Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA.
Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA; Department of Bioproducts and Biosystems, Aalto University, Espoo 02150, Finland; Departments of Chemical & Biological Engineering, Chemistry and Wood Science, University of British Columbia, Vancouver V6T 1Z3, Canada.
J Colloid Interface Sci. 2021 Sep 15;598:369-378. doi: 10.1016/j.jcis.2021.04.032. Epub 2021 Apr 25.
Waterborne sulfopolyesters have gained considerable interest as coating materials due to their excellent film-forming and optical properties. Their commercial use has been limited, however, due to their fragile nature. Incorporating cellulose nanofiber (CNF), a sustainable biopolymer, into the polymer matrix is expected to enhance the mechanical integrity of the nanocomposite as these two components synergistically interact.
In this study, we have investigated the suspension and film characteristics of three sulfopolyesters varying in charge density, glass transition temperature and molecular weight, as well as their mixtures with CNF. We have performed steady-shear rheology on mixtures with different CNF loading levels, and resulting films have been subjected to quasistatic uniaxial tensile and water contact-angle tests to elucidate the effects of CNF on mechanical and surface properties.
Addition of CNF to waterborne polyester promotes shear-thinning behavior that remains unaffected by the CNF content. Solid films cast from these suspensions possess enhanced mechanical properties, as well as tailorable surface hydrophilicity, depending on composition and film-drying temperature. Tensile tests reveal that films containing 10 wt% CNF display the greatest mechanical improvements, suggesting the existence of a previously unidentified Goldilocks composition window.
水基磺化聚酯由于其优异的成膜和光学性能而引起了相当大的关注。然而，由于其脆弱的性质，它们的商业用途受到限制。将纤维素纳米纤维（CNF），一种可持续的生物聚合物，引入聚合物基质中有望增强纳米复合材料的机械完整性，因为这两种成分协同相互作用。
在这项研究中，我们研究了三种电荷密度、玻璃化转变温度和分子量不同的磺化聚酯以及它们与 CNF 的混合物的悬浮液和薄膜特性。我们对具有不同 CNF 加载水平的混合物进行了稳态剪切流变学测试，并且对所得薄膜进行了准静态单轴拉伸和水接触角测试，以阐明 CNF 对机械和表面性能的影响。
向水基聚酯中添加 CNF 可促进剪切稀化行为，而 CNF 含量对此无影响。由这些悬浮液浇铸的固体薄膜具有增强的机械性能，以及可根据组成和薄膜干燥温度进行调整的表面亲水性。拉伸测试表明，含有 10wt%CNF 的薄膜显示出最大的机械改进，表明存在以前未被识别的 Goldilocks 组成窗口。
