Understanding of PMMA injection molding process

Polymethyl methacrylate, acrylic, and lipids converge to obtain polymers commonly known as acrylic esters, the relative plastic is commonly known as polyacrylic acid plastic, which is the most common use of polymethyl methacrylate. Polymethyl methacrylate abbreviation number PMMA, alias Plexiglas plate, is by far the most outstanding material in the generation of fully transparent raw materials, the price is more suitable for the type.

Application-level.

PMMA dissolves solvents, such as formic acid, anisole, etc., and according to the spin coating can produce an excellent plastic film with excellent dielectric properties, which can be used as the material layer of organic chemical field-effect tube (OFET) also known as organic chemical plastic thin-film crystal transistor (OTFT).

PMMA epoxy resin is a non-toxic raw material for environmental protection and can be used to manufacture kitchenware, sanitary ware, etc. It has excellent organic chemical reliability and aging resistance.

PMMA epoxy resin is not easy to cause sharp debris when crushed, and countries and regions such as the UK and Japan have made it mandatory in-laws and regulations to use PMMA epoxy resin for laminated glass in primary and secondary schools and kindergarten projects. Chinese provinces have accelerated the pace of urban planning and construction, and there are many street signs, lightbox advertisements, and public telephone booths, among which a very large part of the commonly used raw materials are PMMA epoxy resin. The outdoor colorful decorative building materials of the Beijing Olympic Games project also apply a lot of low-carbon and environmentally friendly PMMA epoxy resin.

Because PMMA surface strength is not high, easy to rub hair, low impact resistance characteristics, forming circulation will be poor and other defects, PMMA modified materials have emerged one after another. Such as methyl methacrylate and butadiene, butadiene copolymer, PMMA and PC blending, etc. 372 plexiglass sheet is methyl methacrylate and butadiene to carry out copolymer and obtained.

PMMA's liquidity is worse than PS and ABS, and the melt viscosity is more sensitive to the change of temperature, in the whole process of forming, the key is to change the melt viscosity from the injection temperature. 270℃.

1. Solution of plastic

PMMA has a certain ability to absorb water, its water absorption of 0.3-0.4%, and the injection molding process must be at a temperature of 0.1% or less, generally 0.04%. The presence of water makes the melt appear vapor bubbles, airlines, clarity reduction, etc. Therefore, we need to carry out the dry solution. The drying temperature is 80-90℃ and the time is more than 3 hours.

Acquisition material can be applied 100% in some cases, the specific amount depends on the quality regulations, generally can be more than 30%, acquisition material to prevent environmental pollution or will endanger the clarity and characteristics of the finished product.

2. Plastic machine use

PMMA has no special provisions for plastic machines. Due to its high melt viscosity, it must have a deep screw groove and a large diameter nozzle hole. If the compressive strength of the product is high, it is necessary to use a very high diameter extruder screw to implement ultra-low temperature melting. In addition, PMMA must be stored in dry silos. 3.

3. Mold shell and into the rubber mouth design scheme

Die Ken temperature can be 60 ℃ -80 ℃, the diameter of the popular channel should match each other inside the finish, the best perspective is 5 to 7, if you want to injection molding processing 4mm or above products, the perspective should be 7, the popular channel diameter up to 8 to 11mm, the overall length of the rubber inlet does not have to exceed 50 mm.

For products with wall thickness less than 4mm, the diameter of the flow channel should be 6-8mm for products with wall thickness more than 4mm, the diameter of the flow channel should be 8-12mm for edge-shaped, fan-shaped, and pendant sheet-shaped inlet depth should be 0.7 to 0.9t (t for product wall thickness), the diameter of the needle-shaped inlet should be 0.8 to 2mm; high viscosity should be taken with smaller specifications.

The universal discharge air hole has 0.05 to 0.07mm deep and 6mm wide out of the mold inclination of 30′-1 concave mold part 35′-130 middle.

4. Melting temperature

It can be measured by subcutaneous injection into the hollow: from 210℃-270℃, depending on the actual material presented by the distributor.

5. Injection temperature

Can use rapid injection, but to prevent the high aspect ratio thermal stress, it is appropriate to use multi-level injection, such as slow - fast - slow, etc., injection processing thick parts, then choose a slow speed.

6. Dwell time

If the temperature is 260℃, the maximum number of dwell time should not exceed 10 minutes, if the temperature is 270℃, the dwell time should not exceed 8 minutes.