Relevant characteristics of polypropylene
DATE：2022/12/24 8:42:56 / READ： / SOURCE：This station
(1) Performance characteristics
Isotactic polypropylene in polypropylene resin is a kind of thermoplastic resin with regular configuration and high crystallinity (crystallinity up to 95%). Among the commonly used plastics, it is the lightest variety. Polypropylene resin is often referred to as isotactic polylactene. The characteristics of polypropylene introduced here refer to the properties of isotactic polypropylene resin.
① Polypropylene is a milky white wax, non-toxic, tasteless and odorless, with a density of 0.90~0.91g/cm3.
② The mechanical strength, rigidity and stress cracking resistance of polypropylene are superior to those of high-density polyethylene; Good abrasion resistance, high hardness, high temperature impact resistance (but it drops sharply below - 5 ℃), and good repeated folding resistance.
③ Good heat resistance, thermal deformation temperature is 114 ℃, Vicat softening point is greater than 140 ℃, melting point is 164~167 ℃, the service temperature can reach 150 ℃ under no load condition, which can be used for disinfection at 130 ℃, and the maximum continuous service temperature is 110~120 ℃.
④ The chemical stability is good, except that strong oxidizing acids (such as fuming sulfuric acid and nitric acid) can corrode them, they do not react with most chemicals; It is insoluble in water and almost does not absorb water. The water absorption in water for 24h is only 0.01%. However, aliphatic hydrocarbon, aromatic hydrocarbon and chlorinated hydrocarbon with low molecular weight can soften or swell it.
⑤ Excellent electrical insulation performance, good voltage resistance and arc resistance.
⑥ The products are prone to aging due to light, heat and oxygen during use; It will age and become brittle after 12 days in the atmosphere and deteriorate after 4 months in the room. UV absorbers and antioxidants should be added to the materials to improve the weatherability of the products.
⑦ The transparency of polypropylene products is better than that of high-density polyethylene products.
⑧ The products have poor cold resistance, low impact strength at low temperature, poor toughness, high static electricity, poor dyeing, printing and adhesion. In application, additives can be added to raw materials or blending and copolymerization methods can be used to improve the performance in this respect.
(2) Quality standards
See Table 2-42 for the quality standard of isotactic polypropylene.
(3) Key points of forming process
① Generally, resin does not need drying treatment before molding and processing. Its melt fluidity is good, its softening point is high, and its molding cycle is shorter than that of other types of plastics. It is a raw material with good processing performance.
② Selection of materials for resin molding products: select the resin with a melt flow rate (MFR) of 0.15~6g/10min during extrusion molding; The resin with a melt flow rate (MFR) of about 10g/10min is selected for extrusion of blown film; Resin with melt flow rate (MFR) of 0.3~5g/10min shall be selected for injection molding.
③ The resin melting point is 160~170 ℃. The process temperature during extrusion is 260~280 ℃; The process temperature of extrusion blow molding is 220~250 ℃; The process temperature during injection molding shall be controlled at 200~300 ℃. Note that the temperature of molten materials shall not exceed 315 ℃ to avoid decomposition of molten materials.
④ During the processing of molded products, attention shall be paid to the control of the contact time between molten materials and air to prevent high-temperature oxidation of molten materials and reduce the mechanical strength of products; Contact between molten materials and copper will accelerate the oxidation degradation rate of molten materials, which should be noted. If necessary, copper inhibitors such as aromatic amine, oxalamide and other compounds should be added to the raw materials.
⑤ For polypropylene products, according to their working environment conditions, in order to increase the service time and reduce accidents, appropriate auxiliary materials should also be added to the molding resin. If the products are exposed to light for a long time, ultraviolet absorbers, such as UV531, should be added to the raw materials; Antistatic agent, such as carbon black or alkyl amide, shall be added to the resin when the product is in a flammable and explosive working environment; In order to prevent fire, flame retardants, such as antimony trioxide and chlorinated paraffin, shall be added to the resin of molded products.
⑥ Attention shall be paid to the control of cooling speed after molten material forming: the cooling speed is too fast, the crystallinity of products is low, the transparency is good, and internal stress is easy to occur; When the product is slowly cooled, the crystallinity is high and the internal stress is small, but the molding shrinkage of the product is large, and the transparency and toughness will also be slightly reduced.
⑦ Single screw extruder or twin screw extruder can be used for polypropylene resin extrusion. The length diameter ratio of the screw is required to be (20~24): 1, the compression ratio is (3.5~4.0): 1, and 100 mesh filter screen is added in front of the barrel; Plunger type or screw type injection molding machines can be used for injection molding. When screw injection molding machine is used, the melt flow rate of the selected raw materials can be lower than 0.8g/10min. When forming large and thin wall products, larger MFR values should be selected. The maximum melt flow rate (MFR) can reach 18g/10min, the injection pressure is 7~14MPa, and the mold temperature is about 50 ℃.
⑧ Pay attention to the influence of colorants on product performance; Carbon black has a certain role in preventing light aging of products, while phthalocyanine pigments have a certain role in promoting the aging of products.
Isotactic polypropylene in polypropylene resin is a kind of thermoplastic resin with regular configuration and high crystallinity (crystallinity up to 95%). Among the commonly used plastics, it is the lightest variety. Polypropylene resin is often referred to as isotactic polylactene. The characteristics of polypropylene introduced here refer to the properties of isotactic polypropylene resin.
① Polypropylene is a milky white wax, non-toxic, tasteless and odorless, with a density of 0.90~0.91g/cm3.
② The mechanical strength, rigidity and stress cracking resistance of polypropylene are superior to those of high-density polyethylene; Good abrasion resistance, high hardness, high temperature impact resistance (but it drops sharply below - 5 ℃), and good repeated folding resistance.
③ Good heat resistance, thermal deformation temperature is 114 ℃, Vicat softening point is greater than 140 ℃, melting point is 164~167 ℃, the service temperature can reach 150 ℃ under no load condition, which can be used for disinfection at 130 ℃, and the maximum continuous service temperature is 110~120 ℃.
④ The chemical stability is good, except that strong oxidizing acids (such as fuming sulfuric acid and nitric acid) can corrode them, they do not react with most chemicals; It is insoluble in water and almost does not absorb water. The water absorption in water for 24h is only 0.01%. However, aliphatic hydrocarbon, aromatic hydrocarbon and chlorinated hydrocarbon with low molecular weight can soften or swell it.
⑤ Excellent electrical insulation performance, good voltage resistance and arc resistance.
⑥ The products are prone to aging due to light, heat and oxygen during use; It will age and become brittle after 12 days in the atmosphere and deteriorate after 4 months in the room. UV absorbers and antioxidants should be added to the materials to improve the weatherability of the products.
⑦ The transparency of polypropylene products is better than that of high-density polyethylene products.
⑧ The products have poor cold resistance, low impact strength at low temperature, poor toughness, high static electricity, poor dyeing, printing and adhesion. In application, additives can be added to raw materials or blending and copolymerization methods can be used to improve the performance in this respect.
(2) Quality standards
See Table 2-42 for the quality standard of isotactic polypropylene.
(3) Key points of forming process
① Generally, resin does not need drying treatment before molding and processing. Its melt fluidity is good, its softening point is high, and its molding cycle is shorter than that of other types of plastics. It is a raw material with good processing performance.
② Selection of materials for resin molding products: select the resin with a melt flow rate (MFR) of 0.15~6g/10min during extrusion molding; The resin with a melt flow rate (MFR) of about 10g/10min is selected for extrusion of blown film; Resin with melt flow rate (MFR) of 0.3~5g/10min shall be selected for injection molding.
③ The resin melting point is 160~170 ℃. The process temperature during extrusion is 260~280 ℃; The process temperature of extrusion blow molding is 220~250 ℃; The process temperature during injection molding shall be controlled at 200~300 ℃. Note that the temperature of molten materials shall not exceed 315 ℃ to avoid decomposition of molten materials.
④ During the processing of molded products, attention shall be paid to the control of the contact time between molten materials and air to prevent high-temperature oxidation of molten materials and reduce the mechanical strength of products; Contact between molten materials and copper will accelerate the oxidation degradation rate of molten materials, which should be noted. If necessary, copper inhibitors such as aromatic amine, oxalamide and other compounds should be added to the raw materials.
⑤ For polypropylene products, according to their working environment conditions, in order to increase the service time and reduce accidents, appropriate auxiliary materials should also be added to the molding resin. If the products are exposed to light for a long time, ultraviolet absorbers, such as UV531, should be added to the raw materials; Antistatic agent, such as carbon black or alkyl amide, shall be added to the resin when the product is in a flammable and explosive working environment; In order to prevent fire, flame retardants, such as antimony trioxide and chlorinated paraffin, shall be added to the resin of molded products.
⑥ Attention shall be paid to the control of cooling speed after molten material forming: the cooling speed is too fast, the crystallinity of products is low, the transparency is good, and internal stress is easy to occur; When the product is slowly cooled, the crystallinity is high and the internal stress is small, but the molding shrinkage of the product is large, and the transparency and toughness will also be slightly reduced.
⑦ Single screw extruder or twin screw extruder can be used for polypropylene resin extrusion. The length diameter ratio of the screw is required to be (20~24): 1, the compression ratio is (3.5~4.0): 1, and 100 mesh filter screen is added in front of the barrel; Plunger type or screw type injection molding machines can be used for injection molding. When screw injection molding machine is used, the melt flow rate of the selected raw materials can be lower than 0.8g/10min. When forming large and thin wall products, larger MFR values should be selected. The maximum melt flow rate (MFR) can reach 18g/10min, the injection pressure is 7~14MPa, and the mold temperature is about 50 ℃.
⑧ Pay attention to the influence of colorants on product performance; Carbon black has a certain role in preventing light aging of products, while phthalocyanine pigments have a certain role in promoting the aging of products.
Author：admin