Breaker stock

Resorcinol formaldehyde resin is a vital ingredient in the HRH rubber adhesion compounds (such as wire coat stock or breaker stock) in order to achieve good rubber-to-brass-coated steel tire cord adhesion. 

Extrusion of tubes, hose, and profiles is done on standard extruders for rubber. The usual temperature pattern is a gradual increase of temperature from the feed zone to the die. The die temperature is typically 100°C (212°F), and the screw temperature is approximately the same as the temperature of the feed zone [44]. Processing aids are almost always required to improve the surface appearance and to increase the extrusion rate. Extrusion represents only a small proportion (about 10%) of the total consumption of fluorocarbon elastomers [52].Cold feed extruders typically used for extrusion of rubber stocks are also suitable for the extrusion of fluorocarbon elastomers. Extrusion should be carried out at temperatures below 120°C (250°F) to avoid scorch. In most cases a breaker plate and screen pack are used to generate backpressure on the screw and to remove foreign particles from the stock. A straight head is used for the extrusion of profiles or tubing, whereas a cross-head die is used for... 

FIGURE 7.8 Spinning cone foam breaker. (Reprinted from Ghent. Eng. ScL, 60, Stocks, S.M., Cooke, M., Heggs, P.J., 2231. Copyright 2005, with permission from Elsevier.)... 

The cutting operations consist of primary stock removal from drilling operations, using chip breaker drills, and the use of standard spot-facing tools and burning tools, the last of these producing a negligible fraction of the total stock for disposal. 

The material is a machinable EN8. Approximately 95% by volume of stock will be produced by the various drilling operations. Chip breaker tooling has been specified so that about 95% of the stock produced will be as uniform chips, the balance being made up of small stringy segments and extremely fine particles. The nature and volume of the chips will determine that the primary system will require some means of clarification, while the finer particles determine the necessity for some kind of secondary separator. 

The majority of stock is producing drilling chips of fairly uniform character. From this can be determined the volume of stock produced, by using accepted expansion ratios. If chip breaker drills were not being used, then an expansion ratio of 80 1 could result. However, because of the relatively uniform nature of the chips in question, a ratio of 50 1 may be utilized, i.e. for every 1 cc of metal removed, the filter will receive 50 cc of steel chippings. 

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