Studies On The Dicyanophenyl Ether Phenol-biphenyl Phenolic Resin Hollow Microspheres

Hollow phenolic micro-spheres were widely used as surface heat-insulating coating materials in aircraft due to the excellent properties of low specific weight and high heat-insulating properties. However, the traditional phenolic resin matrix cannot meet the higher requirements accompanied by the rapid development of aerospace industry. Thus, the pace of development of high-performance modified phenolic resin microspheres has been speed up in recent years.This work aims to improve the thermal properties of phenolic resin hollow microspheres by using foaming method to form hollow microspheres in dicyanophenyl ether phenol-biphenyl resin. Fourier transform infrared spectroscopy,’H-NMR spectroscopy, gel permeation chromatography, thermal gravimetric analysis, scanning electron microscopy, floating rate testing, etc. have been used. The factors including molar ratio, types of curing agent, different solvents, foaming temperature, the amount of surfactants, etc. have been discussed in details on the synthesis and properties of hollow microspheres.Experimental results show that monomer ratio had a greater impact on the synthesis and properties of resin. Biphenyl phenolic hydroxyl group content of the phenolic resin with the increase in the content of phenol and increase the molecular weight increased with increasing the content of the phenol before the first drop,Press nphenol:n4’4-dichloro-methyl diphenyl:=5:1synthesized biphenyl type phenolic resin with higher molecular weight and smaller molecular weight distribution index. The TGA results show that properties of self-curing resin and curing agent curing resin are quite different. The char yield of cured product at1000℃under nitrogen atmosphere were66%and70%, respectively. The char yield of cured product at600℃in air atmosphere cured product char yield of70%and47%, respectively. Acetone and DMF solvents can be beneficial to reduce the viscosity of the resin foam. The foamed beads were obtained with acetone as the solvent when the morphology of the resulting foamed morphology than microspheres with DMF as the solvent. Suitable oil bath temperature to cure the resin and the foaming rate to match the rate of the blowing agent. When the oil bath temperature of less than150℃, the curing rate of the resin is greater than the rate of foaming of the foaming agent to obtain a number of solid fine ball. When the oil bath temperature is higher than150℃, foam blowing agent is greater than the rate of resin cure rate. Some resin fragments is obtained, when an oil bath temperature of the resulting microspheres at150℃best morphology; Suitable mixing time can make microspheres fully formed and dispersed, when the mixing time is less than15min, the microspheres is not fully formed, when the stirring time is more than15min, the microspheres began adhesions, reunion, when the stirring time when the resulting micro-15min morphology of the best ball; When using A and B surfactant microsphere preparation can remain stable and uniformly dispersed morphology of the resulting microspheres with a foaming A morphology of surface active agent is superior to the surfactant made hair B the resulting foam morphology of microspheres; increase microspheres with A floating rate first increased and decreased usage, A amount resulting microspheres when13%PBN resin morphology of the best quality, highest floating rate; B as a blowing agent and using the A resin can be formed in a hollow structure when the foam obtained by foaming agent B microsphere morphology morphology than obtained with expanded microspheres when A foaming agent; Microspheres B floating rate with increasing dosage after the first rise and fall, B when PBN resin mass amount of4.5%resulting microspheres morphology best floating rate highest.The hollow microspheres prepared according to the optimized method have complete structure, good sphericity, uniform size and hollow higher degree. The diameter of PBN (self-curing) hollow microspheres is around400-800μm and the wall thickness is around25μm. The diameter of PBN (plus DDS, AMD) hollow microspheres is around350-750μm and the wall thickness is around45μm The hollow microspheres with good structure can be obtained.