## 3 Results and Discussion
### Thermal Analysis of PHBV
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{5}{c}{**DSC**} & \multicolumn{5}{c}{**FTIR**} & **TGA** & \\ \cline{2-10}  & \(T_{g}\) & \(T_{m1}\) & \(T_{m2}\) & \(T_{C}\) & \(X_{c}\) & \(I_{C=O}\) & \(T_{onset}\) & \(T_{d}\) & \(T_{onset}\) \\ \cline{2-10}  & (\({}^{\circ}\)C) & (\({}^{\circ}\)C) & (\({}^{\circ}\)C) & (\({}^{\circ}\)C) & (\%) & & (\({}^{\circ}\)C) & (\({}^{\circ}\)C) & (\({}^{\circ}\)C) \\ \hline PHBV-15 & \(-0.7\) & 126.1 & 152.5 & 61.8 & 29.0 & 2.48 & 286 & 318 & 325 \\ PHBV-32 & \(-3.5\) & 150.9 & 166.5 & 107.1 & 19.3 & 2.18 & 304 & 329 & 336 \\ PHBV-39 & \(-5.3\) & 159.7 & 170.1 & 104.8 & 25.8 & 2.35 & 299 & 325 & 333 \\ PHBV-46 & \(-7.4\) & 153.8 & 165.3 & 80.0 & 21.6 & 2.25 & 297 & 325 & 331 \\ PHBV-61 & \(-7.2\) & - & 162.6 & 71.5 & 23.8 & 2.20 & 298 & 327 & 333 \\ PHBV-71 & \(-2.5\) & - & 155.6 & 56.5 & 16.6 & 2.28 & 295 & 322 & 332 \\ PHBV-78 & \(-1.6\) & 128.6 & 152.1 & 64.2 & 23.3 & 2.01 & 289 & 320 & 327 \\ PHBV-84 & \(-1.9\) & 130.9 & 153.1 & 66.4 & 24.3 & 2.59 & 294 & 326 & 331 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Physical and thermal properties of purified PHBV obtained from CHCl\({}_{3}\) extraction of biomass. of (20-60%) have been reported [50]. Another study had shown that PHBV (16.6% HV) extracted with NaClO and CHCl\({}_{3}\) had a \(T_{c}\) value of 109 \({}^{\circ}\)C [51]. TGA analysis was performed to determine the thermal degradation behavior of the purified PHBV samples (Table 4, and Supplementary Material Figure S2). All of the PHBV samples showed a 1-step degradation behavior. Based on the derivative thermogravimetric (DTG) curves the temperature at which the maximum weight loss occurred (\(T_{d}\)) was determined. The \(T_{d}\) values of the PHBV biopolymers was between 318 \({}^{\circ}\)C and 329 \({}^{\circ}\)C, which was higher than those reported in the literature for PHBV (\(T_{d}\) = 286 \({}^{\circ}\)C) [52] and PHB (280 \({}^{\circ}\)C) [53]. For PHB thermal degradation occurs just above its \(T_{m}\) which limits its processability [7]. The presence of 3 HV in PHBV lowers its \(T_{m}\) relative to \(T_{d}\) and thus improves its processing window for molding and extrusion [21; 31; 49; 54]. The thermal degradation of PHBV occurs in a single step due to a nonradical random chain scission process involving a six-membered ring transition state [24; 31; 52; 55]. The onset temperature of degradation was from 286.4 \({}^{\circ}\)C to 303.7 \({}^{\circ}\)C, and the end set temperature of degradation was from 325.3 \({}^{\circ}\)C to 336.1 \({}^{\circ}\)C. These temperatures are higher than those reported in the other literatures [9; 20]. The \(T_{onset}\) of 177-238 \({}^{\circ}\)C, \(T_{d}\) 276-296 \({}^{\circ}\)C, and end set temperature of 291-309 \({}^{\circ}\)C is reported for PHBV (5-20% HV) [9]. Furthermore, the \(T_{d1\%}\) (temperature at which 1% weight loss occurs) of 258 \({}^{\circ}\)C and \(T_{d}\) 284 \({}^{\circ}\)C for PHB is reported [20] indicating an increase in thermal stability of PHBV samples studied here compared to pure PHB. While \(T_{d}\) was found to decrease with increasing 3 HV content (\(R^{2}\) = 0.49), the difference between \(T_{onset}\) and \(T_{endset}\) was found to increase with increasing 3 HV content further reinforcing that the thermal stability of PHBV improved [7].