PP plastic has the characteristics of good heat resistance, no need for drying when stored properly, and good mechanical properties. It can also be used for PP injection molding, PP drawing, PP fiber, PP film, etc. The relevant content will be introduced in detail below.
First, the characteristics of pp plastic
1. Good heat resistance, pp products can be used in a high temperature environment below 100 degrees for a long time, and the temperature will not be significantly deformed when the temperature reaches about 150 degrees.
2. The density is small, 0.81---0.91g/cm3, which is the smallest density among commonly used plastics.
3. PP material has good mechanical properties, high heat resistance, good chemical properties, almost no water absorption, no reaction with most chemicals, pure texture, non-toxicity, and good electrical insulation.
4. If stored properly, no drying treatment is required.
5. The back pressure of the melt glue can be 5bar, and the back pressure of the toner material can be appropriately increased.
6. The melting point is 160-175℃, and the decomposition temperature is 35O℃. However, during injection processing, the temperature setting cannot exceed 275℃, and the mold temperature is 50-90℃. For higher size requirements, use high mold temperature and core temperature. It is more than 5℃ lower than the cavity temperature.
7. The injection pressure adopts higher injection pressure and holding pressure, and the holding pressure is about 80% of the injection pressure. Switch to holding pressure at about 95% of the full stroke, and use a longer holding time.
8. Injection speed. In order to reduce internal stress and deformation, high-speed injection should be selected. However, if the patterned surface appears with light and dark stripes diffused by the gate, low-speed injection and higher mold temperature should be used.
9. Mould. Generally, the runner has a straight length of 4 to 7mm, the length of the needle gate is 1 to 1.5mm, and the diameter can be as small as 0.7mm. The length of the edge gate is as short as possible, about 0.7mm, the depth is half of the wall thickness, the width is twice the wall thickness, and gradually increases with the length of the melt flow in the cavity, the mold must have good exhaust , The vent hole is 0.025mm deep-0.038mm, and 1.5mm thick. To avoid shrinkage marks, use large and round nozzles and circular runners, and the thickness of the ribs should be small.
Second, the application of pp plastic
1. PP injection
PP injection molding is mainly used in small household appliances, toys, washing machines, auto parts and so on. In recent years, the improvement of people's living standards and the implementation of the national two-child policy have gradually increased the downstream demand for polypropylene injection molding. Different injection molding products have different demand in the off-peak and peak seasons. For example, injection molding pots and barrels are in demand in the first school season. It is more prosperous, and the demand for accessories and gifts is affected by many festive celebrations. Generally speaking, the application of PP injection plastics is relatively frequent.
2. PP drawing
Polypropylene wire drawing is mainly used in plastic woven products. The daily used container bags, woven bags, food bags and transparent bags are all PP wire drawing products. Since the implementation of the domestic environmental protection policy in 2017, the demand for cement and building materials packaging has declined. The plastic woven industry has suffered a lot, and the corresponding PP plastic woven market is under pressure. In the future, the proportion of PP plastic woven in the overall use of polypropylene will continue to decline, and the plastic woven industry will gradually expand into high-capacity, high-quality large packaging bags. Or low-volume, low-content small packaging bags.
3. PP film
Polypropylene films are generally divided into BOPP films, CPP films, IPP films, and PP films are mainly used for food packaging. Compared with PE packaging bags, PP film food packaging bags have better transparency, greater hardness, and high-end appearance. The downstream demand is mainly Focus on holidays and holidays.
4. PP fiber
Polypropylene fiber is a fiber product made by melt spinning polypropylene as a raw material. Mainly used in decoration, clothing and other fields. Since the implementation of the second child policy in 2011, downstream wet wipes, diapers and other maternal and child products have surged, and there has been a shortage of domestic fiber materials.
5. PP pipe
Because polypropylene has non-toxic and high temperature resistance characteristics, PP pipe materials are mainly used in water supply and heating systems. Compared with PE pipes, PP pipes are lighter in weight, convenient to transport, and have better environmental performance and can be recycled. Generally speaking, from March to May, and from September to October, PP pipe materials are relatively strong. In recent years, the application of polypropylene in special materials such as fibers and pipes has grown rapidly. With the further implementation of the ban on plastics, the import volume of recycled materials and waste plastics has decreased. According to statistics, the total domestic output of PP pellets in August 2018 was 1.5284 million tons. Compared with last year (1.6227 million tons), a decrease of 94,300 tons, or 5.81%, was a decrease in imported materials, which shows that there is still a certain gap in the domestic polypropylene market.