Basic knowledge of acrylic cosmetic bottle(2)

(4) Thermoforming

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.

(5) 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.

4. 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℃. 4- 5h.

(2) Polymethyl methacrylate has obvious non-Newtonian fluid characteristics in the temperature range of molding processing. The melt viscosity will decrease significantly 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 begins to flow is about 160°C, and the temperature at which it begins to decompose is higher than 270°C, which has a wide processing temperature range.

(4) Polymethyl methacrylate has a higher melt viscosity and a faster cooling rate. 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.