PVC transparent sheet

日期:2019/6/4 8:17:45 / 阅读: / 来源:本站

PVC transparent sheet
1. Material selection and formula design
1) Material selection
(1) Resin selection. The rigid PVC transparent sheet is mainly made of PVC resin, and the performance of the resin directly affects the processing performance and product quality. To this end, the SG-7 resin won the National Quality Product Award from Tianjin Chemical Plant.
(2) Stabilization system. It is well known that PVC resin may affect the structure and purity of the resin during production or due to fluctuations in polymerization temperature control or due to residual of the additive in the resin during polymerization, and its molecular structure is mostly head-to-tail. After the heat collecting action, the degradation occurs and the HCl is removed, and the extracted HCI catalyzes the further degradation of the PVC, so that the incremental dehydrochlorination proceeds very rapidly, and a polyene segment is formed very quickly. To this end, it is necessary to add a stabilizer which inhibits or slows the decomposition of PVC, and the stabilizer is an acceptor of HCI to avoid catalytic degradation of HC. The type of stabilizer has a great influence on the transparency of the product. The color of the stabilizer and the compatibility with PVC, the difference of the refractive index affects the transparency; on the other hand, the color, compatibility and refractive index of the reaction product of the stabilizer and HC There is also a greater impact on transparency. Based on the relevant information and the experience of the brother factory, we selected the Beijing 8831 organic tin stabilizer (ie, di-n-octyl tin) produced by Beijing Chemical Industry Third Plant. The stabilizer has good compatibility with PVC, and the reaction product has good compatibility with PNC, so it has good transparency; it can not only capture PNC degradation product HCl, but the product does not promote the decomposition of PVC. Moreover, it can react with the activating group to form a stable structure, can inhibit the early decomposition of PVC, and thus has good initial coloring property; and the organotin stabilizer has both antioxidant properties. It is an ideal transparent stabilizer in China. Although it is expensive, it is still used because of its unique properties.
(3) Lubrication system. In the process of extruding hard PVC, the lubricant can prevent the material from sticking and staying in the wall of the barrel and the screw groove, thereby promoting the flow of the material, facilitating the release of the product, and ensuring the smoothness and luster of the surface of the product.
The proper amount of lubricant can reduce power consumption, increase production rate, and prevent resin degradation caused by friction to improve the efficiency of the stabilizer.
The amount of lubricant added and the balance of internal and external lubricants are also related to product quality and processing status. If the amount of external lubricant added is too small, the friction between the material and the equipment and the mold is large, the sticking phenomenon is likely to occur, and the surface quality of the product is degraded; if the external lubricant is excessive, the load of the equipment is drastically decreased, and the forced feeding performance in the machine is degraded, which affects the productivity. At the same time, the material is not plasticized, resulting in the force of the product.
The performance of the school deteriorates, and even the finished product cannot be produced. Moreover, since the external lubricant is generally poorly compatible with the PC, precipitation may occur in an excessive amount to affect the transparency of the product. The amount of lubricant added is too small, which is not enough to improve the friction between the material molecules, and local decomposition occurs, and the production capacity is affected by the heavy load of the equipment; when the internal lubricant is excessive, the plasticization is excessive.
As a result, the product becomes brittle, and the heat resistance of the product also decreases as the amount of the internal lubricant added increases.


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