Because PVC transparent material has the advantages of high transparency, good stability, and good weather resistance, it is widely used in consumer toys, daily necessities, auto parts, profiled materials, etc. These plastic products have strict requirements on the appearance quality, and they must not have any defects such as markings, pores, whitening, haze, black spots, discoloration, poor gloss, etc. Therefore, the raw materials, equipment, and molds are very strict and even special throughout the injection molding process. ask.

1. Preparation and boring of PVC transparent material
Since any impurity in the plastic may affect the transparency of the product, it is necessary to pay attention to the seal during storage, transportation, and feeding to ensure that the PVC transparent material is clean. In particular, the raw materials contain water, which will cause the raw materials to change after heating, so it must be boring. It should also be noted that during the drying process, the input air should be filtered and dehumidified to ensure that it will not pollute the PVC transparent material.

2. Cleaning of the barrel, screw and accessories
In order to avoid the pollution of PVC transparent material and the presence of old materials or impurities in the recesses of the screw and accessories, especially the presence of resin with poor thermal stability, screw cleaning agents should be used to clean the parts before use and after shutdown to prevent sticking. Impurities, when there is no screw cleaning agent, you can use PE, PS and other resins to clean the screw. When temporarily shutting down, in order to prevent the raw materials from staying at high temperature for a long time and cause degradation, the temperature of the dryer and barrel should be lowered.

3. The following points should be paid attention to in product design and mold design:
1. Try not to have sharp corners or sudden changes in the product, and try not to change the thickness much to avoid PVC degradation.
2. The mold should have a draft angle of more than 10 degrees, and reserve about 0.5% of shrinkage.
3. Several points should be paid attention to in the design of mold runner:
The injection port of the mold should be slightly larger than the nozzle hole, and larger than the diameter of the interweaving part of the main runner, so that the PVC material flows into the cavity without stagnation and the pressure can be balanced.
Use intercept gates as much as possible so that slag does not flow into the product and the temperature of the flow channel is reduced, and it is easy to form.
The gate should be designed at the thickest wall of the product, and the width is sufficient, the length is preferably between 6-8mm, so that the PVC material flows smoothly.
In order to make the pressure drop and easy demoulding, the runner should be round, and the diameter should be 6-10mm according to the product size and weight.
4. The mold temperature should be installed with cooling water control, so that the mold temperature can be controlled between 30°C and 60°C.
5. The mold should be bright and chrome-plated to prevent corrosion.

4. Due to the special properties of PVC, special PVC injection molding machines are used for consumption, and the following points should be paid attention to:
1. The screw length-to-diameter ratio should be 20:1, and the compression ratio should be between 1:1.6-1:1.2.
2. The screw and nozzle should be specially made of PVC, and the surface should be chrome-plated.
3. The injection pressure, speed, back pressure and temperature can be controlled in multiple stages and finely.

Summary: PVC is a heat-sensitive material, and its injection molding processability is poor. The reason is that too high melting temperature or too long heating time can easily make PVC synthesis, so controlling the melting temperature is the key to injection molding PVC products. The heat source for condensing PVC raw materials comes from two aspects: the shear heat of the plastic produced by the screw movement and the heating of the resistance wire on the outer wall of the barrel, and the shear heat of the screw movement is the main source. The external heating of the barrel is mainly to provide the heat source when the machine is started.

Related knowledge
What are the factors related to the transparency of PVC transparent material?
The transparency of the PVC transparent material should be very clear under normal conditions, and the visibility and field of vision are very good. Then the transparency of some PVC transparent materials is not good, and even mixed with other colors. What factors form the transparency of the PVC transparent material Has it been affected?
1. Silver streak: Affected by the anisotropy of internal stress during the mold filling and condensation process, the stress generated in the vertical direction causes the resin to move upward, and the refractive index is different from the inactive orientation to produce flashing silk stripes. After expansion, the product may show cracks. It is best to anneal the product. For example, the transparent PVC material can be heated to above 160°C for 3-5 minutes, and then cooled naturally;
2. Bubbles: water vapor and other gases in the resin cannot be discharged (during the mold condensation process), or due to lack of mold filling, the condensation surface condenses too quickly to form a "vacuum bubble";
3. Poor surface gloss: Mainly due to the large roughness of the mold, on the other hand, premature condensation makes the resin unable to copy the state of the mold's surface. All these make the surface produce small unevenness and make the product lose its gloss;
4. Shock pattern: refers to the dense corrugation formed from the straight gate as the center. The reason is that the material at the front end has been condensed in the cavity due to excessive melt adhesion, and later the material breaks through the condensation surface, causing the appearance to show shock patterns. ；
5. Whitening and haze: mainly caused by dust falling into the raw material in the air or the raw material has too much water content;
6. White smoke and black spots: mainly caused by the synthesis or transformation of the resin in the barrel due to partial overheating of the PVC transparent material in the barrel.

Wuxi Jiahong Plastic Technology Co., Ltd. can process various filled, flame-retardant, reinforced modified ABS, PS, PC, PC/ABS, polypropylene, PA and other engineering plastic particles according to customer requirements; various car door panels, bumpers, dashboards , Engine cover, car lights and other automotive special materials.

Wuxi Jiahong Plastic Technology Co., Ltd. has nearly 30 years of experience in R&D and pelletizing production of rigid transparent PVC pellets, and experience in R&D and production of modified engineering plastics; the professional technical service team can provide customers with one-stop modified plastic system solutions plan. If you want to know more about the product, please log in to our official website: www.js-plastics.com, consult online customer service or call the hotline. Landline: 0510-68755207 Mobile: 15190220696, we will serve you wholeheartedly.