Optimization of interface microstructure of high‐strength‐high‐modulus polyimide fibers composites utilizing waterborne polyamide and hybrid sizing agent

Abstract

The weak interface adhesion between high‐strength‐high‐modulus polyimide (PI) fibers and epoxy (EP) resin matrix has seriously hampered the application of PI/EP composites. Herein, a waterborne polyamide (WPA) sizing agent was used to modify PI fibers to enhance the interface adhesion strength between the PI fibers and EP resin matrix. The surface characteristics of PI fibers were investigated to determine chemical composition, morphology, roughness, wettability, interfacial shear strength (IFSS) and interlinear shear strength. The results indicated that the WPA sizing agent significantly enhanced the interface adhesion properties between the PI fibers and EP resin matrix with a 132% and 22.35% increment obtained for IFSS and interlaminar shear strength (ILSS) compared with unsized PI/EP composites. Then, the hybrid sizing agent generated by WPA and waterborne EP sizing agent exhibited the highest interface adhesion with 168.65% and 28.62% increment obtained for IFSS and ILSS compared with unsized PI/EP composites. Based on these results, a sizing mechanism with chemical interaction and mechanical interlocking was proposed, which provides an effective and feasible method to enhance the interface adhesion between the PI fibers and EP resin matrix.

Conductive Network Enhanced Carbon Black/Epoxy Composite Coating with Imide Curing for Antistatic and Heat-Resistance Improvement

“…As shown in Fig. 1a, the peaks at δ=7.19-7.30 (d, 4 H) were corresponds to the four hydrogens (14,16,20,24) on the benzene ring, the peaks at δ=7.48-7.59 (d, 4 H) were corresponds to the four hydrogens (13,17,21,23) on the benzene ring, the peaks at δ=8.03-8.13 (d, 2 H) were corresponds to the two hydrogens (6,35) on the imide, the peaks at δ=8.31-8.47 (m, 4 H) were corresponds to the four hydrogens (1,3,32,34) on the imide. The peak at 2.5 is deuterium DMSO reagent.…”

“…The common methods to improve the heat resistance of EPs include introduction of heat-resistant groups or rigid groups into the molecular structure of epoxy, use heatresistant curing agent, and use heat-resistant additives to reduce the free volume of epoxy curing material and improve the heat resistance of epoxy resin [17,18,19,20,21]. For example, the EPs containing epoxy-functionalized tung oil structure and primary diamine hardener decompose only at temperature higher than 360 °C, and the EPs containing waterborne polyamide salt solution decompose only at temperature higher than 403 °C [22,23]. Besides, the coating of stealth high-speed aircraft needs conductivity to achieve electromagnetic shielding effect [24,25,26,27,28].…”

Improving Interfacial and Compressive Properties of Polyimide Fiber by Constructing Inorganic Layers on Fiber Surface

“…Finally, it was cooled and the microsphere debonding sample was obtained. The details can be found in our previous work. , …”

Overmolded hybrid thermoset‐thermoplastic structures: Experimental study on the bonding strength of co‐curing thermoplastic film onto thermoset composite

“…15,16 Therefore, the combination of TSC and thermoplastic polymer opens new design possibilities for multimaterial structure. [17][18][19] Injection overmolding technique is an attractive method to fabricate multi-material structure, which eliminates the requirements for adhesive or mechanical fastening. 20 Kazan et al [21][22][23] firstly undertook a feasibility study on the overmolded hybrid thermoset-thermoplastic structure of thermoplastic polypropylene (PP) and thermoset CF/Epoxy prepreg.…”