, turbine and automobile exhaust, and in emissions from wood pulping, biomass combustion and rubber abrasion (United States National Library of Medicine, 1997). 

In researching resistance on rubber abrasion, a Martindale tester is used for com-parasions of various rubber samples. Five types of rubbers have been tested in five cycles on four tester positions. Design of experiment for five rubber types and five test cycles is the Youdens square shown in Table 2.85... 

It is evident that factor and blocks have no statistically significant effect. However, between sample positions on the tester there exists a statistically significant difference. Position D gives much higher rubber abrasions, which may mean that samples of rubber have not been mounted properly in this position. 

Other than the wear problems, actual in-plant maintenance usually involves removal of wood, pieces of blasting wire, and other trash from the ports. When a reagentized feed is used, layers of oily reagents can build up on the spiral surface and sometimes require scrubbing for removal. With feeds containing oily reagents that attack rubber, abrasion-resistant alloy spiral sections are used. 

Use Roofing, blackboards (as powder) filler in paint, rubber, abrasive. 

MAJOR PRODUCT APPLICATIONS paints, coatings, rubber, abrasive polishes, cleaning waxes, seed coatings, anticaking agent, antiblock applications, pesticide formulations, asphalt extender, automotive windshields, catalyst support, concrete additive, dental molds, drilling mud, filter papers and pads, specialty p ers, paperboard, foundry, waste disposal aids, stucco, battery boxes, plastic film... 

A physical model of rubber abrasion in unsteady state and the corresponding processes of tongue ruptured are shown in Figures 2 and 3 respectively. As seen from Figure 3,... 

Wear Curve Description of General Process of Rubber Abrasion... 

From the physical processes of rubber abrasion and its mathematic description, it can be deduced that a general process of rubber abrasion might be regarded as consisting of three stages and expressed correspondingly in terms of a wear curve (Figure A) ... 

This is the wear equation of rubber abrasion in unsteady state. Assuming that the steady state has been reached when the number of revolution is equal to N, on the basis of Equations(14,a) and (14,b), the sum of volume loss of a tongue after another N revolutions, i.e., from N to 2N revolutions, can be calculated by... 

However, in this equation, the spacing of ridges is S instead of S as it is considered to be unchanged only if the frictional force is kept constant. Obviously, in this case, S = Sjj. Inserting Equations (18), (23), (4), and (21) into the equation above, the wear equation of rubber abrasion in steady state is given by... 

Comparing Equation (22) with Equation (25), as will be readily seen, the term, k o(N, k)> the characteristic of rubber abrasion in unsteady state. It can be termed characteristic function of unsteady state, denoted tJ(N, jr). Thus,... 

In general, the number of revolutions corresponding with the critical point to transform the wear state from unsteady to steady, is a constant under otherwise identical conditions. Hence, it can be considered as a state criterion of rubber abrasion, then... 

Oh the basis of the physical processes and mathematic description of rubber abrasion stated above, a theoretical relationship between N and can be obtained through the use of numerical calculation under the condition of = r, as shown in Figure 11. Moreover, it can be approximately represented as follows... 

A wear curve can be used to describe the general process of rubber abrasion in which it is divided into three regions unsteady, steady and damage stage. 

The wear equation of rubber abrasion in steady state reveals the basic correlation among the material property, running condition and wear characteristic. The wear rate increases with an increase in the frictional force, however, it is inversely proportional to the tensile strength. 

The characteristic function, f (N,6 ), is a characterizing factor of rubber abrasion in unsteady state. Its value increases with an increase in the number of revolutions and tensile rupture ratio. However, it approaches unity as a limit in the unsteady-state process of wear. Hence, a steady state is reached if once 1 (N,6j ) = 1. 

Figure 11. State criterion of rubber abrasion plotted against...

The number of revolutions transformed the wear state from unsteady to steady can be regarded as a state criterion of rubber abrasion to estimate the wear characteristics of rubber under identical r jnning conditions. It was found to be proportional to a negative exponent of the tensile rupture ratio. 

It is concluded that the theory proposed can be applied to clarify the phenomena and processes of rubber abrasion in different stages of wear by a line contact. 

Zhang, S. W. Mechanisms of rubber abrasion in unsteady state, Rubber Chem. Technol., to be published. 

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