Short cellulose nanocrystals (CNCs) are promising lightweight materials with high strength and the potential to serve as reinforcing agents in many polymeric materials. The chemical pretreatments of cellulose fibers can be regarded as potential route to both promote nanocellulose fabrication and to adjust the surface properties of CNCs. Sequential regioselective periodate oxidation and partial chlorite oxidation can be utilized to obtain reactive cellulose nanocrystals (RCNCs) with carboxyl and aldehyde functionalities and further used as reinforcements to prepare acetal-bonding cross-linked poly(vinyl alcohol) (PVA) films. With the addition of 10% acetal-bonding RCNCs with respect to PVA weight, the tensile strength and Young’s modulus were up to 2-fold greater than those of pure PVA film. In addition, PVA’s effective oxygen barrier and thermal properties were preserved when RCNCs were introduced into the films. Significantly lower reinforcement effect was obtained when aldehyde groups of RCNCs were reduced to hydroxyl groups prior addition into PVA. Periodate oxidation can also be used to produce UV-absorbing CNCs after “click-type” reaction between aldehyde groups and p-aminobenzoic acid followed by mechanical disintegration. In the solution state, CNCs exhibit very high UV-absorption properties, especially in UVA and UVB regions and high transparency in the visible light region. Complete UVA and UVB opacity of the nanocomposite was achieved using 10% of CNCs in PVA while simultaneously retaining over 80% transparency over the whole visible light spectrum. In addition, improved tensile strength and modulus were achieved using UV-absorbing CNCs compared to pristine PVA.

Functional cellulose nanocrystal reinforcing fillers in polymer nanocomposite films

253rd National Meeting (2017)

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