AbstractThe effect of long-term storage, at a range of temperatures, on the thermal and mechanical properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)) is reported. P(3HB-co-3HV) was stored at −22, 7, 20, 50, 75, 100, 125 and 150 °C for 672 h. Below 100 °C, the observed increase in melting point, glass transition temperature, modulus and strength are due to the development of crystallinity via a secondary process and facilitated by increasing temperature. At 125 °C, the processes of secondary crystallisation and degradation occur in parallel and there is an interplay between these processes, with the effects of degradation masked by the continuation of secondary crystallisation. At 150 °C there is a deterioration in all the properties noted above and given the reduction in molecular weight (and discolouration), this can be attributed to degradation. The significant observation from these results is that the degradation process remains active well below the melting point and long-term stability of P(3HB-co-3HV) is not only affected by secondary crystallisation, but also degradation. In addition, as no significant changes to the thermal or mechanical properties were observed during storage at −22 and 7 °C it suggests that P(3HB-co-3HV) may be a suitable packaging material for frozen or refrigerated products.The effects of long-term storage of poly(3-hydroxbutyrate-co-3-hydroxyvalerate) were evaluated over a range of temperatures. As the storage temperatures were increased towards 100 °C, secondary crystallisation resulted increasing the melting point, Tg, modulus and strength. At 125 and 150 °C secondary crystallisation and degradation occurred simultaneously; the effects of degradation masked by secondary crystallisation. The significant observation is that the degradation process remains active at storage temperatures well below the melting point and long-term stability of P(3HB-co-3HV) is not only affected by secondary crystallisation, but also sub-melting point degradation.

中文翻译：

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P(3HB-co-3HV) 中的二次结晶和降解：长期稳定性评估

摘要报告了在一定温度范围内长期储存对聚（3-羟基丁酸酯-co-3-羟基戊酸酯）（P（3HB-co-3HV））的热和机械性能的影响。P(3HB-co-3HV) 在 -22、7、20、50、75、100、125 和 150°C 下储存 672 小时。低于 100 °C，观察到的熔点、玻璃化转变温度、模量和强度的增加是由于通过二次过程结晶度的发展，并通过升高温度来促进。在 125 °C 时，二次结晶和降解过程并行发生，这些过程之间存在相互作用，二次结晶的继续掩盖了降解的影响。在 150 °C 时，上述所有性能都会变差，并且由于分子量降低（和变色），这可以归因于退化。从这些结果中可以看出，降解过程在远低于熔点的情况下仍然保持活跃，并且 P(3HB-co-3HV) 的长期稳定性不仅受二次结晶的影响，还受降解的影响。此外，由于在 -22 和 7 °C 下储存期间未观察到热或机械性能的显着变化，这表明 P(3HB-co-3HV) 可能是冷冻或冷藏产品的合适包装材料。在一定温度范围内评估了聚（3-羟基丁酸酯-co-3-羟基戊酸酯）的长期储存。随着储存温度向 100°C 增加，二次结晶导致熔点、Tg、模量和强度增加。在 125 和 150 °C 时，二次结晶和降解同时发生；二次结晶掩盖了降解的影响。重要的观察结果是降解过程在远低于熔点的储存温度下保持活跃，并且 P(3HB-co-3HV) 的长期稳定性不仅受二次结晶的影响，还受亚熔点降解的影响。