| Bisphthalonitrile polymers are an important class of high-performance polymers. Because of their outstanding thermal and thermal-oxidative stability, good mechanical properties, low flammability, moisture and chemical resistance, and easy processability, phthalonitile polymers have been found many applications in advanced technologies such as aerospace and marine. The study on the polymerization mechanism of bisphthalonitrile resins and the investigations of novel bisphthalonitrile resins were very important to the optimization of processing technics and the improvement of processing properties in order to obtain high performance composites with high temperature resistance.A series of model oligomers was synthesized from a certain ratio of model compound-biphenyl bisphthalonitrile and copper chloride as 3:1 via solution reaction by different reaction time. The structure of the model oligomer was characterized by 1H-NMR, UV-vis and FTIR spectrum and the results show that the branched process was separated from other processes of the preparation of bisphthalonitrile polymers to be studied. The formation of the core phthalocyanine rings was faster than that of the branch chain phthalocyanine rings, so the pretreatment at the beginning and the post-curing at the end were necessary. The congeries of the model oligomer was characterized by UV-vis, TEM and SEM, and the results revealed that the congeries was composed of lots of sticks formed by the little slices of the model oligomer molecules. The driving force of this process was the strongπ-πinteraction of phthalocyanine rings and the bezene rings in the model oligomers.A kind of biphenyl bisphthalobitrile containing aromatic ether nitrile linkages (2PEN-BPh) was firstly synthesized from 4-nitrophthalonitrile and a ratio of 4, 4'-biphenol and 2, 6-dichlorobenzonitrile as 2:1 via solution reaction. The structure of 2PEN-BPh was characterized by 1H-NMR and FTIR spectrum. The liquid crystal properties of 2PEN-BPh were characterized by DSC,rheology test and POM and the result indicated that 2PEN-BPh was a kind of schlieren-like nematic liquid crystal. The results of DSC and rheology tests on 2PEN-BPh with different ratios of curing additive 2, 6-bis-(4-diaminobenzoxy) benzonitrile (BDB) show that BDB could low the curing temperature of 2PEN-BPh, accelerate the curing reaction of 2PEN-BPh and improve the processing properties of 2PEN-BPh, effectively. When the content of BDB was 5wt%, the processing window was 143oC, much larger than BPh. TGA and FTIR characterization of the curing process of 2PEN-BPh was taken and the results revealed that, with the increase of the curing temperature and time, the extent of the curing reaction of 2PEN-BPh increased, and the thermal and thermo-oxidative stabilities increased, as well. In nitrogen, the 5wt% decomposing temperature was 551.00 oC and the char yield at 800 oC was 78.43%; while in air, T5% was 549.30 oC and the char yield at 600 oC was 88.74%. The completely cured 2PEN-BPh exhibited excellent thermal and thermo-oxidative stabilities.According to the results of the investigations of the polymerization mechanism and the reaction properties of 2PEN-BPh, the glass fiber reinforced composites was prepared through hot pressing forming process using 2PEN-BPh and 2PEN-BAPh as the matrix resins, respectively. After post-curing process, the bending strength of 2PEN-BAPh/glass fiber composites was 711.60MPa and the bending modulus was 32.38GPa; but after post-curing at 375 oC for 12h, the bending strength and the bending modulus both decreased rapidly. 2PEN-BAPh/glass fiber composites possessed excellent mechanical properties but bad thermo-oxidative stability. After post-curing process, the bending strength of 2PEN-BPh/glass fiber composites was 479.07MPa and the bending modulus was 16.23GPa; and even after post-curing at 375 oC for 12h, the bending strength was still 422.84 MPa and the bending modulus was 13.80 GPa. 2PEN-BPh/glass fiber composites possessed good mechanical properties and excellent thermo-oxidative stability. Both 2PEN-BAPh/glass fiber composites and 2PEN-BPh/glass fiber composites possessed excellent moisture and chemical resistance. |
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