Mbber backing

The belts consist of a synthetic mbber backing, reinforced with glass cord tension members and protected by a nylon fabric coating on the teeth. The size range available is listed. 

Lay-up proceeds by laying down the veneer which is to be the back surface of the panel. Then a sufficient number of pieces of core veneer are passed through the glue spreader to form the next layer of cross-oriented veneer. The glue spreader commonly used in hardwood plywood manufacture is a roU coater in which a pair of opposing mbber roUs are coated with a thin layer of adhesive. As the veneer is passed between the roUs, the adhesive is transferred to the surfaces of the veneer. Adhesive is appHed only to the cross-pfles and in sufficient quantity to provide a continuous layer on both opposing faces of veneer. Thus, in the case of a three-ply panel, only the core layer is spread with adhesive and in that of a five-ply panel, the second and fourth layers both of which are cross-pfles, are spread with adhesive. Then the top surface veneer, which is normally the decorative surface, is placed on the assembly. 

Although the use of simple diluents and adulterants almost certainly predates recorded history, the use of fillers to modify the properties of a composition can be traced as far back as eady Roman times, when artisans used ground marble in lime plaster, frescoes, and po22olanic mortar. The use of fillers in paper and paper coatings made its appearance in the mid-nineteenth century. Functional fillers, which introduce new properties into a composition rather than modify pre-existing properties, were commercially developed eady in the twentieth century when Goodrich added carbon black to mbber and Baekeland formulated phenol— formaldehyde plastics with wood dour. 

The fleshing is done on a multiroller machine that pulls the hide over a rotating blade, similar to a milling machine that cuts off the flesh from the inside of the hide. The machine includes a mbber roUer that holds the hide near the rotating fleshing blades. Through the adjustment of the clearances or the thickness of the hides and the resiUence of the mbber roUer the flesh is effectively removed regardless of the differences in the thickness of the hide from back to belly and flanks. 

Floor mats, carpet backing, and reHef mats have been traditional markets for ground mbber where the material adds resHiency at a lower cost compared to virgin compounds. Certain molded products have also been markets for ground mbber. An interesting use is the manufacture of lawn soaker... 

Flame retardants such as a-alumina trihydrate [14762-49-3] can be added to latex-based foamed carpet backing a combination of antimony oxide [1309-64-4] and chlorinated paraffins is used in dry mbber. 

Natural mbber latex is also used in adhesives for tape, packaging, envelopes, and in the footwear industry. It is used in the carpet industry as a binder for backing compounds, but this is another area in which synthetic SBR latex has competed effectively. There are a number of relatively small and specialized appHcations for natural mbber latex including mbberized coir or hair and cast products such as toys. Latex sheeting which is used in dental dams and for numerous other purposes can be made by dipping or casting onto a continuous belt. 

Copolymers with butadiene, ie, those containing at least 60 wt % butadiene, are an important family of mbbers. In addition to synthetic mbber, these compositions have extensive uses as paper coatings, water-based paints, and carpet backing. Because of unfavorable reaction kinetics in a mass system, these copolymers are made in an emulsion polymerization system, which favors chain propagation but not termination (199). The result is economically acceptable rates with desirable chain lengths. Usually such processes are mn batchwise in order to achieve satisfactory particle size distribution. 

Prior to the eastern adventures of Linschoeten and Tradescant, the sailors of Columbus had discovered the natives of Central America playing with lumps of natural mbber. These were obtained, like gutta percha, by coagulation from a latex the first recorded reference to natural mbber was in Valdes La historia natural y general de las Indies, published in Seville (1535-1557). In 1731 la Condamine, leading an expedition on behalf of the French government to study the shape of the earth, sent back from the Amazon basin mbber-coated cloth prepared by native tribes and used in the manufacture of waterproof shoes and flexible bottles. 

The emulsion polymerization process is used by 17 production facilities to produce latex mbber products as well as solid cmmb mbber. Latex production follows the same processing steps as emulsion cmmb mbber production up to the finishing process. Between 5 and 10% of emulsion polymerized SBR and nearly 30% of nitrile mbber production (NBR) are sold as latex. Latex mbber is used to manufacture dipped goods, paper coatings, paints, carpet backing, and many other commodities. 

Today both natural mbber, an agricultural crop, and synthetic elastomers are multi-billion dollar businesses. Looking back at Fig. 16.1, we see that Synthetic Rubber (NAICS 325212) totals 5.7 billion. It is a large area of polymer use and is 1% of Chemical Manufacturing. But in the related industry covering final end products called Plastics and Rubber Products... 

Many antioxidants in these classes are volatile to some extent at elevated temperatures and almost all antioxidants are readily extracted from their vulcanimates by the proper solvent. These disadvantages have become more pronounced as performance requirements for mbber products have been increased. Higher operating temperatures and the need for improved oxidation resistance under conditions of repeated extraction have accelerated the search for new techniques for polymer stabilization. Carpet backing, seals, gaskets, and hose are some examples where high temperatures and/or solvent extraction can combine to deplete a mbber product of its antioxidant and thus lead to its oxidative deterioration faster (38,40). 

Other than tire use, there are few other significantly large application areas for natural mbber that can be identified, as indicated in Table 10. The use of natural mbber in latex products covers items such as gloves, condoms, balloons, catheters and other dipped goods, latex thread, foam and carpet backing, and rubberized coir and hair. In total, latex goods consume about 11% of world mbber production. Thereafter, there are four categories footwear,... 

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