Codeposition of Polyethyleneimine/Catechol on Fully Drawn Polyester Fiber‐Bundles for Investigating Interfacial Properties with Epoxy Resin

Mussel‐inspiration is extensively utilized for multifunctional modification on the surface of universal materials. Polyphenols are more and more exploited for mussel‐inspired chemistry to replace polydopamine owing to their ubiquitousness and inexpensiveness. Herein, to explore the interfacial properties between fully drawn yarn (FDY) polyester fiber‐bundle and epoxy matrix, codeposition of polyethyleneimine/catechol (PEI/CCh) is used to modify FDY polyester fiber‐bundles by mussel‐inspired method. The orthogonal experiments are performed to obtain the optimum formula which is 2 g L−1 PEI, 1 g L−1 CCh, and 24 h codeposition time. The results of surface structure characterization measured via Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, scanning electron microscope, and energy dispersive X‐ray indicate that PEI/CCh aggregates are uniformly coated on fiber surface to fabricate continuously lamellar structures. The surface hydrophilicity and water infiltration rate constant are acquired by water contact angle. These results elucidated that FDY fiber surface is successfully endowed with polyethyleneimine/catechol aggregates and surface hydrophilicity greatly improved. Single fiber‐bundle pull‐out tests are conducted to evaluate the interfacial strength. Compared to pure fiber‐bundle specimens, there are 67.57%, 57.63%, and 45.07% increase of initial debonding load, peak load, and interfacial shear strength, respectively. Polyethyleneimine/catechol (PEI/CCh) codeposition aggregates are coated onto fully drawn yarn (FDY) polyester fiber‐bundle surface. The surface structure characterization reveals that the PEI/CCh aggregates are equably formed on fiber surface. Water contact angle analysis indicates that the surface wettability is enhanced, which accelerates interfacial strength. The coated FDY is incorporated with epoxy resin to improve the interfacial adhesion.