Rubber sources

Prior to 1940, the use of synthetic elastomers in linings was negligible, but the advent of the Second World War, and the consequent loss of natural rubber sources to the Allies, led to the use of synthetic rubber, namely a styrene-butadiene copolymer which, whilst not having all the properties of natural rubber, proved to have adequate anti-corrosive performance. 

The carbon black generated by a fire from a rubber source increases the smoke density other products are highly toxic and often corrosive. The halogens, phosphates, borates, and their acids evolved during a fire corrode metals and electrical and electronic equipment. Hence many of the fire retardants described below cannot be used in situations where the toxic gases evolved will create their own hazards. In these cases inorganic hydroxides are used, at filler-type addition levels. Aluminium hydroxide and magnesium hydroxide are used as non-toxic fire retardant systems. 

Figure 16.1 U.S. shipments of plastics, fibers, and synthetic rubber. (Source Annual Survey of Manufactures)...

Natural rubber is a polymer of isoprene- most often cis-l,4-polyiso-prene - with a molecular weight of 100,000 to 1,000,000. Typically, a few percent of other materials, such as proteins, fatty acids, resins and inorganic materials is found in natural rubber. Polyisoprene is also created synthetically, producing what is sometimes referred to as "synthetic natural rubber". Owing to the presence of a double bond in each and every repeat unit, natural rubber is sensitive to ozone cracking. Some natural rubber sources called gutta percha are composed of trans-1,4-poly isoprene, a structural isomer which has similar, but not identical properties. Natural rubber is an elastomer and a thermoplastic. However, it should be noted that as the rubber is vulcanized it will turn into a thermoset. Most rubber in everyday use is vulcanized to a point where it shares properties of both, i.e., if it is heated and cooled, it is degraded but not destroyed. 

Tapping rubber (Source The Malaysian Rubber Board). 

Figure 3.10. Chemical structures of a side-on nematic monomer (8a) and a striated artificial muscle with a lamellar structure based on a nematic triblock copolymer, RNR (N nematic R rubber). Source Li et al., 2004.

Typical adhesives in each class are Liquids 1. Solvent—polyester, vinyl, phenolics acrylics, rubbers, epoxies, polyamide 2. Water—acrylics, rubber-casein 3. Anaerobics—cyanoacrylate mastics—rubbers, epoxies hot melts—polyamides, PE, PS, PVA film—epoxies, polyamide, phenolics pressure, sensitive—rubbers. Source Tauernicht, J. O., Bonding and Joining, Weight the Alternatives , Plastics Technology, August 1970. 

Bridgestone Targets Guayule Shrub as Rubber Source, March 9, 2012. Available from www.environmentalleader.eom/2012/03/09/bridgestone-targets-guayule-shrub-as-rubber-source (accessed 18 June 2013). 

FIGURE A3.7 Solubility of chlorinated rubber. Source Parker (1967). 

Rubber crumb is an important resource, but as described above can be derived from a number of different waste rubber sources... 

Solvents with boiling points above 90-95°. The apparatus of Fig. 77,13, 3 (with closed filter flask and rubber lead-off tube) or of Fig. 77,13, 4 (see discussion in previous paragraph but one) should be vtilised vrith an air bath or oil bath as the source of heat. Heating on a Wire gauze is not recommended. 

This procedure is used to separate crystallized product from solvent or to remove crap and solids from a liquid. Figure 8 shows the proper apparatus to use. The collecting flask is called a side arm flask and to that extended nipple (tee heel) is attached a vacuum source. The thing that is shoved through the rubber stopper is called a Buchner funnel and is usually made of white porcelain or, preferably, PP. The Buchner funnel, when viewed from above, can be seen to have lots of pin holes in the bottom surface of its reservoir. Over this surface is layered a single sheet of rounded filter paper or paper towel. 

Numerical values of sinh x versus x are tabulated in standard sources (e.g.. The Handbook of Tables for Mathematics, Chemical Rubber Company) and the tables can be used to evaluate either sinh x or sinh" y. 

Guajule An Alternative Source of Natural Rubber, National Academy of Sciences, Washington, D.C., 1977. 

Eield latex and field coagulum are the source materials for all varieties and grades of dry natural mbber that include the conventional International grades as weH as the Technically Specified Rubbers (TSR). 

Fig. 2. Source materials and production processes used to make the various grades of Standard Malaysian Rubber (SMR).

FIG. 5-12 Variation of absorptivity with temperature of radiation source. (1) Slate composition roofing. (2) Linoleum, red brown. (3) Asbestos slate. (4) Soft rubber, gray. (5) Concrete. (6) Porcelain. (7) Vitreous enamel, white. (8) Red brick. (9) Cork. (10) White dutch tile. (11) White chamotte. (12) MgO, evaporated. (13) Anodized aluminum. (14) Aluminum paint. (15) Polished aluminum. (16) Graphite. The two dashed lines bound the limits of data on gray paving brick, asbestos paper, wood, various cloths, plaster of parts, lithopone, and paper. To convert degrees Ranldne to kelvins, multiply by (5.556)(10 ). 

Vacuum-Shelf Dryers Vacuum-shelf diyers are indirec t-heated batch diyers consisting of avacuumtight chamber usually constructed of cast iron or steel plate, heated, supporting shelves within the chamber, a vacuum source, and usually a condenser. One or two doors are provided, depending on the size of the chamber. The doors are sealed with resihent gaskets of rubber or similar material (Fig. 12-49). 

A mixture of 50 g. (0.26 mole) of anhydrous stannous chloride and 225 ml. of dry ether is placed in a 1-1. three-necked round-bottomed flask fitted with a rubber-tube sealed stirrer, an inlet tube reaching nearly to the bottom of the flask, and a reflux condenser (Note 2) protected by a calcium chloride drying tube. The mixture is saturated with dry hydrogen chloride (Note 3) with continuous stirring. Within 3 hours all the stannous chloride dissolves, forming a clear viscous lower layer. The source of hydrogen chloride is then disconnected, and the freshly prepared imidyl chloride is transferred into the mixture with the aid of 25 ml. of dry ether (Note 4). Stirring is continued for 1 hour, and then the reactants are allowed to stand at room temperature for 12 hours. 

---