Mold Materials

Acute effects of overexposure are as follows. Exposure to dust may cause mechanical irritation of the eye. PPS is essentially nonirritating to the skin, although freshly molded material may occasionally cause dermatitis. Inhalation of PPS dust may cause mechanical irritation to mucous membranes of nose, throat, and upper respiratory tract. 

Diallyl Isophthalate. DAIP polymerizes faster than DAP, undergoes less cyclization, and yields cured polymers of better heat resistance, eg, up to ca 200°C. Prepolymer molding materials such as Dapon M of EMC, are not sticky. Maleic anhydride accelerates polymerization, whereas vinyl isobutyl ether retards it and delays gelation in castings. Copolymers with maleic anhydride are exceptionally hard and tough and may scratch homopolymer surfaces. 

Nickel—beryllium casting alloys are readily air melted, in electric or induction furnaces. Melt surface protection is suppHed by a blanket of argon gas or an alumina-base slag cover. Furnace linings or cmcibles of magnesia are preferred, with zirconium siUcate or mullite also adequate. Sand, investment, ceramic, and permanent mold materials are appropriate for these alloys. Beryllium ia the composition is an effective deoxidizer and scavenger of sulfur and nitrogen. 

Cast molding is an increasingly used manufacturing process for both rigid gas-permeable and hydrogel contact lenses. In this process, two molds, made from a variety of plastics, are used. A female mold forms the lens front surface (convex) and a male mold forms the lens back surface (concave). The plastic molds are made from metal tools or dies that are usually stainless steel, precision lathed, and polished to the specified lens design. A variety of mold materials are used. The polymerized, hardened lens is released from the mated molds and is processed in much the same way as the spin-cast lenses described above. 

Copper(II) oxide [1317-38-0] can also cause porosity in the finished casting by combining with hydrogen formed by the dissociation of water in the mold material to form steam within the melt, thus causing holes during solidification. 

Lampman, H.F. and Reidenbach, F. (Eds.), Engineered Materials Handbook. ASM International, The Materials Information Society, Materials Park, OH, 1995, pp. 157-286. Rogers Corporation, Molded Materials Div., http //www.rogers-coip.com/mmd/ phenolic.htm, 1999. 

Density of a molding material in loose form, such as granular, nodular, etc., with units in g/cm or Ib/ft. ... 

Modell-sand, m. molding sand facing sand, -stoff, 7n. modeling composition, molding material. 

Table 3-8 Guide for wall thicknesses of TS molding materials...

The crossed polarizer effects of both types are used in analysis work. The concentration of optically active organic materials is determined by the degree of rotation. In plastic processing the residual strains in molded materials as well as the degree of orientation of polymers is determined by the effect on polarized light. Crossed polarizers are used with special wave plates to control the amount of light that passes through an optical system. 

Density, bulk Ratio of weight to volume of a solid material including voids but more often refers to loose form (bulk) material such as pellets, powders, flakes, compounded molding material, etc. 

Recently, results of careful experiments were reported by Ito et a/.101 They claimed that formic acid, formaldehyde, and methanol, which had been previously reported as photoelectrochemical reduction products of carbon dioxide, were observed also by photolysis of cell materials, such as electrolytes, including 15-crown-5 ether, and epoxy resin, which has often been used as the molding material of semiconductor electrodes in aqueous solutions. Previously reported reduction products were obtained also under nitrogen with (Table 4) and without (Table 5) a p-GaP photocathode under illumination. These precise experiments under improved conditions, where no photolytic products were observed, gave the result that the main reduction product of carbon dioxide at a p-GaP photocathode in aqueous electrolytes was formic acid. Thus, many kinds of products reported in previous papers83,97,100 were suggested to be due to photolysis of cell materials. 

In conclusion, in the limited study undertaken, the visual defects were indicated as being due to the presence of internal voids in the molded material. 

Molded flexible foam products, 25 470 Molded materials, ionomers in, 14 482—483 Molded phenolic parts, applications for, 18 786t... 

Processing and Uses. Polystyrene is an outstandingly good injection molding material. In this process the material is melted and forced through dies into a mold where it cools and solidifies. The process is very adaptable and is particularly suitable for the mass-production of small articles. Components for the electrical industry, objects for everyday use (buttons, combs, tube tops, fountain pens, etc.) and also articles for the military field (components for detonators in grenades, parts of gas-masks etc.) were manufactured in this way at that time. 

Crystallization of PCT is relatively rapid, but because of its higher Tg (90 °C) the maximum rate of crystallization occurs at a higher temperature than is typical of other crystalline polymers such as PET (Tg at about 70 °C) or PBT (Tg at about 35 °C). Figure 7.2 compares the crystallization half-times of PET and PCT from both the glass and the melt (data were obtained via DSC measurements). The effect of the higher Tg on the temperature of maximum crystallization rate (i.e. minimum half-time) is most clearly seen in the data from the melt. The basic rapid crystallization rate of PCT allows it to be used as a high-performance injection molding material. 

Widespread chlorine-containing polymers would include, 1) stable molding material for practical use such as polyvinyl chloride (PVC), polyvinylidene chloride and poly(epichlorohydrin)(PECH) and, 2) reactive polymers capable to introduce additional functional groups via their active chlorines such as chloromethyl polystyrene, poly (3-chloroethyl vinyl-ether) and poly (vinyl chloroacetate). While the latter, especially the chloromethyl polystyrene, has been widely used recently for the synthesis of variety of functional polymers, we should like to talk in this article about the chemical modification of the former, mainly of PVC and PECH, which was developed in our laboratory. 

When any polymer is to be used as film, plate, fiber, or molded material, the surface properties are as important as the bulk properties. In comparison with the large number of works devoted to the development of new polymers, relatively minor efforts have been directed to the modification of polymer surface. In particular, owing to the difficulties of studying chemical and physical properties of polymer surface, few articles have been published on the correlation between the condition of surface treatments and the imparted surface properties. 

Phenolic resins are the cheapest of all molding materials, since they usually contain more than 50% filler—sawdust, glass fibers, oils, etc. Their main properties are heat resistance, excellent dielectrics, and ease of molding. However, they have poor impact resistance (they crack) and they don t hold most dyes very well, except black. Their use is thereby restricted— they re functional but not pretty. When the telephone companies started making phones in colors, they quit using phenolic resins and instead bought more expensive thermosets. 

Brookfield, Ct., SPE, 2002, Paper 192, Session M38-Rotational Molding Materials, pp.5, CD-ROM, 012 INVESTIGATION OF THE PROCESSING CHARACTERISTICS AND MECHANICAL PROPERTIES OF METALLOCENE POLYETHYLENE FOAMS FOR ROTATIONAL MOULDING... 

---