PP material performance
Polypropylene is a thermoplastic polymer (thermoplastic: refers to a material that can be hardened after being cooled and cooled, and can be repeated; polymer: refers to a natural or synthetic compound whose molecule is composed of a series of simple monomeric babies Repeatedly connected macromolecules are widely used, and even Australian banknotes are made of PP. PP has an unusual resistance to chemical solvents, acid and alkali resistance. Men'S Coats,Funnel Neck Coat,Men′S Funnel Neck Coat,Coat With Removable Gilet shaoxing zida import&export co.,ltd. , https://www.zida-fabric.com
It can produce high purity PP for the semiconductor industry. It is also resistant to bacterial production and is suitable for use as a disposable syringe and medical device. Can be used for injection molding or machining and welding. It can be used for pipes, filter materials, horns and other plastic products with higher quality requirements than polyethylene products. The banknote is made of biaxially stretched PP (BOPP) so that its durability is improved.
Polypropylene was discovered by the Italian chemist Giulio Natta in the early 1950s. In modern science, the invention of a thing may have been invented at the same time by people in different places. Polypropylene is such an extreme example that it was independently invented about nine times. It was a playful script that the patent attorneys had dreamed of, and the dispute ended in 1989.
Polypropylene has been trying to continue this legal series. Two American chemists, J. Paul Hogan and Robert Banks, who work at Phillips Petroleum, are now considered the "official" inventors of this material. Polypropylene, like its cousin polyethylene, is very cheap and abundant. Products from plastic bottles to carpets and plastic furniture are also used in the automotive industry.
Polypropylene is a highly rigid material that belongs to the same polyolefin as PE. The homopolymer density is as low as 0.90. It can be added with fiberglass and minerals such as calcium carbonate. PP is not suitable for use below 0oC. If it is to be used at subzero temperatures, it must be copolymerized with butadiene, which results in copolymerized PP. The operating temperature of homopolymerized PP is 90oC, and the chemical resistance (acid, alkali) is very good. Parts produced with homopolymerized PP have very low hygroscopicity but shrink when injected. The electrical performance is very good, but the UV resistance and other penetration resistance are poor.
A common method for chemical modification: one is to modify the resin monomer as a unit, the modified monomer is another element, graft copolymerization is carried out in the reaction vessel to obtain a new copolymer; the second method is to The modified resin is used as a main raw material, and is effectively modified by increasing a polar element in the resin molecule.
Polypropylene is widely used in the production of plastic pipes, but PP is a material with poor anti-aging properties. In order to improve the performance of PP, PP-B and PP-R resins were invented by chemical modification methods.
The PP-B resin is a block copolymer of propylene and ethylene. Two polymerization reactors are used to synthesize the propylene-ethylene block copolymer. One is used to polymerize monomer propylene into homopolypropylene, and the other is to introduce homopolymerized PP produced in the first reactor into ethylene to form a propylene-ethylene block copolymer, i.e., to form an ethylene-propylene elastomeric segment. The PP-B resin is essentially a copolymerization modification of homopoly PP and ethylene. The modified PP-B resin combines the performance advantages of PE and PP.
PP-R is a random polypropylene modified by ethylene based on copolymerized PP. The random PP has a molecular weight of only tens of thousands, a small cohesive force, a low melting point, and poor mechanical properties. Only the random PP modified by ethylene has practical application value. The modification process is that the propylene is vaporized and then sent to the reaction vessel by a gas phase method, and the material is sent from the first reactor to the second reactor by an air lock system, and ethylene is added to the second reactor. A highly active, highly selective propylene catalyst is used, which is added to the upper portion of the reactor, uniformly dispersed on the powder layer by stirring, and a random copolymer is formed by controlling the ratio of ethylene to propylene. This polymer changes the configuration of the PP molecular chain, allowing ethylene to polymerize randomly and uniformly over the molecular chain of PP.
Compared with ordinary PP, the stress crack resistance of PP-R material is greatly improved. Its performance is very slow under the action of temperature and internal and external pressure. It is one of the most ideal materials for the production of hot and cold water pipes. .
Chemical modification to create new materials Chemical modification can not only change the properties of a resin, but also create new resin materials. Some of the currently used resin materials are obtained by modification, such as ultra high molecular weight polyethylene (UHMPE), which is a chemically modified product. This ultra high molecular weight polyethylene greatly enhances the mechanical properties of HDPE materials. Its wear resistance and self-lubricity exceed other engineering plastics, and its mechanical properties and corrosion resistance are no less than that of polytetrafluoroethylene (PTFE).
LLDPE is also obtained by chemical modification. It is a copolymer formed by introducing a small amount of a-olefin monomers such as butene, hexene or octene into the polymerization of ethylene. It has a similar molecular configuration to HDPE but reduces density and crystallinity. LLDPE has good environmental stress crack resistance and its mechanical properties are superior to LDPE. Therefore, its application range has been expanded accordingly. Chlorinated polyethylene (CPE) is also a product of chemical modification. It is the product of HDPE after chlorination. Chlorine (CL) partially replaces hydrogen (H) in the HDPE molecule, causing the molecule to undergo crystal damage, making it softer and more elastic. It can be processed into CPE products by extrusion or injection molding, widely used in construction, electrical appliances, etc., and CPE itself becomes an excellent modifier, which can improve the flame retardancy of PE materials by physical blending. And the impact resistance of PVC materials.
Physical Modification Blending Modification The resin is mechanically blended with one or more other materials to meet certain special requirements. This method is blending physical modification. Blending modification does not alter the molecular configuration, but can impart new properties to the material.