With the continuous progress of polymer synthesis and processing technology, engineering plastics have penetrated into all fields of people's production and life. In many applications, the flame retardancy of plastics is an important performance index for the application of materials, and some plastic additives, such as halogenated flame retardants, may have potential hazards to the environment and human health, so they are To solve this contradiction, some users of engineering plastics gave up the application of these plastic additives, and turned to those engineering plastics that have flame retardant properties themselves.
Flame retardant polymers also typically have other desirable properties such as strength, dimensional stability, chemical resistance, and abrasion resistance, but these materials are usually more expensive than those that are not flame retardant, however These resins are needed in applications requiring high performance and high flame retardancy. These polymers mainly include: polyether ether ketone (PEEK), polyether imide (PEI), polyphenylene sulfide (PPS), polyphenylene sulfone (PPSU), polyether sulfone (PES), polyvinylidene fluoride ( PVDF) and liquid crystal polymers (LCP). Some other polymers such as PVC, modified polyphenylene ether (PPO), etc. have certain flame retardancy.
1. (PEEK)
PEEK is a linear aromatic semi-crystalline polymer with a service temperature of 260°C. The flame retardancy of PEEK has been tested by the laboratory UL94, which includes the vertical burning rate test and the self-extinguishing time test. According to the information provided by PEEK supplier Wicks, a 1.45mm spline without any additives has a burning rate of V-0, which is the highest flame retardant level. During the combustion process, smoke and toxic gas emissions are extremely low. In addition, PEEK is extremely resistant to chemicals, hot water and hot steam. PEEK can be processed by conventional techniques such as injection molding, extrusion and compression molding.
PEEK is usually blended with other polymers and added with glass fiber or carbon fiber, and is generally used in automobiles, aircraft, medicine, electronics, and chemical industries. At present, many automotive parts are made of PEEK resin, such as gears, bearings, etc. In the chemical process industry, many pumps and valves are made of PEEK, and PEEK resin is often seen in oil well equipment and semiconductors.
2. (PEI)
PEI is an amorphous polymer with a continuous service temperature of 180°C, strong resistance to hydrocarbons, halogenated solvents, water and automotive fluids, and a glass transition temperature of 217°C. According to the data provided by PEI supplier GE, the flame burning rate of the 0.25mm spline has been detected as V-0 by UL94, and has low smoke emission, can withstand a variety of chemical substances, and has high strength, modulus and high temperature creep resistance. PEI resins are available in unreinforced grades and reinforced grades. Typical fillers are carbon fiber, glass fiber and certain minerals.
In the manufacture of auto parts, PEI can replace metal to manufacture dampers, sensors, air conditioners, ignition system parts and transmission system parts. The flame retardancy of PEI as well as its low smoke and toxic gas emissions also allow this material to be used in aerospace applications such as gas and fuel valves, steering wheels, interior trim surfaces, food trays, and more. Electronic lighting components such as connectors and reflectors made of PEI materials are also used to take advantage of the flame retardancy of the polymer.
PEI can be processed by standard injection molding processing methods, and the resulting parts can have wall thicknesses up to 0.25mm. Before processing, PEI should be dried at 140℃~150℃ for several hours.
3. (PPS)
PPS is a semi-crystalline polymer whose molecular structure is alternately connected by sulfur atoms and benzene rings, which endows PPS resin with higher thermal and chemical stability. The use temperature of PPS resin is 200 ℃, and there is a tendency of coking during the combustion process, which is beneficial to prevent the spread of the flame.
The flame retardant rating of the 1.5mm thick PPS spline is UL94V-0. Most PPS resins are made into parts by adding glass fibers and mineral fillers. PPS has high modulus, creep resistance, and chemical resistance, enabling precision molding to manufacture parts with tight tolerances.
Utilizing the flame retardancy and high thermal resistance properties of PPS, in the automotive industry, PPS usually manufactures internal engine parts, brake system parts, and electronic system parts that need to withstand high temperatures. In industrial equipment, PPS is often used in high temperature and chemically corrosive environments. There are also some high-demand electronic equipment housings made of PPS, such as PPS is often used in connectors and sockets. In addition, some office equipment, optical devices and some daily necessities often use PPS to replace metal and thermosetting plastics.
4. (Sulfur-containing resin)
PPSU and PES are a class of flame retardant materials containing sulfur. In addition to the advantages of flame retardancy, PPSU has unusual hydrolysis resistance, high heat distortion temperature, strong resistance to environmental stress cracking, and good electrical insulation properties. Generally PPSU is used in medical equipment, food trays, surgical instruments and certain parts of spacecraft.
The heat deflection temperature of PES reaches 204°C and it has good chemical resistance. Although not as tough as PPSU, PES is also not as expensive as PPUS. The flame retardant grade of typical commercial grade PES is UL94V-0 grade of 0.8mm spline. Usually PES is used in automotive fuses, films, electrical equipment, static dissipative equipment, cookers, light reflectors and other components. The transparency of PES is more prominent in many ways.
5. (PVDF)
In addition to being flame retardant, PVDF also has strong rigidity, abrasion resistance, corrosion resistance, chemical stability and good weather resistance. At 149 °C, PVDF can still maintain mechanical properties. PVDF can be made into profiles, sheets, tubes and films, etc., and is generally used in chemical storage and processing equipment, fluid processing, and semiconductor equipment. PVDF materials are often used in automotive, construction, electronics and other fields.
6. (LCP)
LCP is a semi-crystalline polyester resin with rigid rod-like molecules aligned in the direction of melt flow. LCP has high rigidity and still has good dimensional stability, creep resistance and low thermal expansion coefficient at high temperature. Commercial-grade LCP resins have a flame retardant rating of UL94V-0, a heat distortion temperature of 300°C, an elongation of 2.5%, and have good chemical resistance and high dielectric strength.
LCP can be used in electronic connectors, fuse holders, high temperature spools, pump parts, etc. Microwave ovens, cooking utensils, mobile phones, ignition system parts, chemical equipment, medical equipment, office equipment, aircraft parts, etc. are also often used in LCP resins.
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