Rubber selection

USE Convenient lab source of cyanic acid gas. In prepn of melamine, sponge rubber. Selective herbicide. Very toxic to certain types of barley and radishes. 

The penetration grade, softening point, and ductility of the GRT-modified bitumens were studied as a function of rubber selection, temperature, rotational speed, shearing time, order of rubber, and oil addition (Li et al 2009). It was established that a shearing time of 40 min, a temperature of 180" C, a rotational speed of7000 rpm, and a rubber concentration below 25 wt.% with oil content below 4 wt.% were optimal for carrying out the technological process for preparation the GRT-modified asphalts. 

THERMAL CONDUCTIVITY OF SOFT VULCANIZED NATURAL RUBBER, SELECTED VALUES. FROM ADVANCES IN THERMOPHYSICAL PROPERTIES AT EXTREME TEMPERATURES AND PRESSURES. 

THERMAL CONDUCTIVITY OF SOFT VULCANIZED NATURAL RUBBER. SELECTED VALUES. 

W. J. McKillip and C. N. Impola, Compositions made from (A) Isocyanate-Terminated Prepolymers and (B) Polyesters Prepared from Polyols and a, Ethylenically Unsaturated Monocarboxylic Acids, U.S. Pat. 3,396,210 (1968). IPN-type compositions. P. Mendoyanis, Thermosetting Compositions Containing a Liquid Rubber Selected from Polysulfide, Polymercaptan, and Chlorinated Polyethylene. Together with an Epoxide and Curing Agent, U.S. Pat. 3,316,324 (1967). SIN compositions of epoxy and polysulfide rubber. 

Use of a rubber selection guide should be the first step, since most of the critical properties of a rubber are intrinsic. 

Silicone rubber is soft and elastic. For this reason, silicone rubber membranes are made as composite structures of the type shown in Figure 21.3. A nonwoven support paper provides mechanical strength. The pores of this paper arc too large to be coated directly with the sihcone rubber selective layer, which is usually less than 5 p-m, and sometimes less than 1 pm, thick. Instead, the paper is first coated with a finely microporous ultrafiltration support membrane. This membrane provides a smooth surface on which the very thin sihcone rubber layer can be coated. The permeance of the support membrane is usually 10- to 1000-fold higher than that of the selective sihcone rubber layer, so the overall resistance to flow is predominantly in the sihcone rubber layer. 

Vulcanized Natural Rubber, Selected Values , in Advances in Thermophysical Properties at Extreme Temperatures and Pressures , Ameriean Soeiety of Mechanical Engineers, New York, 1965 Rubber Chem. Technol., 39, 126 (1966). 

The first is an easy processing, low cost compound. The grade of rubber selected cures faster than low-unsaturation grades, accommodates the high oil loading needed to prevent cold buckling and provides excellent ageing and air retention. 

The radiation and temperature dependent mechanical properties of viscoelastic materials (modulus and loss) are of great interest throughout the plastics, polymer, and rubber from initial design to routine production. There are a number of laboratory research instruments are available to determine these properties. All these hardness tests conducted on polymeric materials involve the penetration of the sample under consideration by loaded spheres or other geometric shapes [1]. Most of these tests are to some extent arbitrary because the penetration of an indenter into viscoelastic material increases with time. For example, standard durometer test (the "Shore A") is widely used to measure the static "hardness" or resistance to indentation. However, it does not measure basic material properties, and its results depend on the specimen geometry (it is difficult to make available the identity of the initial position of the devices on cylinder or spherical surfaces while measuring) and test conditions, and some arbitrary time must be selected to compare different materials. 

Table 10.4 Resistance of Selected Polymers and Rubbers to Various Chemicals...

D. M. Byrd and W. A. Carter iu W. A. Carter, ed.. Selective Inhibitors of Viral Function, Chemical Rubber Co. Press, Qeveland, Ohio, 1973, p. 329. 

S. Monthey and X. Zhang, Carbon Black Selection for Industrial Rubber Applications, at the CL Meeting of the 147th Rubber Division, Philadelphia, Pa., May 2—5, 1995, American Chemical Society, Washington, D.C. 

R. R. Juengel, Carbon Black Selection for Conductive Bacbber Compounds, Paper No. 78, Rubber Division, ACS Meeting, Los Angeles, Calif., Apr. 1985. 

Now for some real numbers. Table 3.1 is a ranked list of Young s modulus of materials - we will use it later in solving problems and in selecting materials for particular applications. Diamond is at the top, with a modulus of lOOOGPa soft rubbers and foamed polymers are at the bottom with moduli as low as 0.001 GPa. You can, of course, make special materials with lower moduli - jelly, for instance, has a modulus of about 10 GPa. Practical engineering materials lie in the range 10 to 10 GPa - a... 

In this chapter we introduce the main engineering polymers. They form the basis of a number of major industries, among them paints, rubbers, plastics, synthetic fibres and paper. As with metals and ceramics, there is a bewilderingly large number of polymers and the number increases every year. So we shall select a number of "generic" polymers which typify their class others can be understood in terms of these. The classes of interest to us here are ... 

Figure 9.2. Heal deflection temperatures under a load of 1.82 MPa for selected polymers. Note that incorporation of glass fibre has a much greater effect with crystalline polymers than with amorphous ones (after Whelan and Craft courtesy of British Plastics and Rubber)...

In effect this means that, to achieve reasonable toughness, semicompatible rubbers should be used. Semicompatibility may be achieved (a) by selecting mixtures of slightly different solubility parameter from the polystyrene, (b) by... 

If polypropylene is too hard for the purpose envisaged, then the user should consider, progressively, polyethylene, ethylene-vinyl acetate and plasticised PVC. If more rubberiness is required, then a vulcanising rubber such as natural rubber or SBR or a thermoplastic polyolefin elastomer may be considered. If the material requires to be rubbery and oil and/or heat resistant, vulcanising rubbers such as the polychloroprenes, nitrile rubbers, acrylic rubbers or hydrin rubbers or a thermoplastic elastomer such as a thermoplastic polyester elastomer, thermoplastic polyurethane elastomer or thermoplastic polyamide elastomer may be considered. Where it is important that the elastomer remain rubbery at very low temperatures, then NR, SBR, BR or TPO rubbers may be considered where oil resistance is not a consideration. If, however, oil resistance is important, a polypropylene oxide or hydrin rubber may be preferred. Where a wide temperature service range is paramount, a silicone rubber may be indicated. The selection of rubbery materials has been dealt with by the author elsewhere. ... 

Information about this splendid compilation came to me from a chemist, Robert Weast (1985), who was editor from 1952 until 1988... 37 years He also informed me that the creation (jointly by the American Chemical Society and the American Institute of Physics) of the Journal of Physical and Chemical Reference Data, which began publication in 1972, was encouraged by the results of a survey which indicated how widely the Rubber Bible was used. Weast describes this journal as a truly outstanding source of critically evaluated data . In saying this, he underlined the crucial role of editors and contributors critical judgment in selecting data for such compilations. David Tide, the editor of the journal, in 1989 succeeded Robert... 

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