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Z94.12.6 Plastics

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MAT. A randomly distributed felt of glass fibers used in reinforced plastics lay-up molding.

MATCHED METAL MOLDING. Method of molding reinforced plastics between two close-fitting metal molds mounted in a hydraulic press (similar to compression molding).

MECHANICALLY FOAMED PLASTIC. A cellular plastic whose structure is produced by physically incorporated gases.

MELAMINE FORMALDEHYDE. A synthetic resin derived from the reaction of melamine with formaldehyde or its polymers.

MELAMINE PLASTICS. Plastics based on resins made by the condensation of melamine and aldehydes.

METASTABLE. Describing an unstable condition of a plastic evidenced by changes of physical properties not caused by changes in composition or in environment. Metastable refers, for example, to the temporarily more flexible condition of some plastics after molding. No physical tests should be made while the plastic is in a metastable condition, unless the data regarding this condition are desired.

METHACRYLONITRILE. A vinyl nitrile compound that is similar to ABS.

MIGRATION. The transfer of a material from a plastic to another solid in contact with it.

MOLD BASE. The assembly of all parts making up an injection mold, other than the cavity, cores, and pins.

MOLDING, BAG. A method of molding or laminating which involves the application of fluid pressure, usually by means of air, steam, water, or vacuum, to a flexible material which transmits the pressure to the material being molded or bonded.

MOLDING, BLOW. A method of forming objects from plastic masses by inflating with compressed gas.

MOLDING, COMPRESSION. A method of forming objects from plastics by placing the material in a confining mold cavity and by applying pressure, and usually heat.

MOLDING, CONTACT-PRESSURE. A method of molding or laminating, in which the pressure used is only slightly more than that necessary to hold the materials together during the molding operation. This pressure is usually less than 10 psi (68.948 kPa).

MOLDING, HIGH PRESSURE. Molding or laminating in which the pressure used is greater than 200 psi (1378.96 kPa).

MOLDING, INJECTION. A method of forming plastic objects from granular or powdered plastics by fusing the plastic in a chamber with heat and pressure and then forcing part of the mass into a cooler chamber where it solidifies. This method is commonly used to form objects from thermoplastics.

MOLDING, LOW-PRESSURE. Molding or laminating in which the pressure used is less than 200 psi (1378.96 kPa).

MOLDING TRANSFER. A method of forming molded objects from granular, powdered or preformed plastics by fusing the plastic in a chamber by heat, and then forcing essentially the whole mass into a hot chamber, where it solidifies. This method is commonly used to form objects from the thermosetting plastics.

MOLD INSERT (REMOVABLE). Part of a mold cavity of force which forms undercut or raised portions of a molded article.

MONOMER. A relatively simple compound that can react to form a polymer.

MOUNTING PLATE. (See CLAMPING PLATE.)

MOVABLE PLATEN. The large back platen of an injection molding machine to which the back half of the mold is secured.

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