Acrylic Txhaj Tshuaj Molding

Acrylic is chemically called polymethyl methacrylate (PMMA English). Vim yog qhov tsis txaus ntseeg ntawm PMMA nto hardness, Yooj yim, Kev cuam tshuam tsawg, Tsis zoo moulding futiling, lwm yam., Kev hloov kho ntawm PMMA tau tshwm sim ib qho tom qab lwm. Xws li Copolymerization ntawm methyl methacrylate nrog styrene thiab butadiene, Kev Blending PMMA thiab PC, lwm yam.

The flow of PMMA is worse than that of PS and ABS, and the melt viscosity is more sensitive to temperature changes. During the txheej txheem molding, the melt viscosity is mainly changed from the injection temperature. PMMA is an amorphous polymer with a melting temperature greater than 160°C and a decomposition temperature of 270°C.

1. Plastic processing

PMMA has a certain degree of water absorption, with a water absorption rate of 0.3-0.4%, and the humidity of injection molding must be below 0.1%, feem ntau 0.04%. The presence of water causes bubbles, gas lines, and reduced transparency in the melt. So it needs to be dried. The drying temperature is 80-90℃, and the time is more than 3 teev. Recycled materials can be used 100% qee zaum. The actual amount depends on quality requirements, usually over 30%. Recycled materials should avoid pollution, otherwise it will affect the transparency and the properties of the finished product.

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2. Txhaj tshuaj molding tshuab selection

PMMA has no special requirements for injection molding machines. Because of its high melt viscosity, a deeper screw groove and a larger diameter nozzle hole are required. If the strength of the product is higher, a screw with a larger length to diameter ratio should be used for low-temperature plasticization. Ntxiv thiab, PMMA must be stored in a dry hopper.

3. Pwm thiab rooj vag tsim

Cov pwm kub can be 60℃-80℃, the diameter of the main runner should match the inner taper, the best angle is 5° to 7°, if you want to inject 4mm or more products, the angle should be 7°, and the diameter of the runner should reach 8 to 10mm, the overall length of the gate should not exceed 50mm. For products with a wall thickness of less than 4mm, the diameter of the runner should be 6-8mm

For products with wall thickness greater than 4mm, the runner diameter should be 8-12mm. Diagonal, fan-shaped and tabular gate depth should be 0.7 to 0.9t (t is the thickness of the product wall), and the diameter of the needle gate should be 0.8 to 2mm; smaller size should be used for low viscosity.

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The common vent holes have a depth of less than 0.05 and a width of 6mm. The demolding angle is between 30′-1° and 35′-1°30° in the cavity part.

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4. Melting temperature

It can be measured by air injection method: ranging from 210°C to 270°C, depending on the information provided by the supplier.

Withdraw the back seat, make the nozzle of the injection molding machine leave the sprue bushing, and then manually perform plasticization injection molding, which is air injection molding.

5. Txhaj kub

Fast injection can be used, but to avoid high internal stress, it is advisable to use multi-stage injection, such as slow-fast-slow, lwm yam., when injecting thick parts, use slow speed.

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6. Detention time

If the temperature is 260°C, the residence time cannot exceed 10 feeb, and if the temperature is 270°C, the residence time cannot exceed 8 feeb.

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