Study On The Bicomponent Disposition, Heat-treatment And Structural Analysis Of PET/PTT Self-crimp Filament

In fiber industry, man-made crimpable fiber advances its way from multicomponent viscose, polyacrylic, polyamide, polyolefin to polyester type for more than half a century. PET/PTT side-side bicomponent fiber (also know as elastomultiester) as a relatively new synthetic crimpable fiber belongs to the diversity of polyester fiber. Initiated from DuPont T-400, the development of our domestic PET/PTT bicomponent fiber also has experienced an important period with the increased productions and applications. However, there still has its necessity to endeavor on the crimp behaviour and property-structure relation of PET/PTT bico with the aim to elevate fiber quality and match the extensive end uses.In this dissertation, our main purpose is to investigate the self-crimp and other mechanical behaviors, and interpret the effect of bicomponent disposition, heat-treatment and inner structure on the crimp forming and developing process. The content included is to make review and modifications of the crimp theories to meet the bicomponent disposition of PET/PTT self-crimp fiber, delve on the the mechanical and relative physical behaviours of PET/PTT bico by the correlation to PET and PTT single-component model fibers, discover and reveal the relation of thermal treatment to the crimp extension and retraction behavior and interpret the manifestation process of latent crimp on heating, and PET/PTT fiber structure analysis to explore the correlation of micro substance to fiber crimp morphology.For the typical crimp theories, we have compared and categorized them into geometric and minimum-energy type, and modified them, respectively, to suit the component disposition of PET/PTT bico. The dependence of curvature K of PET/PTT side-side on differential length change AL/L, fiber diameter r, volume ratio s of PET and PTT, and ratio of modulus n, has been deduce, and the specific theories for PET/PTT bico is reached. These theories are analyzed and summarized according to the application feasibility on the PET/PTT self-crimp fiber.On the mechanical behavior of PET/PTT bico, we focus on the unique mechanical properties of PET/PTT bico by the comparison to PET and PTT model fiber, and correlate the mechanical difference between PET and PTT to the asymmetric nature of PET/PTT self-crimp fiber. we have introduced the basic issues on bicomponent fiber spinning and drawing, and the optimal parameters for PET/PTT conjugated melt spinning and drawing are reached. The mechanical behaviors we investigated include one time extention to break, anelastic property, hysteresis stability, fatigue behavior, and fractographic analysis. For ther anelastic behavior, we find PET/PTT fiber along with PTT, PET models all have the same trend that is tensile recovery R increase with the time for extension te and inversely with the time for recovery tr, and the decreasing rate of recovery and increasing rate of recovery have been arranged between them. From the multicycled hysteresis analysis, the relation of stability of hysteresis and fatigue behavior among PET, PTT and PET/PTT are reached. After the constant rate of extension at 200%/min, the fractograph of PET, PTT model and PET/PTT bico are being comparatively analyzed and some unique behaviors for PET/PTT fiber are found.For the variations of crimp behavior on heating, the main purpose is to find the governing law for the changing of crimp forming and developing behavior of PET/PTT bico before and after heating, and to explain crimp releasing phenomenon through its thermomechanical nature of PET and PTT sides. The research areas PET/PTT bico are comprised of the change of crimp extension work We(n) and retraction work Wr(n) and its ratio Wr(n)/We(n) before and after heating, the interpretation of crimp forming and developing process by thermomechanical analysis which include the evolution of differential shrinkage and shrinkage force with temperature, and the isothermal shrinkage kinetics. By comparison, we find that how the multicycle hysteresis behavior and crimp morphology of PET/PTT bico are changed on heating, and the variations of parameter a and P with heating temperature and mechanical action from the numeric calculation and simulation results on the crimp work W(n). From thermomechanical analysis, the release process of latent crimp of PET/PTT bico is elucidated by the theories of differential shrinkage AS(T) and residual shrinkage force Fr(T) of PET and PTT side, and the optimal heating temperature and duration for PET/PTT bico are found from the isothermal shrinkage kinetics analysis of PET and PTT component.In the structural analysis of PET/PTT bicomponent fiber, our target is primarily to find the correlation between the super molecular structure and the crimp properties of PET/PTT bico by the advantages of modern polymer analysis technology. These analysis methods used in this paper include 3D optical microscopy, Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), Wide Angle X-ray Diffraction (WAXD), and Polarized Ligth Microscopy (PLM). By the analysis of the interface of PET/PTT fiber in cross-sectional and longitudinal direction, the evolution of the interface of PET/PTT bico with processing state has been found and related to the crimp morphology of PET/PTT bico. From the comparison of DCS, FTIR, WAXD and PLM analysis, we find the bilateral nature of PET/PTT bico, the variation of crystalline and orientational aggregation state of molecules of PET and PTT side with drawing and heating, and all have a correlation with the crimp morphology of PET/PTT elastomultiester.This thesis generally is composed of research domains for PET/PTT side-side self-crimp fiber in which still lack of probing or in the state of deficiency, and have experimental methodologies that can also be applied to other fibers of multicomponent nature. At the same time, there still exists some inadequacy or insufficiency in this article for the restraint of the time, availability of the tests and so on. We hope this work will benefit the development of PET/PTT elastomultiester with the ongoing fiber sciece and technology.