Preparation Of PBT-based Luminous Composites By Reactive Processing

Organic luminous composite is a kind of functional polymer material which can emit light for a long period of time in darkness after the irradiation of sunlight, lamplight or other visible light. It is composed of rare earth luminous powder (RELP) and organic polymer. It has been widely used in the fields such as aviation, navigation, transportation, night shift running, fire emergency, textile clothing and so on. Due to its excellent mechanical property and processing performance, PBT has become one of the common used organic matrices. However, the high viscosity characteristic of PBT resin leads to a poor dispersion of RELP in the matrix by traditional physical blending process, which seriously affects the following forming process. Therefore, the properties of these products are not satisfactory.In this paper, cyclic butylene terephthalate (CBT), a new oligomer with low viscosity characteristic under high temperature, was used to produce the PBT-based luminous composite to solve the dispersion problem of RELP in the matrix. The effects of processing conditions on the molecule weight of the products were investigated systematically. Meanwhile, suitable processing conditions were obtained. On this basis, the PBT luminous composites with different powder contents were prepared by reactive processing. And the influence of RELP on the PBT structure and properties were discussed. Finally, various models were used to study the non-isothermal crystallization behavior of RELP/PBT composites, which can provide theoretical guidance for the forming process of these materials. The main conclusions are summarized as follow:1. Research on the process conditions of CBT ring-opening polymerization. CBT can be polymerized to PBT when the temperature up to190℃. The rate of polymerization increases with the increase of reaction temperature, the polymerization time decreases correspondingly. The reaction temperature of225～245℃is suitable for the processing. In these cases, the polymerization of CBT can be completed in30min, and the inherent viscosities are all above0.8dL/g. However, higher temperature(≥235℃) and longer residence time(>30min) in the polymerization can lead to the degradation of PBT. 2. Preparation of PBT-based luminous composites by CBT reactive extrusion. Composites with5,10and15wt%content of RELP were prepared under the conditions mentioned above. The inherent viscosities of all obtained products are around0.92dL/g, which can satisfy the forming requirement of these materials. Meanwhile, the emission strength of these composites increases with the content of RELP. Compared with these prepared by traditional physical blending method, the RELP/PBT composites prepared by reactive process shows a better RELP dispersion in the matrix.3. Studies on the crystalline morphology of RELP/PBT blending materials. Polarizing microscope analysis result shows that PBT has typical spherulites morphology, the grain size of PBT decreases with the increase of RELP contents. The crystallization peak temperature increases with increasing content of RELP, while the half crystallization time (Tp) decreases, which indicates that adding RELP can accelerate the crystallization process of PBT. When the luminous powder content reaches15%the crystalline rate arrives at the highest value.4. Studies on the non-isothermal crystallization behavior of RELP/PBT composites. Various models were used to study the non-isothermal crystallization behavior of RELP/PBT composites. The Mo’s model can describe the non-isothennal crystallization of the composites satisfactory. The results show that adding RELP can accelerate the crystallization process of PBT under low cooling rates. On the contrary, high powder content will reduce the crystallization rate of the matrix when the cooling rate is above25℃/min.