Study On The Filament Soft Structural Formation Mechanism And Its Practical Application

The different use characteristics of fibrous materials are due to their different physical and chemical properties.The intrinsic cause of fiber properties is the interaction and arrangement of the basic units of the fibrous structures including inner micro-molecule aggregation,crystalline and organizations.Torsional softness and strong mechanical properties are the premise and basis for fiber textile processing.However,during the fiber formation and primary processing,fiber reinforced treatments often leads to increased fiber stiffness which means the high rigidity.It seems that fiber soft performances cannot get via high-strength forming treatment.This thesis first selects high-strength PE filaments as the research object,and solves the problem that “when the thermoplastic synthetic fibers are processed by hot-drawing forming,the internal macro-molecule orientation is improved to improve fiber strength and stiffness with a deteriorated softness”,a tensional hot twisting method is developed to reinforce and strengthen PE fibers in the same time;systematically studies the effects of heat-stretching and twisting on the properties of single-filament synthetic filaments.Results showed that when the temperature is controlled at 110°C,twisted marks appear on the surface of the filaments after twisting,and the torsion marks tend to be obvious as the degree of twisting increases,creating fiber inner spirals.The space spiral structures greatly reduces the modulus of the filament fibers and improves the flexibility.At a twist of 500 T/m,the initial modulus of the filament is 1.93 cN/dtex,which is 30.82% lower than the original mono-filament’s initial modulus.Secondly,this paper selects silk fibers as the research object to achieve synergistic enhancement and softening;thus pre-wetting tensional twisting method is established and systematically examined under different environments.The effect of tension twisting process on the structure and properties of silk.To regulate the structure of the molecular chains in the silk fibers and to give them the characteristics of the helical configurations,the silk fibers with multiple helical conformations were further explored.The research results and analysis show that the initial modulus of the silk after pre-wetting tensional twisting is significantly reduced,so that the silk becomes soft with little strength loss,which means a soft and tough silk fiber is obtained.This method causes no new functional groups or chemical structures changes;however the silk fiber crystallinity gets enhanced after the pre-wetting tensional treatments.To improve the nano-rigid material filling composite method to strengthen the matrix fiber forming process,polyvinylidene fluoride/carbon nanotube composite fibers is selected for study.Torsional drawing method is employed to get an synergistically enhanced softening,via inducing macro-molecular three-dimensional helical rearrangement of fibers.The internal macro-molecular conformation and fiber softness of polyvinylidene fluoride/multi-walled carbon nanotubes composite fibers were investigated systematically with and without tensional twisting treatments.Results indicate that when the mass fraction of carbon nanotubes increases from 0 to 1.5%,the β-phase crystal content in the composite fiber increases,the tensile strength of the fiber increases from 4.71 cN/dtex to 5.19 cN/dtex,and the initial modulus from 16.80 cN./dtex increases to 20.52 cN/dtex;however after torsion and softening treatment,the initial modulus of the carbon nanotube reinforced composite fiber decrease as high as 62.5%,which significantly improving the fiber flexibility.