The glass transition temperature, Tg, of all the bulk samples was measured using dynamic-mechanical thermal analysis (DMTA) with a Q800 DMA from TA Instruments, UK. A double-cantilever mode at 1 Hz was employed using test specimens 60 × 10 × 3 mm3 in size. The temperature range used was −100 °C to 200 °C with a heating rate of 4 °C/min. The value of Tg was determined at the peak value of tan δ. The number average molecular weight between cross-links, Mnc, was also calculated from the equilibrium modulus in the rubbery region, Er, using [20](1)Mnc=qρRT/Erwhere T is the temperature in K at which the value of Er was taken, ρ is the density of the epoxy at the temperature T, the term R is the universal gas constant, and q is the front factor. As the density of the epoxy was only measured at room temperature, the value of the front factor, q, was taken to be 0.725, as in previous work [21]. The density, ρ, of the epoxy was measured at room temperature according to BS ISO 1183-1 Method A [22] to be 1.20 g/m3 at 20 °C.
double-cantilever mode
1 Hz
Hz
test specimens
size
60 × 10 × 3 mm3
mm3
temperature range
−100 °C to 200 °C
°C
heating rate
4 °C/min
°C/min
epoxy
room temperature
front factor
0.725
epoxy
room temperature
epoxy
density
1.20 g/m3
g/m3
room temperature
20 °C
°C