1. Advantages of blending modified materials:
The PVC/aBS blend is a new type of toughened material with excellent performance. The sheet after the aBS modified PVC has the following advantages compared with the pure pvc sheet:
1 flexible, no internal stress, high impact strength;
2 high thermoforming temperature can improve the pressure level characteristics;
3 good thermal stability, strong resistance to degradation during mixing;
4 high temperature tear resistance, good scratch resistance.
When the polymer material is mixed, the polarity and solubility parameters of the mixture are the key conditions for determining whether or not the mixture can be uniformly mixed. The polarity of PVC and aBS is similar, and the solubility parameters are relatively close, so the mixing of the two is very uniform. PVC/aBS, plasticizer, stabilizer, processing modifier, etc. are made into a nearly uniform PVC/aBS alloy by kneading and kneading.
aBS is a terpolymer. With the difference of the content of the three monomers, the modification function is very different. The increase of the content of acrylonitrile monomer can improve the chemical corrosion resistance, heat resistance and aging resistance; butadiene The increase in monomer content provides cold and impact resistance; while the increase in styrene monomer content provides rigidity, strength, gloss and other properties.
In the blend, as the content of aBS changes, its impact strength, pressure retention and processing properties also change significantly. It is found through experiments that when the amount of aBS added is in the range of 20% to 35%, the sheet has Higher impact strength. However, with the increase of aBS content, although the Vicat temperature, folding resistance and cold resistance of the sheet are obviously improved, the tensile strength and elongation at break of the sheet have a significant downward trend. The total amount of aBS added is 35%.
(1) Selection of polyvinyl chloride resin
PVC resins are available in both compact (XJ) and loose (XS) depending on the polymerization process. Generally, the XJ type has a high apparent density and a slow absorption and plasticization speed of the auxiliary agent, so XS type PVC resin is generally selected in hard and semi-hard products.
The molecular weight of PVC resin has a great influence on the mechanical properties of the material. Generally, the larger the molecular weight, the better the physical and mechanical properties and heat resistance, but the higher the molecular weight of PVC resin, the worse the processing performance, considering the process requirements and comprehensive balance. The formula uses XS-2 resin.
(2) Selection of aBS resin
Industrially produced aBS resins have different compositions and structures. Some of their important factors, the particle size of the elastomer phase, the composition and molecular weight of the resin phase have a great influence on the mechanical properties of the resin. These properties are in a certain proportion to the content of aBS resin in the PVC/aBS alloy. Three different modified aBS resins are selected in this formulation. aBS-1# resin is the most ideal modifier for PVC in plasticization and application. It not only improves the impact resistance of the sheet, but also has a great effect on hot melt strength, good processing depth, and uniformity of stretching. aBS-2# resin is a universal impact modifier, which can effectively resist damage at room temperature and low temperature, and make the sheet have good processability. The combination of aBS-1# and aBS-2# improves the balance of the sheet and ensures optimum sheetability and performance. aBS-3# is a modifier to improve the heat resistance of the sheet. The heat distortion temperature of the sheet can be increased to increase the stretching and bending strength of the sheet. In summary, the addition of the three types of aBS modifier not only significantly improves the processability and rigidity of the sheet, but also improves the brittleness of the sheet, so that the sheet has an ideal impact strength.
(3) Choice of plasticizer
The content of plasticizer in the semi-hard product, the variety of the product is an important factor affecting the physical and mechanical properties, processing properties and low temperature heat aging resistance of the product. In order to improve the compatibility of the plasticizer with the resin, a phthalate ester #1 main plasticizer having excellent heat aging resistance and low volatility was selected. Further, an aliphatic dibasic acid ester 2# auxiliary plasticizer having good cold resistance and an epoxy compound 3# auxiliary plasticizer having excellent heat resistance and a stabilizer function were also selected. The amount of plasticizer added affects the hardness, tensile strength and elongation at break of the sheet. To meet the above requirements, the total amount of plasticizer added was 19 parts.
(4) Selection of stabilizers
PVC heat stabilizers are available in a wide variety according to their different combinations. It is widely used in foreign countries as organic tin. Domestic organotin stabilizers have few types and high prices. Therefore, a composite stabilizer system composed of metal soaps and other liquid stabilizers is generally used to prevent vulcanization pollution under the long-term action of photothermal. To improve the lubricity, the two have a good synergistic effect. The thermal stability of PVC/aBS sheet is very small, depending on the amount and matching of the stabilizer, the amount can not be added too much, otherwise it will affect the plasticizing performance. And deteriorate processing conditions. In addition, ultraviolet absorbers and primary and secondary antioxidants are added to prevent photothermal degradation.
2. Conclusion:
(1) Tested with the 3# formula, the results are better than the test results of similar products.
(2) The amount of aBS used in the formulation is more important than the effect on the properties of the sheet.
(3) The thermoforming property of the sheet is slightly poor and needs to be improved.
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