Thermoset polymer scaling effects in the microbond test

The curing performance of two epoxy resin systems has been investigated using the microbond test and FTIR spectroscopy. A novel sample preparation technique involving curing epoxy droplets on thin steel filaments allowed for high-throughput determination of microbond droplet cure state using a conventional benchtop spectrometer. Parity between steel filament and glass fibre microbond samples was confirmed by infrared microspectroscopy. It is shown that cure schedules used in the manufacture of composite parts produced microbond droplets with degrees of cure lower than that of bulk matrix specimens subjected to an identical thermal history. For a commercial resin system, testable microbond droplets could only be produced when a room temperature pre-curing time of at least 2 hours was introduced. It is concluded that microbond testing be supported by some method of droplet cure state characterisation to ensure that interfacial effects are not artefacts of droplet sample preparation