Study On The Perparation And Spinnability Of Modified Phenolic Resin

Phenolic fiber(PF) with good resistance to high temperature, flame resistance, corrosion resistance and other excellent properties, is widely used in corrosion resistance, flame retardant fabric, aviation composite materials, carbon materials, activated carbon fiber precursor materials and other fields. PF is made from the phenolic resin(PR) by melt spinning, whose spun filament crosslinks in the solution containing the hydrochloric acid and formaldehyde, further curing under high temperature. The performance of PF mainly depends on the structure of PR and degree of crosslinking after being processed. Because of easy oxidation of phenolic hydroxyl and methylene,PR can make its thermal stability performance decreased, which greatly limits the application range of PF. Therefore it is necessary to further modify the PR in order to meet the requirements of high performance fiber materials.This paper mainly explored the synthesis of high ortho phenolic resin in order to increase its fiber crosslinking rate, which was then modified by boric acid and ammonium molybdate to enhance fiber’s heat resistance and crosslinking process of the modified fiber. Fourier infrared spectroscopy(FT-IR), X-ray diffraction(XRD), nuclear magnetic resonance spectrometer(NMR),scanning electron microscope(SEM), thermogravimetric analyzer(TGA) and tensile tester were uesd to characterize structures and performances of the modified phenolic resin and fiber. Effects of spinning and crosslinking treatment technology on the heat resistance and mechanical properties of the modified phenolic fiber was disscussed.This paper firstly explored the best synthetic craft of the high ortho phenolic resin modified with boron(o-BPR), whose Mw and o/p value were 4973 g/mol and 1.52, separately. The high ortho phenolic fiber modified by boric acid(o-BPF) was made from o-BPR through melt spinning and crosslinking treatment. The results showed the introduction of boron and high ortho could effectively block phenolic hydroxyl thermal oxidation and speed up the crosslinking rate, makingthermal stability and mechanical properties of phenolic fiber increased; The best heating rate of crosslinking bath was 25 ℃/h and the best heat treatment temperature was 180 ℃. The tensile strength of the modified fiber under the best crosslinking process could reach 213 MPa; The initial decomposition temperature of modified fiber was higher by 139 ℃ than conventional phenolic fiber in N2 atmosphere, which was also higher by 261 ℃ in air atmosphere.Secondly, this paper explored the optimal preparation process of high ortho phenolic resin modified with ammonium molybdate(o-MoPR). The preparation carft of high ortho phenolic fiber modified by ammonium molybdate(o-MoPF) was got from o-MoPR with Mw and o/p value of4255 g/mol and 1.25 by melt spinning and crosslinking treatment. Through a series of tests, the results showed that the introduction of molybdenum and high ortho could effectively prevent the thermal oxidation of methylene and speed up the crosslinking rate, making thermal stability and mechanical properties of phenolic fiber increased. The best heating rate of crosslinking bath was25 ℃/h and the best heat treatment temperature was 170 ℃. The tensile strength of the modified fiber under the best crosslinking process could reach 185 MPa; The initial decomposition temperature of modified fiber was higher by 123 ℃ than conventional phenolic fiber in N2 atmosphere, whose initial decomposition temperature was lower by 260 ℃ than modified fiber in air atmosphere.Finally, this paper explored the synthesis of high ortho phenolic resin modified with both boric acid and ammonium molybdate(o-B,MoPR), which was got with Mw and o/p value of 4653g/mol and 1.22. The high ortho phenolic fiber modified by boric acid and ammonium molybdate(o-B,MoPF) was obtained from o-B,Mo PR through melt spinning and crosslinking treatment. The results showed that the introduction of the two elements and high ortho could effectively prevent the thermal oxidation of the phenol hydroxyl and methylene and speed up the crosslinking rate,making thermal stability and mechanical properties of phenolic fiber improved. The tensile strength of the modified fiber under the best crosslinking process of heating rate 25 ℃/h in crosslinking bath and heating treatment temperature 170 ℃ could reach 216 MPa; The initial decomposition temperature of modified fiber was higher by 88 ℃ than conventional phenolic fiber in N2 atmosphere; the initial decomposition temperature of modified fiber enhanced by232 ℃ in air atmosphere compared to the conventional phenolic fiber. The o-B,MoPF had the highest tensile strength and the o-MoPF had the best heat resistance of the three modified fibers.