Wang Zhi-liang, Li Jie-fu, Nie Jing, Yang Shu-guang. Effect of Hydrothermal Treatment on Structure and Properties of Polyamide 6 Fibers[J]. Acta Polymerica Sinica, 2016,(12):1710-1716.
Wang Zhi-liang, Li Jie-fu, Nie Jing, Yang Shu-guang. Effect of Hydrothermal Treatment on Structure and Properties of Polyamide 6 Fibers[J]. Acta Polymerica Sinica, 2016,(12):1710-1716. DOI: 10.11777/j.issn1000-3304.2016.16109.
Hydrothermal treatment of polyamide 6 (PA6) fibers at 150℃ was studied.Different characterization and measurement were used to investigate the structural transformation and mechanical properties of PA6 fibers after hydrothermal treatment
which included two dimensional wide angle X-ray diffraction (2D-WAXD)
two dimensional small angle X-ray scattering (2D-SAXS)
differential scanning calorimeter (DSC)
field emission scanning electron microscope (FE-SEM) and single fiber strength test.Under hydrothermal condition
the movement of the molecular chains was enhanced due to permeability of water molecules
which led to structure changes in PA6 fibers.After hydrothermal treatment
the crystal structure of the fibers transformed from γ into α phase
crystallinity degree increased from 25.2% to 45.9%
crystalline perfection was improved and crystallite size became bigger.Hence
the melting peak temperature of the fibers increased from 220.6℃ to 227.7℃ and the melting enthalpy also increased.In addition
the molecule chains in the amorphous region began to crystallize and grew along the radial direction of the fiber to form a crystal lamellae structure during hydrothermal treatment.At 150℃
ellipsoidal micro-pores formed in the fiber
which could be monitored by 2D-SAXS test.The hydrothermal treatment also caused changes of the fiber surface morphology.After the hydrothermal treatment
the smooth surface of the original fiber became rougher and a large number of macro-pores were formed on the surface.However
the micro-and macro-pores in fibers almost did not affect the melting temperature of the fibers.The crystal lamellae in fibers showed very weak orientation
but tensile could promote the lamellae orientation.When tensile strain increased from 0 to 50.7%
the average long period of lamellae increased from 10.6 nm to 14.8 nm.The hydrothermal treatment induced the reduction of amorphous region in the fibers and the formation of micro-and macro-pores
which resulted in the lower breaking strength and elongation of PA6 fibers.