Enhanced interfacial adhesion of fibers to thermoplastic. Comparison of polyaramid and glass

An argon plasma processing technique was investigated in an attempt to improve adhesion of Kevlar and glass to polycarbonate (PC). This technique involves exposing a fiber to the plasma and then immediately coating the fiber with a polycarbonate melt while still in the vacuum environment of the plasma reactor. A statistical analysis showed that the plasma processing did not decrease the strength of the Kevlar or glass, and did not change the fiber diameter. The single filament composite test was used to investigate the effect of the plasma treatment upon interfacial shear strength between fiber and thermoplastic. For Kevlar it was found that 4.1 seconds of 24 Watt plasma exposure followed by immediate coating produced nearly a 20% increase in interfacial shear strength compared to the non-treated control. When the plasma treated Kevlar was exposed to air for one hour before coating, no increased adhesion was observed. These results are very similar to a previous study which used O2 plasma in an identical plasma treatment. On glass fiber, no increase in interfacial shear strength was found over a wide range of plasma powers and exposure times.