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. 2023 Mar 14;16(6):2323.
doi: 10.3390/ma16062323.

The Influence of Cellulose Nanocrystal Characteristics on Regenerative Silk Composite Fiber Properties

Hak Jeon Kim  1 , Won Jun Lee  1
Affiliations

The Influence of Cellulose Nanocrystal Characteristics on Regenerative Silk Composite Fiber Properties

Hak Jeon Kim et al. Materials (Basel). .

Abstract

Cellulose nanocrystals (CNCs), obtained from natural resources, possess great potential as a bioderived reinforcement for natural-fiber-reinforced composites (NFRPs) due to their superior crystallinity and high aspect ratio. To elucidate the specific parameters of CNCs that significantly affect their mechanical performance, various CNCs were investigated to fabricate high-performance nanocomposite fibers together with regenerated silk fibroin (RSF). We confirmed that the high aspect ratio (~9) of the CNCs was the critical factor to increase the tensile strength and stiffness rather than the crystallinity. At a 1 vol% of CNCs, the strength and stiffness reached ~300 MPa and 10.5 GPa, respectively, which was attributed not only to a stable dispersion but also to alignment. This approach has the potential to evaluate the parameters of natural reinforcement and may also be useful in constructing high-performance NFRPs.

Keywords: aspect ratio; cellulose nanocrystals; composite fibers; crystallinity; regenerated silk.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 7
Figure 7
WAXS 2D pattern and angular scattered spectra (left) and SAXS 2D pattern and angular scattered spectra (right); (a) RSF for control, (b) RSF with vol 1% of LCNC, (c) RSF with vol 2% of LCNC, and (d) RSF with vol 5% of LCNC.
Figure 1
Figure 1
Illustration of fiber formation with CNC and RSF. Three different characteristics of CNC, such as (1) aspect ratio, (2) crystal index, and (3) impurities, influence the properties of the composite fiber including alignment and crystallinity, resulting in different mechanical features.
Figure 2
Figure 2
AFM topographic images (on the left) and histograms of the aspect ratio (on the right) from various CNC sources. AFM image shows that the majority of individual CNCs are well dispersed, which provide a direct comparison in nanoscale. (a) FCNC, (b) MCNC, and (c) LCNC.
Figure 3
Figure 3
CNC cluster frequency proportions from a variety of CNC samples. (a) The bar graphs depict the respective frequency proportions for FCNC, MCNC, and LCNC. Optical microscopic images of (b) FCNC, (c) MCNC, and (d) LCNC suspension with a concentration of 1 wt%.
Figure 4
Figure 4
(a) 1D wide-angle X-ray scattering (WAXS) profiles of various CNCs, (b) crystallinity index, and (c) the ratio of cellulose II to cellulose I of CNCs. To calculate the crystallinity index and the ratio, the peak separation was used to separate the background and overlapping peaks of the 1D WAXS integral curves. Dotted lines represent (left) amorphous, and (right) (200) plane of cellulose I, respectively.
Figure 5
Figure 5
Influence of characteristics on mechanical strength of composites reinforced by three different CNCs. Different characteristics of CNC affects tensile modulus, strain at break, and tensile strength in different level. (a) Characteristic stress-strain curves, (b) Bar diagram of tensile modulus, (c) Bar diagram of strain at break, and (d) Bar diagram of tensile strength.
Figure 6
Figure 6
The mechanical properties of regenerated silk fibroin fiber reinforced by LCNC as a function of volume fraction. Different amounts of CNC affects tensile modulus, strain at break, and tensile strength. (a) Characteristic stress-strain curves, (b) Bar diagram of tensile modulus, (c) Bar diagram of strain at break, and (d) Bar diagram of tensile strength.
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