Polyurethane Systems for Composite Applications Having Reduced Sensitivity to Moisture

Polyurethanes are intrinsically water sensitive, and this feature is key to produce foams, mattresses and insulation panels, where the isocyanate and water reaction forming CO2 is desired. However, polyurethanes have been forbidden in processes where foaming is unwanted. For example, composites are fully compact materials that combines fibres and resins. In these materials, bubble formation would detrimentally impact mechanical performance. If polyurethanes could be made insensitive to moisture a new span of applications would be possible such as Filament Winding and vacuum infusion. This research, focuses on understanding the impact of orthoformates as water scavengers, combined with increased polyol hydrophobicity on polyurethane foaming. Several formulations were evaluated by casting the resins in a container having a fixed amount of glass fibers and curing the resin-fiber system under different conditions. While it was not possible to completely avoid foaming formation, it was confirmed that orthoformates (TEOF, TEOP) helps reducing foaming but not eliminating it. More work is needed to reach a fundamental understanding on how to accelerate the scavengers-water reaction kinetic in order to control water sensitivity in polyurethanes.