PP injection molding process

Products generally need to be soaked in hot water.

End to prevent shrinkage deformation after crystallization.

Because of its good anti-breaking performance, PP is generally called polypropylene.

Also called "100 fold glue" PP a kind of translucent, semi-crystalline thermoplastic, with high strength, good insulation, low water absorption, heat on the shape of high temperature, small density, high crystallinity characteristics.

The modified filler usually includes glass fiber, mineral filler, thermoplastic rubber and so on.

Generally used PP flow rate between ABS and PC.

The fluidity of PP for different USES varies greatly.

1. Disposal of plastics

It can be dyed in a variety of colors.

PP dyeing in general injection molding machine can only use color master.

Ramada has independent plasticizing elements to enhance mixing effect, pure PP translucent ivory red.

You can also dye it with toner.

For outdoor use, UV stabilizers and carbon black fillers are generally used.

Do not use more than 15% of raw materials, or it will cause a decline in strength and discoloration.

PP injection processing before the general need for special drying treatment.

2. Selection of injection molding machine

The injection amount is 20%-85%.

There are no special requirements for the selection of injection molding machines.

Because PP has high crystallinity.

A computer injection molding machine with high injection pressure and multi-stage control is required.

Clamping force is generally determined by 3800t/m2.

3. Mold and gate design

For higher dimensional requirements, use high modulus temperature.

The core temperature is more than 5℃ lower than the cavity temperature, and the mold temperature is 50-90℃.

The diameter of the runner is 4-7mm, and the diameter of the needle gate is 1-1.5mm. The shorter the length of the side gate, the better. The depth is about 0.7mm, half of the wall thickness, and the width is twice of the wall thickness.

The mold must have good exhaust property, the vent depth is 0.025mm-0.038mm thick 1.5mm to avoid shrinkage marks, it is necessary to use a large and round injection port and circular flow passage, the thickness of the reinforcement should be small (for example, the wall thickness is 50-60% of the product made of homogeneous PP, thickness cannot exceed 3mm otherwise there will be bubbles

Melt temperature

The decomposition temperature was 350℃, and the melting point of PP was 160-175℃.

However, the temperature setting should not exceed 275℃ during injection processing.

The best temperature of the melting section is 240℃.

5 injection speed

High speed injection should be selected to reduce internal stress and deformation.

But some grades of PP and mold is not applicable (human mantle bubbles, air lines) if the surface engraved with patterns appear by the gate diffusion of light and dark stripes, low speed injection and high mold temperature.

Glue back pressure

The back pressure of toner can be appropriately raised.

5bar glue back pressure is available.

Injection and pressure maintenance

Use a longer holding time.

High injection pressure (1500-1800bar and holding pressure (about 80% of the injection pressure) is used to transfer the holding pressure at about 95% of the full stroke.

8. Post-processing of products

In order to prevent the shrinkage deformation caused by crystallization, the products generally need to be soaked in hot water.