Elastomeric compound

Ca.rca.ss Construction. Carcasses are made of one or more pHes of a woven fabric bonded together with an elastomeric compound. Woven materials that are used include cotton, rayon, nylon, polyester, aramids, and glass, in the pure form or in blends. The fabrics are constmcted with warp yams that mn lengthwise along the belt, and filling (weft) yams that mn crosswise. There are a variety of fabric weaves available for specific appHcations... 

Material of construction - Almost all elastomeric compounds are available in the o-ring configuration. 

Therefore, every effort must be placed on ensuring the quality, consistency, and reliability of supply of the incoming raw materials and components. Since this chapter is about the need for consistent, high-quality elastomeric compound, emphasis will be placed on incoming raw materials, compound mixing, extrusion (where appropriate), and molding. 

The requirement for consistent, high-quality incoming raw materials comes from the need for the elastomeric compounds to have consistent processing properties. Therefore, it is important to ... 

Establish the contribution the individual ingredients in the elastomeric compounds make to both the vulcanized compound properties and the uncured properties required for consistent processability. 

At the present time, the difficulty is correlating incoming raw ingredient properties with processability. Elastomeric compounds can be considered to be made up of four components polymers, fillers, process aids, and other chemicals. 

Unfortunately, at the present time there does not appear to be a detailed understanding of the relationship between the properties of the raw materials or the ingredients making up an elastomeric compound and the compound s processability. Therefore, the most widely used approach presently being adopted is to use the conventional characteristics with the standard specification limits issued by the supplier or special agreed upon limits with the supplier to accommodate specific requirements in the fabricators manufacturing process. 

The choice of process is generally based on economic issues such as volume of seals to be produced elastomeric compound, cost and waste and product design. 

During the shaft seal molding process, the elastomeric compound has relatively large distances to travel/ flow in the mold, particularly when using shelf loaded compression molding (Fig. 17a) and injection molding (Fig. 17b). History has shown that without the use of a vacuum, either applied directly through the mold or... 

Press control is critical it is essential that the elastomeric compound reaches the required cure state to optimize product performance yet remains in the press the shortest time period to maximize productivity. To meet this objective, both compression and injection presses now use microprocessor controls, which enable variations in platen temperatures and compound cure characteristics to be accommodated without sacrificing product performance or productivity. 

Over the years the trend has been toward an increasing use of the more expensive elastomers. Concern has been expressed about the cost of waste compound when using a multicavity mold and injection molding, primarily due to the amount of elastomeric compound in the runner system. There are three approaches to overcome the problem ... 

The use of multicavity injection molds together with a cold runner system. The objective of the cold runner system is to prevent the runner system in the mold from curing during the molding process. The result is that the elastomeric compound held in the run-... 

Duct mastic has replaced duct tape as the most effective sealing material. Mastic is a fibrous, elastomeric compound that permanently seals duct connections and seams. In addition, the boot connections between ducts and floors and between walls and ceilings should be fully caulked and/or foamed airtight. Lastly, air handlers that house the... 

Table 18.17 Chemical resistance rating of elastomeric compounds...

Source Croft, T.C., Elastomeric Compounds Utilizing Polymer Blends for Improved ... 

Croft, T.C. Elastomeric Compounds Utibzing Polymer Blends for Improved Wire Adhesion. Rubber Division, Proceedings of the American Chemical Society, Nashville, TN, Sept. 29-Oct. 2, 1998, Paper No. 63. 

Frictioning involves rubbing or wiping an elastomeric compound into a substrate of textile or metallic cords, which may or may not be held together by pick threads or fill yams, or the substrate may consist of a square woven fabric like hose ducks or belt ducks . 

Antwerp, Belgium, 22nd-23rd Nov. 1999, paper 17 ELASTOMERIC COMPOUNDS FOR CONTACT WITH FOOD... 

Impact modifiers for PET are generally elastomeric compounds that increase impact strength and elongation while usually decreasing modulus. An effective way to enhance the impact strength and to induce a brittle/ductile transition of the fracture mode, is by the dispersion of a rubber phase within the PET matrix. The... 

The largest volume of polymeric materials used for wire and cable insulation are thermoplastics, namely, polyethylene (PE) and polyvinylchloride (PVC), and to a lesser degree elastomeric compounds. The main reason for the prevalence of PE and PVC in wire and cable insulation is their easy processing and relatively... 

The irradiated components can be placed adjacent to sulfur-containing unvulcanized elastomeric compounds and, when necessary, coated with suitable adhesive between the contacting surfaces to ensure good bond after final cure of the tire. ... 

Calender A precision machine equipped rolls with three or more heavy, internally heated or cooled (or both), revolving in opposite directions, used for continuously sheeting and plying up elastomeric compounds, and frictioning or coating with elastomeric compounds. 

Gum (compound) Unfilled elastomeric compound confaining only ingre-dienfs necessary for a sufficienf cross-linking. 

---