Preparation And Characterization Of Nylon 6 Micro/nano Fibers By In Situ Anionic Polymerization Based On Reactive Extrusion

Polyamide 6(PA6)micro/nano fibers are widely used in the fields of clothing fabric,ultra-fine fiber leather,high-performance filter,high-performance wipe cloth and biological medicine due to their low monofilament density,outstanding wear resistance,good resilience,heat resistance and high strength.PA6 micro/nano fibers have been a research focus.Direct spinning,electrostatic spinning,composite spinning and blending spinning are the main methods used at present.However,these methods have the disadvantages of volatile solvent,difficult continuous production and low fiber yield.In this paper,PA6 micro/nano fibers were prepared from styrene(St)and caprolactam(CL)by reactive extrusion in situ anionic process and PA6 nanofibers modified by PA12 and GNs were also studied.Firstly,PA6 micro/nano fiber was prepared by reactive extrusion in situ anionic polymerization using a twin screw extruder as the reactor.The influence of the drawing ratio on the performance of PA6 micro/nano fibers was studied via heat drawing.The results showed that the crystallinity of PA6 micro/nano fibers is improved by the drawing and the transition of PA6 crystal structure between ? and ? crystals appeared.With the increase of the draw,the melting point and thermal decomposition temperature increased 9? and 35? respectively and the fiber diameter was gradually reduced.The final results showed that 3 times of the drawing ratio is the best for PA6 micro/nano fibers,the crystallinity,melting temperature and diameter of PA6 micro/nano fibers were 14.1%,217.8?,fiber 0.8?m respectively.Secondly,PA12 modified PA6 micro/nano copolymer fibers were prepared by reactive extrusion in situ anionic polymerization with laurolactam(LL),CL and PS as raw materials with the content ratio of polyamide to PS was regulated to be 60/40.The properties of micro/nano copolymer fibers with LL content of 5 wt%,15 wt%,25 wt% and 35 wt% were studied,the results showed that the addition of LL promotes the fibrillation and thermal stability of micro/nano fibers.When the content of LL reaches 25 wt%,the thermal decomposition temperature reaches to 472?,which indicates that the thermal resistance of PA 6 is the best.However,the melting point of PA12-co-PA6 fibers reached to 204.2? with the addition of 5 wt % LL.Due to the increase of the number of hydrogen bonds in the molecule resulted from the increasing LL content,? crystal was formed and the wave of methylene in FTIR showed red shift.Thirdly,the effect of graphene(GNs)on the properties of in-situ anionic polymerization PA6/PS(60/40)blends by reactive extrusion were studied.The results showed that when the content of GNs was 25 wt%,the elongation at break was increased to 306% and the tensile strength was up to 59 Mpa.With the increasing GNs content,the CL conversion rate increased and all of them were above 90%.The maximum thermal decomposition temperature reached to 453?.GNs was selectively distributed in PA6 dispersed phase with 5 wt% addition.The crystallization temperature of melting point is 215.4??185.2?,the crystallinity of 15.8%.At last,melt spinning assisted by reactive extrusion in situ anionic polymerization was used to prepare PA6 ultrafine fiber based on PA6/PS(60/40)blend.Subsequent drawing treatment was conducted to study the influence of drafting on the performance of PA6 ultrafine fiber.The results showed that the diameter of the fiber decreased gradually with the increase of the drawing rate and coarse granular material appeared on the surface.The diameter of the fiber could reach to 500 nm.By controlling drawing,PA6 micro/nano fibers with controllable crystal shape can be obtained.After drawing,the melting point can be increased to 225?,melting point crystallinity was improved.