What Difficulties Are Faced in The Manufacturing of Glass Fiber Reinforced Nylon? Attached Are PA66 Applications with Different Fiber Adding Ratios

Nylon (PA) has a series of excellent properties such as high mechanical strength, chemical resistance, oil resistance, wear resistance, self-lubrication, and easy processing and molding. It has become one of the thermoplastic engineering plastics widely used at home and abroad.

However, in actual 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, high rigidity and high dimensional stability; Since nylon has poor low-temperature toughness, it needs to be toughened and modified at this time; In some outdoor applications, nylon materials must undergo weathering modifications and so on in long-term outdoor environments.

The reinforcing materials used in reinforced nylon are mainly fibrous substances such as glass fiber, carbon fiber, and whiskers, among which glass fiber reinforcement is the most widely used. The rigid strength and hardness of the material can be significantly improved through glass fiber reinforcement, and the dimensional stability and heat resistance of the material can be significantly improved. Since nylon itself is not strong enough, 10-30% of fiber is added to increase its strength. In particular, 30% intensity is recognized as the most appropriate ratio.

Production process of glass fiber reinforced nylon

Generally speaking, there are two production processes for glass fiber reinforced nylon: long fiber method and short fiber method.

In the long fiber method, nylon and other ingredients are premixed and then added to the hopper, while the glass fiber is brought into the screw through the screw rotation from the glass fiber inlet, and then mixed with the nylon resin.

The short fiber method is to force the chopped glass fiber to the barrel through side feeding, and then mix it with nylon.

Factors affecting the performance of glass fiber reinforced nylon

First, the interfacial bonding between glass fiber and nylon resin has the most important impact on glass fiber reinforced nylon. If the combination between the two is not good, the strengthening effect will be greatly reduced. At this time, the surface treatment of glass fiber is particularly important.

Secondly, the length of the glass fiber in the nylon material is another major factor affecting its performance. Generally speaking, long glass fibers are better than short glass fibers in terms of tensile strength, flexural strength and modulus, and notched impact strength.

At the same time, the dispersion of glass fiber in the material cannot be ignored. The dispersion of glass fiber mainly relies on the appropriate shearing action of the twin screws and the kneading of the material, which involves the combination and speed of the screws. The choice of screw speed is related to the content of additives such as glass fiber in the formula. For flame retardant reinforced nylon, since the flame retardant has been thermally decomposed, low speed is appropriate.

In addition, processing temperature, glass fiber diameter, and glass fiber type will also affect the final performance of the material.

Glass fiber reinforced nylon undergoes thermo-oxidative aging during processing

Taking glass fiber reinforced nylon 66 as an example, the glass fiber in the twin-screw extruder barrel is prone to extrusion and friction with the material, screw and barrel inner wall, and generates a large amount of friction heat, which often causes the material in the extruder barrel to The actual temperature is much higher than the displayed temperature of the extruder. Such high temperatures can easily cause thermal oxidative aging and degradation of nylon 66 and reduce the mechanical properties of the composite material. Adding antioxidants can effectively block the thermal oxidative aging degradation of nylon 66 during processing and significantly improve the mechanical properties of composite materials. A suitable antioxidant system can play a better role in initial processing stabilization.

Flowability of glass fiber reinforced nylon

Glass fiber reinforced nylon has poor fluidity and is prone to problems such as high injection pressure, high injection temperature, unsatisfied injection molding, and poor surface quality during the injection molding process, which seriously affects the appearance of the product and leads to a high product defect rate. Especially in the production process of injection molded products, lubricants cannot be directly added to solve the problem. The only way to improve the raw materials is to add lubricating ingredients to the modified formula. Generally speaking, this requires adding lubricating ingredients to the modified formula.

Glass fiber reinforced nylon’s resistance to high temperature thermal oxygen aging

In some application fields such as bearings and diesel engine fans, glass fiber reinforced nylon often faces the problem of long-term high-temperature thermal oxygen aging. Although the reinforcement and modification of nylon with glass fiber can moderately improve the heat resistance of nylon, it cannot solve the problem well. Better results can be achieved by adding appropriate anti-thermal oxidative aging additives to glass fiber reinforced nylon composite materials, thereby exerting a better high-temperature thermal oxidative aging protection effect.

Weather resistance of glass fiber reinforced nylon

When nylon is affected by external conditions such as sunlight, temperature changes, wind and rain, it will appear a series of aging phenomena such as fading, discoloration, cracking, powdering and strength reduction, among which ultraviolet rays are the key factor that promotes aging. Weather-resistant nylon is currently mainly a black product, which means adding carbon black and other UV-absorbing additives to nylon to improve its weather resistance. However, in addition to black products, natural or light-colored nylon often faces aging problems when used outdoors, which is mainly manifested as yellowing of the parts.

Application of nylon with different fiber adding proportions (the following takes PA66 as an example:)

1. High strength and glass fiber reinforced products.

Reinforced nylon materials with a glass fiber content of 40-50% are mainly suitable for manufacturing high-strength gears and high-strength parts for professional equipment.

Application: Various precision gears

PA66+GF has high rigidity, dimensional stability, noise reduction, wear resistance, silence, lubrication, antistatic and other properties.

2. Medium strength and glass fiber reinforced products.

Reinforced nylon materials with a glass fiber content of 25-35% are mainly suitable for the manufacturing of medium-strength parts such as auto parts, power tool casings, electrical appliance blades, wind wheels, tableware, toys, etc.

Application 1: Auto parts

Automotive PA66+GF materials can be used in engine intake pipes, engine hoods, automobile chassis, engine fan blades, automobile air conditioning evaporator condensers, etc.

1) Start the air intake pipe with PA66+30%GF, which has a long-term temperature resistance of 140℃ for more than 2000 hours.

2) Automobile chassis fenders and engine fan blades PA66+30%GF require excellent toughness and strength, as well as low deformation and dimensional stability.

3) Automobile air conditioning evaporator needs good warpage, long-term heat resistance, hydrolysis resistance, high dimensional stability, high strength and toughness, PA66+15%GF+10% talc.

Application 2: Various connectors for electronic accessories

This is the application field of halogen-free flame retardant PA66+35%GF in various electronic connectors. Electronic connectors need to have high fluidity, dimensional stability, good electrical properties, and some also require flame retardant properties. At this time, only modified materials can completely replace them.

Application 3: Various high-power fan blades and impellers

High rigidity, high toughness, low warpage, creep resistance, hydrolysis resistance modified PA66+30%GF material.

Application 4: Tableware:

High temperature resistance, food grade, high fluidity, reinforced, PA66+30%GF.

Application 5: Toy field

Toy gun stocks, drone propellers, and motor bracket toys generally use medium and high-strength modified plastics, PA66+30%GF, PA66+30% carbon fiber.

3. Low strength and glass fiber reinforced products.

Reinforced nylon materials with a glass fiber addition ratio of 10-20% are mainly suitable for the manufacturing of connectors, tact switches, medical equipment and other components in electronic and electrical products.

Application: Medical equipment field

Nylon materials have mechanical strength and skin-friendly feel that ordinary materials do not have. Medical equipment such as foot drop correctors, rehabilitation wheelchairs, and medical nursing beds usually require components with a certain load-bearing capacity, so PA66+15%GF is generally chosen.

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