Improved Melt Processabilities of Thermosetting Polyimide Matrix Resins for High Temperature Carbon Fiber Composite Applications

• Published in: Polymers 2022-02, Vol.14 (5), p.965
• Main Authors: Zhang, Hao-Yang, Yuan, Li-Li, Hong, Wei-Jie, Yang, Shi-Yong
• Format: Article
• Language: English
• Subjects: Acids; Carbon fiber reinforced plastics; Carbon fibers; Diamines; Diesters; Elongation; Ethanol; Experiments; Glass transition temperature; Heat resistance; High temperature; Mechanical properties; Nitrogen; Polymers; Resins; Room temperature; Shear strength; Temperature scales; Tensile strength; Thermal stability; Thermodynamic properties; Viscosity
• ISSN: 2073-4360; 2073-4360
• DOI: 10.3390/polym14050965

With the goal of improving processability of imide oligomers and achieving of high temperature carbon fiber composite, a series of Thermosetting Matrix Resin solutions (TMR) were prepared by polycondensation of aromatic diamine (3,4'-oxybisbenzenamine, 3,4-ODA) and diester of biphenylene diacid (BPDE) using monoester of 4-phenylethynylphthalic acid (PEPE) as end-capping agent in ethyl alcohol as solvent to afford phenylethynyl-endcapped poly(amic ester) resins with calculated molecular weight (Calc'd M ) of 1500-10,000. Meanwhile, a series of reactive diluent solutions (RDm) with Calc'd M of 600-2100 were also prepared derived from aromatic diamine (4,4'-oxybisbenzenamine, 4,4-ODA), diester of asymmetrical biphenylene diacid (α-BPDE) and monoester of 4-phenylethynylphthalic acid (PEPE) in ethyl alcohol. Then, the TMR solution was mixed with the RDm solution at different weight ratios to afford a series of A-staged thermosetting blend resin (TMR/RDm) solutions for carbon fiber composites. Experimental results demonstrated that the thermosetting blend resins exhibited improved melt processability and excellent thermal stability. After being thermally treated at 200 °C/1 h, the B-staged TMR/RDm showed very low melt viscosities and wider processing window. The minimum melt viscosities of ≤50 Pa·s was measured at ≤368 °C and the temperature scale at melt viscosities of ≤100 Pa·s were detected at 310-390 °C, respectively. The thermally cured neat resins at 380 °C/2 h showed a great combination of mechanical and thermal properties, including tensile strength of 84.0 MPa, elongation at breakage of 4.1%, and glass transition temperature (T ) of 423 °C, successively. The carbon fiber reinforced polyimide composite processed by autoclave technique exhibited excellent mechanical properties both at room temperature and 370 °C. This study paved the way for the development of high-temperature resistant carbon fiber resin composites for use in complicated aeronautical structures.