Soft Rubber Lining

Unless test coupons are produced alongside the lining, the only method of testing the vulcanisation state is with a hand hardness meter. A Shore A or IRHD meter is used for soft rubber linings and a Shore D meter for ebonites. The usual specification is that the hardness has to conform to 5° of the specified hardness. There is no quantitative non-destructive test for the strength of the bond between the lining and the substrate and so such tests are usually carried out in the laboratory on a sample prepared from the materials used. 

Soft rubber linings have been finding wider use in the coal and iron ore slurry transportation piping systems, where the particle size does not exceed 3 mm. Sharp particles in longer sizes can cause extensive gouging. A properly compounded and applied rubber lining can outlast metal at a rate of 10 to 1 in many cases. 

Figure 6.2a Autoclave curing cycle for soft rubber lining...

Being more highly cross-linked, ebonite linings are even more resistant to swelling and permeation than soft rubber linings. However, they have to be vulcanized in woikshop autoclaves their use is generally restricted to relatively small items whose volume does not exceed about 100 m. ... 

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 ). 

Milk-of-lime transfer pumps should be of the open impeller centrifugal type. Pumps having an iron body and impeller with bronze trim are suitable for this purpose. Rubber-lined pumps with rubber-covered impellers are also frequently used. Makeup tanks are usually provided ahead of centrifugal pumps to ensure a flooded suction at all times. Plating out of lime is minimized by the use of soft water in the makeup tank and slurry recirculation. Turbine pumps and eductors should be avoided in transferring milk of lime because of scaling problems. 

The standard polymers used for rubber linings consist of materials that are cross-linkable macromolecules which, on mixing with suitable reactants that form strong chemical bonds, change from a soft deformable substance into an elastic material. These polymers include natural rubber and its corresponding synthetic, c/s-polyisoprene, styrene-butadiene rubber, polychloroprene, butyl rubber, halogenated butyl rubbers, acrylonitrile-... 

In the case where the material used to make the capillary tube is a soft rubber, Eq. (46) does not apply any more, due to the viscoelastic braking induced by the displacement of the wetting ridge. The viscoelastic braking force, / per unit of length of the triple line depends on the flow speed U according to ... 

Materials Handling Rubber lining for grabs, hooks and clamps. Wear resistant linings for chutes, hoppers storage bins etc. pulley rubber lagging for conveyor rollers. Soft natural rubber for wear resistance. Various rubber materials for roller coverings. 

In the case of centrifuges, stirring rods, fans or blowers, vibrating containers, etc., where big centrifugal forces often show up they should be dynamically balanced immediately after the fabrication and before rubber lining. In the case of soft metals like aluminium, it is recommended that the design should provide for maximum rigidity. 

Before an item of equipment lined with ebonite or any soft rubber leaves the workshop it is tested for non-porosity. According to regular practice, the only reliable method of determining this is that which makes use of a spark tester or inductor and a test voltage of 20,000 to 25,000 volts. For this purpose the spark tester or the inductor has been proved successful. 

Ephithite, H.J. "Rubber Linings—the Soft Options against Abrasion." Paper presented at the Bulk Solids Handling, Conference, Oct 1985. 

Several authors have given a basic theory for the prediction of the modulus of a composite (16-18). The line In Fig, 4 shows the theoretical curve for the reduction of the modulus (E/Eo) due to Incorporation of a soft rubber phase In a hard matrix at a temperature above the transition region of the soft phase and below the transition region of the hard phase (E > flexural modulus of the modified nylon and E0 flexural modulus of the unmodified nylon). The experimental points of systems 1 and 2 fit fairly well onto the theoretical curve. This proves that they are well-dispersed systems without Inclusions. The difference In Impact strength between system 1 and system 2 Is mainly due to the better lnterfaclal adhesion of system 2, by which crazes are stabilized and/or the formation of small shear bands Is Initiated. 

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