Thermal Properties Of Naphthylated Poly(Aryl Ether Ketone)s Containing Antioxidants

The development of the Polymer materials was beginning from the the project, special type, in the 1980s, the compound and functional type was appeared. In the 21st century, composite and functional type polymer materials s is currently receiving considerable attention for potential applications in aerospace, automobile, electronic, and other high technology fields. Unfortunately, these polymers also revealed some shortcomings, the most prominent, is easy to aging and easy to combust. There is far-reaching significance to solve these two problems. During the process of storage, transportation and process, the physical, chemical, and mechanical properties will gradually deteriorate, this is known as aging or degradation. It is important to clearify the nature and causes of aging and manage to avoid it, so the lifetime of the materials will be prolonged. That is the ultimate purpose to study the polymers degradation and stability.The aim of the dissertation is to study the mechanism of thermal oxidation.We chose the naphthylated PAEK with high thermal properties as the object for the investigation. Poly(aryl ether ketone)s containing naphthalene have more active position than the benzene ring, which not only can connect more function group but also easy to excited free radicals. These free radicals will become the center of crosslinking and degradation. Meanwhile, the free radicals on the naphthalene ring somewhat different from that of the benzene, which make it possible to distinguish free radicals on different position and confirm the exact position on which the oxidation reaction occur. And then some kind of antioxidants was added into the polymers through the solution blending method, the effect of the additive was detected, and the mechanism of the stabilization was also discussed. The dissertation mainly contained three parts:Firstly, Poly(aryl ether ketone)s (PAEK) containing 1,5-and 1,4 naphthalene isomer in the backbone have been synthesized, through the nucleophilic displacement condensation reaction. The structures of the polymers were confirmed by 1H NMR and FT-IR. The properties of the polymers were detected by several ways. And then the antioxidant was added in the polymers with the solution-blending method.Thermal stability of a polymeric material is one of the most important properties for both processing and application especially for studying the aging mechanisim. 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 in Air conditions. Judged from the therogravimetric curves the degradation temperature and apparent activity energy of samples were analyzed. The temperatures of 5% and 10% weight-loss of the samples with the antioxidant were much higher than that of the simple samples, and so was the apparent activity energy. The results showed that 1,5-series had a far-improved thermal properties after the additive of the antioxidant. While in the 1,4-series , no obviously change could be detected. In all samples, the 1,5-s9228 had the best results, and the s9228 is an important candidate for the PAEK in the future process as a processing additive. And it implied that the primary and secondary antioxidant had different effective, in our system the main cause to degradation is the RO? and ROO? radicals which were more sensitive to the secondary antioxidants, and it confirmed that the ether bond was the"weak point"of the materials.Finally, we detected the free radicals in the polymers using the Electroni Spins Resonance technique (ESR), the result showed the content of the free radical was much lower when the antixodant in the materials both before and after the samples being heated. And two kinds of free radicals were characterized: one is an RO? type free radical and the other is a naphthalene ring free radical. The measured concentration of RO? was nearly constant at first, and then the concentration increased linearly. Because the concentration of RO? free radicals is higher than that of naphthalene ring free radical, RO? free radicals take a predominant role in crosslinking reactions. The antioxidant was mainly had effect on the RO? free radicals, this result had a good coincidence with that above.Concluding from the whole work, we have synthesized two kinds of poly(aryl ether ketone)s containing naphthalene moieties with different linking position through the nucleophilic displacement condensation reaction, and researched their thermal degradation and stability of the polymers containing antioxidant, colligating the thermal properties and requirments, we think the idea of adding antioxidant in the PAEKs is a effective method to improve the performance of the materials in the future.