Polyamine (PA) commonly known as "NYLON" (NYLON), is a crystalline plastic, there are many varieties, such as NYLON 6, NYLON 66, NYLON 1010 and so on.
The main uses of NYLON are as follows:
Used for mechanical, chemical and electrical instrument, textile and other parts, such as bearings, wheel, roller, roller, pump impeller, fan impeller, wheel, screw, nut, washer, high pressure sealing ring. Pa-6: bearing gear, oil pipe, container, commodity PA-66: gear, machinery parts, wire drawing, electrical device film, shaft sleeve, tool casing.
The main properties of NYLON are as follows:
1, nylon directional obvious, prone to shrinkage, dent, deformation and other defects, forming conditions should be stable.
2. Resistant to weak acids and bases and general solvents, soluble in phenol (phenol can be used as adhesive) at room temperature, also soluble in concentrated formic acid and calcium chloride saturated methanol solution.
3, good low temperature performance, high impact strength, and has a very high tensile strength, good elasticity.
4, nylon has excellent toughness, wear resistance, fatigue resistance, self-lubrication and self-extinguishing.
5, nylon water absorption, water absorption to a certain extent to improve the impact strength, but other strength decreased (such as tensile, stiffness). Molding shrinkage rate is larger (0.3-1.8%), often take 1.5%. Commonly used internal mould S136H.
The molding process of NYLON is as follows:
1. Fully dry before injection molding. Drying conditions: temperature 80-90℃, drying time: 24HRS.
2. Shrinkage rate fluctuates greatly with the change of barrel temperature. High material temperature is easy to appear melt discoloration, brittle quality, silver wire, etc. Nylon material below the melting temperature is very hard, will damage the mold and screw, barrel temperature is generally 220-250℃, should not exceed 300℃.
3, nylon material viscosity is low, good fluidity, easy to appear drape front (flying edge), the pressure should not be too high, generally 60-90mpa
4, annealing treatment and humidification treatment annealing treatment: annealing can make crystallization increase, rigidity improve, not easy to deformation and cracking. Annealing conditions: 10-20 ℃ higher than the service temperature. Time varies according to product thickness, about 10-60 minutes. Humidification treatment: to keep the size stable, to improve toughness, improve internal stress distribution is good. Humidity control condition: soak in boiling water or potassium acetate solution. (Potassium acetate: water = 1.2:1 boiling point 121℃), time 2-16hrs
5, mold temperature control nylon is a crystalline plastic, products are greatly affected by mold temperature, so the mold temperature control requirements are high. High mold temperature: large crystallization, rigidity, hardness, wear resistance, small deformation. Low mold temperature: good flexibility, high elongation, small shrinkage. Mold temperature control range: 20-90℃
6, high speed injection nylon material melting point is high, that is, high freezing point (fast shaping, high production efficiency), in order to smooth mold filling (do not make melt down to the melting point solidification), must use high speed injection. This is especially true for thin - wall or long - distance parts. When the product wall is thicker or overflow occurs, slow injection is used. Exhaust problems caused by high speed mold filling should be paid attention to.
The dehumidification of NYLON baking material is as follows:
1, too much water content will appear steam flowers.
2, absolutely dry (water content is almost 0), the products are fragile, brittle strength 7