Compared with other plastic extruded products, the SUZHOU SUPXTECH production of low-foam skin PVC plastic products not only requires good plasticization under certain melting pressure, but also has corresponding technical requirements for the size, quantity and uniformity of foam holes, as well as the thickness, hardness, brightness and finish of skin. The quality of foaming body is not only related to the formula and raw materials, but also directly affected and restricted by the shear performance of extruder screw, melt pressure, temperature, extrusion (traction) speed, mold lip gap, mold mold gap, cooling water temperature and other factors. Therefore, compared with other extruded plastic products, skin foam plastic products have a certain technical difficulty, from the practice and theory there are many unsolved problems worth the industry technicians to study and solve.
1, skin foam PVC plastic sheet production technology and characteristics
The technical difficulty in the production of skin foaming PVC plastic products is foaming. Foaming is the result of the increase and expansion of melt viscosity, gas pressure produced by foaming agent and atmospheric pressure.
The foaming process generally goes through three stages:
(1) Foaming gas is dissolved into the plasticized uniform mixture melt at a certain temperature and pressure in the extruder and reaches saturation state to form bubble core;
(2) The melt is extruded from the die, and with the pressure release, the supersaturated dissolved gas nucleates, expands and precipitates, forming uniform and dense bubble holes in the gap of the formwork;
(3) Under the cooling effect of the shaping device, the foaming products are solidified and shaped. Excellent quality skin foam PVC plastic products have the characteristics of multiple and dense bubble holes, small and uniform, density and thickness meet the requirements, smooth appearance, high hardness and brightness.
2, skin foam PVC plastic board quality factors
The main raw materials that directly affect the structure quality of plastic bubble are foaming agent and foaming harmonizer. The raw materials such as stabilizer, lubricant, calcium carbonate and extrusion process control can promote and coordinate the foaming quality to a certain extent. Because the plasticization temperature of melt in the extrusion process of foaming products must be slightly lower than the decomposition temperature of foaming agent, the lower the average degree of polymerization of PVC resin, the lower the processing temperature required for melt plasticization. To obtain fully foamed plastic products, the resin viscosity should not be too high. At the same time, compared with other foaming products, because the cross section of sheet forming is wider, from the extrusion head into the mouth die to be distributed to a width of about 1.3m, in order to facilitate the dispersion and expansion of bubbles, the pressure of the entire cross section of the sheet should be coordinated, the liquidity of the melt is higher, and the molecular weight of the resin is generally smaller. Such as SC-7 or SC-8 suspension method loose resin is more suitable. SUZHOU SUPXTECH
Post time: Dec-07-2022