Polyurethane resin is a two-part material combined with Part A (polyether polyol) and Part B (isocyanic acid). This casting resin is easy to use and can be quickly molded in about 15 minutes after mixing in a 1:1 ratio, and is popular in resin types, but a prominent problem with polyurethane resin is that it is easy to produce bubbles, and the following is a solution for polyurethane bubbles to share with you.
Causes of air bubbles:
1. Improper storage: polyurethane resin is a material that is very easy to absorb moisture, it should be sealed well immediately after taking the material, and it can be stored with nitrogen gas if there is a condition.
2. Caused by foreign matter: pigment-containing moisture is added when mixing color, or excessive application of release agent.
3. Air trapped in the mixing of part A and part B.
1. Vacuum Pump and Pressure Tank
First use a vacuum pump to degas part A and part B separately, AB mix and stir then put into a pressure tank to cure at 60-100 psi pressure. This is the most perfect and effective solution to solve the bubbles in transparent polyurethane or large castings.
2. No Vacuum Pump
When weighing Part A or Part B of the resin, allow the liquid material to pour carefully along the side of the measuring cup, avoiding pouring directly from high above the measuring cup, which can cause air bubbles.
Liquid materials are usually thicker in viscosity at low temperatures, and the thicker the material the harder it is to eliminate air bubbles, so instead of using cold resin directly, it is recommended to operate at room temperature to obtain the best consistency, which will prevent micro bubbles.
If you are pouring polyurethane resin into a silicone mold, you can start by heating the silicone mold in the oven, the temperature of the mold will remove any air bubbles in the resin. Remove the mold from the oven and let it air out for a few seconds before pouring the resin into the mold.