This paper reports the thermal, morphological and mechanical properties of environmentally friendly poly(3-hydroxybutyrate) (PHB)/poly(butylene succinate) (PBS) and PHB/poly[(butylene succinate)-co-(butylene adipate)] (PBSA) blends, prepared by melt mixing. The blends are known to be immiscible, as also confirmed by the thermodynamic analysis here presented. A detailed quantification of the crystalline and amorphous fractions was performed, in order to interpret the mechanical properties of the blends. As expected, the ductility increased with increasing PBS or PBSA amount, but in parallel the decrease in the elastic modulus appeared limited. Surprisingly, the elastic modulus was found properly described by the rule of mixtures in the whole composition range, thus attesting mechanical compatibility between the two blend components. This unusual behavior has been explained as due to co-continuous morphology, present in a wide composition range, but also at the same time as the result of shrinkage occurring during sequential crystallization of the two components, which can lead to physical adhesion between matrix and dispersed phase. For the first time, the elastic moduli of the crystalline and mobile amorphous fractions of PBS and PBSA and of the mobile amorphous fraction of PHB at ambient temperature have been estimated through a mechanical modelling approach. © 2021 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.

中文翻译：

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不混溶的 PHB/PBS 和 PHB/PBSA 混合物：弹性模量的形态、相组成和建模

本文报道了环保型聚（3-羟基丁酸酯）（PHB）/聚（丁二酸丁二醇酯）（PBS）和 PHB/聚[（丁二酸丁二醇酯）- co-(己二酸丁二醇酯)] (PBSA) 共混物，通过熔融混合制备。已知共混物是不混溶的，这里介绍的热力学分析也证实了这一点。进行了结晶和非晶部分的详细量化，以解释共混物的机械性能。正如预期的那样，延展性随着 PBS 或 PBSA 量的增加而增加，但同时弹性模量的降低似乎有限。令人惊讶的是，发现弹性模量在整个组成范围内由混合物规则正确描述，从而证明了两种共混组分之间的机械相容性。这种不寻常的行为被解释为由于共同连续的形态，存在于广泛的组成范围内，但同时也是由于两种组分在连续结晶过程中发生的收缩，这会导致基体和分散相之间的物理粘附。首次通过机械建模方法估计了 PBS 和 PBSA 的结晶和移动非晶部分的弹性模量以及环境温度下 PHB 的移动非晶部分的弹性模量。© 2021 作者。由 John Wiley & Sons Ltd 代表工业化学学会出版的Polymer International。