Injection temperature range of pel plastics

Polyetherimide Polyetherimide, abbreviated as PEI polyetherimide, is prepared by heating 4,4'-diaminodiphenyl ether or m (or p) phenylenediamine and 2,2'-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane dianhydride in dimethylacetamide solvent, and then carrying out polycondensation, powdering and imidization. Among the above methods, it can be divided into polynitro substitution method and polycyclic polycondensation method. The former firstly generates imide ring through cyclization reaction, and then forms flexible ether "hinge" through aromatic nucleophilic nitro substitution reaction. The latter is cyclization reaction first, then cyclization reaction, and the polymer formation process is polycyclic polycondensation process. PEI can be prepared by melt polycondensation. From the economic, ecological and technical point of view, this method is very promising. Because this method does not use solvent, the polymer will not contain solvent, which is of great significance to processing and use. PEI can also be produced directly in an extruder through a continuous process. The operation step of that method are as follows: a mixture of star compounds sequentially passes through regions with different temperature in an extruder and moves from a low-temperature region where monomers are mixed to a high-temperature region where final products are melted. The water produced by cyclization reaction is continuously discharged from the extruder through suitable holes, and is usually extracted by vacuum decompression in the last area of the extruder. Polymer pellets or sheets can be obtained from the discharge port of the extruder. PEI can also be directly mixed with various fillers in the extruder to prepare PEI-based composites. Among these methods, solution polymerization is the current industrial production method. However, Shanghai Synthetic Resin Research Institute has successfully developed a continuous extrusion polymerization method by extruder on a small device, which can be pushed to industrial production. The physical and chemical properties of 1, fully aromatic polyimide, according to thermogravimetric analysis, its initial decomposition temperature is generally around 500℃. The thermal decomposition temperature of polyimide synthesized from biphenyl dianhydride and p-phenylenediamine is 600℃, which is one of the best polymers with thermal stability so far. 2. Polyimide can withstand extremely low temperature, for example, it will not become brittle in liquid helium at -269℃. 3. Polyimide has excellent mechanical properties. The tensile strength of unfilled plastic exceeds 65,438+000 MPa, that of homopolyimide film (Kapton) exceeds 65,438+070 MPa, and that of biphenylpolyimides reaches 400Mpa. As an engineering plastic, the content of elastic film is usually 3-4 GPA, and the fiber can reach 200Gpa. According to theoretical calculation, the fiber synthesized by pyromellitic dianhydride and p-phenylenediamine can reach 500Gpa, which is second only to carbon fiber. 4. Some polyimide varieties are insoluble in organic solvents, stable to dilute acids and usually not resistant to hydrolysis. However, this seemingly disadvantage makes polyimide different from other high-performance polymers, because it can recover raw materials dianhydride and diamine through alkali hydrolysis. For example, for Kapton film, the recovery rate can reach 80%-90%. By changing the structure, we can also get a variety that is quite resistant to hydrolysis, for example, it can withstand the temperature of 120℃ and boil in water for 500 hours. 5. The thermal expansion coefficient of polyimide is 2× 10-5-3× 10-5℃, the thermal expansion coefficient of thermoplastic polyimide is 3× 10-5℃, the thermal expansion coefficient of biphenyl polyimide can reach 10-6℃. 6. Polyimide has high radiation resistance, and the strength retention rate of its film after 5× 109rad fast electron irradiation is 90%. 7. Polyimide has good dielectric properties, and its dielectric constant is about 3.4. When fluorine is introduced or air nano-size is dispersed in polyimide, the dielectric constant can be reduced to about 2.5. The dielectric loss is 10-3, the dielectric strength is 100-300KV/mm, and the bulk resistance is1017 Ω/cm. These properties can still maintain a high level in a wide temperature range and frequency range. 8. Polyimide is a self-extinguishing polymer with low smoke generation rate. 9. Polyimide releases very little gas under extremely high vacuum. 10, polyimide is non-toxic, can be used to make tableware and medical devices, and can withstand thousands of times of disinfection. Some polyimides also have good biocompatibility, for example, they are not hemolytic in blood compatibility test and non-toxic in cytotoxicity test in vitro. Injection molding process polyetherimide can be formed by injection molding and extrusion, and it is easy to be post-treated and bonded to other materials by adhesives and various welding methods. Parts with complex shapes can be made by injection molding due to good melt fluidity. Before processing, it must be fully dried at 150℃ for 4 hours, the injection temperature is 337~427℃, and the mold temperature is 65~ 1 17℃. The injection molding conditions of YS30 are: preheating 150℃, 4-hour barrel temperature: front 300-320℃, rear 330-4 10℃, injection pressure 60- 100 MPa, heat preservation time 5-30 seconds, and cooling time 5-30 seconds. Scope of application There are many varieties and forms of polyimide and many synthetic methods, so it can be selected according to various application purposes. This flexibility in synthesis is also difficult for other polymers. 1. Polyimide is mainly synthesized from dianhydride and diamine. Compared with many other heterocyclic polymers (such as polybenzimidazole, polybenzoxazole, polybenzothiazole, polyquinoxaline and polyquinoline), these two monomers have wide sources of raw materials and are easier to synthesize. There are many kinds of dianhydride and diamine, and polyimide with different properties can be obtained through different combinations. 2. Polyimides can be prepared by low-temperature polycondensation of dianhydride and diamine in polar solvents such as DMF, DMAC, NMP or/and methanol mixed solvents to obtain soluble polyamic acid, which is dehydrated to form rings and converted into polyimide after film formation or spinning. You can also add acetic anhydride and tertiary amine catalyst to polyamic acid for chemical dehydration and cyclization to obtain polyimide solution and powder. Diamines and dianhydrides can also be heated and condensed in high-boiling solvents such as phenolic solvents to obtain polyimide in one step. In addition, polyimide can also be obtained by the reaction of binary ester of quaternary ammonium acid with diamine; It is also possible to convert polyamic acid into polyimide first and then into polyimide. These methods are convenient for processing. The former is called PMR method, which can obtain low viscosity and high solid solution, and has a window with low melt viscosity during processing, and is especially suitable for manufacturing composite materials. The latter increases the solubility and does not release low molecular compounds during the conversion process. 3. As long as the purity of dianhydride (or tetracarboxylic acid) and diamine is qualified, it is easy to obtain high enough molecular weight no matter what polycondensation method is adopted, and the molecular weight can be easily adjusted by adding unit anhydride or unit amine. 4. The molecular weight of solid low-molecular-weight prepolymer can be greatly improved by polycondensation reaction of dianhydride (or tetracarboxylic acid) and diamine (as long as the molar ratio is equal) and vacuum heat treatment, thus bringing convenience to processing and crushing. 5. It is easy to introduce reactive groups at the chain end or chain to form active oligomer, thus obtaining thermosetting polyimide. 6. Esterifying or salifying carboxyl groups in polyimide, introducing photosensitive groups or long-chain alkyl groups to obtain amphiphilic polymers, which can be used to obtain photoresist or prepare LB films. 7. The general process of synthesizing polyimide will not produce inorganic salts, which is particularly beneficial to the preparation of insulating materials. 8. As monomers, dianhydride and diamine are easy to sublimate under high vacuum, so it is easy to form polyimide films on workpieces by vapor deposition, especially devices with uneven surfaces. Polyether imide has excellent comprehensive balance performance, which has been effectively used in electronics, electricity and aviation industries, and as a metal substitute for traditional products and stationery. In the electrical and electronic industries, parts made of polyetherimide have been widely used, including connectors with high strength and stable dimensions, ordinary and miniature relay housings, circuit boards, coils, flexible circuits, mirrors and high-precision dense optical fiber assemblies. It is particularly striking that using it instead of metal to manufacture optical fiber connectors can optimize the assembly structure, simplify its manufacturing and assembly steps, and maintain more accurate dimensions, thus ensuring that the cost of the final product is reduced by about 40%. The impact plates Ultem 16 13 are used to manufacture various parts of aircraft, such as portholes, nose parts, seat backs, inner wall panels, door covers and various articles for passengers. Composite materials composed of PEI and carbon fiber have been used in the structures of various parts of the latest helicopters. With its excellent mechanical properties, heat resistance and chemical resistance, PEI is used in the automotive field, such as manufacturing high-temperature connectors, high-power lamps and indicator lamps, sensors for controlling the external temperature of automobile cabins (air conditioning temperature sensors) and sensors for controlling the temperature of air and fuel mixtures (effective combustion temperature sensors). In addition, PEI can also be used as a vacuum pump impeller with high-temperature lubricating oil corrosion resistance, a frosted glass joint (socket) of a steamer with working temperature of 180℃ and a non-illuminating reflector for preventing fog lamps. Polyether imide foam is used as heat and sound insulation material for transportation machinery, aircraft and so on. PEI has excellent hydrolysis resistance, so it is used as handle, tray, fixture, prosthesis, medical lamp reflector and dental instrument for medical surgical instruments. In the food industry, it is used as product packaging and microwave oven tray. PEI has excellent high-temperature mechanical properties and wear resistance, so it can be used to manufacture valve parts of water pipe steering valves. Because of its high strength, flexibility and heat resistance, PEI is an excellent coating and film-forming material, which can be used to form coatings and films suitable for electronic industry and to manufacture apertures.