Hydrocarbon rubbers

Reaction of the natural rubber hydrocarbon with hydrochloric acid yields rubber hydrochloride. The hydrogen chloride adds on according to Markownikoff s rule (that the halogen atom attaches itself to the carbon atom with the least number of hydrogen atoms). 

Moorite Propellant. A series of rocket proplnts submitted to PicArsn for evaluation in 1949. They consisted of an oxidizer (such as K perchlorate) 70, and a cured rubber hydrocarbon plus accelerators, 30%. Although the examined samples proved to possess desirable props for rocket proplnt use, their thermal stability was poor and their press exponent undesirably high. It was concluded that further work was required on the method of prepn to eliminate these defects... 

Expressed in gram mole/gram rubber hydrocarbon X105. 

The French word for rubber, formerly used to denote highly purified natural rubber, also termed rubber hydrocarbon. 

A hard resinous thermoplastic substance of the same chemical composition as rubber hydrocarbon but having the ftvms-structure. See Cis-trans Isomerism. Formerly extensively used for the insulation of submarine cables (now superseded by polyethylene) and in the early manufacture of golf balls (now superseded by... 

Relative ranking of crosslink densities - The apparent crosslink density was determined by swelling the rubber samples in toluene as solvent. The vulcanized samples of 20 x 20 mm2 size were cut from a 2 mm sheet and immersed in 100 mL of toluene at room temperature for 72 h [51]. The solvent was renewed after 24 h. The sample was removed, blotted quickly with filter paper, and weighed. The samples were collected and left for 24 h in vacuo at 105°C to evaporate the solvent. The swelling value Q, defined as grams of toluene per gram of rubber hydrocarbon, was calculated as ... 

Source Percentage of rubber hydrocarbon Specific gravity Percentage sulphur... 

The percentage sulphur (determined in the un-vulcanized reclaim) and the available rubber hydrocarbon are taken into consideration while evolving the compound formulation. It should be noted that reclaimed rubber is not all rubber. In arriving at the total rubber content in the rubber formulation containing reclaim, allowance must be made for its rubber content. For example in the following blend of smoked sheet and whole tyre reclaim, the total rubber content is to be considered as 100 parts instead of 125 parts as below and the proportion of other ingredients should be worked out accordingly on "parts per hundred rubber" (phr) basis. 

Bekkedahl, N., and H. Matheson Heat capacity, entropy and free energy of rubber hydrocarbon. J. Research Natl. Bur. Standards 15, 503—515 (1935). 

NR latex contains about 35wt% natural rubber hydrocarbon as particles that are about 1 pm in diameter and about 5% non-rubber components... 

Tewari, Y. B. Schreiber, H. P., "Thermodynamic Interactions in Polymer Systems by Gas-Liquid Chromatography. II. Rubber-Hydrocarbons," Macromolecules, 5, 329 (1972). 

Vulcanizate Components. A rubber powder (50-100 micron grain size) recovered from old tires was used. The composition of this material was 55 percent rubber hydrocarbon, 14 percent acetone extractables... 

Vulcanization was discovered in 1846 by Charles Goodyear in the U.S. and simultaneously by Thomas Hancock in England. Its overall effect is to convert rubber hydrocarbon from a soft, tacky, thermoplastic to a strong, temperature-stable thermoset having unique elastic modulus and yield properties. 

Significant developments in synthetic rubber began at this time. Outstanding were the introduction of polychloroprene (neoprene) by Carothers, and of the oil-resistant polysulfide rubber Thiokol by Patrick. These were soon followed by styrene-butadiene copolymers, nitrile rubber, butyl rubber, and various other types, some of which were rushed into production for the war effort in the early 1940s. The stereospecific catalysts researched by Ziegler and Natta aided this development, including synthesis of true rubber hydrocarbon (polyisoprene). Since 1935 synthetic rubbers have been referred to as elastomers. 

The best grades of raw rubbar (pate crepe or smoked sheet) contain about 95% rubber hydrocarbon. The rest consists of proteins (2-3%), acetone-sol resins and fatty acids (2%), small amounts of sugar and a tittle mineral matter. Vulcanization, which consists of heating rubber with ] -3% of sulfur, introduces cross links between chains to produce a three-dimensional lattice of improved elasticity, strength, and temp sensitivity. Accelerators such as zinc dimethyldithiocarbamate greatly decrease the time or lower the temp required for vulcanization. 

The density of natural rubber is about 0.913 g per cc, and its bulk density is about 0.85 g per cc. The rubber hydrocarbon content of raw natural rubber is about 94%. The presence of small quantities of non-rubber constituents such as proteins, fats, fatty acids, carbohydrates, and mineral matter in natural rubber influences its physical and chemical properties. 

Synonyms rubber hydrocarbon styrene-butadiene copolymer acrylate resins polyvinyl acetate ... 

Ethylene + EPT rubber Hydrocarbon Coordination 200-500 100 Steam coagulation... 

There are obvious differences between accelerated vulcanization and unaccelerated vulcanization. (Greater crosslinking efficiencies and greater crosslinking rates are obtained with accelerated vulcanization.) But there are more subtle differences. Results from model reactions with curing ingredients indicate that sulfur becomes attached to the rubber hydrocarbon almost exclusively at allylic positions (Skinner, 1972). This is not the case with unaccelerated-sulfur vulcanization, thus ... 

The authors collected the test data shown in Table 9.10. From these data it can be noted that the number-average molecular weight, or Af , of a commercial emulsion SBR such as IISRP 1500 or 1712 is typically 90,000-175,000. The primary molecular weight of a solution-polymerized polymer produced with an anionic lithium catalyst can, in contrast, be increased toward 250,000 without gelation. In addition, emulsion-polymerized SBR contains only about 92% rubber hydrocarbon as a result of the presence of residues from the production process solution polymers tend to be near 100% hydrocarbon. As a consequence, the authors concluded that the number-average molecular weight... 

Rubber Hydrocarbon Content in Liner HIIR/IIR, % vol Liner Permeability (O X 10 ) at 65 C-F Equilibrium Intracarcass Pressure (lOF) (MPa) FMVSS 109 Step-Load Hours to Failure... 

---