High mechanical performance short carbon fiber reinforced polyetherimide composites via solution mixing process

Proper preparation processes of short fiber reinforced thermoplastics are critical to achieving high residual fiber lengths in final composites, which in turn greatly influences the mechanical properties of short fiber reinforced polymers. In this work, the injection molding process was respectively combined with conventional extrusion compounding and a newly developed solution mixing process to fabricate short carbon fiber (SCF) reinforced polyetherimide (PEI) composites. Carbon fiber-filled PEI master batches were prepared for injection molding respectively by conventional extrusion compounding (denoted by CE-MB) and solution mixing process (denoted by SM-MB) diluted with PEI powders. Afterwards, the corresponding two types of composites (SCF/PEIE and SCF/PEIS + D) were prepared by injection molding. Compared with the SCF/PEIE composites, the SCF/PEIS + D composites exhibit significantly enhanced mechanical performances due to greatly higher residual fiber lengths in final composites. As a result, the 20 vol fraction (vol%) SCF/PEIS + D composite obtained shows a record high tensile strength of 239.6 MPa for injection molded PEI composites. Moreover, it is worth mentioning that the tensile strength of the SCF/PEIS + D composite with only 5 vol% SCFs is even higher than that of the SCF/PEIE composite with 25 vol% SCFs. Consequently, the injection molding process combined with the newly proposed solution mixing process is promising to replace the conventional extrusion process for developing high mechanical performance short fiber reinforced high-performance thermoplastic composites, particularly for the cases with low to medium fiber contents (<= 25 vol%).