H Tayeb Ali, Tajvidi Mehdi
School of Forest Resources , University of Maine , 5755 Nutting Hall , Orono , Maine 04469 , United States.
Advanced Structures and Composites Center , University of Maine , 35 Flagstaff Road , Orono , Maine 04469 , United States.
ACS Appl Mater Interfaces. 2019 Jan 9;11(1):1604-1615. doi: 10.1021/acsami.8b16659. Epub 2018 Dec 26.
Cellulose nanofibrils (CNFs) are able to form strong oxygen-barrier films suitable for food packaging but lack the needed water resistance in comparison to plastics. Desired water barrier quality can be achieved by applying mineral additives within the nanofibrils network. In current contribution, a sustainable hybrid system with an improved water barrier function is proposed by incorporating colloidal montmorillonite nanoclay (MMT) and two cross-linking agents, namely, polyamidoamine epichlorohydrin (PAE) and Acrodur thermoset acrylic resin (ACR) into CNF interfaces. Continuous matrices were produced via evaporation-induced self-assembly of colloidal building blocks followed by appropriate heat-curing regime to impart internal cross-linking. The development of chromophore functionalities and formation of ester motifs on the hybrid matrix (with no evidence of degradation) were detected by Fourier-transform infrared (FT-IR) spectroscopy. Intercalation of clay, solely, reduced the water vapor transmission rate (WVTR) to some extent; however, a more remarkable decline (by 60%) was observed upon the curing and cross-linking process. In fact, combination of clay platelets and cross-linkers contributed to a denser film structure and restricted water passage. Also, an excellent resistance to oil and grease was observed in all the studied films (Kit number of 11). A reduction in tensile strengths and resistance to cracking at fold was noted and ascribed to MMT interference in cellulose interchain hydrogen bonds. This however was counteracted by the introduction of cross-linkers, apparently by aiding stress transfer within the matrix. MMT imparted a limited elevation in the surface free energy, pointing out to an induced hydrophilicity; however, surface energy values declined markedly upon using cross-linkers. Finally, thermal stability of hybrids was adversely affected, compared to neat CNFs. Our study suggests the potential utilization of low-cost, sustainable biobarrier films for application in food/drug packaging, where low permeation of moisture is highly desirable.
纤维素纳米纤维（CNFs）能够形成适用于食品包装的强阻氧薄膜，但与塑料相比缺乏所需的耐水性。通过在纳米纤维网络中添加矿物添加剂可以实现所需的阻水性能。在当前的研究中，通过将胶体蒙脱石纳米粘土（MMT）和两种交联剂，即聚酰胺多胺环氧氯丙烷（PAE）和Acrodur热固性丙烯酸树脂（ACR）引入CNF界面，提出了一种具有改进阻水功能的可持续混合体系。通过胶体构建块的蒸发诱导自组装，随后进行适当的热固化处理以实现内部交联，制备出连续的基质。通过傅里叶变换红外（FT-IR）光谱检测到杂化基质上发色团功能的发展和酯基序的形成（无降解迹象）。仅粘土的插层在一定程度上降低了水蒸气透过率（WVTR）；然而，在固化和交联过程中观察到更显著的下降（达60%）。实际上，粘土片层和交联剂的组合导致了更致密的薄膜结构并限制了水的通过。此外，在所有研究的薄膜中都观察到了优异的耐油和耐油脂性（Kit值为11）。注意到拉伸强度和耐折叠开裂性有所降低，这归因于MMT对纤维素链间氢键的干扰。然而，交联剂的引入抵消了这一影响，显然是通过帮助基质内的应力传递。MMT使表面自由能有有限的升高，表明诱导了亲水性；然而，使用交联剂后表面能值显著下降。最后，与纯CNF相比，杂化材料的热稳定性受到不利影响。我们的研究表明，低成本、可持续的生物阻隔薄膜在食品/药品包装中有潜在的应用价值，因为在这些应用中非常需要低水分渗透率。
