Views: 4 Author: Site Editor Publish Time: 2024-04-25 Origin: Site
Nylon (PA) has a series of excellent properties such as high mechanical strength, chemical resistance, oil resistance, wear resistance, self-lubricating, and easy processing and molding, and has become one of the widely used thermoplastic engineering plastics both domestically and internationally.
However, in practical applications, the performance requirements for nylon vary under different usage conditions or environments.
For example, components such as electric drills and motor casings, pump impellers, bearings, diesel engines, and air conditioning all plastic fans require nylon materials to have high strength, rigidity, and dimensional stability; Due to the poor low-temperature toughness of nylon, it is necessary to toughen and modify it at this time; In some outdoor application fields, nylon materials need to undergo weather resistance modification and so on in long-term outdoor environments.
The reinforcing materials used to enhance nylon are mainly fibrous substances such as glass fiber, carbon fiber, and whiskers, among which glass fiber reinforcement is the most widely used. Fiberglass reinforcement can significantly improve the rigidity, strength, and hardness of materials, as well as significantly improve their dimensional stability and heat resistance.
Due to the insufficient strength of nylon itself, its strength can be improved by adding 10-30% fibers. Especially, a strength of 30% is recognized as the most suitable ratio. There are also those that can be added up to 40-50%, depending on the specific requirements of different products, and with appropriate formulas, they can all be successful.
Production process of glass fiber reinforced nylon
Generally speaking, there are two production processes for fiberglass reinforced nylon: long fiber method and short fiber method.
The long fiber method involves pre mixing nylon and other components into a hopper, while glass fiber is introduced into the screw through screw rotation from the inlet of the glass fiber, and then mixed with nylon resin.
Short fiber method, which means that short cut glass fibers are forcibly conveyed to the material barrel through side feeding, and then mixed with nylon.
Factors affecting the properties of fiberglass reinforced nylon
Firstly, the interface bonding between glass fiber and nylon resin has the most important impact on the glass fiber reinforced nylon. If the combination between the two is not good, the strengthening effect will be greatly reduced. At this point, the surface treatment of fiberglass becomes particularly important. Nowadays, glass fiber manufacturers are able to produce glass fiber models with different surface treatments for different materials for use by modified plastic manufacturers, as long as the selection is appropriate.
Secondly, the length of glass fibers in nylon materials is another major factor affecting their performance. Generally speaking, long glass fibers are superior to short glass fibers in terms of tensile strength, flexural strength, modulus, and notch impact strength.
Meanwhile, the dispersibility of glass fibers in materials cannot be ignored. The dispersion of fiberglass mainly relies on the appropriate shear action of twin screws and the kneading cooperation of materials, which involves the combination and speed of screws. The selection of screw speed is related to the content of additives such as glass fiber in the formula. For flame retardant reinforced nylon, low speed is advisable as the flame retardant has been thermally decomposed.
In addition, processing temperature, glass fiber diameter, and type of glass fiber can also affect the final performance of the material, so it will not be repeated here.
Thermal oxidative aging of fiberglass reinforced nylon during processing
Taking fiberglass reinforced nylon 66 as an example, fiberglass is prone to extrusion and friction with the material, screw, and inner wall of the barrel in a twin-screw extruder, generating a large amount of frictional heat. This often leads to the actual temperature of the material in the extruder barrel being much higher than the displayed temperature of the extruder. Such high temperatures can easily cause nylon 66 to undergo thermal oxidative aging and degradation, and reduce the mechanical properties of the composite material.
The flowability of fiberglass reinforced nylon
Fiberglass reinforced nylon has poor fluidity and is prone to problems such as high injection pressure, high injection temperature, unsatisfactory injection, and poor surface quality during injection molding, which seriously affects the appearance of the product and leads to a high defect rate. Especially in the production process of injection molded products, lubricants cannot be directly added to solve the problem, and can only be improved on the raw materials. Generally speaking, this requires adding lubricating components to the modified formula
Resistance of Glass Fiber Reinforced Nylon to High Temperature Thermal Oxygen Aging
In some application fields such as bearings and diesel engine fans, fiberglass reinforced nylon often faces the problem of long-term high-temperature thermal oxidative aging. Although reinforcing and modifying nylon with fiberglass can moderately improve its heat resistance, it cannot solve the problem well. However, adding appropriate anti thermal oxidative aging additives to fiberglass reinforced nylon composites can achieve good results.
Weathering resistance of glass fiber reinforced nylon
Nylon undergoes a series of aging phenomena such as fading, discoloration, cracking, pulverization, and decreased strength under external conditions such as sunlight exposure, temperature changes, and wind and rain. Among them, ultraviolet radiation is the key factor promoting aging. Weathering resistant nylon is currently mainly black products, which are solved by adding additives such as carbon black that absorb ultraviolet rays to nylon to improve its weather resistance. But in addition to black products, natural or light colored nylon often faces aging problems when used outdoors, mainly manifested as yellowing of the parts.
The application of nylon with different fiber ratios
Taking PA66 as an example:
① High strength fiberglass reinforced products
Fiberglass reinforced nylon material with a ratio of 40-50% is mainly suitable for the manufacturing of high-strength components for high-strength gears and professional equipment.
Application: Various precision gears
PA66+GF has high rigidity, stable size, noise reduction, wear resistance, quietness, lubrication, anti-static and other properties.
② Medium strength fiberglass reinforced products
Fiberglass reinforced nylon material with a ratio of 25-35% is mainly suitable for manufacturing medium strength components such as automotive parts, electric tool casings, electrical fan blades, wind turbines, tableware, toys, etc.
Application 1: Automotive Parts
Automotive PA66+GF material can be applied in engine intake pipes, engine covers, automotive chassis, engine fan blades, automotive air conditioning evaporators and condensers, etc.
1) The engine intake pipe PA66+30% GF has a long-term temperature resistance of 140 ℃ for over 2000 hours.
2) The car chassis mudguard and engine fan blades PA66+30% GF require excellent toughness and strength, as well as low deformation and dimensional stability.
Car air conditioning evaporators require good warping, long-term heat resistance, hydrolysis resistance, high dimensional stability, high strength and toughness, PA66+15% GF+10% talc powder.
Application 2: Various connectors for electronic accessories
This is halogen-free flame retardant PA66+35% GF, which is widely used in various electronic connectors. Electronic connectors need to have high fluidity, dimensional stability, good electrical performance, and some also require flame retardant performance. In this case, only modified materials can completely replace them.
Application 3: Various high-power fan blades and impellers
High rigidity, high toughness, low warping, creep resistance, hydrolysis resistance modified PA66+30% GF material.
Application 4: Tableware category:
High temperature resistance, food grade, high fluidity, reinforced, PA66+30% GF.
Application 5: Toy field
Toys such as gun stocks, drone propellers, and motor mounts generally use modified plastics with medium to high strength, such as PA66+30% GF and PA66+30% carbon fiber.
③ Low strength fiberglass reinforced products
Fiberglass reinforced nylon material with a ratio of 10-20% is mainly suitable for the manufacturing of connectors, touch switches, medical equipment and other components in electronic and electrical products.
Application: In the field of medical equipment
Nylon materials have mechanical strength and a skin friendly feel that ordinary materials do not have, while medical equipment such as foot drop correctors, rehabilitation wheelchairs, and medical nursing beds typically require components with a certain load-bearing capacity, so PA66+15% GF is generally chosen.
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