| Last century, special engineering plastics poly (aryl ether ketone) polymer havebeen developed and utilized successfully. Which has aroused great interest of scientistsbecause of their unique combination of stiffness, toughness, excellent electricalproperties, thermo oxidative stability, heat resistance, radiation resistance, fatigueresistance, impact resistance, resistance to creep、wear、heat water, flame resistance andother characteristics. So that such materials had played an important part in manyfields such as aviation, spaceflight, nuclear energy, communication, telecom,electronics, petrochemicals, machine manufacturing and traffic etc, to give full playto its strengths.The heat resistance and processing of traditional poly (aryl ether ketone) materialcan not be improved at the same time when being used as aerospace structuralmaterials. Therefore, it’s important to research and develop new kinds of PAEKmaterials with excellent processing property and high temperature performance. Inorder to meet the application requirements of the thermoplastic poly (aryl ether ketone)polymer in certain areas without sacrificing its excellent performance, active groups ofcrosslink can be introduced into the poly (aryl ether ketone) system to prepare poly(aryl ether ketone) oligomers with low molecular weight. Compared to the poly (arylether ketone) with high molecular weight, this kind of material is easy to process whichcan be processed as thermoplastic materials before curing, and then become thermosetmaterials after curing.In this research we choosed phenylethynyl as cross-linked groups, which wasintroduced to poly (aryl ether ketone) system in the form of end capped, at the sametime mesogenic was introduced. A series of poly (aryl ether ketone) oligomersterminated with phenylacetylene were synthesized, which were of different contend,chemical environment and structure, the oligomers were cured by different conditions.We studied the relationship between structure and properties of the molecular chain, reveals the influence of the molecular structure to the performance of the oligomersand the cured product also to the curing process, including the impact on the thermalproperties, the influence of the liquid crystal properties, rheological properties andcuring behavior. So that we can use the results of analysis to establish the curingkinetics model, then select a best one to make the curing process.This thesis includes a few parts, including the synthesis of phenylethynylterminated poly (aryl ether ketone) resin with different structures and the relationshipsbetween properties and structures, we also studied the curing kinetics of the materials,and specific content are summarized as follows:First, we had synthesized4-(phenylethynyl)benzoylchloride according to themethods from literature, which we named PEBC. Three phenylethynyl terminatedoligomers (PEBC-PEEK-n) with different contents of phenylacetylene were preparedby using the monomers of PEBC, hydroquinone and4,4′-difluorobenzophenone. Thecomposition and structures were characterized by the means of FTIR, MS andelemental analysis etc. The thermal properties of the oligomers were studied by DSC(differential scanning calorimetry) and TGA, cross-linking reaction happened to thephenylethynyl groups under the heating treated. Known by the experimental results, inthe case of the same structure as, the lower the molecular weight was, the more easilyof the curing reaction, so do the Tg and Td, the cured oligomers had good thermalstability. The oligomers existed liquid crystal phase after melting point, we could seethe unique phenomenon of birefringence under the polarizing microscope. theexistence of liquid crystal phase allowed the polymer low melt viscosity and lowmolding pressure, which might effectively improve the processing of poly (aryl etherketone) materials and balance the contradiction of processing properties and heatresistance of the poly (aryl ether ketone) resin.The second part, we used the monomer FPEB, hydroquinone (BP), benzenegeneration of hydroquinone (PH) and bis(4-fluorophenyl)methanone to synthesis aserials of phenylacetylene terminated poly (aryl ether ketone) copolymer oligomerscontaining different ratio of biphenyl mesogenic. Mass spectrometry, elementalanalysis,1H NMR and FTIR test methods were used for structural characterization, theresults were consistent with the expected structure. Differential scanningcalorimetry(DSC) and TGA were used to study the thermal properties of oligomers, theconclusions were the same as the previous ones, the higher the content of alkynyl, thegreater the crosslink density was. FPEB-BP and FPEB-DMBP were crystalline polymers, due to thecopolymerization, there was not only one glass transition temperature, but also amelting point for FPEB-PAEK (m/n), and after the melting transition there are crystal-liquid crystal phase transformation. Oligomers had good thermal stability after curing,the5%weight loss in nitrogen occurred after580℃. The series of oligomers exhibitnematic texture under the hot stage polarizing microscope, which were consistent withthe transition temperature shown in DSC curve, the polymer flew easily and prone toorientation, in the liquid crystal state.At last, we studied the curing behavior of the oligomers, compared the influenceof alkynyl with different chemical environment to the curing behavior. The resultsshowed that the stronger the electron withdrawing ability of functional groups attachedto the alkynyl was more conducive to the thermal crosslinking reaction, which showedlow apparent activation energy; Isothermal cure kinetics studies showed that increasingthe temperature or extending the time of heat treatment could accelerate thecrosslinking reaction speed, so that the curing reaction tended completely. The curingreaction approximated to first order reaction.In summary, the introduction of mesogenic and the low molecular weight reducedthe melt viscosity of poly(aryl ether ketone) oligomers terminated withphenylacetylene, effectively improve the processing property and balance thecontradictions of heat resistance and processability of the material, which could beused as a resin matrix, low viscosity and excellent heat resistance after curing made itpossible to be used as high temperature adhesive material, while its mechanicalproperties needs further investigation and study. |
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