Synthesis of polyamic acid macromolecular coupling agent emulsion and its interface modification of recycled glass fiber-reinforced high-temperature nylon
To enhance the application value of recycled glass fibers(rGF)in reinforced high-temperature nylon composites,a high-temperature-resistant glass fiber sizing agent for rGF surface treatment was prepared.4,4'-Oxydiphthalic anhydride(ODPA)was used as the dianhydride monomer and 4,4'-Oxydianiline(ODA)as the diamine monomer to synthesize polyamic acid(PAA),which then reacted with γ-Aminopropyltriethoxysilane(KH550)to obtain the polyamic acid macromolecular coupling agent(PAA-KH550).By adjusting the ratio of ODPA to ODA monomers,a self-emulsifying PAA-KH550 emulsion with stable dispersion was prepared.The particle size,chemical structure,and high-temperature resistance of the emulsion and the cured film of PAA-KH550 emulsion were tested by laser particle size analyzer,Fourier transform infrared spectrometer,and thermogravimetric analyzer.The morphology,single filament performance,wettability,and interfacial shear strength with polyamide 46(PA46)of the GF coated with the emulsion were tested by scanning electron microscope,single fiber strength machine,automatic surface tension meter,and composite material interface evaluation device.The results show that the average particle size of the emulsion is 110-125 nm,and the particle size distribution is small;the high-temperature resistance of the cured film of PAA-KH550 emulsion is better than that of the cured film of PAA emulsion,and its 5%thermal decomposition temperature(Td5)is above 350 ℃;the prepared emulsion can form a uniform film on the surface of rGF,and effectively compensate for the surface defects of the fiber,thereby improving the mechanical properties of rGF.In addition,the coating formed on the fiber surface after the emulsion is cured can effectively improve the surface energy of the fiber,which helps to improve the interfacial bonding performance of GF and PA46;the experimental measurement shows that the interfacial shear strength(IFSS)of the GF/PA46 composite material treated with PAA-KH550 emulsion reaches up to(31.29±6.39)MPa,which is 37%higher than that of the sample without emulsion treatment.The prepared water-based PAA emulsion and PAA-KH550 emulsion with stable dispersion,when applied to the surface of rGF,can effectively restore the comprehensive performance of rGF,and at the same time can improve the interfacial bonding with PA46,improve the high-temperature performance and mechanical properties of rGF/PA46 composite materials,and provide a new scheme for the application of rGF in high-performance composites.
recycled glass fiberpolyamide acidmacromolecular coupling agenthigh-temperature nyloncomposite material