Introduction to the classification of general plastics for blow molding machinery

Plastic polyvinyl chloride is also a general-purpose plastic for blow molding machinery with good overall performance and low price, and it has many additives, which can change the performance of the product through adjustment of the formula, such as adding less or not Add plasticizer to make hard plastic polyvinyl chloride products. Hard plastic PVC products have excellent rigidity and have good water and moisture resistance and isolation of oxygen, carbon dioxide and nitrogen. Its oil resistance and transparency are also significantly better than polyolefin plastics. However, it is difficult to recycle and incinerate the waste after packaging, and it is relatively easy to decompose during the process of returning to the furnace. When burning and disposing, substances such as hydrogen chloride that damage the environment will be produced, and energy will be consumed. Therefore, plastics The use of polyvinyl chloride in packaging is subject to certain restrictions, and with the continuous improvement of people's awareness of environmental protection, its use in packaging has a tendency to be gradually replaced by other plastics.

Among several kinds of plastic polyethylene, high-density plastic polyethylene is the kind with the best mechanical strength in plastic polyethylene, and the ability to isolate water vapor is the best among various plastics. Among them, it is the type with the worst softness and transparency. When products with softness and good transparency are required, low-density plastic polyethylene should be used. The mechanical strength of linear low-density plastic polyethylene is between that of high-density plastic polyethylene. Between ethylene and low-density plastic polyethylene, its biggest advantages are high puncture resistance, high tear transmission strength, and excellent stress crack resistance; in addition, its heat sealing performance is also better than that of high-density plastics. Polyethylene and the general low-density plastic polyethylene, therefore, it is an excellent substrate for film, one of its main drawbacks is poor molding performance.

Polypropylene and propylene copolymers, polypropylene and plastic polyethylene, are typical polyolefin polymers, so they have many similar properties, such as good chemical stability, non-toxic, odorless, tasteless, reliable cleaning performance, etc. , Compared with plastic polyethylene, the main advantage of polypropylene is good heat resistance, and the use temperature can reach 120 degrees. Therefore, the composite bag with propylene as the heat-sealing layer is used for cooking and sterilization. In addition, the strength of polypropylene is significantly higher than that of plastic polyethylene. One of the biggest defects in the performance of polypropylene is poor low temperature resistance. Polypropylene homopolymers have shown greater brittleness at 0 degrees. The copolymer can significantly improve the cold resistance of polypropylene, but the heat resistance is also reduced accordingly.

Ethylene-vinyl acetate copolymer is also an ethylene polymer used more in packaging. Its price is slightly higher than that of plastic polyethylene, but it is still a relatively cheap variety in plastics. With the increase of vinyl acetate content, its cold resistance Sex, softness, improved heat sealability, and improved transparency, but when the vinyl acetate content exceeds 10%, it may have a sour taste, and it is not suitable for direct contact with food. The thermoplastics in the general-purpose plastics of blow molding machinery hollow blow molding machines have the advantages of balanced performance, convenient molding and processing, convenient recycling and discarded materials, and low product prices. They are widely used in plastic packaging materials. Main types such as: polyethylene and ethylene copolymers, such plastics include high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene, vinyl acetate copolymer, etc.

Used as a plastic packaging material, it is very similar to plastic polyethylene. Polypropylene has excellent moisture resistance and moisture resistance, but has poor isolation to non-polar gases such as oxygen, carbon dioxide, and nitrogen. When the product needs to be stored in an oxygen barrier, it needs The so-called insulating plastic packaging material is used for packaging, or the composite product of polypropylene (polyethylene) and insulating plastic packaging material is used as the plastic packaging material. Plastic Polyethylene plastic is a typical polyolefin compound, non-toxic, odorless, tasteless, reliable cleaning performance, acid, alkali, salt and various chemical substances, stable performance; balanced physical and mechanical properties, excellent moisture resistance, Its molding processing function is special, and it can be conveniently made into various packaging plastic products such as plates, films, containers, flat wires, etc., and the price is low, so it is widely used in packaging. As a plastic packaging material, its main disadvantage is Oxygen resistance is poor.

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