Modification of polyetherimide by phenylethynyl terminated agent for improved tribological, macro- and micro-mechanical properties

The incorporation of 4-phenylethynylphthalic anhydride (4-PEPA) was utilized to synthesize a series of phenylethynyl terminated oligomers, according to different calculated number-average molecular weight (Mn). Modified polyetherimide (PEI) resins were prepared by the thermal curing reaction of phenylethynyl terminated etherimide oligomers. For comparison, unmodified PEI was also prepared. Thermal, macro- and micro-mechanical characterizations showed that the incorporation of phenylethynyl terminated agent resulted in a significant increase in glass transition temperature (Tg), tensile strength and microhardness. The tribological properties of PEI specimens were evaluated on a reciprocating friction and wear testing machine. Higher wear resistance was achieved by the incorporation of phenylethynyl terminated agent. Furthermore, wear rate of modified PEI prepared from the oligomers with the calculated Mn of 5000 g/mol was about five times lower than that of unmodified PEI. At least for the range of this study, while increasing calculated Mn of oligomers, wear rate of modified PEI initially decreased sharply and then increased slightly. This is clearly related to the change in the macro- and micro-mechanical properties. Scanning electron microscope (SEM) observations of worn surfaces showed that type of wear changed from abrasive wear of unmodified PEI into fatigue wear.