Study On The Crimp And Mechanical Properties Of PTT/PET Bi-component Staple Fiber

Along with the improvement of the standard of living and the development of science and technology, people are in great demand of the wearing property of textiles and new textile materials which were produced with all kinds of new technique and technics. Recently a new elastic fiber, PTT/PET bi-component fiber, appears successful commercialization which attracted attention of textile industry. PTT/PET side-by-side bi-component fibers are composite by PTT (Polytrimethylene terephthalate) and PET (Polyethylene terephthalate) polymers, which have different hot shrinkage properties. The different degrees of shrinkage after the same heat treatment of PTT and PET resulted in three-dimensional helical crimps of the bi-component fibers. It can be seen that the density of crimps is smaller than wool fibers. And the crimps have better elasticity and bulking property than the crimps of fiber introduced by machining. The PTT/PET bi-component fiber is a new textile material. It synthesizes the properties of PET and PTT, having particular three-dimensional curls which the PET and PTT do not have independently. It Makes up the disadvantage of the sole component, and obtains the synthesis, ideal properties and shape structure.Previous articles are focus on the PTT/PET side-by-side bi-component filaments, including their appearance and configuration, mechanical property, changes after heat-moisture treatment, etc. However, there is no report about the PTT/PET bi-component staple fiber. So in the paper, the wool-type and cotton-type PTT/PET bi-component staple fiber is been studied. The main work is as followings: (1) Used KESHIDA microscope for observing the appearance and configuration of the staple fiber. PTT/PET bi-component staple fiber has three dimensional spiral-shaped curls. The appearances of wool fiber, wool-type, cotton-type bi-component staple fiber and PTT/PET filament were compared with. The wool-type and cotton-type staple fiber both have more crimps in unit length than wool fiber. And also have more clear and stable appearance of 3D helical crimp. After heat treatment, two types of bi-component staple fibers' three-dimension curls became more crowded and tiny. Using OLYMPUS CH-2 optical microscope for observing the cross section of wool-type PTT/PET bi-component staple fiber, the cross section is like peanut.(2) Testing and analyzing the mechanical properties of two kinds of staple fiber and finding the relation between the stress-strain characteristic curve and fiber structure. Mechanical properties of wool fiber and wool-type bi-component staple fiber were compared with each other. Both the bi-component staple fibers have low tensile stress at break and high breaking elongation. The fabrics made of these two types of staple fibers both have a good elastic recovery and soft hand performance.In crimp properties measurement, the heavy loading added on wool-type and cotton-type PTT /PET bi-component staple fibers could be calculated by the stress-strain curve, using analysis graphic method. The heavy load of PTT /PET bi-component staple fibers was bigger than the standard heavy load of single component fibers which were made by thermal mechanical treatment. A correction measurement method of crimp properties about PTT /PET bi-component staple fibers was discussed in this research.(3) Cotton-type and wool-type composite of PTT/PET was tested according to "the test method of crimps of synthetic staple fiber GB/T 14338 - 2008".Crimp property, including crimps per unit length, crimp frequency, the curly elasticity and crimp recovery, of both cotton type/wool type PTT /PET bi-component staple fibers and chopped fibers was tested. Crimps per unit length of cotton type/wool type PTT /PET bi-component staple fibers without hot treatment were above 17- 20 per 25mm as the same of filament. After heat treatment, the crimps per unit length were much more than general synthetic fiber (10-25 per 25mm). In addition, crimps per unit length decreased with the increase of the linear density. Cotton type PTT /PET bi-component staple fibers with low linear density possessed lower crimp frequency, the curly elasticity and crimp recovery than the others.(4) In the base of experiments, the influence of heat treatment condition to the crimp shape, performance and mechanical properties was analyzed. Time and temperature are the key factors and the control of treatment time was more important. The crimp properties became better with increasing of time and attained best after 15 minutes at 90℃. After heat-moisture treatment, crimp radius decreased while crimps per unit length increased significantly and three-dimensional crimp shape became obviously. Meanwhile, the breaking strength and elastic modulus got lower and breaking elongation increased.