CREPE RUBBER

Crumb/block Sheet/crepe rubber rubber... 

Comminuted and other new process rubbers. In these cases the coagulum is broken up and then dried. The rubber is then packed in flat bales similar in size to those used for the major synthetic rubbers (70-75 lb) unlike the heavier square bales used with smoked sheet and crepe rubbers. 

Heveaplus MG has a higher polarity than NR and it is usually used as primer for NR solutions to increase the adhesion of PVC and synthetic upper materials in crepe rubber soles in footwear. 

Cremor tsrtaru cream of tartar. Cr pekautschuk, m. n. crepe rubber. Cresylaaure,/. cresylic acid (cresol). 

Rubber is a polymer of isoprene (15). Natural rubber is obtained from the bark of the rubber tree as a milky white liquid, which is called latex (Fig. 19.8) and consists of a suspension of rubber particles in water. The rubber itself is a soft white solid that becomes even softer when warm. It is used for pencil erasers and was once used as crepe rubber for the soles of shoes. 

A substance added to latex in the preparation of pale crepe rubber sodium bisulphate prevents darkening of the crepe due to the presence of oxidising enzymes, xylyl mercaptan is an effective bleaching agent proper. 

Crepe rubber of lower quality than pale crepe it is made from the pre-coagulated lumps which form in the latex before the coagulation process is carried out. 

That characteristic of vulcanised elastomers or thermoplastics in showing a gradual increase in deformation under constant load with passage of time also known as strain relaxation or drift. Crepe Rubber... 

Grades of crepe rubber made from lump and other high quality scrap made on rubber estates. Both Thin Brown Crepe and Thick Brown Crepe are produced, in no. 1, no. 2 and no. 3 qualities. Esters... 

The lowest grade of plantation crepe rubber. It is made from earth scrap (rubber from latex which has fallen on the ground) and any other plantation salvage scrap. It was formerly called Rolled Brown Crepe. 

Coagulation of natural rubber latex by stages with the object of removing the yellow colouring matter in the first fraction. The latex in the second fraction produces a white crepe rubber. See Bleaching Agent. 

Also termed first latex crepe . This is the highest quality plantation crepe rubber. Extreme care is taken in preparation to ensure that the lightest possible colour is obtained. 

NaHS03, is added to latex from which pale crepe rubber is to be made. It prevents discoloration of the crepe and destroys microorganisms which may cause later deterioration of the rubber. Sodium Dibutyl Dithiocarbamate SDBC, accelerator. 

Crepe rubber which has been plied up to thicknesses of 1/8 in, 3/16 in or 1/4 in and used in the soling of footwear. It has now been almost entirely superseded by a vulcanised rubber of similar appearance to that of the unvulcanised crepe. 

A modified type of natural mbber which has many processing advantages over normal sheet and crepe rubbers. It shows reduced shrinkage, reduced die swell and much better retention of dimensions especially in complicated extrusions. It is made by adding a quantity of vulcanised latex to normal latex before coagulating. See PA 80. 

An efficient peptising agent for natural rubber it is also used as a bleaching agent in the preparation of pale crepe rubber. 

Watson and coworkers (68,69) studied in details the mechanical reaction of systems of natural rubber plus poly(methyl methacrylate), using a laboratory masticator at 76 rpm, in a nitrogen atmosphere at 15° C. Prior to mastication, the deproteinized crepe rubber was extracted with acetone, imbibed with mdnomer and allowed to homogenize for 16 h, in the absence of light It must be underlined that, with limited mastication and reaction heat dissipation, the actual rubber temperature was much higher the maximum recorded was about 50° C and... 

Pale Crepes. Sri Lanka is the largest producer of crepe rubber, as either thin pale crepe or thick pale crepe, which accounts for 35% of mbber production. Pale crepes are divided into one of three classes, depending on the manufacturing process (11,12) fractionated and bleached mbber (FB) unfractionated, but bleached mbber (UFB) or yellow fraction mbber (YF). 

Cut Rubber. To produce cm rubber Thread, smoked ruhher sheei or crepe rubber is milled with vulcanizing agents, stabilizers, and pigments. This milled slock is calendered into sheets 0 3-1.3 mm thickness, depending on the linal size of the rubber thread desired. Multiple sheets arc layered, heat-treated to vulcanize, then slit into threads for textile uses. Individual threads have either square or rectangular cross-sections. 

R.S.P. Gel (Brit). An antipersonnel incendiary rnixt consisting of ordinary gasoline 76.1, crepe rubber 4.1, white P 15.0, CS2 2.8 and sawdust 2.0%. It was prepd by adding a nearly satd soln of white P in CS2 to a rubber-gasoline soln. The P was pptd in finely divided condition and sawdust was added to prevent the P from settling out... 

Mp 149-150C. Soluble in water, alcohol, acetone, and ether slightly soluble in benzene. Combustible. Use Biochemical research, intermediate, rust inhibitor, antidarkening agent for crepe rubber, tackifier for synthetic rubber. 

In appearance, HR resembles natural crepe rubber, since it is an aliphatic, hydrocarbon polymer the density being the minimum (0.91) attainable for elastic materials of this type. In HR, the original unsaturation is very small, and even this low unsaturation is greatly reduced and may even be entirely eliminated during the compounding and curing process. The fact that once vulcanised it is extremely resistant to chemical attack is understandable because it becomes, after vulcanisation, not only a nonthermoplastic strong elastic material, but also essentially a chemically saturated product as well. This means that whilst physically vulcanised HR resembles soft vulcanised natural rubber, chemically it may be considered most similar to ebonite almost devoid of any unsaturation. 

About 0.4% of the unsaturated groups are pendant vinyl groups in an average sample of acetone-extracted pale crepe rubber. 

The differences lie in molecular weights. They range from 2000 to 20,000 for viscous liquids, to between 100,000 and 400,000 for high molecular weight elastomers that resemble unmilled crepe rubber. The polymers degrade readily from thermal abuse. They can be stabilized effectively, however, by adding small quantities (0.1-1.0%) of such stabilizers as aromatic amines, phenols, or sulfur compounds. Polyisobutylenes are soluble in many hydrocarbons and are resistant to attacks by many chemicals. 

Higlily iiiastic.iied pale crepe rubber extracted by acetone. ... 

Uses Biochemical research intermediate rust inhibitor antidarkening agent for crepe rubber tackifierfor synthetic rubber aluminum anodizing reagent cold permanent hair wave sol ns. possible antidote for heavy metal poisoning... 

Crepe rubber n. A type of crude or sometimes synthetic rubber pressed into crinkled sheets. 

Vulcanization is the most important NR chemical reaction. Most applications require cross-linking via vulcanization to increase resiliency and strength. Exceptions are crepe rubber shoe soles and rubber cements. There are a number of methods for sulfur vulcanization, with certain methods producing polysulfidic cross-linking and other methods producing more monosulfidic cross-links. 

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