The frost line is a term used in plasticfilm manufacturing by extrusion. It refers to the point beyond the die where the temperature of the molten plastic falls below the softening point and the diameter of the extruded plastic bubble stabilizes. The term was borrowed from the notion of "frost line" in soil science and refers to the frosted appearance of the plastic film above the "frost line".
Plastic is material consisting of any of a wide range of synthetic or semi-synthetic organic compounds that are malleable and so can be molded into solid objects.
A film, also called a movie, motion picture, moving picture, or photoplay, is a series of still images that, when shown on a screen, create the illusion of moving images. This optical illusion causes the audience to perceive continuous motion between separate objects viewed in rapid succession. The process of filmmaking is both an art and an industry. A film is created by photographing actual scenes with a motion-picture camera, by photographing drawings or miniature models using traditional animation techniques, by means of CGI and computer animation, or by a combination of some or all of these techniques, and other visual effects.
Extrusion is a process used to create objects of a fixed cross-sectional profile. A material is pushed through a die of the desired cross-section. The two main advantages of this process over other manufacturing processes are its ability to create very complex cross-sections, and to work materials that are brittle, because the material only encounters compressive and shear stresses. It also forms parts with an excellent surface finish.
The distance from the die is called the height of the frost line. It depends on various factors, including the melt temperature, the speed of cooling, the extrusion speed, and the diameter of the bubble. The notion is important, since the higher the frost line, the more difficult to control the uniformity of the film thickness.
For example, a higher frost line due to higher melt temperature and/or lower cooling rate means a longer time to solidify, and a more smooth and transparent film is produced.
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
Related Research Articles
A marshmallow is a sugar confectionery that in its modern form typically consists of sugar, water and gelatin whipped to a squishy consistency, molded into small cylindrical pieces, and coated with corn starch. Some marshmallow recipes call for eggs. This is the modern version of a medicinal confection made from Althaea officinalis, the marshmallow plant.
Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene.
Injection moulding is a manufacturing process for producing parts by injecting molten material into a mould. Injection moulding can be performed with a host of materials mainly including metals,, glasses, elastomers, confections, and most commonly thermoplastic and thermosetting polymers. Material for the part is fed into a heated barrel, mixed, and injected (Forced) into a mould cavity, where it cools and hardens to the configuration of the cavity. After a product is designed, usually by an industrial designer or an engineer, moulds are made by a mould-maker from metal, usually either steel or aluminium, and precision-machined to form the features of the desired part. Injection moulding is widely used for manufacturing a variety of parts, from the smallest components to entire body panels of cars. Advances in 3D printing technology, using photopolymers which do not melt during the injection moulding of some lower temperature thermoplastics, can be used for some simple injection moulds.
Powder metallurgy (PM) is a term covering a wide range of ways in which materials or components are made from metal powders. PM processes can avoid, or greatly reduce, the need to use metal removal processes, thereby drastically reducing yield losses in manufacture and often resulting in lower costs.
Plastic welding is welding for semi-finished plastic materials, and is described in ISO 472 as a process of uniting softened surfaces of materials, generally with the aid of heat. Welding of thermoplastics is accomplished in three sequential stages, namely surface preparation, application of heat and pressure, and cooling. Numerous welding methods have been developed for the joining of semi-finished plastic materials. Based on the mechanism of heat generation at the welding interface, welding methods for thermoplastics can be classified as external and internal heating methods, as shown in Fig 1.
Blow molding is a specific manufacturing process by which hollow plastic parts are formed and can be joined together: It is also used for forming glass bottles or other hollow shapes. In general, there are three main types of blow molding: extrusion blow molding, injection blow molding, and injection stretch blow molding. The blow molding process begins with melting down the plastic and forming it into a parison or, in the case of injection and injection stretch blow molding (ISB), a preform. The parison is a tube-like piece of plastic with a hole in one end through which compressed air can pass.
Linear low-density polyethylene (LLDPE) is a substantially linear polymer (polyethylene), with significant numbers of short branches, commonly made by copolymerization of ethylene with longer-chain olefins. Linear low-density polyethylene differs structurally from conventional low-density polyethylene (LDPE) because of the absence of long chain branching. The linearity of LLDPE results from the different manufacturing processes of LLDPE and LDPE. In general, LLDPE is produced at lower temperatures and pressures by copolymerization of ethylene and such higher alpha-olefins as butene, hexene, or octene. The copolymerization process produces an LLDPE polymer that has a narrower molecular weight distribution than conventional LDPE and in combination with the linear structure, significantly different rheological properties.
A face shield is a device used to protect wearer's entire face from hazards such as flying objects and road debris, chemical splashes, or potentially infectious materials.
Nonwoven fabric is a fabric-like material made from staple fiber (short) and long fibers, bonded together by chemical, mechanical, heat or solvent treatment. The term is used in the textile manufacturing industry to denote fabrics, such as felt, which are neither woven nor knitted. Some nonwoven materials lack sufficient strength unless densified or reinforced by a backing. In recent years, nonwovens have become an alternative to polyurethane foam.
In geology, the frost line is the level down to which the soil will normally freeze each winter. By an analogy, the term is introduced in other areas.
Plastics extrusion is a high-volume manufacturing process in which raw plastic is melted and formed into a continuous profile. Extrusion produces items such as pipe/tubing, weatherstripping, fencing, deck railings, window frames, plastic films and sheeting, thermoplastic coatings, and wire insulation.
Extrusion coating is the coating of a molten web of synthetic resin onto a substrate material. It is a versatile coating technique used for the economic application of various plastics, notably polyethylene, onto paperboard, corrugated fiberboard, paper, aluminium foils, cellulose, Non-wovens, or plastic films.
Twin-wall plastic, specifically twin-wall polycarbonate, is an extruded multi-wall polymer product created for applications where its strength, thermally insulative properties, and moderate cost are ideal. Polycarbonate, which is most commonly formed through the reaction of Bisphenol A and Carbonyl Chloride, is an extremely versatile material. It is significantly lighter than glass, while managing to be stronger, more flexible, and more impact resistant. Twin-wall polycarbonate is used most commonly for green houses, where it can support itself in a structurally sound configuration, limit the amount of UV light due to its nominal translucence, and can withstand the rigors of daily abuse in an outdoor environment. The stagnant air in the cellular space between sheets provides insulation, and additional cell layers can be extruded to enhance insulative properties at the cost of light transmission.
A casting defect is an undesired irregularity in a metal casting process. Some defects can be tolerated while others can be repaired, otherwise they must be eliminated. They are broken down into five main categories: gas porosity, shrinkage defects, mold material defects, pouring metal defects, and metallurgical defects.
A die in polymer processing is a metal restrictor or channel capable of providing a constant cross sectional profile to a stream of liquid polymer. This allows for continuous processing of shapes such as sheets, films, pipes, rods, and other more complex profiles. This is a continuous process, allowing for constant production, as opposed to a sequential (non-constant) process such as injection molding.
Pasta processing is the process in which wheat semolina or flour is mixed with water and the dough is extruded to a specific shape, dried and packaged.
3D printing filament is the thermoplastic feedstock for fused deposition modeling 3D printers. There are many types of filament available with different properties, requiring different temperatures to print. Filament is available in two standard diameters; 1.75 and 2.85 mm/3 mm.
IR welding is a welding technique that uses a non-contact heating method to melt and fuse thermoplastic parts together using the energy from infrared radiation. The process was first developed in the late 1900s, but due to the high capital cost of IR equipment the process was not commonly applied in industry until prices dropped in the 1990s. IR welding typically uses a range of wavelengths from 800 to 11,000 nm on the electromagnetic spectrum to heat, melt, and fuse the interface between two plastic parts through the absorption and conversion of the IR energy into heat. Laser welding is a similar joining process that applies IR radiation at a single wavelength.
