For molding compounds

Dapon [FMC], TM for a series of diallyl phthalate resins. Used for molding compounds, pre-pregs, and coatings. 

Rovings are rope-hke bundles of continnons untwisted strands for nse in snch processes as perform press molding, filament winding, spray-np, pnltmsion, and centrifugal casting. They can also be converted into chopped strand mats or cnt into short fibers for molding compounds. 

The low-volatility, flame-resistant phosphoric acid esters have maintained their position in products subjected to high levels of mechanical strain such as conveyor belts. Triphenyl phosphate, used only for molding compounds made of cellulose esters, is a practically noncombustible product that is not soluble in benzine. Tricresyl phosphate (TCP) is a flame-retardant plasticizer for PVC products subjected to heavy mechanical stress. The esters of the aliphatic dicarboxylic acids (adipic, azelaic, and sebacic acid) are used as plasticizers for PVC and PVAC. These products are resistant to cold and light. The esters of higher fatty acids such as pelargonates, laurates, palmitates, stearates, and ricinoleates are, strictly speaking, not plasticizers, but are rather used as extenders, secondary plasticizers, or lubricants. 

Capillary rheometer. The Monsanto capillary rheometer measures the viscosity properties of polymers, and provides a direct measure of viscosity and the change in viscosity with time and flow rate at plastica-tion temperatures. The capillary orifice simulates the gate and runner system of actual molding conditions, thus providing valuable flow information for molding compounds. 

The principal fillers used for molding compounds and other thermoset and thermoplastic compounds can be classified as (1) agricultural and plant products, (2) conductive fillers, (3) fibrous fillers, (4) mineral fillers, and (5) reclaimed material. 

Figure 3-105. A washer-test apparatus to determine the wear, friction, and limiting PV for molding compounds.

Composites. The history of phenoHc resin composites goes back to the early development of phenoHc materials, when wood flour, minerals, and colorants were combined with phenoHc resins to produce mol ding compounds. In later appHcations, resin varnishes were developed for kraft paper and textile fabrics to make decorative and industrial laminates. Although phenoHcs have been well characterized in glass-reinforced composites, new developments continue in this area, such as new systems for Hquid-injection molding (LIM) and sheet-molding compounds (SMC). More compHcated composite systems are based on aramid and graphite fibers. 

PhenoHc sheet-molding compound is seeing increased use in interior and exterior appHcations in mass transit. The trains in service on the English Channel tunnel have several panels made from phenoHc SMC which had to meet the strict European safety standards for fire and smoke generation. 

Some amino resins are used as additives to modify the properties of other materials. For example, a small amount of amino resin added to textile fabric imparts the familiar wash-and-wear quaUties to shirts and dresses. Automobile tires are strengthened by amino resins which improve the adhesion of mbber to tire cord (qv). A racing sailboat may have a better chance to win because the sails of Dacron polyester have been treated with an amino resin (1). Amino resins can improve the strength of paper even when it is wet. Molding compounds based on amino resins are used for parts of electrical devices, botde and jar caps, molded plastic dinnerware, and buttons. 

The term amino resin is usually appHed to the broad class of materials regardless of appHcation, whereas the term aminoplast or sometimes amino plastic is more commonly appHed to thermosetting molding compounds based on amino resins. Amino plastics and resins have been in use since the 1920s. Compared to other segments of the plastics industry, they are mature products, and their growth rate is only about half of that of the plastics industry as a whole. They account for about 3% of the United States plastics and resins production. 

Melamine resins were introduced about ten years after the Beetle molding compound. They were very similar to those based on urea but had superior quaHties. Henkel in Germany was issued a patent for a melamine resin in 1936 (7). Melamine resins rapidly supplanted urea resins and were soon used in molding, laminating, and bonding formulations, as well as for textile and paper treatments. The remarkable stabiHty of the symmetrical triazine ring made these products resistant to chemical change once the resin had been cured to the insoluble, cross-linked state. 

Amino molding compounds can be compression, injection, or transfer molded. Urea molding compound has found wide use and acceptance in the electrical surface wiring device industry. Typical appHcations are circuit breakers, switches, wall plates, and duplex outlets. Urea is also used in closures, stove hardware, buttons, and small housings. Melamine molding compound is used primarily in dinnerware appHcations for both domestic and institutional use. It is also used in electrical wiring devices, ashtrays, buttons, and housings. 

The excellent electrical properties, hardness, heat resistance, and strength of melamine resias makes them useful for a variety of iadustrial apphcatioas. Some represeatative properties of amino resia molding compounds, including the industrial-grade melamines, are Hsted in Table 2. 

In 1989 quantity costs, which reflect the lowest cost, of urea molding compounds, were approximately 1.41 /kg ( 0.035/in. for black and brown colors, 1.58/kg ( 0.039/in.for white and ivory special colors are somewhat higher in price. The approximate cost of cellulose-filled melamine molding compound is 1.74/kg ( 0.043/in. ). Glass fiber-filled melamine sells for 7.70/kg ( 0.22/in. ). 

By comparison, temperatures as high as 150°C are often required for mold-enclosed hard natural mbber compounds, where mold plattens are directly heated by steam or electricity. Synthetic latex mbber compounds, however, can be vulcanised at temperatures higher than those for natural mbber neoprene and acrylonitrile—butadiene can be vulcanised at as high as 135°C. 

Phenohc resins (qv), once a popular matrix material for composite materials, have in recent years been superseded by polyesters and epoxies. Nevertheless, phenohc resins stiU find considerable use in appHcations where high temperature stabiHty and fire resistance are of paramount importance. Typical examples of the use of phenoHc resins in the marine industry include internal bulkheads, decks, and certain finishings. The curing process involves significant production of water, often resulting in the formation of voids within the volume of the material. Further, the fact that phenoHcs are prone to absorb water in humid or aqueous conditions somewhat limits their widespread appHcation. PhenoHc resins are also used as the adhesive in plywood, and phenohc molding compounds have wide use in household appliances and in the automotive, aerospace, and electrical industries (12). 

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