Synthesis And Thermal Properties Of Poly(Aryl Ether Ketone) Copolymers Containing Naphthalene Moieties

Poly(aryl ether ketone)s are high performance engineering plastics with outstanding physical, chemical, thermal and mechanical properties, and have been applied to aerospace, electronics, automobile, petroleum and chemical industry, medical and food industry extensively. Poly(ether ether ketone) (PEEK), being one of the most important one of poly(aryl ether ketone)s, has been successfully developed for its excellent performance. Along with the development of the science and technology, people hope to get materials with higher temperature classification and more excellent mechanical performances. In order to develop these performances, structural modifications, such as introduction of crosslinkable lateral groups or functional groups onto the main chain, and synthesis of copolymers have been attempted. Naphthalene rings have been introduced into polymer structures by some authors for they have a larger volume than benzene rings, which can enlarge the proportion of the rigid groups in the main chain, decrease the mobility of segments, and therefore increase Tg of a polymer.The aim of the dissertation is synthesize new poly(aryl ether ketone)s containing naphthalene with different linking position through the nucleophilic displacement condensation reaction. The polymers are treated under different conditions. It is to be used several research methods to investigate the thermal degradation behavior and crystallization behavior, discussed the effection of naphthalene with different linking position.The dissertation include three parts: the synthesis and characteraztion of polymers containing diether naphthylene,We used 1,5-dihydroxynaphthalene(1,5-DHN)(or 2,3-dihydroxynaphthalene, 2,6- dihydroxynaphthalene, 2,7- dihydroxynaphthalene), hydroquinone(HQ) and 4,4'-Difluorobenzophenone (DFB) to synthesize the new high molecular weight glass poly(ether ether ketone)s random copolymers containing diether naphthalene moieties(PENEK). The glass transition temperature (Tg) increases with increasing the content of naphthalene moieties. The wide-angle X-ray diffraction (WAXD) data of PANEK showed that the molar fraction of DHN is over 30%, while the clear cold-crystallization temperature (Tc) and Tm were not detected. The result proves that the copolymers become amorphous. For the copolymer samples with a 2,7-DHN molar fraction of less than 30%, the Tm decreases with increasing the contents of 2,7-naphthalene moieties, while the Tg shows a reverse tendency. The crystal structures of the copolymers are a rhombic system in the same manner as PEEK. The thermal property of copolymers decreases a litter but retaines the advantage of poly(aryl ether ketone). These results can be attributed to the disturbance of the segmental movement and the destruction of the symmetry and regularity of the molecular chains due to the introduction of the naphthalene moiety. But we found that it's difficult to synthesize copolymers containing high content of naphthalene, because the activity of naphthalene is much higher than that of benzene to take place crosslinking reaction during the polymerization.Thermal stability of a polymeric material is one of the most important properties for both processing and application. Thermogravimetry (TG) is a technique widely used to characterize thermal degradation of polymer materials. In this dissertation, TG and differential thermogravimetry (DTG) measurements of poly(aryl ether ketone) containing naphthalene moieties were reported. The thermal degradation temperature and the kinetics of polymer were studied through nonisothermal and isothermal conditions. The weight-loss curves were obtained in both nitrogen and air atmospheres and its degradation behavior with respect to PEEK was discussed. The dynamic experiments showed that The Ti, T5 and T' of PAEK containing 2,7-naphthalene moieties are little higher than that of PEEK, and are almost independent of naphthalene content. The thermal stability of poly(aryl ether ketone) containing 2, 7-naphthalene moieties in air is substantially less than that in nitrogen, and the degradation mechanism is more complex. The results obtained under the isothermal condition are in agreement with the corresponding results obtained in nitrogen and air under the dynamic condition. The results of thermal degradation expressed that the 1,5-PENEK is different with 2,3-PENEK,2,6-PENEK and 2,7-PENEK. The degradation temperature and apparent activity energy of 1,5-PENEK is much lower than that of 2,3-PENEK,2,6-PENEK and 2,7-PENEK, and judged from the therogravimetric curves and apparent activity energy, the degradation reactions are different at nitrogen and air. The degradation reactions can be divided into two parts at air environment.Finally, we investigate the crystallization kinetics of poly (aryl ether ketone) copolymers containing naphthalene moieties. It is well known that the properties of semicrystalline polymers are strongly dependent on their crystalline structures formed during processing. In order to search for the optimum processing conditions in an industrial process and to obtain products with better properties, it is necessary to study the crystallization process quantitatively. In this dissertation, experiments conducted using DSC indicate that both nucleation stage and crystal growth stage are influenced by the temperature at which PENEK is heated and the duration it is kept for. At the same crystallization temperature, along with the increment of the content of naphthalene moieties, the Z value descends; but with the same content of naphthalene moieties, the Z value will decrease with the increase of the crystallization temperature, which shows that the increment in crystallization temperature and the content of naphthalene moieties will cause the crystallization rate to descend. The Avrami analysis indicated that both the isothermal and nonisothermal processes of PENEK can be distinctly divided into the primary region and the secondary crystallization region. The processes of nucleation and growth of the primary and secondary crystallization for both isothermal and nonisothermal are very different from each other. It is shown that the increment of the crystallization temperature and the content of naphthalene moieties will make the crystallization rate descend. At the same cooling/heating rate, the Tmax of PENEK is longer than that of PEEK, which suggests that the crystallization rate of PEEK is faster than that of PENEK in the nonisothermal crystallization condition. The n value was found to be ca. 3, which indicates that the nucleation mechanism and the crystal growth will not be influenced by the increase in crystallization temperature. The value of parameter Z decreases with the increase in crystallization temperature and the content of naphthalene moieties, while the nucleation mechanism and crystal growth of PENEK are not influenced with by the increasing in the content of naphthalene moieties.The crystallization behave is no influenced with different linking position.The modified Avrami-Ozawa equation has been used to deal with nonisothermal data. We found that F(T) increases with raising the relative degree of crystallinity, but the values ofɑare almost constant.Concluding from above, we have synthesized four kind of new poly(aryl ether ketone)s containing naphthalene moieties with different linking position through the nucleophilic displacement condensation reaction, and researched their basic characterization, kinetic study of the thermal degradation and the crystallization kinetics of poly(aryl ether ketone)s containing naphthalene moieties. Colligating all of the property and requirment, we think 2,7-PENEK has the excellent applied foreground as aromatic poly(aryl ether ketone).