AIR-ASSIST FORMING A method of thermoforming Q.V., in which air flow or pressure is employed to partially preform the sheet immediately prior to the final pull down onto the mold using vacuum.
(American National Standards Institute)
An organization that publishes guidelines for plastics in specific applications as an aid for the manufacturer and consumer for the general publics safety. Guides are not requirements or standards requiring compliance.
(American Society for Testing and Materials)
A not-for-profit volunteer organization for material standards development and test procedures. Representatives from industry (procedures and users), consumers, academia, and government meet and write standards for materials, products, systems, and services. The ASTM Headquarters is located in Philadelphia, publishes books of standards, but does not provide research or testing. Plastics are covered in Books D and E.
BLISTER A raised area on the surface of a molding caused by pressure of gases inside it on its incompletely hardened surface.
FILM An optional term for the sheeting having a nominal thickness not greater than 0.001 inch.
FLOCK Short fibers of cotton, etc., used as fillers, q.v., for plastic materials.
FLOCKING A method of coating by spraying finely dispersed powders or fibers.
IMPACT RESISTANCE Relative susceptibility of plastics to fracture by force, e.g., as indicated by the energy expanded by a standard pendulum type impact machine in breaking a standard specimen in one blow.
IMPACT STRENGTH 1) The ability of a material to withstand shock loading. 2) The work done in fracturing, under shock loading, a specified test specimen in a specified manner.
INHIBITOR A substance that slows down chemical reaction. Inhibitors are sometimes used in certain types of monomers and resins to prolong storage life.
(International Standards Organization)
This organization is similar to ASTM with a global focus. ISO is attempting to write procedures and standards that satisfy needs by providing consistency on a global basis.
LAMINATE A product made by bonding together two or more layers of material or materials.
(Synthetic Resin-Bonded Laminate)
A plastics material consisting of superimposed layers of a synthetic resin-impregnated or gel-coat filler which have been bonded together, usually by means of heat and pressure, to form a single piece.
MONOMER A relatively simple compound, which can react to form a polymer.
MULTI-CAVITY MOLD A mold with two or more mold impressions, i.e., a mold which produces more than one molding per mold cycle.
NYLON The generic name for all synthetic fiber-forming polyamides; they can be formed into monofilaments and yarns characterized by great toughness, strength and elasticity, high melting point, and good resistance to water and chemicals. The material is widely used for bristles in industrial and domestic brushed, and for many textile applications; it is also used in injunction molding gears, bearings, combs, etc.
OLEFINS A group of unsaturated hydrocarbons if the general formula CnH2n, and named after the corresponding paraffin’s buy the addition if “ene” or “ylene” to the stem. Examples are ethylene and propylene.
ORIENTATION The alignment of the crystalline structure in polymeric materials so as they produce a highly uniform structure. Can be accomplished by cold drawing or stretching during fabrication.
PELLET A small ball, cylinder, cube or spherical shape. Most plastics are supplied in pellets.
PELLETIZING A process of producing pellets.
PHOTOTYPE MOLD A simplified mold construction often made from a light metal casting alloy or from an epoxy resin in order to obtain information for the final mold and/or part design.
PLASTIC (N) One of many high-polymeric substances, including both natural and synthetic products, but excluding the rubbers. At some stage in its manufacture every plastic is capable if flowing, under heat and pressure, if necessary, into the desired final shape. (V) Made of plastic; capable of flow under pressure or tensile stress.
PLASTIC MEMORY A phenomenon of plastics to return to its original molded form. Different plastics posses varying degrees of this characteristic.
PLATENS The mounting plates of a thermoforming machine to which the mold assembly is bolted.
PLUG FORMING A thermoforming process in which a plug or male mold is used to partially perform the part before forming is completed using vacuum or pressure.
POLYCARBONATE RESINS Polymers derived from the direct reaction between aromatic and aliphatic dihydroxy compounds with phosgene or by the ester exchange reaction with appropriate phosgene-derived precursors.
POLYESTER A resin formed by the reaction between a dibasic acid and a dihydroxy alcohol, both organic. Modification with multi-functional acids permits cross-linking to thermosetting resins. Polyesters modified with fatty acids are called Alkyds.
POLYETHYLENE A thermoplastic material composed by polymers of ethylene. It is normally a translucent, tough, waxy solid which is unaffected by water and by a large range of chemicals.
POLYOLEFIN A polymer prepared by the polymerization of an Olefin(s) as the sole Monomer(s).
POLYPROPYLENE A tough, lightweight rigid plastic made by a polymerization of high-purity propylene gas in the presence of an organometallic catalyst at relatively low pressure and temperatures.
POLYSTYRENE A transparent thermoplastic produced by the polymerization of styrene (ethyl benzene). The electrical insulating properties of polystyrene are good and the material is relatively unaffected by moisture.
POLYVINYL ACETAL A member if the family of vinyl plastics, q.v., polyvinyl acetal is the general name for resins produced from a condensation of polyvinyl alcohol with an aldehyde. There are three main groups: polyvinyl acetal itself, polyvinyl butyral, and polyvinyl formal, q.v. Polyvinyl acetal resins are thermoplastics which can processed by casting, extruding, molding and coating, but their main uses are in adhesives, lacquers, coatings and films.
POLYVINYL ACETATE A thermoplastic material composed of polymers of vinyl acetate in the form of a colorless solid. It is obtainable in the form of granules, solutions, latices, and pastes. It is used extensively in adhesives, for paper and fabric coatings, and in bases for inks and lacquers.
POLYVINYL CHLORIDE (PVC) A thermoplastic material composed of polymers of vinyl chloride; a colorless solid with outstanding resistance to water, alcohols, and concentrated acids and alkalies. It is obtainable in the form if granules, solutions, latices, and pastes. Compounded with plasticizers it yields a flexible material superior to rubber in aging properties. It is widely used for cable and wire coverings, in chemical plants, and in the manufacture of protective garments.
POLYVINYL CHLORIDE ACETATE A thermoplastic material composed of copolymers of vinyl chloride and vinyl acetate; a colorless solid with good resistance to water, and concentrated acids and alkalies. It is obtainable in the form of granules, solutions, and emulsions. Compounded with plasticizers it yields a flexible material superior to rubber in aging properties. It is widely used for cable and wire coverings, in chemical plants, and in the manufacture of protective garments.
PRESHEETING In sheet thermoforming, the distorted printing sheets before they are formed. During forming the print assumes its proper proportions.
PRESSURE FORMING A thermoforming process wherein pressure is used to push the sheet to be formed against the mold surface as opposed to using a vacuum to suck the sheet flat against the mold.
PRINTING OF PLASTICS Methods of printing plastics materials, particularly thermoplastic film and sheet, have developed side by side with the growth of usage of the materials, and are today an important part of finishing techniques. Basically, the printing processes used are the same as in other industries, but the adaption of machinery and development of special inks have been a constant necessity, particularly as new plastics materials have arrived, each with its own problems of surface decoration. Among the printing processes commonly used are the gravure, flexographic, inlay (or valley) and silkscreen.
RECYCLED PLASTIC A plastic prepared from used articles, which have been cleaned and reground.
REFORMULATED PLASTIC Recycled plastic that has been upgraded to alter or improve performance capability or to change characteristics through use of plasticizers, fillers, stabilizers, pigments, etc.
REGROUND See reworked Plastics.
REPROCESSED PLASTIC A thermoplastic prepared from scrap industrial plastic by other than the original processor.
RESIN Any of a generic class of solid or semi-solid organic products of natural or synthetic origin, generally of high molecular weight with no definite melting point. Plastics are called polymers and resins.
RIGID PVC Polyvinyl chloride or a polyvinyl chloride/acetate copolymer characterized by a relatively high degree of hardness; it may be formulated with or without a small percentage of plasticizer.
ROCKWELL HARDNESS A common method of testing a plastics material for resistance to indentation (surface hardness) in which a diamond or steel ball, under pressure, is used to pierce the test specimen. The load used is expressed in kilograms and 10-kilogram weight is first applied and the degree of penetration noted. The so-called major load (60 to 150 kilograms) is next applied and a second reading is obtained. The hardness is then calculated as the difference between the two loads and expressed with nine different prefix letters to denote the type of penetration used and the weight applied as the major load. ASTM D785
SANDWICH HEATING A method of heating a thermoplastic sheet prior to forming which consists of heating sides of the sheet simultaneously.
SARAN PLASTIC See Vinylidene Chloride Plastics
SHEAR STRENGTH The ability of a material to withstand shear stress or the stress at which a material fails in shear.
A flat section of thermoplastic resin which is 10 mils or grater in thickness.
SILICONE One of the family of polymeric materials in which the recurring chemical group contains silicone and oxygen atoms as links in the main chain. At present these compounds are derived from silica (sand) and methyl chloride. The various forms obtainable are characterized by their resistance to heat. Silicones are used in the following applications: (a) Greases for lubricants. (b) Rubber-like sheeting for gaskets, etc. (c) Heat-stable fluids and compounds for waterproofing, insulating, etc. (d) Thermosetting insulating varnishes and resins for both coating and laminating.
SPECIFIC VISCOSITY The specific viscosity of a polymer is the relative viscosity of a known concentration of the polymer minus one. It is usually determined for a low concentration of the polymer (0.5 g. per 100-ml. of solution or less).
STRETCH FORMING A plastic sheet forming technique in which the heated thermoplastic sheet is stretched over a mold and subsequently cooled.
THERMOFORMING Any process of forming a thermoplastic sheet, which consists of heating the sheet and pulling it down onto a mold surface.
TOLERANCE A specified allowance for deviations in weighting, measuring, etc., or for deviations from the standard dimensions or weight.
(Underwriters Laboratories Inc.)
A not-for-profit independent organization for the testing for public safety. The primary concern is fire and electrical hazards. UL publishes a Plastics Components Recognition List known as “Yellow Cards”. UL is head quartered in Northbrook, IL and has laboratories around the country. Most plastics testing occur in Northbrook or Research Park, NC.
ULTRAVIOLET Zone or invisible radiations beyond the violet end of the spectrum of visible radiations. Since UV wavelengths are shorter that visible, their photons have more energy, enough to initiate some chemical reactions and to degrade most plastics.
UNDERCUT (a)Having a protuberance or indentation that impedes withdrawal from a two-piece; rigid mold. Flexible materials can be ejected intact even with slight undercuts. (n) Any such protuberance or indentation; depends also on design of the mold.
Ant chemical compound which, when mixed with a thermoplastic resin, selectively absorbs UV rays, or prevents degradation of the plastic due to exposure to UV light.
VACUUM FORMING Method of sheet forming in which the plastic sheet is clamped in a stationary frame, heated, and drawn down by a vacuum into a mold. In a loose sense, it is sometimes used to refer to all sheet forming techniques, including Drape Forming q.v., involving the use of vacuum and stationary molds.
VENT In a mold, a shallow channel or minute hole cut in the cavity to allow air to escape as the material enters.
VINYL CHLORIDE PLASTICS Plastics based on polymers of vinyl chloride or copolymers, the vinyl chloride with other monomers, the vinyl chloride being in greatest amount by mass.
VINYLIDENE CHLORIDE PLASTICS Plastics based on polymer resins made by the polymerization of vinylidene chloride or copolymerization of vinylidene chloride with other unsaturated compounds, the vinylidene chloride being the greatest amount by weight.
VIRGIN MATERIAL A plastic material in the form of pellets, granules, powder, flock, or liquid that has not been subjected to use or processing other than that requires for its initial manufacture.
VISCOSITY Internal friction or resistance to flow of a liquid. The constant ratio of shearing stress to rate of shear. In liquids for which this ratio is a function of stress, the term “apparent viscosity” is defined as this ratio.
VOIDS (1)In solid plastic, an unfilled space of such size that it scatters radiant energy such as light. (2) A cavity unintentionally formed in a cellular material and substantially larger than the characteristic individual cells.
WEATHERABILITY The ability of a polymer to withstand the deleterious effects of UV radiation and other atmospheric conditions.