Grind rubber

An article has been published by Shell [6] that discusses the fundamentals of grinding rubber at low temperatures. It covers a wide range of subjects including the nature of the product produced, its required storage conditions, the economics of the process and the management and quality systems that need to be installed. The article also includes data on the particle size distributions of hydrogenated nitrile rubber (HNBR) crumb and the properties of fluorocarbon rubber (FKM) and HNBR compounds containing different amounts of rubber crumb. 

Although the techniques in this section can be classified as methods that grind rubber under ambient conditions, this is for convenience rather than a precise scientific definition, because any mechanical action on rubber will result in it heating up above ambient due to a combination of the inherent hysteresis in the material and its poor conduction of heat. The classification of ambient is more to enable a distinction to be made between these types of processes and those where a medium (e.g., water or liquid nitrogen) is deliberately added to the process, or used in the process. 

Rubber. Both natural and synthetic rubber are used as bonding agents for abrasive wheels. Rubber-bond wheels are ideal for thin cut-off and slicing wheels and centerless grinding feed wheels. They are more flexible and more water-resistant than resinoid wheels. 

Oxidized castor oils are excellent nonmigrating, nonvolatile plasticizers (qv) for ceUulosic resins, poly(vinyl butyral), polyamides, shellac, and natural and synthetic mbber (see Rubber, natural). The high viscosity products are also used as tackifiers in gasket compounds and adhesives (qv) because of good oil and solvent resistance. They also serve as excellent pigment grinding media and as a base for inks (qv), lubricating oils, and hydrauHc oils (62). 

G. C. Lowrison, Crushing and Grinding Chemical Rubber Co., Boca Raton, Fla., 1974. 

To grind 3.2 Mg/h (3V2 tons/h) of a raw clay, power consumption will be about 75 kW (100 hp), and it takes about 31 m (1100 ff) of natural gas 3.7 MJ/m (1000 Btu/fF) to dry the clay from 10 percent moisture down to about 1 percent. The product is used in paint pigments and rubber fillers. 

By rolling on a two-roll mill the molecular weight of the polymer can be greatly reduced by mechanical scission, analogous to that involved in the mastication of natural rubber, and so mouldable materials may be obtained. However, bulk polymerisation is expensive and the additional milling and grinding processes necessary make this process uneconomic in addition to increasing the risk of contamination. 

Many grades of recycled rubber produced from grinding and heating of vulcanized rubber products such as tyres, baby bottle nipples and other goods are also available. Although reclaimed rubber offers some processing advantages, its use has declined in recent years because of the extensive use of blended polymers. 

A number of reviews are already available on the above subject. Rothemeyer [50] discussed the effects of grinding and sieving on the particle size, stmcture, and distribution of powders obtained from waste rubber and also studied the effects of different powders on the physical properties of the... 

This method has gained wide acceptance due to its simplicity and environmental friendliness. Research is under way to improve the economy of this method. The most important step is the preparation of ground rubber, since the size and topography of the particles vary with the different techniques of grinding [30]. The characteristics of the ground rubber play a vital role in determining the properties of the ground rubber-filled rubber composites. 

Ambient grinding involves the comminution of scrap rubber, including tires, at ambient temperatures, typically in a toothed-wheel mill, bench grinder, shear mill, or two-roll miU, to give particles... 

Worn tyres are prepared for retreading by a buffing/grinding process to provide a fresh rubber surface. 

A term which generally applies to vulcanised rubber unfit for any other use than reclaiming or grinding to crumb rubber. In the rubber factory scrap may also refer to unvulcanised trimmings which can be reprocessed. 

Rubber-bonded grinding wheels, 1 19 Rubber chemicals, sodium nitrite in, 22 858-859... 

Because of the slow permeation of water, a method is standardised in BS 903 Part 18 [18] for rubbers, in which the material is cut into small particles by cutting, rasping or grinding. This results in a large ratio of surface area to volume and a relatively short time to equilibrium. The same approach could be applied to plastics. 

---