Injection Molding: Process Analysis Of Six Recycled Plastics
First,recycled low density polyethylene (LDPE) process
LDPE, the scientific name of high-pressure polyethylene, generally refers to plastic packaging film. Such as: woven bag inner liner film, food packaging film, daily necessities packaging film, greenhouse film. Most of these films are natural, light blue, and black. It is best to separate the color samples before recycling. It is impossible to put the low-pressure film and the PP film together, and it is impossible to put the OPP and the PVC film into it. Recycling and reusing LDPE is the process of regenerating LDPE.
There are four main processes in the entire regenerative LDPE process:
1. The pulverization process. It is better to have a water pulverizing effect. Since some good high pressure membranes are kept clean enough, the membrane can be re-blown without adding new material. Therefore, it is necessary to pay attention to cleaning during the pulverization process. When the pulverized material flows to the water tank, it is best to roll again to further clean the cleaning point.
2. Drying process. Generally, the drying machine is used to dry the remaining water. If it is conditional, it can be dried. This can save electricity costs and improve quality. Of course, attention should be paid to preventing secondary pollution of materials during drying.
3. Granulation process. There are two basic uses for pellets made from special extruders: re-blowing and injection molding. The material from the 60 to 80 mesh filter can be blown again; the material from the 40 to 60 mesh filter can meet the quality requirements of the injection molding. Generally, the high-pressure material blows the film again, and the good blowing color is a little bit blown by the black film and the garbage bag, and the price after the injection of the plastic is lower.
4. The pelletizing process is generally cold water pelletizing. This procedure must pay attention to the labeling when packaging. A kind of blow molding, a kind of injection molding, so as not to make a mistake. In addition, the packaging bag for blow molding must be covered with a liner bag to avoid secondary pollution.
Second, recycled polypropylene (PP) process
Most of PP comes from daily necessities, plastic boxes, foot basins, buckets, rice bran, plastic chairs, stools, woven bags and other packaging woven fabrics, packing belts, etc.
1. First separate the colors of the various materials, because the separation will make the user convenient and the price can be high.
2. Smash and rinse with water, dry the remaining water in the dryer, and then dry and bag. Mix with a mixer and add some color and additives.
3. Special plastic machine for granulation on the car, but the granulation temperature should not be too high, it is easy to be brittle, so we must pay attention to the temperature.
4. Water-cooled pellets, the standard 3X4mm, otherwise the appearance of the good material is not good, not standard.
Third, recycled polyethylene terephthalate (PET) process
PET, the scientific name polyethylene terephthalate, is a linear thermoplastic. It is usually a kind of crystalline plastic. PET bottles are used in food, beverage, cosmetics and other fields because of their light weight, not easy to break, and low energy consumption. They replace some traditional packaging materials. The recycling and reuse of PET is the process of regenerating PET.
The PET bottle is recycled by separating the PET bottle from the lid, label, etc., and then pulverizing, washing, and drying.
Its specific process is as follows:
1. The first step is the selection process: picking and sorting various PET bottle flakes. Tear off the outer logo,
2. In the pulverization process, rinse with water during the pulverization process to remove dirt from various PET bottle flakes.
3. Place the pieces in a steam treatment unit and add the caustic soda to remove greasy and other intractable impurities.
4. Wash with water, dry the remaining water and bag. Then go to a vacuum oven for drying.
5. Spinning, shaping, stretching with hot water steam, and then shaping.
Fourth, ABS plastic process
ABS plastics, mostly come from electrical products, a variety of daily necessities and some mechanical small parts.
1. ABS is more, computer case, TV case, instrument case, car panel, decorative materials, pick this material, special plating, painting color, etc. to be separated.
2. Chemical treatment, deplating, and lacquering, but de-plating and lacquering must be cautious. Because chemical syrup has a certain ratio, use protective equipment and containers, otherwise it will cause injury and other events.
3. Clean the tank to clean, then dry, color or auxiliary materials, the purpose is to improve the quality.
4. Special extruder to granulate, but must put the filter, but the filter is placed according to product requirements.
Fifth, recycled polycarbonate (PC) process
Polycarbonate, amorphous plastic, engineering plastics. Most of them come from textile accessories, car headlights, taillights, turn signals, candy making molds, discs, telecommunications equipment, photographic equipment, etc.
1. First select the PC to be purchased, transparent and opaque, blue, red, green, black must be separated; also modified, such as textile parts are mostly modified; such as discs, lamp holders are coated.
2. Clean the color PC, and the disc deplating process, etc., and operate the same principle as ABS. Then dried, then classified, and sent to the extruder for production.
3. PC has a relatively yellow color, can produce porcelain white; transparent still produces transparent; other colors can add coloring agents and material additives.
4. Special extruder granulation, but the PC itself is easy to age, so it can not be returned multiple times. The granulation must be cautious and granulated.
Sixth, recycled polyvinyl chloride (PVC) hard material process
Most of the PVC hard materials come from building materials, plastic steel window doors, electroplated hard plates, plastic valves for chemical plants, sewer pipes, and decorative materials.
1. First select the process and separate the colors. These materials are divided into white, gray, and black, but do not mix PP and PE.
2. Smash to the pulverizer, but also smash with water. Remove the contaminated water and wash it, then dry it to prevent secondary pollution.
3. Mix the ingredients on the upper mixer and mix. If it is a white material and add a coloring agent, add an auxiliary agent as needed.
4. The special PVC extruder is used for scraping and cooling bagging.