| A set of controllable mould specially producing melt orientation in shear field and sheet formation mould were designed and made. PET was blended with modifying resins, nucleators and fillers through double-screw extruder. The samples used for analyzing and testing polymer structure and properties of PET were cut form PET sheet which has been processed with PET blend pellet successively through plasticizing in single-screw extruder, melt orientation in the controllable mould and forming in the sheet die. The influences of the kinds and contents of components of PET blend and the change of the shearing field on the structure and properties of PET sheet were investigated through characterizing and measured orientation degree and its distribution, the crystallization degree, dispersing morphology of the dispersed phase of PET blend by SALS, WAXD, SEM as well as testing mechanical and rheological properties of PET materials. The main conclusions were given as follows:1. The controllable mould and sheet forming die were designed and manufactured for researching the influences of the shearing field on the polymer structure and properties of PET sheet. This controllable mould is provided with the below distinguished features: (1)the shear field in channel of screw produced by screw-rotating inside the controllable mould may be changed by adjusting screwspeed. (2) the melt orientation carries out continuously. (3) the control of the strength of shear field, plasticization and production output can go on separately. Therefore, the controllable mould is important and basic equipment for investigating the effect of shear field on melt orientation.2. Through investigating the effects of kinds and dosage of modified resins, nucleators and fillers on the polymer structure and mechanical properties of PET sheet, we have discovered that the changed shearing field affected on obviously phase morphology of double-component blend system, the crystallization degree and the crystal orientation of PET / nucleators blend and that influence of the shear field on polymer structure and properties of PET is relative to the content of additives.3. By SALS, WAXD, SEM characterizing the structure of PET sheet processed through the controllable mould, we have discovered that the polymer structure of PET sheet processed through the controllable mould was obviously different from those system processed by traditional formation method.4. SEM results proved that the PBT pellet in PET blend passed through shear field was drew into cylinder and PC drew too, however the drawing length of PC was shorter than PBT resulting form greater viscosity, and that the change rule of polymer structure of PET/PBT system with shear field strength was different from PET/PC system, because the melt viscosity of PC was greater than PBT value.5. SALS results proved that the increasing shear field had some effect on improvement of longitudinal orientation of PET containing l%white carbon, but a little effect on that containing 1% CaCO36. WAXD results showed that the increase of screw rotating speed had a little effect on improvement of the crystal orientation along the surface of PET sheet containing !%TiO2, which was higher than that of PET containing 1% white carbon. Because crystallization degree and longitudinal elongation strength of PET containing 1% white carbon is greater than that of PET containing 1%CaCO3, the higher crystallization degree, the greater longitudinal elongationstrength of PET under the condition of the same shear field strength and degree of orientation of PET.7. It is significant to research the influences of the kinds and dosage of components and the shear field change resulted by the screw-rotating speed on the polymer structure and properties of PET sheet. There are still a few problems to require solution such as the function mechanism of shear field on polymer structure of PET blend and The influences of shear field change on transverse orientation and mechanical proper... |
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