Preparation And Properties Of Poly (Aryl Ether Ketone) Based Phthalonitrile Resins And Their Composites

Phthalonitrile resins are an unique class of high-performance materialshaving a variety of potential uses in aerospace, ships, machinery, electronics andother fields, owing to their outstanding thermal stability, good chemical stability,excellent mechanical properties, superior moisture resistance, fire resistance andgood processability. However, the performances of bisphthalonitrile resins arelimited by the following disadvantages:(1) A small processing window (20-30oC)and high processing temperatures prevent these resins from being fully utilizedfor extreme applications, such as in aerospace industry; meanwhile, thesedisadvantages also cause high cost and processing difficulties.(2) The highcrosslinking density and the high rigidity structure led to the brittleness of thecured bisphthalonitrile resins, which limited their applications in some fields.(3)The functionalization of bisphthalonitrile resins has not been abundant enough,and their application range needs to be expanded. In the light of these aboveissues, the dissertation focuses on the modification and functionalization ofbisphthalonitrile resins. In this work, bisphthalonitrile resins were modified by avariety of methods, and their combination properties have been improved.Specific research contents are as follows:(1) In order to solve the processing problems, we synthesized a series of poly(aryl ether ketone) oligomers (PAEK-CN) containing phthalonitrile with variablemain chain length and cyano side groups by molecular structure design.Incorporating linear ether linkages and extra cyano functional groups intophthalonitrile terminals could efficiently lower melting piont and improve thecrosslink rate, thus better processability could be obtained without evidentlysacrificing other properties necessary for high temperature applications. Theresearch results showed PAEK-CN had low melting points (109-142oC), largeprocessing windows (over100oC) and good processability. The cured phthalonitrile resins possessed outstanding chemical stability, good thermalmechanical properties and excellent thermal stability. This kind of the oligomericbisphthalonitrile resins may be used as a good candidate matrice for advancedcomposites.(2) In order to improve the toughness of bisphthalonitrile resins, biphenylpoly (ether sulfone) containing cyano side groups (PPSU-CN) was selected as theguest polymer in bisphthalonitrile resin matrix to improve the intrinsic brittlenessof its network structure. The results indicated that PPSU-CN could improveobviously the toughness and strength of bisphthalonitrile resin without sacrificingthe excellent thermal stability.(3) In order to improve the heat resistance of bisphthalonitrile resin, wemodified montmorillonites by the organic modifiers with good thermal stability,and then prepared the bisphthalonitrile resin/montmorillonite nanocomposites bymelt mixing method. The results showed the nanocomposites possessedoutstanding thermal stability, good thermal mechanical properties and high heatdeformation temperatures.(4) In order to develop the application of bisphthalonitrile resins in theconductive composite membrane materials field, we first synthesized a series ofpoly (aryl ether ketone) polymers (m-PAEK-CN) containing phthalonitrile withrelatively high molecular weights, and the polymers have good film-formationand toughness. Then, we prepared the phthalonitrile resin/multi-walled carbonnanotubes (MWNTs) conductive composite membranes by solution blendingmethod. The conductive composite membranes have a low percolationthreshold (0.25vol.%) and excellent conductive properties. They have thepotential to be alternative candidates in the field of high-temperature, conductivecomposite membrane materials.