A Review of Wet Compounding of Cellulose Nanocomposites

Abstract

Cellulose nanomaterials (CNs) are an emerging class of materials with numerous potential applications, including as additives or reinforcements for thermoplastics. Unfortunately, the preparation of CNs typically results in dilute, aqueous suspensions, and the lack of efficient water removal methods has hindered commercialization. However, water may also present opportunities for improving overall efficiencies if its potential is better understood and if it is better managed through the various stages of CN and composite production. Wet compounding represents one such possible opportunity by leveraging water’s ability to aid in CN dispersion, act as a transport medium for metering and feeding of CNs, plasticize some polymers, or potentially facilitate the preparation of CNs during compounding. However, there are also considerable challenges and much investigation remains. Here, we review various wet compounding approaches used in the preparation of cellulose nanocomposites as well as the related concepts of wet feeding and wet extrusion fibrillation of cellulose. We also discuss potential opportunities, remaining challenges, and research and development needs with the ultimate goal of developing a more integrated approach to cellulose nanocomposite preparation and a more sophisticated understanding of water’s role in the compounding process.

Influence of Lactic Acid Surface Modification of Cellulose Nanofibrils on the Properties of Cellulose Nanofibril Films and Cellulose Nanofibril–Poly(lactic acid) Composites

“…Due to their hydrophilic character and high aspect ratio, CNFs tend to agglomerate through hydrogen bonding [ 1 ]. Once dried, CNFs are difficult to disperse in hydrophobic polymer-based matrices [ 2 ]. Achieving nanoscale dispersion of cellulose nanomaterials (CNMs) in thermoplastic composites using melt-blending techniques is difficult, and challenges include drying the nanomaterials without losing their nanoscale structure and compounding dry CNMs into polymeric matrices.…”

“…Wet compounding, in which CNM aqueous suspensions are compounded with polymers and dried in a single processing step, is emerging as a potential solution to overcome these challenges [ 2 , 3 , 4 , 5 ]. During this process, compounding and drying occur simultaneously, and dispersion of unmodified cellulose nanomaterials in polymer-based matrices has been demonstrated [ 2 , 3 , 4 , 5 ]. Employing such a strategy enables the processing of CNMs in an aqueous suspension, which is how they are typically produced.…”

Current international research into cellulose as a functional nanomaterial for advanced applications

“…Many researchers have reviewed this topic; for example, Oksman et al, Wang et al, Zheng and Pilla, and Clemons and Sabo [288][289][290][291]. These reviews explore the developments in the extrusion processing of cellulose nanocomposites; Oksman et al [288] focused on the processing and properties of cellulose nanocomposites, Wang et al [289] focused on potential industrial processes, Zheng and Pilla [290] focused on melt processing with CNCs, and Clemons and Sabo focused on the wet compounding of cellulose nanocomposites [291].…”

Polylactic Acid Cellulose Nanocomposite Films Comprised of Wood and Tunicate CNCs Modified with Tannic Acid and Octadecylamine

“…This resulted in PLA samples with 1 wt.% and 2 wt.% CNC loadings. Samples were initially mixed at 500 rpm for 30 s to ensure consistent mixing, after which time the mixer was ramped to 6000 rpm, in accordance with previously established protocols [28,29]. Frictional heat from the k-mixing process evaporated the water and melted the PLA.…”