Glossary

ABS - Acrylontrile Butadiene Styrene - Acrylonytrile and styrene liquids and butadiene gas are polymerized together in a variety of ratios to produce the family of ABS resins

Annealing - A process of holding a material at a temperature mean, but below its melting point, the objective being to permit stress relaxation without distortion of shape. It is often used on molded articles to relieve stresses set up by flow into the molds.

Blow molding - A method of fabrication in which a parison (hollow tube) is forced into the shape of the mold cavity by internal air pressure.

Calender - (v.) To prepare sheets of material by pressure between two or more counter-rotating rolls. (n.) - The machine performing this operation.

Cold Molding - A procedure in which a composition is shaped at room temperature and cured by subsequent baking.

Crazing - Fine cracks which may extend in a network on or under the surface or through a layer of a plastic material.

Cylindrical - Refers to the shape of a container which has a circular cross section parallel to the minor axis and a rectangular cross section parallel to the major axis.

Decorative Sheet - A laminated plastics sheet used for decorative purposes in which the color and/or surface pattern is an integral part of the sheet.

Drape Forming - Method of forming thermoplastic sheet in which the sheet is clamped into a movable frame, heated, and draped over high points of a male mold. Vacuum is then pulled to complete the forming operation.

Embossing - Techniques used to create depressions of a specific pattern in plastics film and sheeting.

Environmental Stress Cracking - The susceptibility of a thermoplastic article to crack or craze formation under the influence of certain chemicals and stress.

Extrusion - The compacting of a plastic material and the forcing of it through an orifice in more or less continuous fashion.

Fabricate - To work a material into a finished form by machining, forming, or other operation or to make flexible film or sheeting into end products by sewing, cutting, sealing, or other operation.

Film - An optional term for sheeting having a nominal thickness not greater than 0.010 inch.

Flexible Molds - molds made of rubber or elastomeric plastics used for casting plastics. They can be stretched to remove cured pieces with undercuts.

Gloss - The shine or luster of the surface of a material.

Guide Pins - Devices that maintain proper alignment of force plug and cavity as mold closes.

Haze - The degree of cloudiness in a plastic material.

Honeycomb - Manufactured product consisting of sheet metal or a resin impregnated sheet material (paper, fibrous, glass, etc.) which has been formed into hexagonal-shaped cells. Used as core material for sandwich constructions.

Hot–stamping - Engraving operation for marketing plastics in which roll leaf is stamped with heated metal dies onto the face of the plastics. Ink compounds can also be used. By means of felt rolls, ink is applied to type and by means of heat and pressure, type is impressed into the material, leaving the marking compound in the indentation.

Impact Resistance - Relative susceptibility of plastics to fracture by shock, e.g., as indicated by the energy expended by a standard pendulum type impact machine in breaking a standard specimen in one blow.

Infra-red - Part of the electromagnetic spectrum between the visible light range and the radar range. Radiant heat is in this range, and infra-red heaters are used in sheet thermoforming.

Injection Molding - A molding procedure whereby a heat-softened plastic material is forced from a cylinder into a relatively cool cavity which gives the article the desired shape.

ISO - International Organization of Standardization.

Kydex - is an acrylic-polyvinyl chloride alloy. Engineered for thermoforming fabrication, Kydex, combines the advantageous properties of both the acrylic and the polyvinyl chloride components. From acrylic, it obtains superior rigidity and formability; from PVC, outstanding toughness, chemical resistance and good interior finish ratings.

Laminate - A product made by bonding together two or more layers of material or materials.

Lexan – Lexan sheet with its unique combination of high impact strength, flame retardancy, and thermoformability makes it ideally suited for security applications.

Mold - To shape plastic parts or finished articles by heat and pressure. (n.) (1) The cavity or matrix into which the plastic composition is placed and from which it takes its form. (2) The assembly of all the parts that function collectively in the molding process.

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 melt point, and good resistance to water and chemicals. The material is widely used for bristles in industrial and domestic brushes, and for many textile applications; it is also used in injection molding gears, bearings, combs, etc.

Opaque - Descriptive of a material or substance which will not transmit light. Opposite of transparent. Materials which are neither opaque nor transparent are sometimes described as semi-opaque, but are more properly classified as translucent.

PETG - glycol-modified polyethylene terephthalate, is a copolyester that is a clear amorphous thermoplastic. PETG sheet has high stiffness, hardness, and toughness as well as good impact strength.

Platens - The mounting plates of a press to which the entire mold assembly is bolted.

Polycarbonate - sheet with its unique combination of high impact strength, flame retardancy, and thermoformability makes it ideally suited for security applications.

Plug-and-ring - Method of sheet forming in which a plug, functioning as a male mold, is forced into a heated plastic sheet held in place by a clamping ring.

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.

Plexiglas® is acrylic plastic sheet. In its natural form, Plexiglas® acrylic sheet is a crystal clear (with transparency equal to optical glas), lightweight material having outstanding weatherability, high impact resistance, good chemical resistance, and excellent thermo-formability and machinability. Aside from colorless sheet, the two forms of Plexiglas® G & MC, come in a wide variety of transparent, translucent, and opaque colors, as well as in several different surface patterns.

Polymethyl methacrylate (PMMA) or poly (methyl 2-methylpropenoate) is the synthetic polymer of methyl methacrylate. This thermoplastic and transparent plastic is sold by the tradenames Plexiglas, Limacryl, R-Cast, Perspex, Plazcryl, Acrylex, Acrylite, Acrylplast, Altuglas, Polycast and Lucite and is commonly called acrylic glass or simply acrylic

Polystyrene - A water-white thermoplastic produced by the polymerization of styrene (vinyl benzene). The electrical insulating properties of polystyrene are outstandingly good and the material is relatively unaffected by moisture.

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 of granules, solutions, lattices, and pastes. Compounded with plasticizers it yields a flexible material superior to rubber in ageing properties. It is widely used for cable and wire coverings, in chemical plants, and in the manufacture of protective garments.

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 against the mold.

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.

Rotational Molding - A method used to make hollow articles from plastisols and lattices. Plastisol is charged into a hollow mold capable of being rotated in one or two planes. The hot mold fuses the plastisol into a gel after the rotation has caused it to cover all surfaces. The mold is then chilled and the product stripped out.

Sintra / pvc – Sintra is a closed-cell expanded plastic that has a high strength-to-weight ration for superior workability.

Shrink Wrapping - A technique of packaging in which the strains in a plastic film are released by raising the temperature of the film thus causing it to shrink over the package. These shrink characteristics are built into the film during its manufacture by stretching it under controlled temperatures to produce orientation of the molecules. Upon cooling, the film retains its stretched condition, but reverts toward its original dimensions when it is heated. Shrink film gives good protection to the products packaged and has excellent clarity.

Snap-back Forming - Sheet forming technique in which an extended heated plastic sheet is allowed to contract over a male form shaped to the desired contors.

Thermoplastic - is a plastic that melts to a liquid when heated and freezes to a brittle, very glassy state when cooled sufficiently. Most thermoplastics are high molecular weight polymers whose chains associate through weak van der Waals forces (polyethylene); stronger dipole-dipole interactions and hydrogen bonding (nylon); or even stacking of aromatic rings (polystyrene). Thermoplastic polymers differ from thermosetting polymers (Bakelite; vulcanized rubber) as they can, unlike thermosetting polymers, be remelted and remoulded. Many thermoplastic materials are addition polymers; e.g., vinyl chain-growth polymers such as polyethylene and polypropylene.

Thermoforming - Any process of forming thermoplastic sheet which consists of heating the sheet and pulling it down onto a mold surface.

Tolerance - A specified allowance for deviations in weighing, measuring, etc., or for deviations from the standard dimensions or weight.

Translucent - Descriptive of a material or substance capable of transmitting some light, but not clear enough to be seen through.

Transparent - Descriptive of a material or substance capable of a high degree of light transmission e.g., glass. Some polypropylene films and acrylic moldings are outstanding in this
respect.

UHMWPE - Ultra high molecular weight polyethylene also known as high modulus polyethylene (HMPE) or high performance polyethylene (HPPE), is a thermoplastic.

UHMW is a very tough material, with the highest impact strength of any thermoplastic presently made. It is highly resistant to corrosive chemicals, with exception of oxidizing acids. It has extremely low moisture absorption, very low coefficient of friction, is self lubricating and is highly resistant to abrasion (15 times more resistant to abrasion than carbon steel). Its coefficient of friction is significantly lower than that of nylon and acetal, and is comparable to teflon, but UHMWPE has better abrasion resistance than teflon. It is odorless, tasteless, and nontoxic.

Ultraviolet - Zone of invisible radiation beyond the violet end of the spectrum of visible radiation. Since UV wavelengths are shorter than the visible, their photons have more energy, enough to initiate some chemical reactions and to degrade most plastics.

UV Stabilizer - Any chemical compound which, when mixed with a thermoplastic resin, selectively absorbs UV rays.

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 involving the use of vacuum and stationary molds.

Warpage - Dimensional distortion in a plastic object after molding.