| PTT/PET side-by-side bi-component fibers are composite by PTT (Polytrimethylene terephthalate) and PET(Polyethylene terephthalate) polymers.Because of the two types of polymer PTT and PET have different degrees of shrinkage after the same heat treatment,the bi-component fibers have three-dimensional helical crimp along the fiber axial direction.This sort of spiral coil is generated by the heat shrinking difference of two components,thus the crimp has higher elasticity and bulking property than other crimps of fiber by machining.Therefore,in recent years,PTT/PET fibers such as the CM800 made by Haining Xingao Company were popular in the market which demonstrates the rapid development trend of this kind of fibers.However,there haven't any theory can apply for the crimp design or forecast of PTT/PET side-by-side composite fibers,as well as the existed restrictions of patented technology,the development and production of PTT/PET fibers has been limited.On the basis of the previous theory,a series of experiments was done on the effect of cross-sectional shape and line density on the crimp configuration,and a calculated method of the shrinkage difference of PTT and PET was concluded.The fundamental parameters of the crimp configuration would be provided for the produce and design of new type PTT/PET fibers.In the last place,the various knitted PTT/PET fabric were collected,and the influence of configurations of PTT/PET fiber on knitted fabric appearances were studied.The main methods and conclusions listed were as follow.(1) Use optical microscope to observe the cross-section shape of PTT/PET fibers from different manufacturers,the results show that in domestic and foreign markets,different PTT/PET fiber brands have clearly distinct cross-sectional,namely circular,peanut,pear shape respectively.(2) Use three-dimensional digital microscope measuring instruments took the photos of crimp configuration of PTT/PET fibers.With the help of computer drawing board,the crimp pitch and crimp radius were measured.In assuming that the crimp configuration belongs to a standard three-dimensional spiral,according to the pitch and radius of the crimp and use the helix formula to calculate the crimp curvature of the fiber.The result shows that when the single fiber linear density was fixed,as the cross-section's long and short axis'r atio decreasing, the crimp curvature gets lower.Circular cross-section of the ESS fibers are the smallest crimp curvature,Peanut-shaped cross-section of the X55 are the largest crimp curvature,CM800 crimp curvature is between them.(3) After measurement and calculation,it can conclude that bi-component filament owned same cross-sectional shape(the same brand);the linear correlation between crimp curvature and linear density is distinct.The three-dimensional spiral crimp radius and crimp pitch increase as linear density increasing,the crimp curvature decrease as the linear density raise.(4) On the basis of the Denton's theory of bi-component fibers curvature,a mathematical relationship between cross-sectional parameters and crimp curvature was founded.Furthermore,according to the result of cross-section parameters and crimp curvature. Calculated that the difference of heat shrinking rate of PTT and PET is between 7.7%-7.8%.Due to the mutual influence of the shrinkage of PTT,PET when they form the bi-component fiber,so it is not exactly equal to the difference of shrinking rate when form the fiber individually.This could be valuable parameters for exploit a new PTT/PET side-by-side bi-component fiber.(5) The self-crimp analogue with the twist in the longitudinal of PTT/PET fibers.In fact,PTT/PET filament hasn't twist.In order to balance the twist,crimp direction changed from right to the left from time to time in the direction of the longitude of the fibers.The special crimp configuration will result in random strip unevenness on surface of its knitted fabric.We have developed a patent technology CN101245518 which used for solving the problem of random strip unevenness.
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