Acrylic Encyclopedia

Main Classification of Acrylic | YUEFENG

August 26, 2021

Main classification
There are many types of acrylic boards.

Common boards include: transparent board, dyed transparent board, milk white board, color board;

Special boards include: bathroom board, cloud board, mirror board, cloth board, hollow board, impact board, flame retardant board, super wear-resistant board, surface pattern board, frosted board, pearlescent board, metal effect board, etc.

Different performance, different colors and visual effects to meet the ever-changing requirements.

1. Acrylic boards are divided into cast boards and extruded boards according to the production process. According to the transmittance, they can be divided into transparent boards, semi-transparent boards (including dyed transparent boards), color boards (including black and white and color boards); according to performance Impact board, anti-ultraviolet board, ordinary board and special board such as high impact board, flame retardant board, frosted board, metal effect board, high wear-resistant board, light guide board, etc.

A: Casting plate: high molecular weight, excellent rigidity, strength and excellent chemical resistance. Therefore, it is more suitable for processing large-size identification plaques, and the time in the softening process is slightly longer. This kind of board is characterized by small batch processing, incomparable flexibility in color system and surface texture effect, and complete product specifications, which can be used for various special purposes.

B: Extruded plate: Compared with the cast plate, the extruded plate has a lower molecular weight, slightly weaker mechanical properties, and higher flexibility. However, this feature is conducive to bending and hot forming processing, and the softening time is shorter. When processing large-sized plates, it is beneficial to various rapid vacuum forming. At the same time, the thickness tolerance of the extruded plate is smaller than that of the cast plate. Because the extruded plate is mass-produced and automated, the colors and specifications are inconvenient to adjust, so the variety of product specifications is subject to certain restrictions.

2. Acrylic There is also a kind of recycled acrylic board that uses recycled acrylic scrap, which is thermally degraded to obtain recycled MMA (methyl methacrylate) monomer, which is then obtained after chemical polymerization. After a rigorous process, the pure MMA monomer can be re-obtained, and there is no difference in quality from the newly synthesized monomer. However, the purity of the produced degradable monomers is not high, and the quality and performance of the sheet are very poor after the sheet is formed.

Summary: The extruded plate uses granular raw materials, which are extruded after being dissolved at high temperature, while the cast plate is directly cast with MMA monomer (liquid). Although the extruded plate is relatively smooth and smooth in appearance, it is because it is formed when the granular raw material is formed. To complete the polymerization. When processed into plates, its structure and performance are weak, and it is not suitable as a material for outdoor marking products. It is only suitable for indoor products such as crystal letters or product brackets.

In addition, since most of the extruded panels do not have the function of UV protection, their outdoor use life is not the same as that of the cast panels. The color will gradually fade and it is easy to become brittle until it breaks. The casting plate is to complete the structural polymerization during the processing of the plate, during which the ultraviolet absorber is added, which has extremely high strength and UV function. The outdoor service life is more than 5 years or even 10 years, and the color is always bright as new during use.

Process characteristics

1. Polymethyl methacrylate contains polar pendant methyl groups and has obvious hygroscopicity. The water absorption rate is generally 0.3%-0.4%. It must be dried before molding. The drying condition is 80℃-85℃ for 4-5h. .

2. Polymethyl methacrylate has obvious effective non-Newtonian fluid characteristics in the temperature range of molding processing. The melt viscosity will obviously decrease with the increase of shear rate, and the melt viscosity is also very sensitive to temperature changes. Therefore, for the molding process of polymethyl methacrylate, increasing the molding pressure and temperature can significantly reduce the melt viscosity and achieve better fluidity.

3. The temperature at which polymethyl methacrylate starts to flow is about 160°C, and the temperature at which it starts to decompose is higher than 270°C, which has a wide processing temperature range.

4. Polymethyl methacrylate has higher melt viscosity and faster cooling rate, and the product is prone to internal stress. Therefore, the process conditions are strictly controlled during molding, and post-processing is also required after the product is molded.

5. Polymethyl methacrylate is an amorphous polymer, and the shrinkage rate and its variation range are small, generally about 0.5%-0.8%, which is conducive to forming plastic parts with high dimensional accuracy.

6. The cutting performance of polymethyl methacrylate is very good, and its profile can be easily machined to various required sizes.


Processing technology

Polymethyl methacrylate can be cast, injection, extrusion, thermoforming and other processes.


Casting is used to form plexiglass plates, bars and other profiles, that is, the profiles are formed by bulk polymerization. After casting, the product needs to be post-treated. The post-treatment conditions are heat preservation at 60°C for 2h and heat preservation at 120°C for 2h.

Injection molding

Injection molding uses pellets made by suspension polymerization and molding on a common plunger or screw injection molding machine. Table 1 shows the typical process conditions of polymethyl methacrylate injection molding.

Injection molding products also need post-processing to eliminate internal stress. The processing is performed in a 70-80°C hot air circulating drying oven. The processing time depends on the thickness of the product, and generally takes about 4 hours.

Extrusion molding

Polymethyl methacrylate can also be extruded, and plexiglass plates, rods, pipes, sheets, etc. can be prepared from particles produced by suspension polymerization. However, the profiles prepared in this way, especially plates, have a small molecular weight due to the low molecular weight of the polymer. The mechanical properties, heat resistance, and solvent resistance are not as good as cast-molded profiles. Its advantage is high production efficiency, especially for pipes and other profiles that are difficult to manufacture when using the casting method. Single-stage or double-stage vented extruder can be used for extrusion molding, and the ratio of screw length to diameter is generally 20-25. Table 2 is the typical process conditions of extrusion molding.


Thermoforming is the process of making plexiglass plates or sheets into products of various sizes and shapes. The blank cut to the required size is clamped on the mold frame, heated to soften it, and then pressurized to make it close to the mold surface , To obtain the same shape as the molding surface, and trim the edge after cooling and shaping to obtain the product. Pressurization can be done by vacuum drafting or by directly pressurizing a convex mold with a profile. The thermoforming temperature can refer to the recommended temperature range in Table 3. When adopting rapid vacuum low-draft molding products, the temperature should be close to the lower limit, and the deep drawing products with complex shapes should be close to the upper limit temperature. Normally, the normal temperature should be used.

Engraving and cutting

Mainly for hollowing out and engraving formed acrylic or colored acrylic materials. Ordinary laser engraving and cutting machines can meet the engraving and hollowing needs of most acrylic products.

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