Plastic Extrusions

About Plastic Extrusions and Custom Plastic Extrusions Including: Acrylic Extrusions, Extruded Plastics, Plastic Channels, Plastic Extruders, Plastic Profiles, Plastic Rods, Plastic Shapes, Plastic Sheets, Plastic Strip, Plastic Trim, Polymer Extrusion & PVC Extrusions.

The plastic extrusion process is responsible for manufacturing countless items we encounter every single day at home, at the office, at school and in the commercial world. A fairly simple process capable of producing high volume products at relatively low cost, extrusion is one of the most popular methods of plastic fabrication. Common extruded plastic products include plastic profiles, plastic channels, plastic rods, plastic tubing, plastic trim, plastic sheets, blow-molded extrusions and coextrusions. Due to the linear nature of the plastic extrusion process, plastic channels and profiles can have almost limitless length and are manufactured into plastic strips for window profiles, building siding and plastic trim, gutters and channels, sealing sections, hoses, curtain rods, pipes, drinking straws and many other common products in the construction, automotive, medical and aerospace industries. Extruded plastic sheets are an essential part of the plastic fabrication industry, since most thermoforming processes use plastic sheeting of various gauges as a raw material. Consumer products, packaging, plastic container and many other industries use plastic sheets and plexiglass sheets in thermoforming processes such as vacuum forming, pressure forming and inline thermoforming.

A number of thermoplastic polymers are used in plastic extrusions; high density polyethylene (HDPE), low density polyethylene (LDPE), PETG, PVC, butyrate, vinyl, polypropylene, acrylic and polystyrene are all capable of being used in thermoplastics, although PVC extrusions are most commonly used to make profiles, channels, rods and tubing extrusions. To be extruded, thermoplastic pellets or flakes are fed into a hopper placed atop a closed extruding channel. Gravity feeds the raw plastic material down into the extruding channel; running through the length of the channel is a screw conveyor which moves the raw plastic along towards the opposite end, shearing and heating the plastic through friction. Electric heaters built into the extruding channel often help the screw conveyor to melt, or "plasticize" the plastic pellets, so that the plastic is completely molten by the time it comes to the end of the channel. On the end of the conveyor channel a die is secured which forms the molten plastic into a specific profile as it is pushed, or "extruded" through by the screw conveyor in much the same way toothpaste is squeezed through the opening of a toothpaste tube. The newly formed plastic profile is instantly cooled with cold water, pulled through by a series of conveyors and cut to appropriate lengths.

The number of profile shapes capable of being extruded is virtually limitless; a die can be made to reflect any profile, from basic hollow piping to complex insulating window channels. Plastic sheeting is also extruded this way; molten plastic is pushed through a flat die, and the flat shape is pulled and stretched by grips into wider sheets which are then fed into a series of round metal cooling "calendars" and are ultimately wound onto spools. Thicker gauge sheets are cut and stacked flat, ready to be thermoformed into plastic shapes. Dies for plastic sheeting can also be round, so that as plastic is extruded through the conveyor its tube shape is sheared in half, and both top and bottom are stretched into flat sheets separately. Sometimes additives and coating resins are added to the surface of the plastic sheet during the calendering process.

Plastic extrusion techniques can be applied not only to making linear profiles and sheets, but also to blow molding and coextrusions. Blow molded extrusions are fabricated by using vacuums to conform molten extruded plastic to the inside of a mold as it is extruded. Coextrusion is the process of adhering multiple layers together during the process of extrusion; during coextrusion, multiple screw conveyors will extrude plastic, layering different materials or colors on top of each other for added strength, function, or material efficiency. Plastic extrusions are not only responsible for everyday necessities like PVC pipes, indoor and outdoor window trim, sealing bars, siding, rods for machining and raw materials, plastic gutters and plastic sheets, but also for blow-molded bottles, plastic containers, point of purchase displays, packaging and much more as well. The extrusion process is highly customizable and is capable of high volume production as well as short runs, making plastic extrusion one of the most diverse and economical methods of plastic fabrication.

Plastic Extrusions and Custom Plastic Extrusions Image Provided by Preferred Plastics, Inc.

Plastic Extrusion Types

• Co-extruded plastic is material that is a combination of one or more polymers combined in the extrusion process.
  
• Extruded plastics are made by pouring liquid plastic into dies.
• Extruded plastic channels are strips of plastic that are shaped for a specific purpose and cut to length.
  
• Extruded plastic netting is produced in a continuous process resulting in a stable net structure in which the hole size is held constant, unlike a woven or knitted product. Extruded plastic netting is typically utilized in vertical applications such as walls for pens, separation in water, filtration, predator control or barriers.
  
• Extruded plastic sheets are plastic powder or pellets that have been formed into sheet products with a range of thickness from less than 0.010 in. (film) up to and exceeding 2.0 inches, with widths as great as 30 ft. This sheet can be further processed into parts via thermoforming.
  
• Extruded tubing is any tube product that has been made through the extrusion process out of thermoplastic or other rigid, semi-rigid or flexible materials.
  
• Plastic extruders are capable of making sheets, tubes, rods and other molded plastic materials.
• Plastic profiles are extruded stock shapes of plastics including HDPE, polystyrene, butyrate, vinyl, PVC, LDPE, nylon, polyurethane, acrylics and fiberglass.
• Plastic rods are cylinder-shaped components made of plastic materials.
• Plastic trim is a linear extruded profile that can be extruded to any length.
• Vinyl extrusions are extruded products that are made of polyvinyl chloride (PVC), including pipes, siding and floor coverings

Plastic Extrusion Terms

Adiabatic Plastic Extrusions - Plastic extrusions whose only source of heat is the conversion of the drive energy through the viscous resistance of the plastics mass in the plastic extruders.
 
Back Pressure - The resistivity of molten plastic material to forward flow.
 
Barrel - The part of the plastic extruders encasing the screw or plunger.
 
Barrel Liner - The sleeve forming the inner surface of the plastic extrusions barrel.
 
Calendering - The plastic extrusions process of pressing or smoothing material between rollers.
 
Cladding - Sometimes referred to as sidings it is extruded PVC-U boards that are used as outdoor weather-resistant fade panels.
 
Compound - Any plastic material prepared for subsequent manufacturing processes, specifically plastic extrusions, molding or calendering.
 
Compression Section - The transition section of a screw channel in which a reduction in the screw channel volume occurs.
 
Cooling Tank - A tank typically containing water through which plastic extrusions are constantly passed for cooling.
 
Cure - The technique of cross-linking a plastics material.
 
Decompression Section - The section of two-stage plastic extruders in which an increase in screw channel volume occurs.
 
Die - The component on plastics extruders affixed to the plastic extruders head through which the melt is pushed to form the desired profile.
 
Die Plate - In moulds, the main support for the punch or mould cavity.
 
Dry Blend - A free flowing blend of compound or resin and other ingredients as prepared for an additional manufacturing operation specifically for plastic extrusions or molding.
 
Extrudate - The product or result of the plastic extrusions process. An extrudate is a product or material forced through a shaping orifice as a continuous body.
 
Extruder Size - The minimal inner diameter of the plastic extruders barrel
 
Extrusion Coating - A coating technique in which molten plastic feeds directly from plastic extruders dies into a nip-roll assembly combined with the substrate.
 
Haul-off - Also called a caterpillar it is an apparatus used for the continual removal of extrudate from the die.
 
Heat Aging - The unique process of aging a thermoplastic or thermoset product and examining the percentage of retained physical and chemical properties after exposure to heat for a prolonged period of time.
 
Melt - Any plastic extrusions material heated to a plastic condition.
 
Melt Strength - A term that refers to the strength of molten plastic.
 
Outer Die Ring - The element of tubing tie that shapes the outer surface of a tube.
 
Pellets - Resins or mixtures of resins with compounding additives in the shape of similar-sized tablets and granules that have been extruded or chopped into short segments to prepare them for molding operations.
 
Ram Extruder - A barrel with a temperature control, wherein a plunger pushes material in a melted state to the die.
 
Resin - Any of several physically similar polymerized synthetics or chemically altered natural resins, such as thermoplastic materials (polyvinyl, polystyrene, polyethylene) or thermosetting materials (polyesters, epoxies, silicones used with fillers, stabilizers, pigments).
 
Screw - A helically grooved rotating element inside the barrel of screw plastic extruders. The main purpose of a screw is to melt and feed raw material from the feeder to the die, but it also homogenizes, compresses and pressurizes the material.
 
Screw Extruder - A machine comprised of a barrel with a temperature control. It houses one or more rotating screws, which pass plastic materials from the feed aperture and move them in the form of melt under pressure through a die.
 
Take-up - An apparatus for reeling extruded plastics material.
 
Thermoset - A term that refers to the family of materials that can be melted only once during the original processing and cannot be reprocessed after the original part is made.
 
Thermoplastic - Any material, such as polyethylene, Santoprene and ABS, which can be remelted and reprocessed without considerable loss of properties or scrap loss.
 
Torpedo - An apparatus at the discharge stage of the screw for finishing homogenizing and blending of the melt.
 
Trunking - An extruded PVC-U channel used to contain and protect pipes or cables.
 
Vacuum Sizing - A procedure utilizing a sizing die with a vacuum applied to the outer surface of the extrudate.
 
Vinyl - A generic term for PVC, it is one of various compounds of ethylene that are polymerized to form resins and plastics (e.g. polyvinyl or polyethylene plastics).