A vacuum forming process in which a male mold in enclosed in a box which forms an air cushion as the mold advances toward the hot plastic sheet, this keeping the mold from contacting the sheet until the end of its travel.  At this point, vacuum is applied to destroy the air cushion and pull the sheet against the mold (see thermoforming)

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

Plastic parts are joined to other articles by many methods. Self-tapping screws are made with special thread configurations to suit specific resins.  Threaded inserts to receive mounting screws may be molded or installed by press-fitting or by self-tapping external threads.  Press fitting is used to join plastics to similar or dissimilar materials.  Snap fitting joints are made by molding or machining an undercut in one part, and providing a lip to engage this undercut in a mating component.  Other methods are cementing, heat sealing, staking, ultrasonic inserting and welding.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

A method of molding or bonding involving the application of fluid pressure, usually by means of air, steam, water or vacuum, to a flexible cover which, sometimes in conjunction with the rigid die, completely encloses the material to molded or bonded.   A flexible bag or mattress is employed to apply pressure uniformly over one surface of the laminate. A preform comprising a fibrous sheet impregnated an A- or B-stage resin is placed over or in a rigid mold forming one surface of the article.  The bag is applied to the other surface, then pressure is applied by vacuum, an autoclave, press or by inflating the bag.  Heat may be applied by steam in the autoclave, or through the rigid mold portion.  When an autoclave is the used the process is sometimes called autoclave molding.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

A variation of the thermoforming process, in which the hot plastic sheet is clamped in a frame and billowed upwards against a male plug or die as the plug or die descends into the frame.  The process is suitable for thin-walled containers with a high draw ration.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

A methods of packaging articles in thermoformed “blister” or pouches shaped to more-or-less fit the contours of the article.  The preformed blisters, usually slightly oversized to provide ample room, are made of thermoplastics such as vinyls, polystyrene, or cellulosic plastics.  They are placed inverted in fixtures, loaded with the articles, then cards coated with an adhesive are applied and sealed to the flanges of the blisters by means of heat and pressure.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

A method of producing hollow plastic objects by stretching and hardening softened plastic material against a mold through the application of internal pressure, usually compressed air.  Most commonly, the process involves extruding a tube (parison) downward between the opened halves of a metal mold, closing the mold to pinch off and seal the parison at top and bottom, injecting air through a needle inserted through the parison wall, cooling the mass in contact with mold, opening the mold and removing the formed article. Many variations of the process exist. In the earliest use of the process, two sheets of cellulose nitrate were sued instead of a parison.  The parison is sometimes formed by injection molding, and sometimes is extruded in advance, cut into lengths and reheated when needed. [PE, LW]

The process of forming thermoplastic sheeting or film by passing the material through a series of heated rollers.  The gap between the last pair of heated rollers determines the thickness of the sheet. Subsequent cold rollers cool the sheet.  The plastic compound is usually premixed and plasticated on separate equipment, then fed continuously into the nip of the first pair of calendar rolls.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

To form a plastic material into a certain shape by pouring it into a mold and letting it harden without applying external pressure.

The process of forming pipes or other hollow cylindrical objects by introducing a measured amount of fluid resin or resin dispersion into a r­­otable container or mold, rotating the mold about one axis at a speed high enough to force the fluid against all parts of the mold by centrifugal force, maintain such rotation while solidifying the plastic by applicable means such as heating, then cooling if necessary and removing the formed part.  This should not be confused with Rotational casting, which involved rotation at slow speeds about one or more axes and distribution under the force of gravity.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

A process similar to centrifugal casting except that the materials are dry, sinterable powders such as polyethylene. Such powders are fused by the application of heat to the rapidly rotating mold. 

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

A term applied to film extrusion in which the extruded film is drawn over cooled rollers, imparting improved gloss.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

A stretching process employed to improve the tensile properties of thermoplastic filaments and films.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

A bonding operation in which an assembly is subjected to pressure without the application of heat.

The term encompasses processes for forming shapes of reinforced plastics in which little or no pressure is applied during the forming and curing steps.  It is usually employed in the connection with the processes of Spray-up and Hand Lay-up Molding when such processes do not includes the application of pressure during curing.

Process by which laminates bonded with contact pressure resins can, by means of specially developed machinery, by produced on a continuous as opposed to a batch-wise basis.

A coating process in which the substrate to be coated is a conveyed rapidly through a free-falling liquid “curtain” of a low-viscosity resin, solution, suspension or emulsion.  The coating thickness is governed by the rate of flow of the fluid and the speed of travel of the substrate.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

The process of cutting shapes from sheets of plastic by pressing a shaped knife edge into one or several layers of sheeting.  The dies are often called steel rule dies, and pressure is applied by hydraulic or mechanical presses.  Die cut pieces are often the fabricated and assembled.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

A coating process wherein the object to be coated, preheated or cold depending on the nature of the coating material, is dipped into a tank of fluid resin, solution or dispersion, withdrawn and subjected to further heat or drying to solidify the deposit.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

A process for production of two-color parts by means of successive molding operations.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

The method of forming a thermoplastic sheet into three-dimensional articles in which the sheet is clamped in a movable frame, heated, and lowered to drape over the high points of a male mold. Vacuum is then applied to complete the forming operation. 

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

The process of adding colorant to molding compounds and resin in particulate form by tumble blending them with dyes, pigments or color concentrates.  This process enables custom molders or extruders to carry a large inventory of uncolored compound, preparing smaller batches or colored compounds to customers’ specifications. 

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

The process of construction of a laminate by the layering of pre-impregnated, partly cured reinforcements in or on a mold, usually followed by bag molding or autoclave molding.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

Filament winding using pre-impregnated roving, as differentiated from wet winding in which unimpregnated roving is pulled through a resin just prior to winding on a mandrel.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

A process used for making molds for plastics processes, usually those employing low or moderate pressures, comprising electroplating a pattern which is usually of wax or flexible material. [PE]

Articles of almost any common plastic can be plated by conventional processes used for metals, after their surfaces have been rendered conductive by precipitation of silver or other conductive substance.  A layer of copper is usually applied first, followed by a final plating of gold, silver, chrome or nickel.  ABS resins have been most widely used for articles to be electroplated, especially in the automotive industry.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

The process of encasing an article in a resinous mass performed by placing the article in a mold, pouring a liquid resin into the mold to completely surround the article, curing the resin and removing the encased article form the mold. In the case of electrical components, the lead wires or terminals may protrude from the embedment.  The main difference between embedding and potting is that in potting the mold is a container which remains fixed to the resinous mass.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

Techniques used to create depressions of a specific pattern in plastics film or sheeting.  In the case of cast films, embossing can be accomplished directly by casting on a textured belt or roll.  Calendered films are frequently embossed by rollers just after the calendaring process. Other films or coated fabrics can be embossed subsequent to manufacture be reheating and passing through embossing rollers, or compressing between plates. Extruded sheets, up to 1/8” or thicker, are commonly embossed as the sheets emerge form the extruder.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

Extrusion blow molding can be used to process many different polymers including polyethylene, polyvinyl chloride, polypropylene and more. The process begins with the conventional downward extrusion of a tube. When the tube reaches the desired length the mold is closed catching and holding the neck end open and pinching the bottom end closed. Then a blow-pin is inserted into the neck end of the hot tube to form the threaded opening and inflate the tube inside the mold cavity. When the mold is completely cooled it is opened to eject the bottle and the excess plastic is trimmed from the neck and bottom areas.

http://www.plasticmolding.ca/techniques/blow_molding.htm

A laminating process in which a plastic layer is extruded between two layers of substrate. 

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

The process of compacting of a plastifiable material and forcing it through an orifice to form continuous shapes.  Typical shapes extruded are hose, tubing, flat films and sheets, jackets around electrical wires, parisons for blow molding, filaments and fibers, strands for pelletizing, and webs for coating and laminating.

Fabrication is the process of working materials that can include the assembly or modification of preformed plastic articles by processes such has welding, heat-sealing, adhesive joining, machining and joining by mechanical devices.

The process of forming thermoplastic film wherein an extruded plastic tube is continuously inflated by internal air pressure, cooled, collapsed by rolls and wound up on subsequent rolls.  The tube is usually extruded vertically upward, and air is admitted as the hot tube emerges from the die.  An air ring is often employed to control cooling.  Air is retained within the blown bubble by means of a pair of pinch rolls which collapses the film.  Thickness of the film is controlled by varying the internal air pressure and rate of extrusion.  Extremely thin films with some degree of orientation can be produced by this method.

A method of rendering inert thermoplastics, particularly polyolefins, receptive to inks, lacquers, paints, adhesives and the like by bathing the surface of the article in a high oxidizing flame.  This treatment oxidizes the surface later of the article, making it receptive to coatings.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

The molding and curing of laminates at pressures no lower than 1000 p.s.i. and more commonly in the range of 1200 to 2000 p.s.i.

A method of marking plastics in which a special pigmented, dyed or metalized foil is pressed against the plastic article by means of a heated die, welding selected areas of the foil to the article. The term also includes the process of impressing inked type into the materials when the type is heated.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

The process of applying labels or decorations to plastic articles simultaneously with the molding operation by which they are formed. Two basic, methods, each with many variations, have been used. The first employs a pre-printed label of plastic film, paper of cloth which is positioned in the mold prior to molding. During the molding cycle, the label or its printed image fuses to and becomes an integral part of the article.  In the second basic method, the image is printed directly onto the mold surface with wet or dry ink, or applied to the mold by an offset process.  In-mold decorating processes can be used in injection molding, blow molding and casting operations.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

A blow molding process in which the parison is formed over a mandrel by injection molding, after which the mandrel and parison are shifted to a blow mold where the remainder of the cycle is completed.  While the part is being blown, cooled and ejected, another parison is being injection molded.  Advantages of the process are that a completely finished part is formed requiring no post finishing operations, closer tolerance are possible, and parison wall thicknesses can be varied at desired areas. First used to make small medical and single serving bottles, injection blow molding is now widely used for all types of plastic bottles.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

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

Injection molding has seen steady growth since its beginnings in the late 1800's. The technique has evolved from the production of combs and buttons to major consumer, industrial, medical, and aerospace products.  In 1868, perhaps in response to a request by billiard ball maker Phelan and Collander, John Wesley Hyatt invented a way to make billiard balls by injecting celluloid into a mold. By 1872, John and his brother Isaiah Hyatt patented the injection molding machine. The machine was primitive yet it was quite suitable for their purposes. It contained a basic plunger to inject the plastic into a mold through a heated cylinder.

Revolutionizing the plastics industry in 1946, James Hendry built the first screw injection molding machine with an auger design to replace Hyatt's plunger. The auger is placed inside the cylinder and mixes the injection material before pushing forward and injecting the material into the mold. Today, almost all injection molding machines use this same technique.

The process of foaming polyethylene by exposing it to ionizing radiation which evolves hydrogen from the polymer, causing it to foam.

A modification of the injection molding process designed for thermosets. An elongated nozzle or “jet” is attached to the front of the molding cylinder, provided with a high intensity heating element and rapid cooling means.  It is also necessary to control cylinder temperatures carefully to prevent premature hardening of the resin.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

A method of forming reinforced plastics articles comprising the steps of placing a web of reinforcement, which may or may not be impregnated with a resin, in a mold or over a form and applying fluid resin to impregnate and/or coat the reinforcement, followed by curing of the resin.  When little or no pressure issued in the curing process, the process is sometimes called contact pressure molding. When pressure is applied during curing, the process is often named after the means of applying pressure, such as bag molding and autoclave molding.  A related process is spray-up.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

Molding or laminating in which the pressure used in 200 p.s.i. or less.

Source: Whittington, Lloyd R.  Whittington's Dictionary of Plastics (Stamford, CT: Technomic, 1968).

Many machine operations commonly applied to metals are applicable to plastics with slight variations in tooling and speeds.  These include blanking, boring, drilling, grinding, milling, planning, punching, routing, sanding, sawing, shaping, tapping, threading and turning.  [LW]

Low pressure method for handling a laminate filled with glass mat – a jackstraw arrangement of fine glass fibers uniformly distributed to form a thin, highly porous, felt-lie material – which generally makes use of metal molds and a pneumatic press. Pressures may be as low as 5 p.s.i.

A term covering all process by which plastics are coated with metal, including electroplating, vacuum metallizing and silver spray process.

An injection molding process in which the first molded part is removed from a mold and placed into a second mold where the other color of material is molded into, or onto, the first part.

A printing process in which the image to be printed is first applied to an intermediate carrier such as a roll or plate, then is transferred to a plastic film or molded article. [LW]

A urethane foam molding process in which the reactants, usually an isocyanate, a polyol and catalyst, are fed in separate streams to a mixing head from which the mixed reactants are discharged into a mold.  The polyol and catalyst are sometimes combined along with other additives, but the isocyanate is always fed separately to the mixing head. [LW]

The process of softening a material to make it plastic or moldable.

A special technique for blow molding large parts.  To prevent excessive sag of the heavy parison the machine employs a table which, after rising to meet the parison at the die, descends with the parison but at a slightly lower rate than the parison extrusion speed. [LW]

A thermoforming process in which a plug or male mold is used to partially preform the part before forming is completed by means of vacuum or pressure. [LW]

A 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. [LW]

The process of encasing an article in a resinous mass performed by placing the article in a mold, pouring a liquid resin into the mold to completely surround the article, and curing the resin.  The mold is a container which remains attached to the potted article, assisted, when required, by the use of bonding agents.  The main difference between potting and encapsulation, is that in encapsulation the mold is removed from the encapsulated article.  These processes are widely used in the electrical industry.

A finishing process used to impart high gloss, improved clarity and mechanical properties to sheets of vinyl, cellulosic and other thermoplastics.  The sheets are hot-pressed against thin highly polished metal plates.

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. [LW]

Process by which a resin-impregnated pulp material is preformed by application of a vacuum and subsequently oven cured or molded.

A term for a reinforced plastics technique in which continuous strands of resin-impregnated reinforcing materials are pulled through the orifice of a steel di, then through a heating chamber.  The process yields continuous lengths of materials with high unidirectional strengths, used for building siding, fishing rods, pipe, golf club shafts, etc. [LW]

The process of forming hollow articles from fluid materials by rotating a mold containing a charge of the material about one or more axes at relatively low speeds until the charge is distributed on the inner mold walls by gravitational forces and hardened by heating, cooling or curing.  Rotation about one axis is suitable for cylindrical objects. Rotation about two axes and/or rocking motions are employed for completely closed articles.  The process dates back to 1855, when a British patent was granted for the rotational casting of hollow articles from molten metals.  Vinyl plastisols were first used in the process in 1947 by Claude Delacoste, a French toy manufacturer.  The process of rotational casting of plastisols comprises placing a measured charge of plastisol in the bottom half of an open mold, closing the mold, rotating the mold about one or more axes in the presence of heat until the charge has been distributed and fused against the mold walls, cooling the mold until the deposit is of sufficient strength, opening the mold and removing the article. [LW]

A process that is a variation fo the rotational casting process utilizing dry, finely divided sinterable powders, such as polyethylene rather than fluid materials.  The powders are first sintered, then fused against the mold walls.  This variation of the process dates back to 1947, when a British patent issued to I.C.I. ltd. for the rotational molding of powders such as polyethylene and PVC. [LW]

Method for casting either heat hardening or heat softening plastics, in which the resin in liquid form is poured into a mold, allowed to cure or cool until the required wall thickness is obtained, after which the remaining liquid is poured out.

Process for producing synthetic fibers and filaments by forcing a viscous resin solution through sine holes in a spinneret.

A general term covering several processes using a spray gun.  In reinforced plastics, the term applies to the simultaneous spraying of resin and chopped reinforcing fibers onto the mold or mandrel.  In the foamed plastics field, the term refers to the spraying of fast-reacting polyurethane or epoxy resin systems onto a surface where they react to foam and cure.  In both processes, resins and catalysts are usually sprayed through separate nozzles so that they become mixed externally, thus avoiding pot life problems in the spray equipment and tanks. [LW]

A process for molding parts of pre-expanded beads of polystyrene, using steam as a source of heat to further expand the blowing agent in the materials. The steam in most cases is contacted intimately with the beads directly or may be used to heat mold surfaces which are in contact with the beads. [LW]

The main applications of stretch blow molding includes jars, bottles, and similar containers because it produces items of excellent visual and dimensional quality compared to extrusion blow molding. The process first requires the plastic to be injection molded into a 'preform' with the finished necks (threads) of the bottles on one end.  The preform is then heated above its glass transition temperature and blown, using high pressure air, into bottles using metal blow molds. At the same time the preform is stretched with a core rod to fill inside of the mold. Strain hardening occurs as part of the stretching process of some polymers (such as Polyethylene Terepthalate) which allows the bottles to resist deforming under the pressures resulting from carbonated beverages (typically around 60 psi).

The process of forming a thermoplastic sheet into a three-dimensional shape by clamping the sheet in a frame, heating it to render it soft and flowable, then applying differential pressure to make the sheet conform to the shape of the mold or die positioned below the frame.  When the pressure is applied entirely by vacuum, the process is called vacuum firming.  When air pressure is employed to partially preform the sheet prior to application of vacuum the process becomes air assist vacuum forming.  In another variation, mechanical pressure is applied by a plug to partially preform the sheet (plug assist forming).  In the drape forming modification, the softened sheet is lowered to drape over the high points of a male mold prior to application of vacuum.  Still other modifications are plug-and-ring-forming, ridge forming, slip forming or air slip forming, and bubble forming. The term thermoforming also includes methods employing only mechanical pressure, such as matched mold forming, in which the hot sheet is formed between registered male and female molds. [LW]

A method of molding thermosetting materials, in which the plastic is first softened by heat and pressure in a transfer chamber, then transferred through suitable sprues, runners and gates into a closed mod for final curing.

A finishing operation for small plastic articles by which gates, flash and fins are removed and/or surfaces are polished by rotating them in a barrel together with wooden pegs, sawdust and polishing compounds.

A series of methods for forming three-dimensional parts from thermoplastic sheets by the application of a vacuum.  The plastic sheet is clamped in a frame suspended above a mold, heated until it becomes softened, drawn down into contact with the mold by means of vacuum, and cooled while in contact with the mold.