Zhang Yi, Haque Abu Naser Md Ahsanul, Naebe Maryam
Institute for Frontier Materials, Deakin University, 75 Pigdons Road, Geelong, VIC 3216, Australia.
Nanomaterials (Basel). 2022 Apr 12;12(8):1320. doi: 10.3390/nano12081320.
Lignin is a natural source of UV-shielding materials, though its recalcitrant and heterogeneous structure makes the extraction and purification processes complex. However, lignin's functionality can be directly utilised when it stays as native with cellulose and hemicellulose in plant biomass, rather than being separated. The fabrication process of this native lignin is sustainable, as it consumes less energy and chemicals compared to purified lignin; thus, it is an economic and more straightforward approach. In this study, the properties of native and purified lignin-cellulose nanocrystals (L-CNCs) sourced from hemp hurd waste were compared to explore the differences in their morphology, UV-shielding properties and chemical structure affected by their distinct fabrication process. These two kinds of L-CNCs were further added into polyvinyl alcohol (PVA) to evaluate their reinforcement characteristics. The resulting native L-CNCs/PVA film showed stronger UV-shielding ability than purified L-CNCs. Moreover, the native L-CNCs showed better compatibility with PVA, while the purified L-CNCs/PVA interfaces showed phase separation. The phase separation in purified L-CNCs/PVA films reduced the films' tensile strength and Young's modulus and increased the water vapour transmission. The laboratory-scale cost of native L-CNCs production (AUD 80/kg) was only 10% of purified L-CNCs (AUD 850/kg), resulting in a comparatively lower cost for preparing native L-CNCs/PVA composite films. Overall, this study shows that the proposed method of production and use of native L-CNCs can be an economic approach to deliver UV-shielding properties for potential applications, such as food packaging.
木质素是一种天然的紫外线屏蔽材料来源，尽管其顽固且不均一的结构使得提取和纯化过程复杂。然而，当木质素与植物生物质中的纤维素和半纤维素保持天然状态而非被分离时，其功能可以直接被利用。这种天然木质素的制备过程是可持续的，因为与纯化木质素相比，它消耗的能源和化学物质更少；因此，这是一种经济且更直接的方法。在本研究中，对源自大麻茎秆废料的天然和纯化木质素 - 纤维素纳米晶体（L - CNCs）的性能进行了比较，以探究其不同制备过程对形态、紫外线屏蔽性能和化学结构的影响。将这两种L - CNCs进一步添加到聚乙烯醇（PVA）中，以评估它们的增强特性。所得的天然L - CNCs/PVA薄膜显示出比纯化L - CNCs更强的紫外线屏蔽能力。此外，天然L - CNCs与PVA表现出更好的相容性，而纯化L - CNCs/PVA界面出现相分离。纯化L - CNCs/PVA薄膜中的相分离降低了薄膜的拉伸强度和杨氏模量，并增加了水蒸气透过率。天然L - CNCs生产的实验室规模成本（约80澳元/千克）仅为纯化L - CNCs（约850澳元/千克）的10%，从而使得制备天然L - CNCs/PVA复合薄膜的成本相对较低。总体而言，本研究表明，所提出的天然L - CNCs的生产和使用方法可以成为一种经济的途径，为食品包装等潜在应用提供紫外线屏蔽性能。
