Because nylon has many characteristics, it is widely used in automobiles, electrical equipment, mechanical parts, transportation equipment, textiles, papermaking machinery and so on.
With the miniaturization of automobiles, the high performance of electronic and electrical equipment, and the acceleration of the weight reduction of mechanical equipment, the demand for crowning and setting will be even higher. In particular, nylon, as a structural material, places high demands on the strength, heat resistance and cold resistance of the twist setting. The inherent shortcomings of nylon are also important factors limiting its application. Especially for PA6 and PA66, it has a strong price advantage compared with PA46 and PAl2, although some properties can not meet the development requirements of related industries. Therefore, it is necessary to expand the application field by modifying and improving certain properties for a certain application field. Due to the strong polarity of PA, it has strong hygroscopicity and poor dimensional stability, but it can be improved by modification.
Glass fiber reinforced PA
When 30% glass fiber is added to PA, the mechanical properties, dimensional stability, heat resistance and aging resistance of PA are obviously improved, and the fatigue strength is 2.5 times that of unreinforced. The molding process of glass fiber reinforced PA is almost the same as that of unreinforced, but the injection pressure and injection speed should be appropriately increased due to the increased flow front, and the barrel temperature is increased by 10-40 °C. Since the glass fiber is oriented in the flow direction during the injection molding process, the mechanical properties and shrinkage rate are enhanced in the orientation direction, resulting in deformation and warpage of the product. Therefore, when the mold is designed, the position and shape of the gate should be reasonable, and the process can be improved. The temperature of the mold, the product is taken out and placed in hot water to allow it to cool slowly. In addition, the greater the proportion of the glass fiber added, the greater the wear of the plasticized component of the nylon twisting injection molding machine, preferably using a bimetallic screw and a barrel.
Transparent PA
Has good tensile strength, impact strength, rigidity, wear resistance, chemical resistance, surface hardness and other properties, high light transmittance, similar to optical glass, processing temperature is 300--315 ° C, when molding processing, need Strict control of the barrel temperature, too high melt temperature will cause discoloration of the product due to degradation, too low temperature will affect the transparency of the product due to poor plasticization. The mold temperature should be as low as possible, and the high mold temperature will reduce the transparency of the product due to crystallization.
Flame retardant PA
Due to the addition of flame retardant in PA, most of the flame retardants are easily decomposed at high temperatures, releasing acidic substances and corrosive to metals. Therefore, plasticizing components (screws, rubber heads, aprons, glues) Washers, flanges, etc.) must be hard chrome plated. In terms of technology, try to control the temperature of the nylon twisting barrel not to be too high, and the injection speed should not be too fast to avoid discoloration and mechanical properties degradation caused by the decomposition of the rubber temperature.
Weather resistant PA
Ultraviolet absorbing agents such as carbon black are added to the PA, which greatly enhances the self-lubricating property of the PA and the wear of the metal, and affects the blanking and wear parts during the molding process. Therefore, it is necessary to use a combination of a screw, a barrel, a rubber head, an apron, and a rubber gasket with high feeding ability and high wear resistance. The repeating structure on the polyamide molecular chain is simply a class of polymers which are amide groups.
In summary, it is mainly modified in the following aspects.
1. Improve the antistatic property of the twisted nylon to meet the requirements of mining and its mechanical applications.
2. Improve the mechanical strength of nylon to achieve the strength of metal materials, replacing metals
3. Improve the low temperature resistance of nylon and enhance its ability to resist environmental strain.
4. Improve the flame retardancy of nylon to meet the requirements of the electronics, electrical, communications and other industries.
5. Improve the wear resistance of the twisted nylon to meet the requirements of high wear resistance.
6. Improve the water absorption of nylon and improve the dimensional stability of the product.
7. Reduce the cost of nylon and improve product competitiveness.
8. Improve the heat resistance of twisted nylon to adapt to the field of high temperature resistant conditions such as automobile engines.
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