Misplaced Pages

#292707

91-609: The term styrofoam is often used in the United States as a colloquial term to refer to expanded (not extruded) polystyrene foam ( EPS ). Outside the United States, EPS is most commonly referred to as simply "polystyrene" with the term "styrofoam" being used in its capacity to describe all forms of extruded polystyrene, not just the Dupont brand itself. Polystyrene (EPS) is often used in food containers , coffee cups, and as cushioning material in packaging . Styrofoam is, however,

182-475: A polymerisation process. About 80 years later it was realized that heating of styrol starts a chain reaction that produces macromolecules , following the thesis of German organic chemist Hermann Staudinger (1881–1965). This eventually led to the substance receiving its present name, polystyrene. The company I. G. Farben began manufacturing polystyrene in Ludwigshafen , about 1931, hoping it would be

273-462: A "blowing agent", a material that enables the beads to be expanded. Pentane is commonly used as the blowing agent. The beads are added to a continuously agitated reactor with the blowing agent, among other additives, and the blowing agent seeps into pores within each bead. The beads are then expanded using steam. EPS is used for food containers , molded sheets for building insulation , and packing material either as solid blocks formed to accommodate

364-414: A 1 mm square. Several microextrusion processes have been developed since microforming was envisioned in 1990. Forward (ram and billet move in the same direction) and backward (ram and billet move in the opposite direction) microextrusion were first introduced, with forward rod-backward cup and double cup extrusion methods developing later. Regardless of method, one of the greatest challenges of creating

455-563: A US patent for polystyrene foam as an insulation product in 1935 (USA patent number 2,023,204). PS foams also exhibit good damping properties, therefore it is used widely in packaging. The trademark Styrofoam by Dow Chemical Company is informally used (mainly US & Canada) for all foamed polystyrene products, although strictly it should only be used for "extruded closed-cell" polystyrene foams made by Dow Chemicals. Foams are also used for non-weight-bearing architectural structures (such as ornamental pillars ). Expanded polystyrene (EPS)

546-437: A US patent was filed for "process for warm extrusion of metal". Patent US3156043 A outlines that a number of important advantages can be achieved with warm extrusion of both ferrous and non-ferrous metals and alloys if a billet to be extruded is changed in its physical properties in response to physical forces by being heated to a temperature below the critical melting point. Warm extrusion is done above room temperature, but below

637-466: A chain of polystyrene, giving a molar mass of 100,000–400,000 g/mol. Each carbon of the backbone has tetrahedral geometry , and those carbons that have a phenyl group (benzene ring) attached are stereogenic . If the backbone were to be laid as a flat elongated zig-zag chain, each phenyl group would be tilted forward or backward compared to the plane of the chain. The relative stereochemical relationship of consecutive phenyl groups determines

728-456: A combination of heating elements and shear heating from the extrusion screw. The screw, or screws as the case with twin screw extrusion, forces the resin through a die, forming the resin into the desired shape. The extrudate is cooled and solidified as it is pulled through the die or water tank. A "caterpillar haul-off" (called a "puller" in the US) is used to provide tension on the extrusion line which

819-508: A die. Twin-screw high shear extruders blend materials and simultaneously break up particles. The resulting particle can be blended with compression aids and compressed into tablets or filled into unit dose capsules. The extrusion production technology of fuel briquettes is the process of extrusion screw wastes (straw, sunflower husks, buckwheat, etc.) or finely shredded wood waste (sawdust) under high pressure when heated from 160 to 350 °C. The resulting fuel briquettes do not include any of

910-515: A far less dense material than EPS and is more commonly suited to tasks such as thermal insulation . Additionally, it is moderately soluble in many organic solvents, cyanoacrylate , and the propellants and solvents of spray paint . In the 1940s, researchers, originally at Dow 's Chemical Physics Lab, led by Ray McIntire , found a way to make foamed polystyrene . They rediscovered a method first used by Swedish inventor Carl Georg Munters , and obtained an exclusive license to Munters's patent in

1001-468: A grey/black color which distinguishes it from standard EPS. Several EPS producers have produced a variety of these increased thermal resistance EPS usage for this product in the UK and EU. Water vapor diffusion resistance ( μ ) of EPS is around 30–70. ICC-ES ( International Code Council Evaluation Service) requires EPS boards used in building construction meet ASTM C578 requirements. One of these requirements

SECTION 10

#1732776696293

1092-419: A lubricant. A thick solid glass ring that is 0.25 to 0.75 in (6 to 18 mm) thick is placed in the chamber on the die to lubricate the extrusion as it is forced through the die. A second advantage of this glass ring is its ability to insulate the heat of the billet from the die. The extrusion will have a 1 mil thick layer of glass, which can be easily removed once it cools. Another breakthrough in lubrication

1183-672: A metallocene catalyst for the polymerisation reaction. Polystyrene is relatively chemically inert. While it is waterproof and resistant to breakdown by many acids and bases, it is easily attacked by many organic solvents (e.g. it dissolves quickly when exposed to acetone ), chlorinated solvents, and aromatic hydrocarbon solvents. Because of its resilience and inertness, it is used for fabricating many objects of commerce. Like other organic compounds, polystyrene burns to give carbon dioxide and water vapor , in addition to other thermal degradation by-products. Polystyrene, being an aromatic hydrocarbon , typically combusts incompletely as indicated by

1274-454: A nozzle. Rubber extrusion is a method used to make rubber items. In this process, either synthetic or natural rubber that hasn't been hardened yet is put through a machine called an extruder. This machine has a desired shaped mold and a pressurized conveyor system. The rubber gets heated and softened in the extruder, making it bendable. It then gets pushed through the mold, which gives it its final shape. The extruder consists of two main parts:

1365-464: A screw that moves the rubber along the conveyor while adding other materials, and a mold where the soft rubber is squeezed into. After the rubber gets its shape from the mold, it is then vulcanized to harden it into a usable product. This method is effective for large rubber pieces that are long and have a consistent shape, and the dies used in this process are inexpensive. It is often used to make things like rubber seals or hoses. Polymers are used in

1456-401: A simple flat extrusion die, because there would be no way to support the centre barrier of the die. Instead, the die assumes the shape of a block with depth, beginning first with a shape profile that supports the center section. The die shape then internally changes along its length into the final shape, with the suspended center pieces supported from the back of the die. The material flows around

1547-722: A smoke-developed index of less than 450. ICC-ES requires the use of a 15-minute thermal barrier when EPS boards are used inside of a building. According to the EPS-IA ICF organization, the typical density of EPS used for insulated concrete forms ( expanded polystyrene concrete ) is 1.35 to 1.80 pounds per cubic foot (21.6 to 28.8 kg/m ). This is either Type II or Type IX EPS according to ASTM C578. EPS blocks or boards used in building construction are commonly cut using hot wires. Extruded polystyrene foam (XPS) consists of closed cells. It offers improved surface roughness, higher stiffness and reduced thermal conductivity. The density range

1638-566: A split via a channel system of gates and runners. EPS is colloquially called "styrofoam" in the Anglosphere , an genericization of Dow Chemical's brand of extruded polystyrene . Sheets of EPS are commonly packaged as rigid panels (common in Europe is a size of 100 cm x 50 cm, usually depending on an intended type of connection and glue techniques, it is, in fact, 99.5 cm x 49.5 cm or 98 cm x 48 cm; less common

1729-496: A sprayed-on coating is necessary to prevent saturation. Oriented polystyrene (OPS) is produced by stretching extruded PS film, improving visibility through the material by reducing haziness and increasing stiffness. This is often used in packaging where the manufacturer would like the consumer to see the enclosed product. Some benefits to OPS are that it is less expensive to produce than other clear plastics such as polypropylene (PP), (PET), and high-impact polystyrene (HIPS), and it

1820-539: A successful microextrusion machine is the manufacture of the die and ram. "The small size of the die and ram, along with the stringent accuracy requirement, needs suitable manufacturing processes." Additionally, as Fu and Chan pointed out in a 2013 state-of-the-art technology review, several issues must still be resolved before microextrusion and other microforming technologies can be implemented more widely, including deformation load and defects , forming system stability, mechanical properties, and other size-related effects on

1911-513: A suitable replacement for die-cast zinc in many applications. Success was achieved when they developed a reactor vessel that extruded polystyrene through a heated tube and cutter, producing polystyrene in pellet form. Ray McIntire (1918–1996), a chemical engineer of Dow Chemical, rediscovered a process first patented in early 1930s by Swedish inventor Carl Munters . According to the Science History Institute, "Dow bought

SECTION 20

#1732776696293

2002-427: Is carcinogenic for humans and experimental animals , meaning that there is a positive association between exposure and cancer and that causality is credible, but that other explanations cannot be confidently excluded. See also the expansive list of environmental issues of polystyrene , among which it being non-biodegradable. Polystyrene Polystyrene ( PS ) / ˌ p ɒ l i ˈ s t aɪ r iː n /

2093-497: Is 120 x 60 cm; size 4 by 8 ft (1.2 by 2.4 m) or 2 by 8 ft (0.61 by 2.44 m) in the United States). Common thicknesses are from 10 mm to 500 mm. Many customizations, additives, and thin additional external layers on one or both sides are often added to help with various properties. An example of this is lamination with cement board to form a structural insulated panel . Thermal conductivity

2184-481: Is a distinct compound). By 1845 Jamaican-born chemist John Buddle Blyth and German chemist August Wilhelm von Hofmann showed that the same transformation of styrol took place in the absence of oxygen. They called the product "meta styrol"; analysis showed that it was chemically identical to Simon's Styroloxyd. In 1866 Marcellin Berthelot correctly identified the formation of meta styrol/Styroloxyd from styrol as

2275-524: Is a rigid and tough, closed-cell foam with a normal density range of 11 to 32 kg/m . It is usually white and made of pre-expanded polystyrene beads. The manufacturing process for EPS conventionally begins with the creation of small polystyrene beads. Styrene monomers (and potentially other additives) are suspended in water, where they undergo free-radical addition polymerization. The polystyrene beads formed by this mechanism may have an average diameter of around 200 μm. The beads are then permeated with

2366-449: Is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene . Polystyrene can be solid or foamed . General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a poor barrier to air and water vapor and has a relatively low melting point. Polystyrene is one of the most widely used plastics , with the scale of its production being several million tonnes per year. Polystyrene

2457-450: Is about 28–34 kg/m . Extruded polystyrene material is also used in crafts and model building, in particular architectural models. Because of the extrusion manufacturing process, XPS does not require facers to maintain its thermal or physical property performance. Thus, it makes a more uniform substitute for corrugated cardboard . Thermal conductivity varies between 0.029 and 0.039 W/(m·K) depending on bearing strength/density and

2548-427: Is also used to produce modified starch , and to pelletize animal feed . Generally, high-temperature extrusion is used for the manufacture of ready-to-eat snacks, while cold extrusion is used for the manufacture of pasta and related products intended for later cooking and consumption. The processed products have low moisture and hence considerably higher shelf life, and provide variety and convenience to consumers. In

2639-403: Is also utilized in pharmaceutical solid oral dose processing to enable delivery of drugs with poor solubility and bioavailability. Hot melt extrusion has been shown to molecularly disperse poorly soluble drugs in a polymer carrier increasing dissolution rates and bioavailability. The process involves the application of heat, pressure and agitation to mix materials together and ‘extrude’ them through

2730-497: Is approximately 5 °F⋅ft⋅h/BTU for 1 inch thick sheet. Styrofoam can be used under roads and other structures to prevent soil disturbances due to freezing and thawing. DuPont also produces styrofoam blocks and other shapes for use by florists and in craft products. DuPont insulation styrofoam has a distinctive blue color; styrofoam for craft applications is available in white and green. The EPA and International Agency for Research on Cancer reported limited evidence that styrene

2821-437: Is commonly injection molded , vacuum formed , or extruded, while expanded polystyrene is either extruded or molded in a special process. Polystyrene copolymers are also produced; these contain one or more other monomers in addition to styrene. In recent years the expanded polystyrene composites with cellulose and starch have also been produced. Polystyrene is used in some polymer-bonded explosives (PBX). Polystyrene (PS)

Styrofoam - Misplaced Pages Continue

2912-426: Is defined as the starting cross-sectional area divided by the cross-sectional area of the final extrusion. One of the main advantages of the extrusion process is that this ratio can be very large while still producing quality parts. Hot extrusion is a hot working process, which means it is done above the material's recrystallization temperature to keep the material from work hardening and to make it easier to push

3003-618: Is done at room temperature or near room temperature. The advantages of this over hot extrusion are the lack of oxidation, higher strength due to cold working , closer tolerances, better surface finish, and fast extrusion speeds if the material is subject to hot shortness . Materials that are commonly cold extruded include: lead , tin , aluminium , copper , zirconium , titanium , molybdenum , beryllium , vanadium , niobium , and steel . Examples of products produced by this process are: collapsible tubes, fire extinguisher cases, shock absorber cylinders and gear blanks. In March 1956,

3094-415: Is essential for overall quality of the extrudate. Pelletizers can also create this tension while pulling extruded strands in to be cut. The caterpillar haul-off must provide a consistent pull; otherwise, variation in cut lengths or distorted product will result. In some cases (such as fibre-reinforced tubes) the extrudate is pulled through a very long die, in a process called "pultrusion". The configuration of

3185-489: Is exploited for extrusion (as in Styrofoam ) and also for molding and vacuum forming , since it can be cast into molds with fine detail. The temperatures behavior can be controlled by photocrosslinking. Under ASTM standards, polystyrene is regarded as not biodegradable . It is accumulating as a form of litter in the outside environment , particularly along shores and waterways, especially in its foam form, and in

3276-468: Is generally considered to be non-biodegradable. However, certain organisms are able to degrade it, albeit very slowly. In 2015, researchers discovered that mealworms , the larvae form of the darkling beetle Tenebrio molitor , could digest and subsist healthily on a diet of EPS. About 100 mealworms could consume between 34 and 39 milligrams of this white foam in a day. The droppings of mealworm were found to be safe for use as soil for crops. In 2016, it

3367-410: Is initiated with free radicals . Ziegler–Natta polymerization can produce an ordered syndiotactic polystyrene with the phenyl groups positioned on alternating sides of the hydrocarbon backbone. This form is highly crystalline with a T m (melting point) of 270 °C (518 °F). Syndiotactic polystyrene resin is currently produced under the trade name XAREC by Idemitsu corporation, who use

3458-401: Is its cost for machinery and its upkeep. The extrusion process is generally economical when producing between several kilograms (pounds) and many tons, depending on the material being extruded. There is a crossover point where roll forming becomes more economical. For instance, some steels become more economical to roll if producing more than 20,000 kg (50,000 lb). Cold extrusion

3549-446: Is less hazy than HIPS or PP. The main disadvantage of OPS is that it is brittle, and will crack or tear easily. Extrusion Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex cross-sections; and to work materials that are brittle, because

3640-560: Is measured according to EN 12667. Typical values range from 0.032 to 0.038 W/(m⋅K) depending on the density of the EPS board. The value of 0.038 W/(m⋅K) was obtained at 15 kg/m while the value of 0.032 W/(m⋅K) was obtained at 40 kg/m according to the datasheet of K-710 from StyroChem Finland. Adding fillers (graphites, aluminum, or carbons) has recently allowed the thermal conductivity of EPS to reach around 0.030–0.034 W/(m⋅K) (as low as 0.029 W/(m⋅K)) and as such has

3731-548: Is naturally transparent , but can be colored with colorants. Uses include protective packaging (such as packing peanuts and optical disc jewel cases ), containers, lids, bottles, trays, tumblers, disposable cutlery , in the making of models, and as an alternative material for phonograph records . As a thermoplastic polymer, polystyrene is in a solid (glassy) state at room temperature but flows if heated above about 100 °C, its glass transition temperature . It becomes rigid again when cooled. This temperature behaviour

Styrofoam - Misplaced Pages Continue

3822-412: Is not produced commercially. [REDACTED] The only commercially important form of polystyrene is atactic , in which the phenyl groups are randomly distributed on both sides of the polymer chain. This random positioning prevents the chains from aligning with sufficient regularity to achieve any crystallinity . The plastic has a glass transition temperature T g of ~90 °C. Polymerization

3913-471: Is now used for other materials that have melting temperatures higher than steel or that require a narrow range of temperatures to extrude, such as the platinum-iridium alloy used to make kilogram mass standards. The process starts by heating the materials to the extruding temperature and then rolling it in glass powder. The glass melts and forms a thin film, 20 to 30 mils (0.5 to 0.75 mm), in order to separate it from chamber walls and allow it to act as

4004-732: Is often done to introduce polar groups. Much of modern biomedical research relies on the use of such products; they, therefore, play a critical role in pharmaceutical research. Thin sheets of polystyrene are used in polystyrene film capacitors as it forms a very stable dielectric , but has largely fallen out of use in favor of polyester . Polystyrene foams are 95–98% air. Polystyrene foams are good thermal insulators and are therefore often used as building insulation materials, such as in insulating concrete forms and structural insulated panel building systems. Grey polystyrene foam, incorporating graphite , has superior insulation properties. Carl Munters and John Gudbrand Tandberg of Sweden received

4095-404: Is that the limiting oxygen index of EPS as measured by ASTM D2863 be greater than 24 volume %. Typical EPS has an oxygen index of around 18 volume %; thus, a flame retardant is added to styrene or polystyrene during the formation of EPS. The boards containing a flame retardant when tested in a tunnel using test method UL 723 or ASTM E84 will have a flame spread index of less than 25 and

4186-412: Is that the force required to extrude the billet is greater than that needed in the indirect extrusion process because of the frictional forces introduced by the need for the billet to travel the entire length of the container. Because of this the greatest force required is at the beginning of process and slowly decreases as the billet is used up. At the end of the billet the force greatly increases because

4277-528: Is the main way to produce wire . Metal bars and tubes are also often drawn. Extrusion may be continuous (theoretically producing indefinitely long material) or semi-continuous (producing many pieces). It can be done with hot or cold material. Commonly extruded materials include metals , polymers , ceramics , concrete , modelling clay , and foodstuffs. Products of extrusion are generally called extrudates . Also referred to as "hole flanging", hollow cavities within extruded material cannot be produced using

4368-411: Is the use of phosphate coatings. With this process, in conjunction with glass lubrication, steel can be cold extruded. The phosphate coat absorbs the liquid glass to offer even better lubricating properties. Plastics extrusion commonly uses plastic chips or pellets, which are usually dried, to drive out moisture, in a hopper before going to the feed screw. The polymer resin is heated to molten state by

4459-416: Is used because it has good lubricity and high pressure properties. The design of an extrusion profile has a large impact on how readily it can be extruded. The maximum size for an extrusion is determined by finding the smallest circle that will fit around the cross-section, this is called the circumscribing circle . This diameter, in turn, controls the size of the die required, which ultimately determines if

4550-723: Is used for producing disposable plastic cutlery and dinnerware , CD "jewel" cases , smoke detector housings, license plate frames, plastic model assembly kits, and many other objects where a rigid, economical plastic is desired. Production methods include thermoforming ( vacuum forming ) and injection molding . Polystyrene Petri dishes and other laboratory containers such as test tubes and microplates play an important role in biomedical research and science. For these uses, articles are almost always made by injection molding, and often sterilized post-molding, either by irradiation or by treatment with ethylene oxide . Post-mold surface modification, usually with oxygen -rich plasmas ,

4641-425: Is used, for example, when producing texturised vegetable proteins (TVP). For use in pharmaceutical products, extrusion through nano-porous, polymeric filters is being used to produce suspensions of lipid vesicles liposomes or transfersomes with a particular size of a narrow size distribution . The anti-cancer drug Doxorubicin in liposome delivery system is formulated by extrusion, for example. Hot melt extrusion

SECTION 50

#1732776696293

4732-408: The column strength of the stem. Because the billet moves with the container the frictional forces are eliminated. This leads to the following advantages: The disadvantages are: In the hydrostatic extrusion process the billet is completely surrounded by a pressurized liquid, except where the billet contacts the die. This process can be done hot, warm, or cold, however the temperature is limited by

4823-411: The crystallite (grain) structure and boundaries. There are many different variations of extrusion equipment. They vary by four major characteristics: A single or twin screw auger, powered by an electric motor, or a ram, driven by hydraulic pressure (often used for steel and titanium alloys), oil pressure (for aluminium), or in other specialized processes such as rollers inside a perforated drum for

4914-401: The sooty flame. The process of depolymerizing polystyrene into its monomer , styrene , is called pyrolysis . This involves using high heat and pressure to break down the chemical bonds between each styrene compound. Pyrolysis usually goes up to 430 °C. The high energy cost of doing this has made commercial recycling of polystyrene back into styrene monomer difficult. Polystyrene

5005-428: The tacticity , which affects various physical properties of the material. In polystyrene, tacticity describes the extent to which the phenyl group is uniformly aligned (arranged at one side) in the polymer chain. Tacticity has a strong effect on the properties of the plastic. Standard polystyrene is atactic. The diastereomer where all of the phenyl groups are on the same side is called isotactic polystyrene, which

5096-602: The Pacific Ocean. Polystyrene was discovered in 1839 by Eduard Simon , an apothecary from Berlin. From storax , the resin of the Oriental sweetgum tree Liquidambar orientalis , he distilled an oily substance, that he named styrol, now called styrene . Several days later, Simon found that it had thickened into a jelly, now known to have been a polymer , that he dubbed styrol oxide ("Styroloxyd") because he presumed that it had resulted from oxidation ( styrene oxide

5187-478: The United States. Dow found ways to adapt Munters's method to make large quantities of extruded polystyrene as a closed cell foam that resists moisture. The patent on this adaptation was filed in 1947. Styrofoam has a variety of uses. Styrofoam is composed of 98% air, making it lightweight and buoyant. DuPont produces styrofoam building materials, including varieties of building insulation sheathing and pipe insulation. The claimed R-value of styrofoam insulation

5278-416: The average value is ~0.035 W/(m·K). Water vapor diffusion resistance (μ) of XPS is around 80–250. Commonly extruded polystyrene foam materials include: Although it is a closed-cell foam, both expanded and extruded polystyrene are not entirely waterproof or vapor proof. In expanded polystyrene there are interstitial gaps between the expanded closed-cell pellets that form an open network of channels between

5369-422: The billet is thin and the material must flow radially to exit the die. The end of the billet (called the butt end) is not used for this reason. In indirect extrusion, also known as backwards extrusion, the billet and container move together while the die is stationary. The die is held in place by a "stem" which has to be longer than the container length. The maximum length of the extrusion is ultimately dictated by

5460-454: The binders, but one natural – the lignin contained in the cells of plant wastes. The temperature during compression causes melting of the surface of bricks, making it more solid, which is important for the transportation of briquettes. The majority of synthetic materials in textiles are manufactured with extrusion only. Fiber forming substances are used in extrusion to form various synthetic filaments. The molten materials are passed through

5551-694: The bonded pellets, and this network of gaps can become filled with liquid water. If the water freezes into ice, it expands and can cause polystyrene pellets to break off from the foam. Extruded polystyrene is also permeable by water molecules and can not be considered a vapor barrier. Water-logging commonly occurs over a long period in polystyrene foams that are constantly exposed to high humidity or are continuously immersed in water, such as in hot tub covers, in floating docks, as supplemental flotation under boat seats, and for below-grade exterior building insulation constantly exposed to groundwater. Typically an exterior vapor barrier such as impermeable plastic sheeting or

SECTION 60

#1732776696293

5642-453: The charge (billet or other precursor) rotates relative to the extrusion die. An extrusion force is applied so as to push the charge against the die. In practice either the die or the charge may rotate or they may be counter-rotating. The relative rotary motion between the charge and the die has several significant effects on the process. First, the relative motion in the plane of rotation leads to large shear stresses, hence, plastic deformation in

5733-586: The cost of tooling as well as the rate of production. Thicker sections generally need an increased section size. In order for the material to flow properly legs should not be more than ten times longer than their thickness. If the cross-section is asymmetrical, adjacent sections should be as close to the same size as possible. Sharp corners should be avoided; for aluminium and magnesium the minimum radius should be 0.4 mm (1/64 in) and for steel corners should be 0.75 mm (0.030 in) and fillets should be 3 mm (0.12 in). The following table lists

5824-405: The die when extruding. If a solid billet is used as the feed material then it must first be pierced by the mandrel before extruding through the die. A special press is used in order to control the mandrel independently from the ram. The solid billet could also be used with a spider die, porthole die or bridge die. All of these types of dies incorporate the mandrel in the die and have "legs" that hold

5915-408: The extrusion process, raw materials are first ground to the correct particle size. The dry mix is passed through a pre-conditioner, in which other ingredients may be added, and steam is injected to start the cooking process. The preconditioned mix is then passed through an extruder, where it is forced through a die and cut to the desired length. The cooking process takes place within the extruder where

6006-430: The gut of superworms that contain encoded enzymes associated with the degradation of polystyrene and the breakdown product styrene. The bacterium Pseudomonas putida is capable of converting styrene oil into the biodegradable plastic PHA . This may someday be of use in the effective disposing of polystyrene foam. It is worthy to note the polystyrene must undergo pyrolysis to turn into styrene oil. Polystyrene

6097-424: The interior screws are a driving force dependent on the application. Mixing elements or convey elements are used in various formations. Extrusion is common in the application of adding colorant to molten plastic thus creating specific custom color. Extrusion is also a process used in fused filament deposition 3D printers , whereby the extruder is often composed of a geared motor pushing plastic filament through

6188-471: The item being protected or as loose-fill "peanuts" cushioning fragile items inside boxes. EPS also has been widely used in automotive and road safety applications such as motorcycle helmets and road barriers on automobile race tracks . A significant portion of all EPS products are manufactured through injection molding. Mold tools tend to be manufactured from steels (which can be hardened and plated), and aluminum alloys. The molds are controlled through

6279-432: The layer of charge in contact with and near the die. This plastic deformation is dissipated by recovery and recrystallization processes leading to substantial heating of the deforming charge. Because of the deformation heating, friction extrusion does not generally require preheating of the charge by auxiliary means potentially resulting in a more energy efficient process. Second, the substantial level of plastic deformation in

6370-468: The mandrel in place. During extrusion the metal divides, flows around the legs, then merges, leaving weld lines in the final product. Direct extrusion, also known as forward extrusion, is the most common extrusion process. It works by placing the billet in a heavy walled container. The billet is pushed through the die by a ram or screw. There is a reusable dummy block between the ram and the billet to keep them separated. The major disadvantage of this process

6461-423: The material encounters only compressive and shear stresses. It also creates excellent surface finish and gives considerable freedom of form in the design process. Drawing is a similar process, using the tensile strength of the material to pull it through the die. It limits the amount of change that can be performed in one step, so it is limited to simpler shapes, and multiple stages are usually needed. Drawing

6552-421: The material through the die. Most hot extrusions are done on horizontal hydraulic presses that range from 230 to 11,000 metric tons (250 to 12,130 short tons). Pressures range from 30 to 700 MPa (4,400 to 101,500 psi), therefore lubrication is required, which can be oil or graphite for lower temperature extrusions, or glass powder for higher temperature extrusions. The biggest disadvantage of this process

6643-441: The minimum cross-section and thickness for various materials. Metals that are commonly extruded include: Magnesium and aluminium alloys usually have a 0.75 μm (30 μin) RMS or better surface finish. Titanium and steel can achieve a 3 micrometres (120 μin) RMS. In 1950, Ugine Séjournet, of France , invented a process which uses glass as a lubricant for extruding steel. The Ugine-Sejournet, or Sejournet, process

6734-467: The molecules consist of thousands of atoms, the cumulative attractive force between the molecules is large. When heated (or deformed at a rapid rate, due to a combination of viscoelastic and thermal insulation properties), the chains can take on a higher degree of confirmation and slide past each other. This intermolecular weakness (versus the high intramolecular strength due to the hydrocarbon backbone) confers flexibility and elasticity. The ability of

6825-697: The most common because they are reliable and robust. They can deliver over 35 MPa (5,000 psi). They supply a constant pressure throughout the whole billet. The disadvantage is that they are slow, between 50 and 200 mm/s (2–8 ips). Accumulator water drives are more expensive and larger than direct-drive oil presses, and they lose about 10% of their pressure over the stroke, but they are much faster, up to 380 mm/s (15 ips). Because of this they are used when extruding steel. They are also used on materials that must be heated to very hot temperatures for safety reasons. Hydrostatic extrusion presses usually use castor oil at pressure up to 1,400 MPa (200 ksi). Castor oil

6916-402: The part will fit in a given press. For example, a larger press can handle 60 cm (24 in) diameter circumscribing circles for aluminium and 55 cm (22 in) diameter circles for steel and titanium. The complexity of an extruded profile can be roughly quantified by calculating the shape factor , which is the amount of surface area generated per unit mass of extrusion. This affects

7007-434: The polymerization, the carbon-carbon π bond of the vinyl group is broken and a new carbon-carbon σ bond is formed, attaching to the carbon of another styrene monomer to the chain. Since only one kind of monomer is used in its preparation, it is a homopolymer. The newly formed σ bond is stronger than the π bond that was broken, thus it is difficult to depolymerize polystyrene. About a few thousand monomers typically comprise

7098-523: The process was called "squirting". In 1894, Alexander Dick expanded the extrusion process to copper and brass alloys. The process begins by heating the stock material (for hot or warm extrusion). It is then loaded into the container in the press. A dummy block is placed behind it where the ram then presses on the material to push it out of the die. Afterward the extrusion is stretched in order to straighten it. If better properties are required then it may be heat treated or cold worked . The extrusion ratio

7189-403: The product produces its own friction and heat due to the pressure generated (10–20 bar). The main independent parameters during extrusion cooking are feed rate, particle size of the raw material, barrel temperature, screw speed and moisture content. The extruding process can induce both protein denaturation and starch gelatinization , depending on inputs and parameters. Sometimes, a catalyst

7280-412: The production of many simultaneous streams of material. There are several methods for forming internal cavities in extrusions. One way is to use a hollow billet and then use a fixed or floating mandrel . A fixed mandrel, also known as a German type, means it is integrated into the dummy block and stem. A floating mandrel, also known as a French type, floats in slots in the dummy block and aligns itself in

7371-483: The production of plastic tubing, pipes, rods, rails, seals, and sheets or films. Ceramic can also be formed into shapes via extrusion. Terracotta extrusion is used to produce pipes. Many modern bricks are also manufactured using a brick extrusion process. With the advent of industrial manufacturing, extrusion found application in food processing of instant foods and snacks, along with its already known uses in plastics and metal fabrication. The main role of extrusion

7462-676: The raw material for molding parts or extruding sheets. BASF and Stastny applied for a patent that was issued in 1949. The molding process was demonstrated at the Kunststoff Messe 1952 in Düsseldorf. Products were named Styropor. The crystal structure of isotactic polystyrene was reported by Giulio Natta . In 1954, the Koppers Company in Pittsburgh , Pennsylvania, developed expanded polystyrene (EPS) foam under

7553-615: The recrystallization temperature of the material the temperatures ranges from 800 to 1,800 °F (424 to 975 °C). It is usually used to achieve the proper balance of required forces, ductility and final extrusion properties. Friction extrusion was invented at the Welding Institute in the UK and patented in 1991. It was originally intended primarily as a method for production of homogeneous microstructures and particle distributions in metal matrix composite materials. Friction extrusion differs from conventional extrusion in that

7644-430: The region of relative rotary motion can promote solid state welding of powders or other finely divided precursors, such as flakes and chips, effectively consolidating the charge (friction consolidation) prior to extrusion. Microextrusion is a microforming extrusion process performed at the submillimetre range. Like extrusion, metal is pushed through a die orifice, but the resulting product's cross section can fit through

7735-423: The rights to Munters's method and began producing a lightweight, water-resistant, and buoyant material that seemed perfectly suited for building docks and watercraft and for insulating homes, offices, and chicken sheds." In 1944, Styrofoam was patented. Before 1949, chemical engineer Fritz Stastny (1908–1985) developed pre-expanded PS beads by incorporating aliphatic hydrocarbons, such as pentane. These beads are

7826-494: The stability of the fluid used. The process must be carried out in a sealed cylinder to contain the hydrostatic medium. The fluid can be pressurized two ways: The advantages of this process include: The disadvantages are: Most modern direct or indirect extrusion presses are hydraulically driven, but there are some small mechanical presses still used. Of the hydraulic presses there are two types: direct-drive oil presses and accumulator water drives. Direct-drive oil presses are

7917-444: The supports and fuses to create the desired closed shape. The extrusion of metals can also increase their strength. In 1797, Joseph Bramah patented the first extrusion process for making pipe out of soft metals. It involved preheating the metal and then forcing it through a die via a hand-driven plunger. In 1820 Thomas Burr implemented that process for lead pipe, with a hydraulic press (also invented by Joseph Bramah). At that time

8008-458: The system to be readily deformed above its glass transition temperature allows polystyrene (and thermoplastic polymers in general) to be readily softened and molded upon heating. Extruded polystyrene is about as strong as an unalloyed aluminium but much more flexible and much less dense (1.05 g/cm for polystyrene vs. 2.70 g/cm for aluminium). Polystyrene is an addition polymer that results when styrene monomers polymerize (interconnect). In

8099-523: The trade name Dylite. In 1960, Dart Container , the largest manufacturer of foam cups, shipped their first order. In chemical terms, polystyrene is a long chain hydrocarbon wherein alternating carbon centers are attached to phenyl groups (a derivative of benzene ). Polystyrene's chemical formula is (C 8 H 8 ) n ; it contains the chemical elements carbon and hydrogen . The material's properties are determined by short-range van der Waals attractions between polymer chains. Since

8190-478: Was also reported that superworms ( Zophobas morio ) may eat expanded polystyrene (EPS). A group of high school students in Ateneo de Manila University found that compared to Tenebrio molitor larvae, Zophobas morio larvae may consume greater amounts of EPS over longer periods of time. In 2022 scientists identified several bacterial genera, including Pseudomonas , Rhodococcus and Corynebacterium , in

8281-606: Was originally developed for conveying and shaping fluid forms of processed raw materials. Present day, extrusion cooking technologies and capabilities have developed into sophisticated processing functions including: mixing, conveying, shearing, separation, heating, cooling, shaping, co-extrusion, venting volatiles and moisture, encapsulation, flavor generation and sterilization. Products such as certain pastas , many breakfast cereals , premade cookie dough , some french fries , certain baby foods , dry or semi-moist pet food and ready-to-eat snacks are mostly manufactured by extrusion. It

#292707