Reducing the formation of six-membered ring ester during thermal degradation of biodegradable PHBV to enhance its thermal stability |
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Authors: | Qing-Sheng Liu Mei-Fang Zhu Wen-Hua Wu |
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Institution: | a State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620, PR China b College of Material Science and Engineering, Donghua University, Shanghai 201620, PR China |
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Abstract: | Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) has attracted the attention of academia and industry because of its biodegradability, biocompatibility, thermoplasticity and plastic-like properties. However, PHBV is unstable above 160 °C during melt processing at a temperature above the melting temperature, which restricts practical applications as a commodity material. It is widely believed that thermal degradation of PHBV occurs almost exclusively via a random chain scission mechanism involving a six-membered ring transition state. Here, 2,2′-bis(2-oxazoline) (BOX) was selected to modify PHBV to control the formation of six-membered ring ester during thermal degradation. The resulting hydroxyl-terminated PHBVs (HT-PHBVs) had improved thermal stability due to a decrease in the negative inductive effect of the neighboring group of methylene groups at the β-position to the ester oxygen, and a decrease in the electron-denoting effect of substituent group of carbon atoms at α-position to the ester oxygen. The optimal reaction temperature and time were determined to be 95 °C and 6 h, respectively. Compared with those of original PHBV, the temperature determined at 5% weight loss (T5%), the initial decomposition temperature (T0), the maximum decomposition temperature (Tmax), the complete decomposition temperature (Tf) of HT-PHBV prepared under the optimal conditions increased by 31, 24, 19 and 19.1 °C, respectively. |
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Keywords: | Biomaterials 2 2&prime -Bis(2-oxazoline) Poly(3-hydroxylbutyrate-co-3-hydroxylvalerate) (PHBV) Renewable resources Thermal stability |
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