Table 2. Thermal Properties of Electrospun Fibers: PHB, pec-PHB2, pec-PHB5, pec-PHB10, and pec-PHB20.
| electrospun fibers | thermal decomposition temperature, Tda (°C) | residueb (%) | glass-transition temperature, Tgc (°C) | cold crystallization temperature, Tccc (°C) | heat of cold crystallization, ΔHccc (J g–1) | melting temperature, Tmc (°C) | heat of melting, ΔHmc (J g–1) | degree of crystallinity, Xcd (%) |
|---|---|---|---|---|---|---|---|---|
| PHB | 247.75 | 0.98 | 0.07 | 36.32 | 3.34 | 149.63 | 77.52 | 50.81 |
| pec-PHB2 | 242.76 | 1.30 | 6.76 | 161.00 | 79.27 | 53.21 | ||
| pec-PHB5 | 250.68 | 1.47 | 3.07 | 41.57 | 1.77 | 161.20 | 77.97 | 49.40 |
| pec-PHB10 | 257.40 | 1.86 | 2.22 | 40.45 | 1.97 | 158.85 | 72.93 | 43.77 |
| pec-PHB20 | 247.27 | 3.13 | 0.14 | 37.96 | 5.35 | 158.06 | 68.89 | 34.82 |
a
Td is defined as the temperature at which the mass of the sample has a 5% weight loss, determined by TGA.
b
Residue is defined as the mass percentage of the sample at 500 °C, determined from TGA.
c
Tg, Tcc, ΔHcc, Tm, and ΔHm were deduced from the second heating curve by DSC. Tm was taken as peak maxima. ΔHm and ΔHcc were determined from the endothermic melting peak and exothermic cold crystallization peak, respectively.
d
Xc was
calculated using the following equation
where ΔHmO is a reference
value, which represents the heat of melting for 100% crystalline PHB,
146 J g–1.69Xc values were normalized based on the mass percentage
of PHB segments in the fibers: 100% for PHB, 98% for pec-PHB2, 95%
for pec-PHB5, 90% for pec-PHB10, and 80% for pec-PHB20.
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