Study On The Preparation Of The PU/PF Foam

Phenolic foam is well known for its excellent fire properties, including low flammability, low peak heat release rate, no dropping during combustion, and low smoke density and toxicity. Over the past few decades, there have been numerous efforts to make phenolic foam tougher, intensity, flame resistant properties.This study from the perspective of chemical modification, use the polyurethane(PU) prepolymer temtinated with NCO groups as a monomer,because of the chemical methods of copolymerization,flexible polyurethane unit is introduced to the network structure of phenolic resin. The phenolic resin synthesized by the catalyst of Ba(OH)2is used in this study. This phenolic resin can be easily reacted with NCO groups,and mixed well-proportioned with it.Because of the Symmetrical structure of the PAPI,the foam can be tougher, and good intensity.Experimental temperature of copolymerization between PAPI and polyethylene glycol (PEG-400) prepolymer is75℃, and the suitable time is30min. The start time of foam is about30s. the density of the foam is gradually increased with the increasing amount of Phenolic resin. When The amount of Phenolic resin is over57%, because of the amount of phenolic resin are too much, there are too many amount of phenolic resin which did not participate in the reaction,and Foam is difficult to be formed.Formic acid in the system is used as vesicant.with the more amount of Formic acid,the time for foaming is shorter,and foam is easy to get. Because of the increased amount of acid, NCO groups is reacted fastly,constantly giving off heat that can make the reaction faster between hydroxymethyl and NCO groups. Finally a foam will be shaped. When the increased amount of acid is more than3.1%, a structured structure, fully cross-linked foam can be get, and the diameter of the cell is becoming larger. The suitable amount of the polyethylene glycol is30to40percent of the amount of papi.