What is pp material, detailed?

PP has unusual chemical solvent resistance, acid resistance and alkali resistance. It can produce high-purity polypropylene for semiconductor industry. It can also resist the generation of bacteria and is suitable for disposable syringes and medical equipment. Can be used for injection molding or machining and welding. It can be used for plastic products with higher quality requirements than polyethylene products, such as pipes, filter materials and loudspeakers. Banknotes are made of biaxially stretched polypropylene (BOPP), so their durability is improved. Polypropylene was discovered at the beginning of 1950 by Italian chemical scientist Leo Nata. In modern science, an invention may be invented by people in different places at the same time. Polypropylene is such an extreme example, which has been invented independently for about 9 times. This is a wonderful script that patent agents dream of, and the lawsuit didn't end until 1989. Polypropylene has been trying to continue this legal series. Two American chemists, J paul hogan and Robert Banks, who work for Philip Oil Company, are now considered as the "official" inventors of this material. Polypropylene, like its close relative polyethylene, is very cheap and abundant. Products ranging from plastic bottles to carpets and plastic furniture are also used in the automobile industry. Polypropylene is a highly rigid material, which belongs to polyolefin with PE. The density of homopolymer is as low as 0.90. Glass fiber and minerals (such as calcium carbonate) can be added for reinforcement. PP is not suitable for use below 0oC. If it is to be used at sub-zero temperature, it is necessary to use butadiene * * * poly to produce * * * poly PP, and the working temperature of homopolymer PP is 90oC, and its chemical resistance (acid and alkali resistance) is very good. Parts produced by homopolymerized PP have very low hygroscopicity, but they shrink greatly during injection molding. The electrical properties are very good, but the penetration resistance such as ultraviolet rotation is very poor. Common methods of chemical modification: one is to take modified resin monomer as one unit and modified monomer as another unit, and carry out graft polymerization in a reaction kettle to obtain a new polymer; The second method is to take modified resin as the main raw material and effectively modify it by increasing polar elements in resin molecules. Polypropylene is widely used in the production of plastic pipes, but PP is a material with poor aging resistance. In order to improve the properties of polypropylene, PP-B and PP-R resins were invented by chemical modification. PP-B resin is a block copolymer of propylene and ethylene. The synthesis of propylene-ethylene block copolymer requires two polymerization reactors. One is to polymerize monomer propylene into homopolymer polypropylene, and the other is to introduce homopolymer PP generated in the first reactor into ethylene to form propylene-ethylene block polymer, that is, to form ethylene-propylene elastic segment. PP-B resin is essentially the modification of homopolymer PP and ethylene. Modified PP-B resin has both the performance advantages of PE and PP, and PP-R is a random polypropylene modified by ethylene on the basis of PP * * * *. Random PP has a minimum molecular weight of tens of thousands, small cohesion, low melting point and poor mechanical properties. Only ethylene modified random PP has practical application value. The modification process is that propylene is gasified and sent to the reaction kettle by gas phase method, materials are sent from the first reaction kettle to the second reaction kettle by gas lock system, and ethylene is added to the second reaction kettle. The propylene catalyst with high activity and high selectivity was added to the upper part of the reactor, which was evenly dispersed on the powder layer by stirring, and a random polymer was formed by controlling the ratio of ethylene to propylene. This kind of polymer changes the configuration of PP molecular chain and makes ethylene polymerize randomly and uniformly on PP molecular chain. Compared with ordinary PP, the stress cracking resistance of PP-R material is greatly improved, and its performance decays very slowly under the action of temperature and internal and external pressure, so it is one of the most ideal materials for producing and transporting hot and cold water pipes. Chemical modification can not only change the properties of resin, but also make new resin materials. Some commonly used resin materials are obtained by modification, such as ultra-high molecular weight polyethylene (UHMPE), which is the product of chemical modification. This ultra-high molecular weight polyethylene greatly improves the mechanical properties of HDPE materials. Its wear resistance and self-lubrication are better than other engineering plastics, and its mechanical properties and corrosion resistance are no less than PTFE. LLDPE is also obtained by chemical modification. It is a polymer formed by introducing a small amount of α -olefin monomers such as butene, hexene and octene in ethylene polymerization. It has a molecular configuration similar to HDPE, but its density and crystallinity are reduced. LLDPE has good environmental stress cracking resistance, and its mechanical properties are better than LDPE. Therefore, its application scope has also expanded accordingly. Chlorinated polyethylene (CPE) is also the product of chemical modification. It is the product of HDPE chlorination. Chlorine (CL) partially replaced hydrogen (H) in HDPE molecules, which destroyed the crystallinity of the molecules and made them softer and more elastic. Not only can it be processed into CPE products by extrusion or injection molding, which are widely used in buildings and electrical appliances, but also CPE itself becomes an excellent modifier, which can improve the flame retardancy of PE materials and the impact resistance of PVC materials through physical mixing. Physical Modification * * * Mixed Modification The resin is mixed with one or more other materials by mechanical means to meet some special requirements. This way is * * * mixed physical transformation. * * * Mixed modification can not change the molecular configuration, but can give new properties to the material. The compatibility of PE resin is poor, and blending modification is difficult. In order to improve the compatibility of two phases, it is usually necessary to introduce another intermediate. For example, HDPE and PP are incompatible. In order to mix these two resins, intermediates such as ethylene-propylene rubber (ethylene-propylene copolymer, also known as binary ethylene-propylene rubber) can be introduced to improve their compatibility. The PP-H resin used in the production of plastic pipes is also modified by * * *. Based on homopolymer PP resin, it introduces a certain amount of toughening modifiers, such as mixing PP resin with rubber substances such as polybutadiene, or mixing PP resin with EVA. The amount of toughening agent can be varied from 5% to 20% to obtain different characteristics. In actual production, many additives are usually added in the modification of materials, so the feeding sequence is also very important in the process of * * * mixed modification, otherwise the mixture can not achieve the ideal effect.