The Preparation And The Properties Of Polyurethane/Phenolic Foam

Phenolic foam uses in a wide range of fields for its good performance. However, it is extremely too brittle and powdered to be used in certain aspects.In the study, PU prepolymer was employed to replace the inorganic acid to experience reactions with foamable phenolic resins to prepare novel PU/PF foam. The problems including poor compatibility and fast reaction rate of traditional PU/PF foam was improved. The PU/PF foam is a novel foam material with good thermal stability and good toughness.Main works are as follows.Foamable phenolic resin with low viscosity and high solid content was prepared by condensation of phenol and paraformaldehyde, which performed good compatibility and relatively mild reaction intensity with polyurethane prepolymers as well as high foaming ratio.PAPI/PPG polyurethane/phenolic foam was prepared. Various types of polyether isocyanate that have different-NCO concentration were mixed together to adjust the relative amount of monomers and trimer prepolymers in the systems. The effect of ratio of isocyanate groups and phenolic resin, relative amount of-NCO groups and trimer of PU on the preparation of foam and property of foam were investigated. The experimental results showed as follows. The resultant foam is of nice volume stability and low shrinkage when the condition is satisfied with mass ratio of-NCO groups and foamable PF resin being 40/100, and content of trimer of PU lower than 17.33%.The structure of foamable phenolic resin was controlled by adjusting the reaction time. The effect of viscosity(molecular weight)of foamable phenolic resin on the forming process and performance of foam was investigated. The experimental results showed that the resultant foam is of nice volume stability and low shrinkage when viscosity of foams the phenolic resin more than 2.15Pa.s. With the molecular weight increasing of foamable phenolic resin(equal to the viscosity increasing from 2.15Pa.s to 5.05 Pa.s), the density of foam stabilizes between 60.16 kg.m-3 to 63.96 kg.m-3. Meanwhile, the bending strength of the novel foam reaches 0.2MPa, and bending strain is more than 15%, which is much better than that of pure phenolic foam (6%); The mass lose of the foam is 5%-6%℃and the volume change is about-5% when the foam is heated at 150℃for 2h, which shows a good thermal stability property. With the density decreasing from 95 kg.m-3to 55 kg.m-3, foam still maintain good toughness and good dimensional stability.The PU/PF foam was prepared with different flame retardant systems and other additives. The results indicated that, when the low viscosity liquid flame retardant was added into the foaming system, the foam may contract after it was foamed. When only EG was added into the foaming system, the foam obtained was toughness and almost did not contracted, when the amount of EG was 30 phr, the OI value of the foam increased to 28.2%. When 1 phr DMMP,1 phr Sb2O3,1 phr Al(OH)3 and 20 phr foamable graphite(EG) were added into the foaming system, the foam with good toughness was obtained, the 01 of the foam increased to 27.5%. When used in conjunction with EG, Zinc borate may heighten the retardant effect of EG. The highest OI reached 32.1%.