There should be no issues with applying TotalBoat Flotation Foam in a plastic canoe, but it is very important to apply the product in multiple small batches to avoid melting the plastic. TotalBoat Flotation Foam generates heat during the reaction, and unless it is able to dissipate the heat, a large pour could potentially soften or melt some plastics. Always perform a very small test sample of flotation foam on the surface before attempting the main project, to ensure that it performs as desired.