A biobased composite material with heat-triggered shape memory ability was successfully formulated for three-dimensional (3D) printing. It was produced from cellulose nanocrystals and cellulose micro-powder particles within a bioderived thermally cured polyester matrix based on glycerol, citric acid, and sebacic acid. The effect of curing duration on the material's shape memory behavior was quantified by using two thermo-mechanical approaches to measure recovery: (1) displacement in three-point bending and (2) angular recovery from a beam bent at 90° in a single cantilever setup. Extending curing duration increased the material's glass-transition temperature from −26°C after 6 h to 13°C after 72 h of curing. Fourier-transform infrared spectroscopy confirmed the associated progressive conversion of functional groups consistent with polyester formation. Slow recovery rates and low levels of shape recovery (22–70%) were found for samples cured less than 24 h. Those results also indicated a high dependence on the measurement approach. In contrast, samples cured for 48 and 72 h exhibited faster recovery rates, a significantly higher recovery percentage (90–100%) and were less sensitive to the measurement approach. Results demonstrated that once a sufficient curing threshold was achieved, additional curing time could be used to tune the material glass-transition temperature and create heat-triggered 3D-printed products.

中文翻译：

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量化三维打印生物基聚酯/纤维素复合材料的形状记忆性能

一种具有热触发形状记忆能力的生物基复合材料已成功配制用于三维 (3D) 打印。它由基于甘油、柠檬酸和癸二酸的生物衍生热固化聚酯基质中的纤维素纳米晶体和纤维素微粉颗粒制成。通过使用两种热机械方法测量恢复来量化固化持续时间对材料形状记忆行为的影响：(1) 三点弯曲中的位移和 (2) 在单个悬臂中弯曲 90° 的梁的角度恢复设置。延长固化时间可将材料的玻璃化转变温度从固化 6 小时后的 -26°C 提高到固化 72 小时后的 13°C。傅里叶变换红外光谱证实了与聚酯形成一致的官能团的相关渐进转化。对于固化时间少于 24 小时的样品，发现恢复速度慢且形状恢复水平低 (22–70%)。这些结果还表明对测量方法的高度依赖。相比之下，固化 48 和 72 小时的样品表现出更快的恢复率、明显更高的恢复百分比 (90–100%) 并且对测量方法不太敏感。结果表明，一旦达到足够的固化阈值，就可以使用额外的固化时间来调整材料的玻璃化转变温度并创建热触发的 3D 打印产品。这些结果还表明对测量方法的高度依赖。相比之下，固化 48 和 72 小时的样品表现出更快的恢复率、明显更高的恢复百分比 (90–100%) 并且对测量方法不太敏感。结果表明，一旦达到足够的固化阈值，就可以使用额外的固化时间来调整材料的玻璃化转变温度并创建热触发的 3D 打印产品。这些结果还表明对测量方法的高度依赖。相比之下，固化 48 和 72 小时的样品表现出更快的恢复率、明显更高的恢复百分比 (90–100%) 并且对测量方法不太敏感。结果表明，一旦达到足够的固化阈值，就可以使用额外的固化时间来调整材料的玻璃化转变温度并创建热触发的 3D 打印产品。