Cellulose nanofibril-reinforced composites using aqueous dispersed ethylene-acrylic acid copolymer

Abstract

In order to explore the reinforcing capabilities of cellulose nanofibrils, composites containing high contents of cellulose nanofibrils were prepared through a combination of water-assisted mixing and compression moulding, the components being a cellulose nanofibril suspension and an aqueous dispersion of the polyolefin copolymer poly(ethylene-co-acrylic acid). The composite samples had dry cellulose nanofibril contents from 10 to 70 vol%. Computed tomography revealed well dispersed cellulose fibril/fibres in the polymer matrix. The highest content of 70 vol% cellulose nanofibrils increased the strength and stiffness of the composites by factors of 3.5 and 21, respectively, while maintaining an elongation at break of about 5%. The strength and strain-at-break of cellulose nanofibril composites were superior to the pulp composites at cellulose contents greater than 20 vol%. The stiffness of the composites reinforced with cellulose nanofibrils was not higher than for that of composites reinforced with cellulose pulp fibres.

Melt Processing of Ethylene‐Acrylic Acid Copolymer Composites Reinforced with Nanocellulose

“…The addition of reinforcement to EAA7 had a negligible effect on the crystallinity of the composite, see Fig. a, as has been reported for other EAA‐based nanocellulose composites []. Thus, the improvement in the mechanical properties can be associated with the presence of nanocellulose reinforcements rather than with changes in the crystallinity of the composites.…”

“…The CNF used exhibited a wide distribution of fiber dimensions ranging from fibers to micro‐ and nano‐fibrils, see Fig. a []. The CNC, which was characterized by AFM, see Fig.…”

“…The masterbatch‐containing CNF and EAA15 was prepared by a method similar to that described in an earlier study where the EAA15 dispersion was mixed with the CNF suspension in excess of water []. The CNF‐based masterbatch, having a solids content of 3–4 wt%, was mixed using a L&W pulp disintegrator (Lorentzen & Wettre, Sweden) for 60,000 revolutions at 2900 rpm.…”

“…For the preparation of the CNC‐based masterbatch, the Celluforce powder was first dispersed in water using a magnetic stirrer and then exposed to high shear rates using an Ultra Turrax at 14,000 rpm for 8 min to obtain a CNC dispersion with a solids content of 4 wt%. The CNC dispersion was then mixed with EAA15 as described in the literature [].…”

“…In the present work, a grade of poly(ethylene‐acrylic acid) copolymer, with a relatively high content of acrylic acid, has been mixed with nanocellulose to obtain a 40 vol% masterbatch as described previously []. The poly(ethylene‐ co ‐acrylic acid), which have been used in the packaging industry, has shown to have good compatibility and adhesion with cellulose due to the presence of the acrylic acid groups [].This masterbatch was compounded with another grade of poly(ethylene‐acrylic acid) copolymer with a lower content of acrylic acid. Composites containing 20 vol% dry content of nanocellulose were processed with variables ranging from screw configuration during compounding and shaping to the effect of reinforcement morphology on the final composite.…”