PVC low foaming building board
日期：2022/3/7 8:37:34 / 閱讀： / 來源：本站
PVC low foaming building board1. Material selection and formula design
(1) PVC resin low foaming board hard products shall use less or no plasticizer as far as possible, and low viscosity resin shall be selected. Vlans5920 resin of DS company in the Netherlands, with a value of 59; Tk800 resin of shinyue chemical company of Japan, with K value of 62; Loose resins with an average polymerization degree of 700 ~ 800 produced in China are applicable.
(2) In the stabilization system, due to the high longitudinal flow rate of materials in cm80 extruder and the good self-cleaning effect of twin-screw, the residence time of materials in the barrel is short and concentrated, and there will be no material accumulation, so there are no strict requirements for the stabilization system. Considering the economy and processability, the three salt epoxy soybean oil stabilization system can produce good stabilization effect.
(3) If the amount of lubricant added to the lubrication system is small, the friction between the material and the equipment and mold is large, which is easy to stick to the mold, and the surface quality of the product is reduced: if there is too much external lubricant, the lubrication is excessive, resulting in slipping, the equipment load decreases rapidly, the forced feeding performance in the machine decreases, which affects the productivity, and the uneven plasticization of the materials makes its mechanical properties worse. When the amount of internal lubricant is too small, the friction between materials is large, which will decompose due to local overheating, and the production capacity will be affected due to the increase of equipment load; If there is too much internal lubricant, it will be over plasticized, which will make the product brittle and reduce the heat resistance of the product. The imported composite lubricant such as vpg1503 has good application effect, ensuring the balance of internal and external lubrication, and the application amount is about 2.5 phr; Domestic internal and external lubricants can also meet the requirements after being mixed in an appropriate proportion.
(4) Chemical foaming method is selected for low foaming board with hair agent, and board (sheet) materials in Chapter 2 of gas generation 230 are selected
Large and stable organic foaming agent Azodicarbonamide (AC) is used as foaming agent, and at foaming agent can also be selected. When the amount of AC foaming agent is too much, the yellow solid residues (cyanuric acid, etc.) decomposed by C will be precipitated on the inner wall of the mold and the surface of the plate after a certain time of production (usually a few hours), affecting the continuous production. Since AC does not necessarily decompose during processing, zinc compounds and other "hair promoters" can be added to promote the full decomposition of AC. T-410 foaming agent produced by Shanghai Xiangyang Chemical plant has uniform and fine foaming pores and good application effect.
(5) poor sensitivity, high processing temperature, narrow area, large melt viscosity, poor thermal strength and slow gelation. If a small amount of plasticizer is added to change this condition, the physical and mechanical properties of foamed sheet will be affected.
Adding processing modifier ACR can solve the above problems. Because ACR rubs with PVC particles in the initial stage of processing, it increases the melting rate, which is conducive to the synchronous and uniform plasticization of PVC resin and shortens the plasticization time. As the plasticizing rate increases, the processing temperature is reduced and the thermal degradation of the resin is reduced. The addition of ACR improves the flow performance of PVC and makes it plasticized evenly. At the same time, it improves the thermal strength and thermal extension, and makes the foaming of the plate fully and evenly. ACR is only compatible with PVC at high temperature (within the range of resin high elastic state and viscous flow state), so it does not affect the physical and mechanical properties of the products.
(6) Impact modifier rigid PVC products are brittle, especially with strong notch sensitivity. In addition, the micro unevenness formed after foaming greatly reduces the impact strength of the plate. Therefore, rubber elastomer that can be partially compatible with PVC must be added to improve the toughness of foamed plate and reduce its notch sensitivity.
If CPE is selected as impact modifier, the processability will become worse, especially unfavorable to foaming. The effect of MBS is better.