Abstract

Industrial production of low-charge microfibrillated cellulose (MFC) typically results in wide fibril size distributions. This polydispersity influences viscosity, overall colloidal stability, and rheological properties of MFC suspensions and gels in aqueous systems. In this work, a systematic rheological analysis is performed for industrially prepared MFC and fractions of different size distributions. Gel formation and flow characteristics (e.g., shear-thinning) of each fraction are examined under neutral and acidic conditions and compared with the unfractionated MFC suspension. The effects of size, aspect ratio, and surface charge on the rheology of semi-dilute MFC suspensions are discussed. The results demonstrate that particle size and aspect ratio distribution control the viscoelasticity and shear-thinning properties of MFC suspensions. An increased fraction of small diameter nanofibrils, by ex situ addition of the fine particles with high aspect ratio or removal of the coarsest particles (with lower aspect ratio) by fractionation, significantly enhances the storage modulus and the yield stress of the complex mixture, compared to the properties of the coarser fractions. New insights are also reported on the tailoring of the rheology of highly polydisperse fibrillar mixtures, where the rheological contributions of each fraction are discussed.

Graphic abstract

中文翻译：

---

量身定制微纤维化纤维素悬浮液的流变特性和结构多分散性效应

摘要

低电荷微纤化纤维素（MFC）的工业生产通常会导致较宽的原纤维尺寸分布。这种多分散性影响水性体系中MFC悬浮液和凝胶的粘度，整体胶体稳定性和流变性质。在这项工作中，对工业制备的MFC和不同尺寸分布的馏分进行了系统的流变分析。在中性和酸性条件下检查每个部分的凝胶形成和流动特性（例如，剪切稀化），并与未分级的MFC悬浮液进行比较。讨论了尺寸，长宽比和表面电荷对半稀释MFC悬浮液流变性的影响。结果表明，粒径和纵横比分布控制着MFC悬浮液的粘弹性和剪切稀化特性。通过异位添加高纵横比的细颗粒或通过分馏去除最粗的颗粒（具有较低的纵横比）来增加小直径纳米原纤维的比例，从而显着提高了复杂混合物的储能模量和屈服应力粗级分的性质。在高度多分散的原纤维混合物的流变学定制方面，也报道了新的见解，其中讨论了每个级分的流变学贡献。

图形摘要