Abstract
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 Mw) of 1500–10,000. Meanwhile, a series of reactive diluent solutions (RDm) with Calc’d Mw 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 (Tg) 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.
Highlights
Aromatic polyimide materials such as films, fibers, engineering plastic, matrix resins and coatings, due to their excellent combined thermal, mechanical and electrical properties [1,2], have been extensively used in many high-tech industries such as aerospace and aviation [3–5], microelectronics [6–8] and opto-electric display [9–11], etc
The first generation of high temperature resistant polyimide resin represented by PMR-15 can be used at 316 ◦C for a long time, and its carbon fiber composites have excellent mechanical properties, while the melt viscosity is lower than 100 Pa·s, which is suitable for hot press tank process [18,19]
Wu et al have synthesized a carborane-containing monofunctional imide monomer (CB-phenylethynyl phthalic anhydride (PEPA)), which was used as a reactive diluent for phenylethynyl-terminated imide oligomer (PETI) to reduce the minimum melt viscosity and broaden the process window of composite
Summary
Aromatic polyimide materials such as films, fibers, engineering plastic, matrix resins and coatings, due to their excellent combined thermal, mechanical and electrical properties [1,2], have been extensively used in many high-tech industries such as aerospace and aviation [3–5], microelectronics [6–8] and opto-electric display [9–11], etc. The second generation of high temperature resistant polyimide resin represented by PMR-II-50 adopts 6FDA monomer containing -CF3 structure, and the long-term use temperature reaches 371 ◦C, but the resin has high melt viscosity, poor flowability, and easy to prepare composites with high porosity [20,21]. For this reason, mostly used in hot molding to prepare bearings and bushings for aircraft, etc. Wu et al have synthesized a carborane-containing monofunctional imide monomer (CB-PEPA), which was used as a reactive diluent for phenylethynyl-terminated imide oligomer (PETI) to reduce the minimum melt viscosity and broaden the process window of composite. The influence of Calc’d Mw of the reactive diluents as well as thermosetting poly(amic ester) resins on the melt processability, thermal and mechanical properties of the thermosetting blend resins have been systematically investigated
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