2.3. Differential scanning calorimeter (DSC)
A three step method of alternating heating and cooling cycles was
used to determine the thermal transitions of the samples utilizing a
TA Instrument DSC model Q200. The first heating cycle was to reset
the thermal history of the polymer. The cooling cycle illustrated the
crystallization temperature and enthalpy, while the melting temperatures
were derived from the second heating cycle. Samples of 5–
10 mg were tested in a temperature range of 0 to 250 °C in a nitrogen
gas atmosphere, where it was heated at 10 °C/min and cooled at 5 °C/
min. The percentage of crystallinity (χc)was determined fromthe equation:
[20]
%Crystallinity ðXcÞ ¼ ΔHmelt
w ΔHref
100:
ΔHmelt is themelting enthalpy, ΔHref is themelting enthalpy of 100%
crystalline parent polymer (where the melting enthalpy of 100% PTT is
145.5 J/g [7] and PE is 293 J/g [21]), and w is a fraction of the polymer
added to the system by weight.