GR-rubber

Polyesters from propylene glycol and dicarboxylic acids, especially adipic and sebacic acid, are commercial products suggested for PVC as well as for cellulose esters. The well known Paraplex resins of Rohm Haas, which are compatible with nitrile and GRS rubber, belong to this group. Other products are the Ultramolls of Farbenfabriken Bayer. Some polyesters of this type have a tendency to exude on storage, especially if esterification is not complete. 

Chain transfer reduces the average molecular weight of the polymer without wasting initiator radicals. Dodecanethiol has considerable use in the manufacture of GRS rubber (Section 13-4) as a regulator to hold down the molecular weight in the emulsion polymerization of 1,3-butadiene and ethenylbenzene. 

Notwithstanding its deficiencies as an incendiary, phosphorus has a certain tactical value because of the power of obscuration caused by the volatility of its final combustion product, phosphorus pentoxide (PgOs), the spontaneous re-ignitibility of doused, unburned residues, and the severity of the wounds caused by burning phosphorus when it comes in contact with human skin. Its burning properties can be improved by mixing it with synthetic (GRS) rubber, a mixture called plasticized white phosphorus (PWP). ... 

While at Goodyear, Flory investigated chain transfer which was essenti for controlling the chain lengths of GRS rubber (SBR). He also expanded the Flory-Hu ns theory to evaluate the free energy requirements for the overlap of polymer coils (9). Flofy, Hke other experts in the field of polymer sdence, recognized that fundamental principles of macromolecules were not limited to rubber, fiber or plastics but included biopolymers as well. 

Their efforts were mainly directed toward a continuous polymerization system. On our return to America, the rubber group here adapted this redox system to low temperature polymerization and the present process for the polymerization of styrene and butadiene in emulsion at 0 to 5 developed. This greatly improved the quality of our GRS rubber and made it very satisfactory for use in building passenger car tires. 

Figure 18 Relative change in glass-transition temperature vs, stretch X for various values of Gjl Cp r(l) = Y, as indicated. Experimental data are from Gee et al. Circles are for natural rubber, for which Y = 0.0032 squares are for GRS rubber, for which Y = 0.0012 the triangle is for Hycar, for which Y = 0.005, (after ref. 59, with permission)...

Mix 50 ml. of formalin, containing about 37 per cent, of formaldehyde, with 40 ml. of concentrated ammonia solution (sp. gr. 0- 88) in a 200 ml. round-bottomed flask. Insert a two-holed cork or rubber stopper carrying a capillary tube drawn out at the lower end (as for vacuum distillation) and reaching almost to the bottom of the flask, and also a short outlet tube connected through a filter flask to a water pump. Evaporate the contents of the flask as far as possible on a water bath under reduced pressure. Add a further 40 ml. of concentrated ammonia solution and repeat the evaporation. Attach a reflux condenser to the flask, add sufficient absolute ethyl alcohol (about 100 ml.) in small portions to dissolve most of the residue, heat under reflux for a few minutes and filter the hot alcoholic extract, preferably through a hot water fuimel (all flames in the vicinity must be extinguished). When cold, filter the hexamine, wash it with a little absolute alcohol, and dry in the air. The yield is 10 g. Treat the filtrate with an equal volume of dry ether and cool in ice. A fiulher 2 g. of hexamine is obtained. 

Dissolve 180 g. of commercial ammonium carbonate in 150 ml. of warm water (40-50°) in a 700 ml. flask. Cool to room temperature and add 200 ml. of concentrated ammonia solution (sp. gr. 0 88). Introduce slowly, with swirling of the contents of the flask, a solution of 50 g. of chloroacetic acid (Section 111,125) in 50 ml. of water [CAUTION do not allow chloroacetic acid to come into contact with the skin as unpleasant burns will result]. Close the flask with a solid rubber stopper and fix a thin copper wire to hold the stopper in place do not moisten the portion of the stopper in contact with the glass as this lubrication will cause the stopper to slide out of the flask. Allow the flask to stand for 24-48 hours at room temperature. Transfer the mixture to a distilling flask and distil in a closed apparatus until the volume is reduced to 100-110 ml. A convenient arrangement is to insert a drawn-out capillary tube into the flask, attach a Liebig s condenser, the lower end of which fits into a filter flask (compare Fig.//, 1) and connect the... 

Styrene-butadiene rubber (SBR) is also known as government rubber styrene (GRS) and Buna S. 

Initially, all of the SBR polymer known as GR-S produced during World War II was by the batch process. Later, it was thought that a higher volume of polymer would be needed for the war effort. The answer was found in switching from batchwise to continuous production. This was demonstrated in 1944 at the Houston, Texas, synthetic mbber plant operated by The Goodyear Tire Rubber Company. One line, consisting of 12 reactors, was lined up in a continuous mode, producing GR-S that was mote consistent than the batch-produced polymer (25). In addition to increased productivity, improved operation of the recovery of monomers resulted because of increased (20%) reactor capacity as well as consistent operation instead of up and down, as by batchwise polymerisation. 

In 1942 the Japanese overran Malaya and the then Dutch East Indies to cut off the main sources of natural rubber for the United States and the British Commonwealth. Because of this the US Government initiated a crash programme for the installation of plants for the manufacture of a rubber from butadiene and styrene. This product, then known as GR-S (Government Rubber-Styrene), provided at that time an inferior substitute for natural rubber but, with a renewed availability of natural rubber at the end of the war, the demand for GR-S slumped considerably. (Today the demand for SBR (as GR-S is now known) has increased with the great improvements in quality that have been made and SBR is today the principal synthetic rubber). 

Amberlang, J.C. and Smith, G.E.P., Jr., Behavior of reclaiming agents in sulfur and nonsulfur GR-S vulcanizates, Rubber Chem. TechnoL, 28, 322, 1955. 

Fig. 90.—The force of retraction at 25°C and its internal energy component for gum-vulcanized GR-S synthetic rubber. Upper curve, total force / middle curve, dE/dL)T,p from the intercepts of force-temperature plots at constant length lower curve, dE/dL)T.v from the intercepts of stress-temperature plots at constant elongation. (Roth and Wood. )...

The equilibrium tension r at a = 2 for GR-S synthetic rubber vulcanized in this manner is plotted in Fig. 99 against the mole fraction (pXlOO) of units cross-linked. The straight line has been calculated... 

The results of Cohan on the force of retraction r at a = 1.5 for GR-S synthetic rubbers vulcanized with various proportions of a calcium carbonate filler are shown in Fig. 104. The agreement with the theoretical curve drawn according to Eq. (52) is good. In further confirmation of the theory, variations in average particle diameter... 

Fig. 104.—Tension r at O = 1.5 for GR-S synthetic rubber containing various proportions of calcium carbonate (particle diameter 3900 mju), but vulcanized under otherwise identical conditions. The solid curve has been calculated according to Ed. (52) the broken curve by neglecting the third term in this equation. (Cohan. s)...

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