The main steps in the production of thick and thin sheets of thermoplastic forming materials are: polymer products; Polymer mixed molding materials (granules or powders); These molded materials are processed into sheets with thicknesses ranging from 0.5 to 15mm.
Formulations can be pigments, fillers, lubricants, processing AIDS, plasticizers, anti-aging agents, light stabilizers, flame retardants, antistatic agents, etc., mixed with polymers to become processable plastic materials, or can be blended with other plastics or recycled materials.
Typical extruders can produce materials ranging from 0.1mm thick films to sheets 50mmX2000mm wide, and even widths up to 5000mm. The extruder heats, mixes the grain, powder, crushing or return material, exhausts, and then extrudes through the slit die under pressure. Depending on the type of plastic and the thickness of the material, the hot extrudates are pulled out and shaped, or squeezed onto a synchronous rotating traction roll with cooling (roll cooling process). The extrudates pass through a cooling section and are then edged and rolled. The sheet is cut to specification. Both single-layer and composite forming materials can be produced.
Defects in the extruder can cause problems with thermoformed sheets as follows.
The thickness tolerance can form uneven sheet thickness, the thickness tolerance generated by the raw material manufacturing part is about 5%, the tolerance percentage of the thickness is less than 2mm is slightly larger, and the tolerance percentage of more than 5mm is slightly smaller. If large quantities of thermoformed materials are produced, tighter tolerances should be used. Advanced extruder line with automatic thickness feedback control system, thickness from 0.25 to 1mm film, thickness tolerance of 0.005mm.
② If the melt temperature of the extrude is too low or the calender roll is too cold, the smooth surface of the sheet will become rough or orange peel when heated on the hot forming machine.
③ Too high traction speed will result in high orientation along the longitudinal.
④ The very low internal stress in the sheet causes melting during heating.
⑤ Too large melt marks form on the calender roller, such as regular horizontal stripes on the film or sheet.
⑥ The slight lines produced by the hanging material on the head bulge when the sheet is heated.