Microfibrillation Behavior And Enhancement Mechanism Of Poly(Styrene-Acrylate)/Halloysite Hybrid Microspheres In PMMA Fibers

With the continuous rise of the status of industrial textiles in China’s textile field,the demand for high-performance chemical fibers continues to increase,but at present,the technical level of high-performance fibers in China is relatively backward,and the overall output is insufficient,so it is necessary to increase the research and development of highperformance fibers and increase the output of composite fibers.In situ microfibrillation is a simple processing,convenient manufacturing of composite material production method,which can effectively improve the mechanical properties of composite materials.However,due to the influence of microfiber strength,the upper limit of composite fiber performance is obvious,so the project prepared a structure in which one-dimensional nanotubes are arranged in orientation within microfibers,and studied the formation mechanism and properties of its structure.In this project,different dispersed phase microspheres were prepared by blending Halloysite(HNTs),styrene(St),methyl methacrylate(MMA)and butyl acrylate(BA)by in situ suspension polymerization.Using the above-mentioned composite microspheres as the dispersion phase and polymethyl methacrylate as the continuous phase,microfibrillated composite fibers are prepared by shear-extrusion-drawing.The morphological changes of dispersed phase microspheres in the shear-extrusion-drafting process were observed by the multi-point sampling method,the microfibrillation mechanism of composite microspheres was revealed,and the mechanical properties were tested.The specific findings are as follows:(1)Chemically modified Halloysite(HNTs)are treated and characterized.The experimental results show that the double bonds provided by 3-(trimethoxysilyl)propyl methacrylate(MPS)grafted HNTs can be used to graft polystyrene to form polystyrene grafted Halloysite(PMHNTs),and the MPS and polystyrene grafted by HNTs are 1.13 wt.%% and 8.48 wt.%,respectively.(2)Poly(styrene-acrylate)microspheres of different monomer compositions were prepared by suspension polymerization as dispersion phases,and composite fibers were prepared by blending with PMMA by micro twin-screw extruders.Experimental results show that dispersed phase microspheres correspond to different morphological changes in the shear-extrusion-drafting process,and the microspheres form ellipsoidal particles of uniform size in the shear flow field,and the extrusion flow field appears to form large diameter microfibers,and the microfibers continue to extend to form nanofibers under the action of the drawn flow field.However,the microfiber formed by adding a dispersed phase of a soft monomer is the finest and the composite fiber has the lowest strength.The poly(styrene-methyl methacrylate)(PSM)microsphere microfiber has high strength and excellent mechanical properties,and compared with pure PMMA,the tensile strength and elongation at break are increased by 10.85% and 152.81%,respectively.(3)During the polymerization process,polystyrene grafted Halloysite(PMHNTs)were added to the PSM to prepare poly(styrene-methyl methacrylate)@ polystyrene grafted Halloysite(PSM@PMHNTs)microspheres,and the scanning electron microscopy showed that the PMHNTs within the microspheres were evenly distributed.The results show that PSM@PMHNTs will tear under shear action to form uniformly sized pellets,and PMHNTs inside the microspheres exist in free orientation form;Under the action of extrusion,microspheres appear end-to-end to form microfibers,and PMHNTs in microfibers begin to orient;With the extension of the microfibers to form nanoscale microfibers,the PMHNTs in the microfibers form an orientation arrangement structure,and the axial orientation angle of more than 75% of the PMHNTs present is less than 15°.This method forms a special orientation structure in the polymer matrix of inorganic particle orientation arrangement within microfibers.However,when the PMHNTs content is too high,a large number of nanoscale microspheres formed during the preparation of microspheres will appear end-to-end to form microfibers during the stretching process.(4)By comparing the PMHNTs content and the influence of the drafting ratio(DR)on the mechanical properties of composite fibers.It is concluded that when the PMHNTs content in PSM microfibers is 5 wt.%,DR=6,the mechanical properties of composite fibers are the most excellent,and the tensile strength and elongation at break are68.94±3.07 MPa and 31.30±3.12%,which are 26.94% and 256.36% higher than pure PMMA.The reason for the improvement of the mechanical properties of composite fibers is that PMHNTs can effectively improve the strength of microfibers,while microfibers can hinder the expansion of cracks and connect the substrates on both sides of the crack to play a bridging role.