Acrylic sheet is a typical product of methyl methacrylate bulk polymerization. The bulk polymerization process can be divided into two stages, pulping and polymerization. However, in order to obtain products with certain specifications and meeting certain quality indicators in industrial production, there must also be appropriate auxiliary links.
In order to facilitate operation and management, the polymerization process of acrylic (plexiglass) sheet is divided into five parts:
Pulping part
After adding quantitative initiator, plasticizer and mold release agent to the monomer, the slurry with a conversion rate of about 10 was prepared after five dissolutions:
1. Determine the production cycle and improve production efficiency. In the prepolymerization reaction, the initiator is decomposed at high temperature, the induction period is shortened, the monomer is activated, and the chain length is increased. By stirring, heat exchange is accelerated, and more heat of polymerization is eliminated in a short time. To promote the increase in monomer viscosity, the gel effect comes earlier. The degradation method can increase the monomer viscosity and facilitate the operation.
2. Reduce volume shrinkage during polymerization. The monomer ratio is 0.94, and the ratio of the finished organic glass is 1.17 ~ 1.19. If the monomer is polymerized directly into the acrylic sheet in the mold, volume shrinkage of 19 and 22% can be achieved. Such a large shrinkage rate creates difficulties for mold manufacturing, casting, and polymerization processes. After stirring well. The specific gravity is generally about 0.96 to 0.98, which can reduce the shrinkage during polymerization.
3. When the viscosity of the slurry increases, the leakage loss after the casting mold can be reduced.
Mechanical mold part
In two clean and dry silica flat glass, the four sides are filled with cellophane tape (or rubber tube), the gap distance is controlled, the thickness of the finished product is adjusted, and it is filled with a clamp.
Irrigation Festival
Through calculation and measurement, the slurry produced in the pulping section is poured into the mold made in the molding section, and the gas in the gap is discharged, so that the slurry is covered and sealed by the template.
Assembly part
Put the finished feed liquid into the water tank (or drying room). If it is a degraded slurry in the mold, it should be induced at a higher temperature for a period of time, and then kept at a lower temperature for a longer time until the polymer in the mold hardens and the temperature increases.
If the mold is a pre-polymerized slurry, it can be directly held at a low temperature for a long time until the polymer in the mold is hardened, and then increase the temperature and heat treatment: After the polymerization is completed, the temperature drops below 40OC. The mold is removed and the required polymer is taken out, producing what is known as a "wool flake".
Finished part
Check the appearance of the "wool flakes", trim, cut, and sort them into the warehouse.
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