Preparation And Properties Of Novel Vinyl Sizing Agent For Carbon Fiber

Vinyl resin(VE)has excellent mechanical properties,high corrosion resistance,high hydrolysis resistance,etc.Lightweight and designable carbon fiber reinforced vinyl resin(CF/VE)composite materials are widely used in national defense and transportation,high-end sporting goods,marine structural composite materials and other fields.The surface of carbon fiber(CF)is inert and non-polar,which is not conducive to the physical and chemical interaction between the fiber and VE,resulting in poor interfacial adhesion.When CFRP is subjected to excessive load,the failure often occurs first in the interface phase,and the interface adhesion is closely related to the interaction between carbon fiber and the polymer matrix and the molecular structure of the interface.Therefore,surface modification of CF improves the performance of CF/VE composites.Interface bonding performance is the prerequisite for its practical application.Sizing treatment has the advantages of strong design and low cost,and is currently the most used carbon fiber surface treatment method in industrialization.However,there are few vinyl emulsion sizing agents that can meet the needs of practical applications and endow CF/VE with high interfacial strength.Therefore,this topic prepares an environmentally friendly vinyl emulsion sizing agent to enhance the interface properties of CF/VE composites from the perspective of interfacial covalent bonding,thereby improving the comprehensive mechanical properties of CF/VE composites.In this paper,polyethylene glycol(PEG)with different molecular weights(1000/2000/3000/4000),2,4-toluene diisocyanate(TDI),epoxy resin(E44),allyl polyethylene glycol(APEG)and N-methylol acrylamide(NMA)were used as reaction raw materials to synthesize NY with hydrophilic group(ether bond),oleophilic group(amide group,ester group,benzene ring)and active reaction functional group C=C.Resin NE with functional group C=C at both ends of molecular chain was prepared by modifying epoxy resin E51 with N-hydroxymethyl acrylamide(NMA).The emulsion sizing agent were prepared by reverse emulsification,and the mass ratio of different main sizing materials and resins was optimized.Using the main slurry NY3000 and resin NE,the mass ratio(NY:NE=1:2),the prepared sizing agent NY-NE has the best stability and the smallest particle size distribution,the average particle size is 203.0 nm,the centrifugal precipitation is 0.049 g,the solid content of the upper emulsion is 0.58%,and the emulsion NY-NE(2.0 wt%)can be statically stored for three months without demulsification and stratification.The surface morphology and surface functional groups of carbon fibers before and after sizing were analyzed by scanning electron microscopy(SEM),atomic force microscopy(AFM)and X-ray photoelectron spectroscopy(XPS).SEM and AFM images show that after sizing,a uniform sizing layer is attached to the surface of the carbon fiber to make the grooves on the surface of the fiber shallow.XPS results show that the surface of NCF with sizing agent NY-NE has more oxygen-containing functional groups and more C=C(20.62%),NCF fiber surface(O+N)/C value of 0.32 compared with UCF(0.11)increased by 190.9%.As NY-NE sizing fibers have more C=C on the NCF surface,the ILSS of NCF/VE is 62.44MPa,which is higher than that of UCF/VE(36.88 MPa).69.3%,the storage modulus of NCF/VE is 86.73 GPa,T_g is 139.09℃,which is 101.8%and 15.8%higher than that of UCF/VE,and the highest flexural strength and flexural modulus are 805.65 MPa and 55.65GPa,respectively.