How to enhance the fiber-glass with the nylon during injection molding?
Introduction of glass fiber reinforced nylon during injection molding process:
1. Processing temperature
Glass fiber reinforced nylon PA has a high melting point and poor thermal stability.
So the processing temperature should not be too high, generally about 30°C higher than the melting point of the PA.
2. Drying requirement
Glass fiber reinforced nylon has high hygroscopicity. And the amide group is easy to be hydrolyzed at high temperature. These will cause a serious decrease in molecular weight. It must be strictly dried until the water content is less than 0.05%.
3. For melt nylon with fiber-glass
The melt viscosity of glass fiber reinforced nylon is low, and the apparent viscosity is sensitive to temperature. Due to the fast cooling speed of the melt plastic, it is necessary to prevent the plastic from blocking the nozzle holes, runners, gates, etc. To prevent the melt from flowing backwards, the screw head should be equipped with a non-reverse ring. In addition, to prevent the “salivation” phenomenon of the melt at the nozzle, a self-locking nozzle should be used.
4. Injection rate
High injection pressure is not required for nylon reinforced with the glass fiber. The general selection range is 70-100 MPa, and usually no more than 120 MPa. The injection rate should be slightly faster, so as to prevent problems such as ripples and insufficient mold filling due to the fast cooling speed.
5. Mold temperature
The mold temperature is generally controlled at 40～90℃. The mold temperature has a greater impact on the performance of the plastic product.
6. For amidogent
The amidogent is sensitive to oxygen at high temperatures and is prone to oxidative discoloration. A special heat stabilizer for nylon can be added if necessary.
7. High crystallinity
Large molding shrinkage rate, easy to produce crystallization stress. And it obviously increase with the increase of the thickness of the product.
8. Slow moisture absorption
The slow moisture absorption of the glass fiber reinforced nylon product after molding can easily cause a large change in dimensional accuracy. This is also used for humidity control, usually in boiling water or potassium acetate aqueous solution. The ratio of potassium acetate to water is 1.25:1, and the boiling point is 121°C.