Oberlintner Ana, Likozar Blaž, Novak Uroš
Department of Catalysis and Chemical Reaction Engineering, National Institute of Chemistry, SI-1000 Ljubljana, Slovenia.
International Postgraduate School Jožef Stefan, SI-1000 Ljubljana, Slovenia.
Polymers (Basel). 2023 Mar 27;15(7):1663. doi: 10.3390/polym15071663.
Cellulose nanocrystals (CNCs) were acetylated to the various parametrised degrees of substitution (DS), determined through attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and incorporated into alginate (ALG) and chitosan (CH) film-forming solutions. An investigation of morphology with scanning electron microscopy (SEM) revealed increased chemical compatibility with the CH matrix after acetylation, producing a smooth surface layer, while ALG mixed better with pristine CNCs. The ATR-FTIR analysis of films demonstrated inter-diffusional structural changes upon the integration of pristine/modified CNCs. Films were evaluated in terms of water contact angle (WCA), which decreased upon CNC addition in either of the biocomposite types. The HO barrier assessed through applicative vapour transmission (WVT) rate increased with the CNC esterification in CH, but was not influenced in ALG. To evaluate the relationship between environmental humidity and mechanical properties, conditioning was applied for 48 h under controlled relative humidity (33%, 54% and 75%) prior to the evaluation of the mechanical properties and moisture content. It was observed that tensile strength was highest upon specimens being dry (25 ± 3 MPa for ALG, reinforced with neat CNCs, or 16 ± 2 MPa in the CH with CNCs, reacting to the highest DS), lowering with dewing, and the elongation at break exhibited the opposite. It is worth noting that the modification of CNCs improved the best base benchmark stress-strain performance. Lastly, (thermal) stability was assessed by means of the thermogravimetric analysis (TGA) technique, suggesting a slight improvement.
纤维素纳米晶体（CNCs）被乙酰化至不同的取代度（DS），通过衰减全反射傅里叶变换红外光谱（ATR-FTIR）测定，然后将其掺入藻酸盐（ALG）和壳聚糖（CH）成膜溶液中。通过扫描电子显微镜（SEM）进行的形态学研究表明，乙酰化后与CH基质的化学相容性增加，形成了光滑的表面层，而ALG与原始CNCs混合得更好。对薄膜的ATR-FTIR分析表明，原始/改性CNCs整合后发生了相互扩散的结构变化。根据水接触角（WCA）对薄膜进行评估，在两种生物复合材料类型中添加CNCs后，水接触角均降低。通过应用水蒸气透过率（WVT）评估的防潮性能随着CH中CNC的酯化而增加，但在ALG中不受影响。为了评估环境湿度与机械性能之间的关系，在评估机械性能和水分含量之前，在受控相对湿度（33%、54%和75%）下进行48小时的调节。观察到，样品干燥时拉伸强度最高（用纯CNCs增强的ALG为25±3MPa，或CNCs与CH反应达到最高DS时为16±2MPa），随着结露而降低，断裂伸长率则相反。值得注意的是，CNCs的改性改善了最佳基础基准应力-应变性能。最后，通过热重分析（TGA）技术评估（热）稳定性，结果表明略有改善。
