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Using softwood pulp as the starting material, the synthesis of regioselectively substituted mixed cellulose esters with varying degree of substitution and ratio of short/long chains was successfully completed. The structures of the cellulose esters were characterised. The impact of the structural changes and the degree of substitution of the cellulose esters on thermal properties and processability were investigated. The study shows that the sequential esterification is a promising modification route for cellulose to improve its thermal processability and mechanical properties without the use of external processing aids such as plasticisers. In particular, the hexanoate group in the C6 position on the cellulose backbone acts as an internal plasticiser and improves thermal processability and increases the strength and stiffness of the cellulose ester. The properties of sequentially esterified cellulose promote its practical use in plastics, coatings, films and drug delivery. Sequentially esterified cellulose hexanoate-acetate was used successfully in a coating formulation for the preparation of tablets and showed a stable extended release profile for three water-insoluble drugs in this context. The pH of the release medium had no notable effect on the release properties.

The increasing demand for the use of sustainable materials in industrial applications has created an urge to develop technologies that enable the use of biopolymers such as cellulose for the improvement of properties of commercial products. In this study, the potential of the silyl functionalized cellulose nanofibrils (CNF) as a reinforcing additive for the water- and solvent-based two-component polyurethane (PU) lacquer coatings was evaluated. The addition of the silylated CNF improved the abrasion resistance, strength, and elasticity of the PU coatings. When using the silylated CNF as an additive, the adhesion of the PU coatings was retained. The oxygen permeation rate of the silylated CNF films was strongly influenced by the nature of the solvent. The silylated CNF showed potential as a reinforcing additive even at low loadings in the two-component PU lacquers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 133, 44801.

In this study surface-modified nanofibrillated cellulose (NFC) was used at low levels (0.5 to1.5 wt%) as a reinforcement in a polyvinyl alcohol (PVA) matrix. The modified-NFC-PVA composite films prepared using the solution casting technique showed improved mechanical performance. Birch pulp cellulose was initially modified by allylation using a solvent-free, dry modification method followed by subsequent epoxidation of the allyl groups and finally grinding the pulp to yield epoxy-NFC. In order to obtain optimal mechanical performance, epoxy-NFC with different degrees of substitution was evaluated in the reinforcement of PVA. The addition of 1 wt% epoxy- NFC (degree of substitution, DS 0.07) enhanced the modulus, strength, and strain of pure PVA film by 307, 139 and 23 %, respectively, thus producing the best performing film. The results demonstrate the favourable effect of chemically functionalized NFC on the mechanical properties of polyvinyl alcohol compared to unmodified NFC as reinforcement. In order to improve industrial and economic feasibility, the manufacture of the composite was also done in situ by grinding cellulose directly in PVA to produce the new biocomposite in a one-step process.

PLA offers a competitive and CO2 neutral matrix to commonly used polyolefin polymer based composites. Moreover, the use of PLA reduces dependency on oil when producing composite materials. However, PLA has a tendency of hydrolytic degradation under melt processing conditions in the presence of moisture, which remains a challenge when processing PLA reinforced natural fibre composites. Natural fibres such as cellulose fibres are hygroscopic with 6–10 wt% moisture content at 50–70% relative humidity conditions. These fibres are sensitive to melt processing conditions and fibre breakage (cutting) also occur during processing. The degradation of PLA, moisture absorption of natural fibres together with fibre cutting and uneven dispersion of fibres in polymer matrix, deteriorates the overall properties of the composite. In the given research paper, bleached softwood kraft pulp (BSKP) reinforced PLA compounds were successfully melt processed using BSKP with relatively high moisture contents. The effect of moist BSKP on the molecular weight of PLA, fibre length and the mechanical properties of the composites were investigated. By using moist never-dried kraft pulp fibres for feeding, the fibre cutting was decreased during the melt compounding. Even though PLA degradation occurred during the melt processing, the final damage to the PLA was moderate and thus did not deteriorate the mechanical properties of the composites. However, comprehensive moisture removal is required during the compounding in order to achieve optimal overall performance of the PLA/BSKP composites. The economic benefit gained from using moist BSKP is that the expensive and time consuming drying process steps of the kraft pulp fibres prior to processing can be minimized.

In this study chemically surface-modified nanofibrillated cellulose (NFC) was used at low levels (0.5 to 3 wt%) as reinforcement in a polyvinyl alcohol (PVA) matrix. The modified NFC-PVA films prepared by a solution casting technique showed improved mechanical performance and good optical properties. NFC was allylated and further epoxidised with hydrogen peroxide. The addition of 1 wt% epoxy-NFC enhanced the modulus and strength of the pure PVA film, 474% and 224%, respectively. This composite film exhibited visible light transmittance of 83%. The results also showed that 1 wt% epoxy-NFC loading was beneficial to improve the crystallinity of PVA. SEM characterization confirmed better dispersion of modified NFC within the PVA matrix compared to unmodified NFC. The result showed the favourable effect of chemically modified NFC on the mechanical properties of PVA compared to unmodified NFC as reinforcement.