Effect of water-soluble thermoplastic polyimide sizing agent on interfacial properties of domestic high strength and high modulus carbon fiber reinforced composites

Abstract

The water-soluble thermoplastic polyimide sizing agent was synthesized from bisphe- nol A-type diether diether dianhydride (BPADA), m-phenylenediamine and 4, 4′-(1, 3-phenylenedioxy) dianiline (TPE-R). The surface of domestic high-strength and high-modulus carbon fiber (HMCF) was sized and prepared into composite material. The effects of molar ratios of different monomers on the characteristics of the sizing agent and the surface structure properties of the fibers after sizing treatment were studied, and the effects of thermoplastic sizing agents on the interfacial properties of domestic high-strength and high-modulus carbon fiber reinforced thermoplastic polyetherketone (PEKK) resin matrix composites were further analyzed. The results show that when the monomer molar ratio of BPADA to TPE-R is 1∶1, the synthesized thermoplastic sizing agent not only has a uniform molecular weight distribution, but also has excellent thermal stability, e.g. its thermal weight loss is only 5% with the temperature up to 554 ℃. After sizing, the surface O/C ratio is increased from 0.08 to 0.18 (increased by 125%). Besides, the fiber strength is slightly increased and the modulus is almost unchanged. More importantly, the interfacial performance of the composites is significantly improved after sizing treatment, and the interlaminar shear strength of the HMCF/PEKK composites can be improved from 38.5 MPa to a maximum of 59.4 MPa with an increase of up to 54.3%.

Keywords

• sizing agent
• composite material
• polyimide
• polyetherketone