Two part Polyurethane Systems

CROSSLINK^® Systems are designed for hand batching according to the following procedure:

There is no need to warm Part-A or B as both the resin and the Polyol Curatives are low viscosity liquids at room temperature. We recommend that all mixing should be carried out at room temperature.

1. Pre-weigh Part-A according to the recommended mix ratios (by weight) in a plastic or metal container at room temperature. Any additives such as pigments and fillers should be added to part-A at this point
2. Place the sample in a vacuum chamber and adjust the vacuum to minimum of 29 in. of Mercury. Degassing should continue until most of the bubbling has ceased. De-gassing of Part-A should not take more than 5 min
3. While Part-A is degassing, weigh out the correct amount of Part-B in a container at room temp. Degas Part-B at RT. Degassing aid (Sag-47) can be added to part-B to speed up degassing process
4. Add the Part-B to Part-A and mix thoroughly without whipping too much air in to the mix. Make sure that the walls and the bottom of the container are scraped during mixing and there should be no swirls visible. The mixture should be completely homogeneous
5. Place the mixture back into vacuum chamber and degas until most of the air that was mixed-in is gone. This usually takes no more than 5 minutes. There is enough time for degassing for most of our systems. A good rule of thumb is when the surface of the mixture is more than half clear of bubbles under good vacuum, degassing is usually adequate
6. Pour the mixture into a preheated mold that has been sprayed or coated with mould release. The temperature of the mould should determine the de-mould time for the cast part. The processors should determine their own mould temperature. It could be anywhere between 60°C to 100°C. Higher the mould temperature shorter the de-mould time. In most cases cured part can be de-moulded in minutes. However, keep in mind that the longer the gel time, the longer the de-mould time
7. Recommended post cure time:
   • 4 hrs. @ 100°C
   • or 6-8 hrs. @ 80°C
   • or 16 hrs. @ 60°C
   • or 7 days @ RT

The preceding steps are meant to be a guide for hand batching Crosslink Urethane Systems. After becoming familiar with this technology, it will become apparent that steps may be shortened or eliminated.