Injection molding process for Nylon II
Use mold and post-molding processing conditions
Mold temperature
Mold temperature has a certain effect on crystallinity and molding shrinkage rate. High mold temperature has high crystallinity, abrasion resistance, hardness, elastic modulus increase, water absorption decrease, product molding shrinkage rate increases, suitable for thick products; low mold temperature Low crystallinity, good toughness, high elongation, reduced shrinkage, suitable for thin products with good transparency. If the wall thickness is greater than 3mm, it is recommended to use a low-temperature mold of 20~40C. The product wall is thin and difficult to form or requires high crystallinity mold heating control. Generally, cold water temperature control is used for products that require a certain degree of flexibility. The aperture of the runner and gate should not be less than 0.5*t (where t is the thickness of the plastic part). With a submerged gate, the minimum diameter of the gate should be 0.75mm
Post-treatment of nylon products Post-treatment of nylon products is to prevent and eliminate residual stress in the product or dimensional changes caused by moisture absorption. There are two types of post-treatment methods: heat treatment and humidity control.
1. Heat treatment
Commonly used methods: in mineral oil, glycerin, liquid paraffin, and other high-boiling liquids, the heat treatment temperature should be 10-20℃ higher than the use temperature. The treatment time depends on the wall thickness of the product. The thickness is less than 3mm for 10-15 minutes, and the thickness is 3 The -6mm time is 15-30 minutes. The heat-treated products should be slowly cooled to room temperature to prevent the stress from regenerating in the product due to sudden cooling.
2. Humidity conditioning treatment
Humidification treatment is mainly carried out on products with high environmental humidity. There are three methods: one boiling water humidity control method; 2. normal temperature water soaking method 3. steam method.
The first method has a faster processing speed but is prone to oversaturation. The third method has better efficiency and uniformity, but it needs to add a steam device.
