Extrusion coating


Industrial polymer processing encompasses a wide range of operations such as extrusion, coating, mixing, moulding, etc. for a multiplicity of materials carried out under various operating conditions. The design and organization of each process should therefore be based on a detailed quantitative analysis of its specific features and conditions. The common - and probably the most important part in the majority of these analyses is, however, the simulation of a non-isothermal, non-Newtonian fluid deformation and flow process.  [c.287]

The Extrusion Coating of Wire, 2nd ed., technical service note, Wilmington, Del., 1969.  [c.357]

Extrusion Coating. In extmsion coating, a thin film of molten polymer is pressed onto or into the substrate. Coating thickness may range from 6.5 pm or less to more than 100 pm. In polymer lamination, a related operation, two or more substrates, such as paper or aluminum foil, are combined by using the polymer film as adhesive and moisture barrier. In order to coat a substrate, the polymer must be extmded through a narrow sHt in the extmsion coating die by an extmder screw. The molten film is then drawn down into the nip below the die and between two roUs the driven, water-cooled chill roU and the mbber-covered pressure roU. While coming in contact with the faster moving substrate, the hot film is drawn out to the desired thickness and forced into the substrate, where both layers are pressed together by the two roUs (Fig. 4). The pressure exerted by two roUs is usually in the range of 9—18 kg per linear cm. The hot film shrinks (neck-in) at the edges. Neck-in is the difference between the hot melt width at the die face and the coating width on the substrate it is undesirable since it forces more than the usual trimming of the substrate edges and increases the loss of material. However, neck-in can be reduced by lowering the polymer melt index, density, or by increasing the elasticity.  [c.377]

Extrusion Coating. A coating of an appropriate thermoplastic, such as polyethylene, may be appHed to a substrate of paper, thin cardboard, or foil to provide a surface property which enables heat sealing or better barrier performance (see Barrier polymers). Figure 9 is a sketch of the extmsion-coating process. A molten web of resin is extmded downward, and the web and substrate make contact at the nip between a pressure roU and a chill roU. Typical coating thicknesses are 0.005—0.25 mm the die opening is ca 0.5 mm. The melt web is narrower than the die, which is characteristic of a neck-in, and the edge tends to bead or thicken. Coated substrate is trimmed to the desired width. The highly poHshed and water-cooled chill roU determines the nature of the surface and removes the heat from the resin. The pressure roU pushes the substrate and the molten resin against the chill roU. Pressure and high melt temperatures are needed for adhesion of resin and substrate.  [c.140]

The development of the all-polyethylene sack has somewhat reduced the relative importance of extrusion coating. At one time paper-polyethylene laminates were widely used for sacks but their use has declined. However, techniques have been developed for coating a wide range of substrates to provide a useful range of materials of interest to the packaging industry.  [c.245]

Fig. 4.26 Extrusion coating process Fig. 4.26 Extrusion coating process
Lamination is the process of bringing together two or more webs/films and bonding them with an adhesive or by heating under pressure. Laminates are one of the finest packaging materials where flexible packaging is required. As with coating, laminating produces a multilayer film for packaging. A synthetic binder can be added to the dry-formed paper (or any other nonwoven structure) in the form of latex, powder, fiber, or a solution. Typical lattices used in this connection are those based on styrene-butadiene rubbers, vinyl acetate copolymers, acrylic copolymers, and vinyl chloride copolymers. The latex systems can be applied to the dry-formed structures by means of impregnation (saturation) or spraying. In practice, the latter technique is usually preferred, although both spraying and impregnation appear to be most efficient. Composite sheet lamination techniques can be classified as wet adhesive bonding, dry adhesive bonding, dry bonding (without adhesive), and extrusion coating.  [c.579]

C. Dry Bonding Without Adhesives and Extrusion Coating Techniques  [c.579]

A high-quality extrusion-coated paper for high-quality printing was produced by the extrusion of PE onto a highly smoothed base sheet of paper and passing the coated base through the nip of two rolls. The roll is a low-friction gloss chill roll with a surface finish roughness between that of high-gloss and a mat finished roll [26],  [c.580]

Extrusion coating is ideal for rods, tube and wire. The article is passed through a paint reservoir and then out via a die, which leaves only the correct thickness of paint in place. There are further techniques suitable for flat articles in sheet or web form. Knife coating is ideal for very thin coats, especially on continuous paper or plastic webs. The knife is either a metal doctor blade or a curtain of high velocity air (an air knife) directed onto the surface and it removes surplus material applied previously.  [c.623]

Melt Extrusion. By far the most important method for producing film and sheeting materials reties on one or another of the various melt extmsion techniques (5). The main variations of melt extmsion are the slot (or flat) die-cast film process, the blown films process, and the flat die sheeting-stack process. These may be combined with one or more steps such as coextmsion wherein multilayer film or sheet is formed, biaxial orientation, and in-line coating (6).  [c.379]

Extrusion. Conventional melt-extmsion equipment is used in processing FEP resins. Commercial pigments are mixed with the resin before extmsion into wke coating, tubing, rods, mol ding, heading channels, etc. Coating thicknesses of 0.076—2.54 mm have been extmded over such materials as sihcone mbber, poly(vinyl chloride), glass braid, metal-shielded cables, twisted conductors, and parallel multiconductor cables.  [c.361]

Extrusion. Extmsion coating and slot coating are in principle very similar. In extmsion coating a high viscosity material, often a polymer melt, is forced out of the slot of the coating die unto a substrate, where it is cooled to form a continuous coating. As can be seen in Figure 14a, the highly viscous hquid does not wet the bps of the die. Similarly in slot coating, a relatively low viscosity liquid, usually < several thousand mPa-s (=cP), which is often a polymer solution, is forced out of the slot and onto the web. In slot coating the coating liquid does wet the lips of the die, as shown in Figure 14b.  [c.311]

Slot Distributors These are generally used in sheeting dies for extrusion of films and coatings and in air knives for control of thickness of a material apphed to a moving sheet. A simple slotted pipe for turbulent flow conditions may give severe maldistribution because of nonuniform discharge velocity, but also because this type of design does not readily give perpendicular discharge (Koestel and Tuve, Heat. Piping Air Cond., 20[1], 153-157 [1948] Senecal, Ind. Eng. Chem., 49, 993-997 [1957] Koestel and Young, Heat. Piping Air Cond., 23[7], 111-115 [1951]). For slots in tapered ducts where the duct cross-sectional area decreases linearly to zero at the far end, the discharge angle will be constant along the length of the duct (Koestel and Young, ibid.). One way to ensure an almost perpendicular discharge is to have the ratio of the area of the slot to the cross-sectional area of the pipe equal to or less than 0.1. As in the case of perforated-pipe distributors, pressure variation within the slot manifold and pressure drop across the slot must be carefully considered.  [c.659]

Approximately three-quarters of the polyethylene produced is formed into products by means of extrusion processes. These processes will differ according to the product being made, i.e. according to whether the end-product is film, coated paper, sheet, tube, rod or wire covering. In principle the extrusion process consists of metering polymer (usually in granular form) into a heated barrel in which a screw is rotating. The rotation of the screw causes the granules to move up the barrel, where they are compacted and plasticised. The resultant melt is  [c.233]

Current usage is almost entirely associated with the good adhesion to aluminium. Specific applications include the bonding of aluminium foil to plastics films, as the adhesive layer between aluminium foil and polyethylene in multilayer extrusion-laminated non-lead toothpaste tubes and in coated aluminium foil pouches. Grades have more recently become available for manufacture by blown film processes designed for use in skin packaging applications. Such materials are said to comply with FDA regulations.  [c.277]

Silicone greases do, however, have uses in extrusion for coating dies etc., to facilitate stripping down. Greases have also found uses in the laboratory for lubricating stop cocks and for high-vacuum work.  [c.826]

Acrylate polymerization is also relatively simple, requiring typical free-radical initiators to start the reaction and minimal, if any, heat to run the actual polymerization. This has allowed both larger chemical companies to supply these adhesives at moderate cost, and some of the larger PSA article manufacturers to make the adhesives in house for captive use. The first acrylic PSAs were polymerized in solvent but this was quickly followed by the synthesis in emulsion. Today, acrylic PSAs are available as solution, emulsion, radiation curable, and hot-melt materials. This wide range of formats also allows coating to be done using a number of methods, including processes such as knife coating, curtain coating, gravure coating, slide coating, extrusion, and the like.  [c.486]

When formulating a silicone adhesive, sealant, or coating, based on hydrosilylation addition cure, one must consider the following properties of the uncured product pot life, dispensing technique, rheology, extrusion rate, cure performance. These characteristics directly affect the processing properties of the polymer base or crosslinker parts. The degree of cure conversion at the temperature of interest is determined by properties such as tack free time, cure profile and cure time. Once  [c.703]

For more than a decade now, the baking industry, the chemical process industry, pharmaceutical industry, fabric coating, rubber extrusion, electronic components, soil remediation, metal coating, wood working, formaldehyde, and sterilizers have become the specific industries being targeted by the environmental authorities. The reason for this is clear these industry sectors are large generators of VOC emissions. Table 4 provides a list of industry operations and the typical VOC, solvents, and other offgases associated with them.  [c.472]

Acrylic Plastics 1931 G P P F-P F-P Injection, compression, extrusion or blow molded Lenses, aircraft and building glazing, lighting fixtures, coatings, textile fibers  [c.106]

P Injection, blow, extrusion and rotational Pipe, pipe fittings, surgical implants, coatings, wire and cable insulation  [c.109]

Wire covering can be analysed in a very similar manner to that described for extrusion. The coating on the wire arises from two effects  [c.274]

Paper coating by extrusion up to 260  [c.82]

Where aluminium is to be used in direct contact with cold natural waters with no possibility of regular cleaning, clad aluminium alloys are the preferred materials. An Al-l -2Mn alloy clad with Al-l -2Zn is suitable. The cladding is anodic to the core and corrosion is therefore restricted to the surface cladding, thus obviating the risk of perforation. Cladding with super-purity aluminium is preferable where it is important to have the minimal degree of total corrosion, but in this case the potential relationship with the core is more critical and in some circumstances the cladding can actually become cathodic. Sacrificial protection may also be obtained from sprayed coatings of appropriate composition which can be applied to extrusions and castings as well as to sheet, rod, plate and tubes. In practice, unclad aluminium-manganese alloys have been used for piping soft waters in this country and, more widely, in the USA.  [c.667]

Cladding by pressing, rolling or extrusion can produce a coating in which the thickness and distribution can be readily controlled over wide ranges and the coatings so produced will be completely free from porosity. Although there is very little practical limit to the thickness of coatings which can be produced in this way, the application of the process is limited to comparatively simple shaped articles which do not require much subsequent mechanical deformation. Among the principal uses are lead and aluminium sheathing for cables, lead-sheathed sheets for architectural applications and composite extruded tubes for heat-exchangers.  [c.452]

Extruded/sintered polyethylene DIN 30670 DIN 30674 By extrusion or sintering in factory 1-8-3-5 Rugged, heavy coating. Limited track record.  [c.669]

Polyethylene coating on ferrous pipes may be applied by means of one of the following processes circular or ring-type head extrusion, side extrusion and wrapping or powder sintering. The commercially available coating systems also differ further in that the extruded polyethylene may be applied in conjunction with various primer/adhesive systems.  [c.670]

Thermoplastics which are used for corrosion protection can be applied in coatings as thin as 0.025 mm by solution techniques and in excess of 5 mm by extrusion or plastisol dipping. They are used where environmental resistance, chemical resistance, abrasion resistance, sound deadening or cushioning are required. They are used in those market areas that necessitate metallic mechanical strength plus thermoplastic corrosion resistance.  [c.745]

The two major plastics processing techniques of extrusion and injection moulding are used for coating metals.  [c.750]

Other common coating flows include premetered flows, such as slide and curtain coating, where the film thickness is an independent parameter that may Be controlled within limits, and the curvature of the mensiscus adjusts accordingly the closely related blade coating and roll coating and extrusion coating. See Ruschak (ibid.), Cohen and Gutoff Modern Coating and Drying Teehnology, VCH Publishers, New York, 1992) and Middleman Fundamentals of Polymer Proeessing, McGraw-Hill, New York, 1977). For dip coating of wires, see Taughy Int. J. Numerieal Meth. Fluids, 4, 441-475 [1984]).  [c.668]

Schmitz-Pranghe, N. and von Baeckmann, W., Polyethylene—Extrusion—Coating of Buried Steel Pipe-. Properties, Experiences, Valuation, Corrosion 1977, NACE, San Francisco DIN 30674, Coating of Ductile Cast Iron Pipes—Polyethylene Coating DIN 30670, Polyethylene Sheathing of Steel Tubes and of Steel Shapes and Fittings ANSI/AWWA C209-76, Cold Applied Tape Coatings for Special Sections, Connections and Fittings for Steel Water Pipelines  [c.672]

There has been considerable growth in the use of thermoplastics as corrosion-resistant coatings in the last 30 years. In the 1950s a few hundred tons per year were being applied by techniques such as fluid-bed coating, plastisol dipping and solution spraying. Since then a large number of other metal finishing technologies have been introduced, including coil coating and extrusion coating. The current tonnage of thermoplastics used in Europe must by now be some tens of thousands of tons.  [c.745]

In these problems, flow geometry is not known a priori and some sections of the domain boundary may change with flow. This situation arises in a variety of polymer processes such as injection moulding and mixing in partially filled chambers. Free surface flow regimes are also encountered in extrusion and wire coating operations where die swell is a common phenomenon. Various techniques for the modelling of free boundary flow regimes have been developed in the last two decades. Some of these methods are process specific, or they were developed in conjunction with particular numerical schemes and cannot be regarded as general simulation tools.  [c.101]

Compressor blading is variously made by forging, extrusion, or machining. All production blades, until recently, have been made from Type 403 or 403 Cb (both 12 Cr) stainless steels. During the 1980s, a new compressor blade material, GTD-450, a precipitation hardened, martensitic stainless steel, was introduced into production for advanced and uprated machines, as shown in Table 2. This material provides increased tensile strength without sacrificing stress corrosion resistance. Substantial increases in the high-cycle fatigue and corrosion fatigue strength are also achieved with this material, compared to Type 403. Superior corrosion resistance is also achieved due to high concentrations of chromium and molybdenum. Compressor corrosion are usually caused by moisture and salt ingested by the turbine. Coating of compressor blades is also highly recommended.  [c.427]

After the war developments in Britain and the United States were concerned largely with plasticised PVC, handled mainly by extrusion, calendering and paste techniques. However, on the continent of Europe, particularly in Germany, development work was also proceeding with unplasticised PVC, a rigid material which only achieved significance in Britain in the 1960s. The use of copolymers has not grown in the same way as the homopolymer in spite of their early importance. Instead the former have become useful special purpose materials for the flooring, gramophone record and surface coating industries. Perhaps the greatest developments over the past few years have not been concerned with the molecular structure of the polymers but rather with the particles formed during polymerisation. Such factors as particle shape, size, size distribution and porosity vitally affect the processing characteristics of the polymer and a more complete knowledge of their influence has led to many useful new grades of polymer.  [c.312]

Polymer interfaces are ubiquitous. They play a critical role in determining the properties, reliability and function of a broad range of materials. For example, polymer melt processing via injection molding (for plastic auto parts) and extrusion (for plastic pipe) create many interfaces in the form of internal weldlines where the fluid fronts coalesce and weld. Compression molding and sintering (of artificial hip joints) requires the coalescence of pellets or powder when their surfaces contact in the mold. Drying of latex paints and coatings entails a very large number of interfaces per unit volume, as the relatively tiny (ca. 1000 A) latex particles interdiffuse together to form a continuous film. Construction of composites with thermoplastic matrices (aircraft bodies) requires the fiber filled laminates to weld by an interdiffusion process at the interface. Welding of two pieces of polymer by thermal or solvent bonding is a commonly encountered example of strength development at a polymer-polymer interface tack between uncured rubber sheets during auto tire manufacture is an important example of this kind of welding.  [c.351]

Plasticizers, lubricants, fillers, and stabilizers are used to produce the versatility necessary to meet a wide range of applications. PVC, when modified by plasticizers, produces flexible materials which are desirable for certain applications. Elimination of plasticizers results in compounds termed rigid PVC, that are used in other applications. Flexible PVC is generally used for raincoats, baby pants, dolls, shoes, draperies, garden hose, gaskets, shower curtains, show welting, cable and wire insulation, floor covering, coating on hazardous materials handling garments, etc. The principle markets for rigid PVC are pipe, pipe fittings, conduit, ducting, rain gutters and drain spouts, sliding window tracks and other profile extrusions, house siding, decorative trim and edging, bottles, etc. The conventional approach to manufacturing PVC is via suspension polymerization. Monomer droplets are dispersed in water and polymerized using a monomer soluble, free radical initiator. The particle size is controlled in the 100-150 micron range, and the particle porosity is controlled in the 0-50% range by agitation design and by the use of suspending agents which are colloids and wetting agents. The process is an economical one, and residual concentrations of suspending agent, etc. are low, resulting in good electrical properties and chemical resistance. This is the most versatile process, as the particle properties can be tailored to give optimum processing performance with any of a number of plasticizer levels, and types of processing equipment. Other common manufacturing processes for PVC are bulk or mass polymerization and solution polymerization.  [c.239]

The membrane itself is a polymeric coating or extrusion with inverted conicalshaped pores. Membrane filters do not plug because the pore diameter is smaller at the top, which is the point of contact with the wastewater. Material passing through the membrane passes unimpeded through the membrane structure, therefore eliminating accumulation of material within the filter. Wastewater is pumped across the membrane surface at high flow rates. This parallel fluid flow eliminates the cake-like build-up typical of conventional filters such as bags and cartridges which must be frequently replaced. Some wastewater contaminants slowly accumulate on the membrane surface, forming a thin film, during normal operating conditions. This fouling process is normal and causes the filtration rate to slowly decrease with  [c.335]

Some early results for zinc-coated steel show that electroplated coatings of zinc are more efficient in protecting steel against corrosion fatigue than either hot-dipped or sherardised coatings, no doubt on account of the compressive stress present in the electroplated coatings. Zinc has also been used with some success as a pigment in priming paint but this is not so efficient as a plated or galvanised zinc coating because the contact between the zinc particles in the pigment and the steel is not nearly as good as in the metallic coatings. Zinc can also be applied by metal spraying. Another group of materials frequently given corrosion protection by a metal coating is the high-strength aluminium alloys. The protective coating is usually pure aluminium and is applied by spraying in the case of extrusions, or by cladding in the case of sheet.  [c.1323]

Extrusion In very simple terms the extruder is a heated cylinder containing a rotating screw. There is a hopper at one end to supply the plastic granules and a die at the other through which the molten polymer is extruded. The technique is widely used for producing garden hose, automotive trim, window profiles, plastic films etc. But it is also used for the corrosion protection of metal tube, rod and wire. Fencing wire is coated in PVC using this technique. The wire may then be woven into chainlink mesh fencing. However, there is normally no adhesion between the coating and the wire. Adhesion can be achieved if the fluidised bed process is used.  [c.750]


See pages that mention the term Extrusion coating : [c.389]    [c.1951]    [c.273]    [c.178]    [c.349]    [c.559]    [c.108]    [c.274]   
Plastics engineering Изд.3 (2002) -- [ c.273 ]