The Study On The TDI Polyurethane Prepolymer Modified Phenolic Foam

The phenolic foam insulation board is a highly efficient thermal insulation material. Itscharacteristics make it be used in building industry very attractive, such as flame retardant,low smoke, low toxicity and heat-resistant. However, its disadvantages can’t be ignored, thephenolic hydroxyl and methylene of the phenolic resin are easily oxidized, which make itphysical strength lower, easier powder, easier to bend, brittleness and many other defects. Thedefects make the phenolic foam could not used widely. So, it is very necessary to be modified.The polymer which polyisocyanate and the polyether/polyester polyols formed by thereaction in certain conditionsis named polyurethane.The polyurethane’s prepolymer is a kindof semi-finished products in the reaction when the reactant are in a certain proportion, it isstill reactive. There are not only the flexible polyether segment in the polyurethaneprepolymer, but also the isocyanate reactive end groups can be bonded with thehydroxymethyl of phenol. So the structure of interpenetrating cross-linked networks areformed in the curing process of the phenolic resin and the polyurethane prepolymer, thus thetoughness and the powder phenolic foam was improved. The paper chooses the TDIpolyurethane prepolymer to modified phenolic foam, because it is stable to storage.In this paper, the author modified the phenolic foam by adding the TDI typepolyurethane prepolymer into the phenolic foam. Based on researching the blendingperformance of them in different experimental materials, the author discussed the relationshipbetween the TDI prepolymer’s amount and the phenolic foam’s thermal conductivity andphysical properties. In the same time, the author discussed how the blend viscosity of thephenolic resin and the polyurethane prepolymer, foaming temperature, surface active agent,curing agent and foaming agent affect the phenolic foam’s foam and properties. The resultsshow that, if the polyurethane prepolymer are increased, the modified phenolic foam’sapparent density and compressive strength would increase, but the impact strength wouldincrease firstly, and then which would decrease. When the polyurethane prepolymer is added8%(relative to the dosage of phenolic resin, the same below) into the phenolic foam, theimpact strength is the best. When the polyurethane prepolymer is added6%, the modified phenolic foam’s comprehensive performance are the best. The performance parameters are:the apparent density of71kg/m3, the compressive strength of0.32Mpa, the impact strength of290J m-2, the drop rate of3.86%.This experiment studied the phenolic foam’s molecular structure and chemical bond withspectral analysis. The results showed that, there are different peak values of differentmoleculars. Thus we can distinguish among the different stages material reaction. Forexample, there is a characteristic peaks of the carbamate carbonyl group in the1731.13cm-1carbamate, in the characteristic peak of carbonyl, and it noticed the polyurethane prepolymerwith the—CH2OH of the phenolic resin being reacted.