Design And Preparation Of PP-g-MAH Nanofibers Aggregates

With the rapid development of economy and society,the emission of water pollutants（mainly the leakage of crude oil in the ocean,industrial wastewater and domestic sewage）poses a significant threat on the ecological environment protection.Therefore,it is imminent to develop efficient and convenient water treatment methods.Nanofiber materials are widely used in filtration,adsorption and other fields due to its advantages of large specific surface area,high porosity and so on.In this paper,polypropylene grafted maleic anhydride（PP-g-MAH）nanofibers were prepared by a cost-effective melt blending phase separation method,and two-dimensional nanofiber membranes and three-dimensional nanofiber aerogels were designed and hydrophobized.The basic structure and oil-water separation properties of nanofiber membranes and aerogels were investigated by field emission scanning electron microscopy（FESEM）,Fourier transform infrared spectroscopy（FTIR）,automatic surface area and pore size analyzers automatic video contact angle testers and electronic universal material testing machines.PP-g-MAH nanofibers were prepared by melt-extrusion phase separation method.Polypropylene（PP）non-woven fabrics were used as the base film to prepare PP-g-MAH nanofiber membranes with controllable quality by high-speed airflow deposition method.The structural properties were analyzed.With the increase of nanofiber mass per unit area,the porosity of the film increased from 64.84% to 76.92% and then tended to be relatively balanced;the maximum contact angle was 138.7° which indicated that was a highly hydrophobic material.The mechanical properties also came into enhancement,resulting in the tensile strength of nanofiber membrane reach 2.35 MPa after heat treatment.PP-g-MAH nanofiber membranes had different adsorption effects on different types of oils and organic solvents,which had the best absorption effect on pump oil and carbon tetrachloride reaching respectively 17 times and 21 times their own weight.And the adsorption rate revealed very fast.1g PP-g-MAH nanofiber membrane could still float on the surface after completely adsorb 11.09 g of surface oil within 6s.PP-g-MAH nanofibers were cut into a suspension by a high-speed dispersion and a threedimensional network PP-g-MAH nanofiber aerogel was prepared by freeze-drying.The effects of different types and concentrations of cross-linking agents on the structure and properties of nanofiber aerogels were studied.As a result,the nanofiber aerogel exhibited a good shape with 1,5-pentanediol as the cross-linking agents.With the concentration of 1,5-pentanediol increased,the porosity of PP-g-MAH nanofiber aerogels gradually decreased,while the hydrophobicity and mechanical properties increased obviously.When the volume of the cross-linking agent was 400 μL in the 30 m L suspension,the porosity of aerogels could reach 98.28%,and the water contact angle would be up to 152.6° after the hydrophobic treatment（superhydrophobic）.Specially,the compressive stress could reach 5.42 KPa at the strain of 60%.PP-g-MAH nanofiber aerogels had different adsorption effects on various oils and organic solvents and the absorption capacity of PPg-MAH nanofiber aerogels could range from 43 to 94 times their own weight.The result was almost four times higher than that of nanofiber membranes.Silica（SiO₂）nanoparticles were introduced to prepare PP-g-MAH/SiO₂ nanofiber composite aerogels and the superhydrophobic composite aerogels were obtained after a simple chemical vapor deposition.With the concentration of SiO₂ increased in composite aerogels,the water contact angle of PP-g-MAH/SiO₂ nanofiber composite aerogel increased significantly,which could reach 144.8°.The porosity of composite aerogels increased to 98.75%,and the specific surface area increased 6 times.In addition,after the introduction of SiO₂ nanoparticles,the mechanical properties of the nanofiber composite aerogel significantly increased from 5.42 KPa to 11.37 KPa at the strain of 60%.The water contact angel of PP-g-MAH/SiO₂ nanofiber composite aerogel could reach 157.5° after hydrophobization,and the obtained hydrophobized samples exhibited excellent oil-water separation performance.PP-g-MAH nanofiber aerogels had different adsorption effects on various oils and organic solvents and the absorption capacity of PP-g-MAH nanofiber aerogels could range from 43 to 94 times their own weight.This result was comparable to that of PP-g-MAH nanofiber aerogels.