Sheets extrusion

Extruded sheet is produced with a die having a wide slit-like outlet. The internal flow geometry is designed to transform the cylindrical melt flow received from the extruder to this slit form, while at the same 

The distinction between sheet and film arises from the thickness sheets are usually thicker than 0.25 mm. PP sheets can be produced with slit dies in a range of widths and thicknesses. The width of the sheets may be as high as 2.5 m. Sheets may be used for 

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Sheet Extrusion and Thermoforming. Sheet for thermoforming and analogous operations is usually formed by extmding the melt through a slot die onto a set of poHshed chill roUs. The sheet is usually approximately 150 cm wide. After rapid cooling, the web is coiled or cut into sheets. Polystyrene, PVC, polyethylene, polypropylene, and filled polypropylene are prepared in sheet form by extmsion. 

Fig. 8. Sheet extrusion A, die inlet B, die C, three-roll finisher D, support roUers E, edge-trim cutter F, puU roUs and G, saw or shear (15).

Fig. 4.19(a) Sheet extrusion (1) thick sheet (2) thin sheet... 

Multilayer sheet extrusion, VDC copolymers in, 25 725, 734 Multilayer soft lithography, for lab-on-a-chip valves, 26 975... 

Sheet and shape dental wax, 8 298 specification, 8 300t Sheet coaters, 7 2-3 Sheet copper, 7 724 Sheet extruded food packaging, 18 48 Sheet extrusion... 

VDC copolymers in, 25 725, 734 Sheet extrusion, 10 546-547 Sheet-fed offset inks, 14 320 Sheet fluorosilicates, 12 634-636 Sheet forming, of paper, 18 118-122 Sheetmetal forming dies... 

The dispersibility of an organic pigment which is to be incorporated in a polyolefin is of particular importance. This is especially true for the coloration of extrusion films and for HDPE or PP ribbon made from stretched blown film or from sheeted extrusion film, as well as for the coating or melt spin dyeing. 

Uses. Plasticizer in polyvinyl chloride films, sheeting, extrusions, and plastisols solvent and emollient in cosmetics... 

HIGH-MELT-STRENGTH PP PERMITS FOAM SHEET EXTRUSION... 

Fig. 11 Foamed sheet extrusion line. 1 Primary extruder, 2 blowing agent metering and flow control, 3 screen pack/breaker plate, 4 secondary extruder, 5 annular die, 6 cooling mandrel, 7 guide rolls, 8 winders. [38]...

The advantage of calendering over direct sheet extrusion is that a complicated and expensive die is not required. Some additional mixing can be done as part of the calendering process, as well, and a surface finish can be applied by the final roller, if desired. Sheet up to a few millimeters thick and a meter wide can be made using calendering. 

With mixed aramid fibre/particulate flake compositions in polycarbonate, however, the previously mentioned processing operations significantly reduced the levels of fibre and flake orientation relative to corresponding observations with single particle compounds [167]. For example, in sheet extrusion and injection moulding, the flakes oriented perpendicular to the fibres losing their biaxial orientation parallel to the surrounding machine surfaces. 

In a 2-year study, the emissions produced during the processing of a series of thermoplastic materials were investigated. In the case of HIPS, the emissions at sheet extrusion and injection molding processes were monitored. Sheet extrusion was done at 193°C, whereas, injection molding was done at 225°C. 

The species that have been detected at sheet extrusion were mostly aromatics, styrene being the most prominent compound. From the injection molding experiments a wider range of volatiles with significantly higher concentrations was measured in comparison to those for the sheet extrusion experiments. 

Finally, we developed testing procedures that included Brabender studies and the use of high temperature Mooney machines, and our program began to move. We were able to correlate with production sheet extrusion conditions which enabled us to make our numerous product development changes rapidly on a small scale. 

A small bubble test was adopted that allowed us to evaluate performance and appearance after vacuum forming. This technique requires a small sheet sample which is heated under specified vacuum forming conditions and then blown into a bubble of predetermined size. Now our engineers were able to predict the appearance of the final vacuum formed part during a laboratory or plant sheet extrusion run. 

Drawdown from the die to nip is typically ca 10%. Sheet extrusion requires that the resin be of high melt viscosity to prevent excessive sag of the melt between the die and the nip. The melt should reach the nip before touching any other part of the middle roll to prevent uncontrolled cooling of the resin. The appearance of the lower surface of the sheet is determined by the middle roll, ie, its polish, surface temperature, and freedom from condensed materials. The upper surface is cooled by air and has a more glossy appearance. Neither the top roll nor the bottom roll greatly affect the appearance of the top surface of the sheet. Edges of the sheet are trimmed. 

Polyethylene is readily fabricated by all methods of thermoplastic processing. The principal methods used are film and sheet extrusion, extrusion coating, injection molding, blow molding, pipe extrusion, wire and cable extrusion coating, rotomolding, and hot melt and powder coatings. 

Sheet extrusion requires a broad die, in which an even distribution of the flowing polymer along its width, and an equal flow resistance at each point, has to be taken care of. Sheets are being extruded up to a width of 3 or 4 m, in thickness up to 3 cm. If desired, sheets can be produced with a wave-shape, by passing the, still plastic, extrudate between two profiled rolls. Film extrusion can be done in a similar way, as a matter of fact with a narrower die gap. After extrusion, sheets and films are cooled in a water bath or on polished cooling rolls. 

Although Eq. 3.11 does not fit with all experimental data in literature, the dependence of the extrudate swell on the first normal stress difference is nevertheless shown by B°c Figure 3.11 was used to determine the extrudate swell of the PEO solution, where B = Bex = 1.6. For polymer melts, B can even reach values of 2 or more. The extrudate swell has practical relevance for extrusion, e.g., in pipe or sheet extrusion. 

Chemicals Manufacturing Distribution Plastics Sheet Extrusion Pharmaceuticals Paints Coatings... 

These ASRs are produced either chemically in a reactor or by blending GPPS and rubber in downstream operations. This family of plastics has good toughness and gloss, and very good processability. ASRs can be processed on conventional sheet extrusion and thermo-forming equipment. They are recommended for applications where intermediate... 

SB copolymers are produced via anionic polymerization by sequential addition of styrene and 1,3-butadiene monomers. These clear, tough plastics are easily processed with conditions and equipment similar to those used for HIPS. Various amounts of GPPS are usually mixed with the SB copolymers during sheet extrusion to maximize rigidity and economics in the thermoformed parts. Typical applications include drinkware, medical packaging, lids, containers, and blister packages. 

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