What are the high temperature resistant resins?
In the aerospace industry, in order to maximize the limited carrying capacity, the weight control of each component is very strict. Resin-based composites are increasingly being used in this field due to their excellent overall properties. In addition to the very high requirements for the mechanical properties of the material, there are also high requirements for temperature resistance. The following Xiaji network Xiaobian introduces several common high temperature resistant resins.
Polyimide, English name Polyimide (referred to as PI), a type of polymer containing an imide ring (-CO-NH-CO-) in the main chain. It is one of the best organic polymer materials with high comprehensive performance, high temperature resistance up to 400 °C, long-term use temperature range -200-300 °C, no obvious melting point, high insulation performance, dielectric constant of 103 Hz, dielectric loss Only 0.004 - 0.007, belonging to F to H.
According to the chemical structure of the repeating unit, the polyimide can be classified into three types: aliphatic, semi-aromatic, and aromatic polyimide. According to thermal properties, it can be divided into thermoplastic and thermosetting polyimides.
Polytetrafluoroethylene, the English name is Poly tetra fluoroethylene, abbreviated as PTFE. If you don't know much about this resin, you can be very familiar with the alias Teflon and Teflon. That's right, it's the coating that's commonly used on non-stick pans.
What are the high temperature resistant resins?
This material is resistant to acids and bases and to various organic solvents and is almost insoluble in all solvents. At the same time, PTFE has the characteristics of high temperature resistance, and its friction coefficient is extremely low, so it can be used as a lubricant and it is also an ideal coating for easy cleaning of the inner layer of water pipes.
It has a melting point of up to 327 ° C and its long-term stability is stable from -180 to 250 ° C.
Polyphenylene ether (PPO/PPE)
Polyphenylene ether is a high-strength engineering plastic developed in the 1960s. Its chemical name is poly(2,6-dimethyl-1,4-phenylene ether), or PPO (Polyphenylene Oxide) or PPE (Polypheylene ether). It is a polyphenylene oxide or a polyphenylene ether.
It has high heat resistance, glass transition temperature of 211 ° C, melting point of 268 ° C, heating to 330 ° C has a tendency to decompose, the higher the content of PPO, the better the heat resistance, the heat distortion temperature can reach 190 ° C.
PPO is non-toxic, transparent, and relatively low in density, and has excellent mechanical strength, stress relaxation resistance, creep resistance, heat resistance, water resistance, water vapor resistance, and dimensional stability. It has good electrical properties in a wide range of temperature and frequency. The main disadvantages are poor melt flow and difficult processing. Most of the practical applications are MPPO (PPO blends or alloys). For example, PS modified PPO can greatly improve the processing performance. Improves stress crack resistance and impact resistance, reduces cost, and only slightly reduces heat resistance and gloss.
Polyphenylene sulfide (PPS)
Polyphenylene sulfide is a polyphenylene sulfide, a thermoplastic resin with a phenylthio group in the main chain of the molecule, abbreviated as PPS in English. Polyphenylene sulfide is a crystalline polymer.
The undrawn fiber has a large amorphous region (crystallinity of about 5%), and an crystallization exotherm occurs at 125 ° C, the glass transition temperature is 150 ° C; and the melting point is 281 ° C. The drawn fiber produces partial crystallization during the stretching process (increased to 30%), and heat treatment of the drawn fiber at a temperature of 130-230 ° C can increase the crystallinity to 60-80%. Therefore, the drawn fiber has no significant glass transition or crystallization exotherm and has a melting point of 284 °C.
As the crystallinity increases after stretching heat setting, the density of the fiber increases correspondingly, from 1.33 g/cm? before stretching to 1.34 g/cm? after stretching, and up to 1.38 g after heat treatment. Cm?. Molding shrinkage: 0.7% Molding temperature: 300-330 °C.
The heat distortion temperature is generally greater than 260 degrees and can be used in the temperature range of 180-220 ° C. PPS is one of the best heat-resistant varieties in engineering plastics.
Polyetheretherketone (English poly-ether-ether-ketone, PEEK for short) is a high polymer composed of a repeating unit containing a ketone bond and two ether bonds in the main chain structure, and is a special polymer material. It has a physicochemical property such as high temperature resistance and chemical corrosion resistance. It is a kind of semi-crystalline polymer material with melting point of 334 ° C, softening point of 168 ° C and tensile strength of 132-148 MPa. It can be used as high temperature resistant structural material and electrical insulating material. , can be combined with glass fiber or carbon fiber to prepare reinforcement materials. A type of polyarylene ether polymer obtained by condensation with an aromatic dihydric phenol is generally used.
PEEK has excellent heat resistance and high temperature resistance. It can be used for a long time at 250 °C. The instantaneous temperature can reach 300 °C. It has high rigidity, dimensional stability and small coefficient of linear expansion. It is close to metal aluminum. PEEK has good chemical stability. It has strong corrosion resistance to acid, alkali and almost all organic solvents, and has the properties of flame retardant and radiation resistance. PEEK has excellent resistance to sliding wear and fretting wear, especially at 250 ° C. High wear resistance and low friction factor; in addition, PEEK is easy to extrude and injection molding.
Bismaleimide (BMI) is another type of resin system derived from polyimide resin system. It is a bifunctional compound with maleimide (MI) as the active end group. Similar fluidity and moldability can be processed by the same general method as epoxy resin, which overcomes the shortcomings of relatively low heat resistance of epoxy resin. Therefore, it has been rapidly developed and widely used in the past two decades. .
BMI has excellent heat resistance due to its high benzene ring, imide heterocyclic ring and high crosslink density. Its Tg is generally greater than 250 ° C, and the temperature range is from 177 ° C to 232 ° C. Ethylenediamine in the aliphatic BMI is the most stable, and the thermal decomposition temperature (Td) will decrease as the number of methylene groups increases. The Td of aromatic BMI is generally higher than that of aliphatic BMI, and the Td of 2,4. diaminobenzene is higher than other types. In addition, Td has a close relationship with the crosslink density, and Td increases with the increase of crosslink density within a certain range.
Furan resin is a general term for resins produced from sterols and furfurals with furan rings as raw materials. It cures to insoluble and infusible solids under the action of strong acids. The types are sterol resins, furfural resins, fluorenone resins, fluorenone- Formaldehyde resin, etc.
The heat-resistant material furan glass fiber reinforced composite material has higher heat resistance than the general phenolic glass fiber reinforced composite material, and can be used for a long time at around 150 °C.
Cyanate resin (CE)
Cyanate resin is a new type of thermosetting resin with two or more cyanate functional groups (-OCN) in the molecular structure developed in the 1960s. Its molecular structure is: NCO-R-OCN; The cyanate resin is also called triazine A resin, and the full name of the English is Triazine A resin, TA resin, Cyanate resin, abbreviated as CE.
Cyanate ester CE has excellent high temperature mechanical properties, higher bending strength and tensile strength than bifunctional epoxy resin; very low water absorption (<1.5%); low molding shrinkage, good dimensional stability; heat resistance Well, the glass transition temperature is 240-260 ° C, the highest can reach 400 ° C, the modification can be cured at 170 ° C; the heat and humidity resistance, flame retardancy, adhesion are very good, and glass fiber, carbon fiber, quartz fiber Reinforcing materials such as whiskers have good bonding properties; excellent electrical properties, extremely low dielectric constant (2.8 - 3.2) and dielectric loss tangent (0.002 - 0.008), and dielectric properties versus temperature and The change in the frequency of the electromagnetic wave shows a characteristic stability (i.e., has a wide band).
Polyarylethynyl (PAA) resins are a class of high performance polymers formed by addition polymerization of ethynyl aromatic hydrocarbons. It is an ideal material for fiber-reinforced ablation-resistant high-carbon resin, and is widely used in aerospace materials such as rocket nozzles and missile engine nozzles.
The above is the introduction of high temperature resistant resin. The so-called high temperature is relatively speaking. In general, the temperature resistance of resin-based composite materials is slightly inferior to composite materials such as metal-based and ceramic-based materials. However, the greatest attraction of composite materials lies in their designability. Through reasonable design and molding process, they can develop their strengths and avoid weaknesses.