| 2013th Postgraduates |
|
|
Title: Study on Toughening Effect and Mechanism of PEN Toughening System through Melting Blending Writer: Liying Bi Supervisor: Wei Wu, Abstract:This paper systematically studies the PEN’s performance influenced by three different kinds of tougheners, EPDM-g-MAH, TPEE and Surlyn®9320. The impact test, tensile test and bending test methods were used to analyze the toughening effect and mechanism of these toughness systems. Differential scanning calorimeter (DSC), vicat softening point tester, as well as thermal gravimetric analysis (TGA) were used to characterize the melt crystallization properties, heat deformation properties and thermal degradation stability of these different toughness systems. Comparison the toughening effects of three different tougheners, we found that EPDM-g-MAH as the toughener greatly improved the impact strength and elongation at break of the system, but significantly reduced the strength and modulus of the toughness system. When the content of TPEE was less than 10wt%, the strength and modulus of the blend were not dropped significantly, while the impact strength was not significantly improved. The content of TPEE was further increased, the impact strength of the system would be greatly improved, but the strength and modulus decreased significantly. When Surlyn®9320 as the toughener, the addition of a small amount of Surlyn®9320 could significantly improve the impact strength as well as elongation at break of the system, meanwhile the tensile strength was increased slightly, and only a slight decrease in the flexural strength and modulus. The addition of three different kinds of tougheners all decreased the system's thermal deformation resistance and thermal degradation stability. Considering the toughening effect of three different tougheners, Surlyn®9320 has the best toughening effect with little addition, EPDM-g-MAH is suitable for the material which demands less for strength but high impact toughness. TPEE can be used in the system where the impact toughness is not very high requirements, while the strength and modulus should not be significantly reduced.
Title: Study on Compatibilizing Mechanism of PET-PEN Melt Transesterification Copolymer on PET/PEN Blends Writer: Tao Wang Supervisor: Wei Wu Abstract:PET/PEN Blends were prepared via melt processing in a twin-screw extruder and a mixer torque rheometer. Compatibilizing effect of PET-PEN copolymers formed during melt transterification was discussed. The properties of PET/PEN Blends and influence of mixing time, screw rates, blending temperature and PEN content on the properties were studied. Compatibilizing effect of PET-PEN copolymer added to the blends was also investigated. The feasibility of applying PET-PEN copolymer films to film capacitors to replace pure PET films was also studied. The results showed that PET-PEN copolymer has significant compatibilizing effect on PET/PEN blends. The transterification reaction is mainly determined by mixing time. With mixing time of 25min, the randomness of PET/PEN blends is 0.60. With the increase of mixing time, two glass transitions approach closer and merge gradually. Under longer processing time, a smaller domain size of the dispersed-phase particles is obtained and the miscibility of PET/PEN blends is improved. As the mixing time increases, the crystallization and intrinsic viscosity decrease. The properties of PET/PEN Blends can be optimized with appropriate screw rates, blending temperature and PEN content. Compared with PET, tensile strength and tensile modulus increase by 16.1% and 13.9% respectively when PEN content is 30 wt%; Vicat softening temperature increases by 5.4℃ when PEN content is 20 wt%. The results showed that PET-PEN added to PET/PEN blends can improve the thermal stability of the blends effectively. Higher PET-PEN copolymer content is, better thermal stability of PET/PEN blends is obtained. The starting temperature of weight loss increases by 20.3℃ when PET-PEN copolymer content is 15phr. The Vicat softening temperature, tensile and bending properties, impact toughness of PET/PEN blends are improved by PET-PEN copolymer. The comprehensive properties of the blends are best when PET-PEN copolymer content is 5phr. The dielectric constant of PET-PEN copolymer films is stable in the range from -80 to 80℃ and PET-PEN copolymer films have better dielectric stability. PET-PEN copolymer is a promising candidate to take the place of PET in film capacitor application.
|
 |