1. Introduction and characteristics of polypropylene.
Polypropylene (PP) is a thermoplastic resin and is one of the five general resins. The appearance is white granular, odorless, non-toxic, due to the regular crystal structure, with easy processing, impact strength, flexural resistance and good electrical insulation, etc., it has a wide range of applications in household appliances, electronics, packaging and building materials and furniture.
The structural characteristics of PP determine its five characteristics:
1) Its molecular structure is similar to that of polyethylene, but the interphase carbon atoms on the carbon chain carry a methyl group (CH3).
2) It is usually a translucent colorless solid, odorless and non-toxic.
3) Due to the regular structure and high crystallization, the melting point is as high as 167, and the heat resistance and the product can be sterilized by steam is its outstanding advantage.
4) Density 0At 90g cm3, it is an ultra-light general-purpose plastic.
5) Corrosion resistance, tensile strength 30MPa, strength, rigidity and transparency are better than polyethylene.
However, the disadvantage of PP is that it has poor impact resistance at low temperature and is easy to age, which can be overcome by modification and the addition of antioxidants.
In the past ten years, China's polypropylene consumption has grown at an average annual rate of 10, greatly exceeding the global average growth level, and is the second largest consumer of synthetic resin in China, second only to polyethylene. The strong market demand has also given birth to the rapid growth of polypropylene production capacity and output, and the output is second only to polyethylene and poly among the five major general plastics, ranking third.
Second, the classification of polypropylene.
Polypropylene can be classified in a variety of ways, according to the spatial position of methyl (-ch3) in the polypropylene molecule, it is divided into three categories: isoregular, inter-gauge and random, according to the polymerization process, the polymerization of isometric polypropylene can be divided into several methods such as slurry method, bulk method, solution method and gas phase method. According to the use, it can be divided into flat wire (narrow belt), fiber, film, extrusion, blow molding, injection molding and other grades, and according to the type of monomer, it can be divided into homopolymer polypropylene and copolymer polypropylene.
Third, the application of polypropylene.
1) Woven products.
PP resin consumed in woven products (plastic woven bags, tarpaulins and ropes, etc.) has always accounted for a high proportion in China, and it is a large market for polypropylene consumption in China, mainly used for the packaging of grain, fertilizer and cement.
2) Injection molded products.
Injection molded products are mainly used in small household appliances, daily necessities, toys, washing machines, automobiles and turnover boxes.
3) Film products.
Polypropylene film mainly includes BOPP, CPP, ordinary packaging film and microporous film, etc., BOPP has many excellent characteristics such as light weight, high mechanical strength, non-toxic, transparent, moisture-proof, etc., and is widely used in packaging, electrical, electronic appliances, tape, label film, film, composite and many other fields, among which the packaging industry is used in large quantities.
4) Fiber products.
Polypropylene fiber (i.e. polypropylene) refers to a fiber product made of polypropylene as raw material through melt spinning. Because polypropylene fiber has many excellent properties, it is increasingly widely used in the three major fields of decoration, industry and clothing, and has become the second largest variety of synthetic fibers.
5) Pipes. Polypropylene pipes have the characteristics of high temperature resistance, convenient pipe connection (hot melt connection, electric fusion connection, pipe fitting connection), and can be used, and are mainly used in building water supply systems, heating systems, farmland water transmission systems, and chemical pipeline systems.
Fourth, polypropylene production process and technology.
There are five main types of polypropylene production processes: solution method, slurry method, bulk method, gas phase method and body-gas phase combination process. At present, the more advanced production technology is mainly the gas phase process and the body-gas phase combination process.
Main series: general plastics: ABS, PP, PE, HIPS, GPPS, PVC, EVA;
Engineering plastics: PMMA, PC ABS, PC, PA6, PA66, PA46, PA4T, PA6T, PA ABS, PA PPE, POM, PBT, PC PBT;
High temperature plastics: PPA, PA46, PA6T, PA9T, LCP;
Special engineering plastics: PPS, COC, COP, IXEF, PTFE, PFA, ETFE, FEP, PVDF, PEI, PEEK, PI, PPA, PES, PSU, PPSU, PSF, PUR, PA12, PA11;
Thermoplastic elastomers: TPE, TPEE, TPV, TPR, SBS, SEBS, TPU.
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