Cellular Rubber Products

There are no ISO, ASTM or British fire test method standards specifically for solid mbbers and there is no active fire test work being pursued in TC 45. There are, however, a number of published international test methods for cellular materials and plastics, the majority of which could be applied to rubbers. A comprehensive account of fire testing of plastics has been given by Paul in the Handbook of Polymer Testing81. There may be fire resistance requirements for particular rubber products and some examples were given by Schultz110. 

Rubber products with a cellular structure have been used widely for many years. The earliest developments of these products predated World War I. The two forms of natural rubber—raw rubber, and latex, form the basis for different product types, one being blown dry rubber, and the other foamed and dried latex. Blown sponge and latex foam are distinctly different materials, although the end-products may appear simUar and have some overlapping applications. 

This is a comprehensive volume containing much useful information on many aspects of rubber and rubber-like products. There is a short section on cellular rubber, including properties of eight (8) foam rubbers. Notice 1, 24 July 1987, incorporated two (2) page changes. 

Provides information in tabular form on all known Federal, Military and nationally recognized technical society specifications and standards for those flexible rubber products of interest to the DOD. Pages 17 through 28 cover cellular materials. 

Thermal insulators comprise an equally broad range of materials. Such inorganics as mineral fibers, magnesia, aluminum silicate, cellulose, and glass fibers are widely used for steam and hot-water pipes, furnaces, and blown-in home insulation. Organic products that are effective include plastic foams (polyurethane, polyvinyl chloride, polystyrene) and cellular rubber. There are a number of materials that may be called double insulators, since they have both electrical and thermal insulating properties,... 

In contrast to the considerable number of fire tests for plastics, there are relatively few fire tests specifically for rubbers as such. There are a number of tests for rubber products including cable insulation, hoses of various types, and cellular products. In some cases, e.g.. cellular products, the test relates to both cellular plastics and rubbers, e.g.. BS 4735 and ISO 3582. Horizontal burning characteristics when subjected to a small flame or BS 5111. Determination of smoke generation. For convenience, these have been described in the section dealing with plastics tests, Other tests for rubber products include ISO 8030 [51], Flammability of rubber hoses for underground mining, ISO 3401 [52], Conveyor belts Flame retardation specification and test method, and BS 5173, Part 103 [53], Fire rc.sistance of plastics and rubber hoses and hose assemblies, and linings of hoses, etc. 

Cellular rubber may be described as an assembly of a multitude of cells distributed in a rubber matrix more or less uniformly. The cells may be interconnected (open cells) as in a sponge or separate (closed cells). Foam rubber made from a Uquid starting material such as latex, described earKer, is of open-cell type. Cellular products made from solid rubber are commonly called sponge (open cell structure) and expanded rubber (closed cell structure). 

Fig. 1. Viscosity of cellular rubber stock during a production cycle (110).

Recommended for products adhesives, blood bags, cellular rubber goods, film sheeting, gaskets, general purpose film, industrial hose and tubing, low viscosity plastisols, packaging, sealants, PVC film, vinyl foam ... 

A substantial part of the market for the ethylene-vinyl acetate copolymer is for hot melt adhesives. In injection moulding the material has largely been used in place of plasticised PVC or vulcanised rubber. Amongst applications are turntable mats, base pads for small items of office equipment and power tools, buttons, car door protector strips and for other parts where a soft product of good appearance is required. Cellular cross-linked EVA is used in shoe parts. 

A more common contraceptive device is the intrauterine device (IUD). The first type of intrauterine device used was undedicated. These have received increased attention since the use of polyethylene plastics and silicone rubbers [194-196], These materials had the ability to resume their shape following distortion. Because they are unmedicated, these IUDs cannot be classifieds as sustained-release products. It is believed that their mechanism of action is due to local endometrial responses, both cellular and cytosecretory... 

Physical testing of rubbers is the concern of PRI/22 which has a panel to deal with electrical tests. Until recently, there were 4 other active panels to split the detailed work on test methods but, as a result of the drive to economise effort and the effects of virtually all test methods coming from ISO, they were disbanded. Other committees which should be mentioned in the context of testing are PRI/71 which deals with flexible cellular materials, PRI/20 for accuracy of test machines, PRI 26 for burning behaviour of plastics and rubber and PRI/23 for chemical testing. Unfortunately, systems are never as simple as we would like specialised tests may be considered in product committees and not all products containing rubber are covered in PRI committees... 

The moisture resistance, low cost, and low-density closed-cell structure of many cellular polymers resulted in their acceptance for buoyancy in boats, floating docks, and buoys. Because each cell is a separate flotation unit, these materials cannot be destroyed by a single puncture. Foamed-in-place polyurethane between thin skins of high tensile strength is used in pleasure craft [98]. Other cellular polymers that have been used where buoyancy is needed are produced from polystyrene, polyethylene, poly(vinyl chloride), and certain types of rubber. Foams made from styrene-acrylonitrile copolymers are resistant to petroleum products [99,100]. 

Another example of an alternative rubber system is the asymmetric radial polymer (ARPS). ARPS has four equal arms of polybutadiene, with a polystyrene segment attached to one of the polybutadiene arms. A HIPS product made with ARPS blends polybutadiene produces two separate rubber phases with different morphologies and particle size distributions. The ARPS produces a capsular morphology and the polybutadiene produces a normal cellular morphology surrounded by a lamellar structure that provides a reactor product with both high gloss and high impact. 

Covers only sponge rubber items, including chemically blown or expanded-rubber items having either open or closed cells. Also includes cellular products made from chemically or mechanically foamed latices or liquid elastomers. Provides word descriptions and photographs of defects. 

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