Dispersion Of Cellulose Nanocrystals Research Articles

Fabrication of branching poly (butylene succinate)/cellulose nanocrystal foams with exceptional thermal insulation

Branching poly (butylene succinate) (BPBS) nanocomposite foams incorporated with cellulose nanocrystals (CNCs) were prepared by supercritical CO2. Surface modification of CNCs by acetylation was achieved through replacing hydrophilic hydroxyl groups with hydrophobic acetyl groups, which improved the dispersibility of CNCs significantly. The crystallite sizes of CNCs and acetylated CNCs were calculated by Scherrer's formula as 25 and 19 nm, respectively. The initial crystallization temperature of diverse poly (butylene succinate) (PBS) specimens, a crucial factor for regulating cell nucleation type, increased remarkably by 11.8 °C as well as their storage modulus increased by 2 orders of magnitudes, due to branching reaction and bio-filler addition. BPBS/CNCs foam possessed a high volume expansion ratio as 37.1 times and displayed an exceptional thermal conductivity as 0.021 W(m K)−1. This study provided a promising potential strategy to develop exceptional thermal-insulation polymer foams for composite structures, energy conservation and environment protection.

Native Structure of the Plant Cell Wall Utilized for Top-Down Assembly of Aligned Cellulose Nanocrystals into Micrometer-Sized Nanoporous Particles.

Despite their sustainable appeal, biomass components are currently undervalued in nanotechnology because means to control the assembly of bio-based nanoparticles are lagging behind the synthetic counterparts. Here, micrometer-sized particles consisting of aligned cellulose nanocrystals (CNCs) are prepared by crosslinking cellulose in cotton linter fibers that are prehydrolyzed with gaseous HCl, resulting in chemical cleavage necessary for CNC formation but retaining the morphology of the native fibers. That way, the intrinsic alignment of cellulose microfibrils within the fiber cell wall can be retained and utilized for top-down CNC alignment. Subsequent crosslinking with citric acid cements the alignment and preserves it, following the dispersion of CNCs trapped end-to-end, connected, and crosslinked within the colloidally stable micrometer-sized particles. Furthermore, thermoporosimetry and cryogenic transmission electron microscopy (Cryo TEM) shows that the particles possess mainly nanoporous (<2nm) character in water. The approach challenges the current paradigm of predominantly bottom-up methods for nanoparticle assembly.

Effect of preparation method on the properties of polylactide/cellulose nanocrystal nanocomposites

AbstractPolylactide (PLA)/cellulose nanocrystal (CNC) nanocomposites with 1, 3, and 5 wt% CNC contents were prepared through (a) solution casting and (b) dilution of solution‐casted PLA/CNC masterbatch though melt mixing in a twin‐screw extruder. The effect of preparation method on the CNC dispersion quality and hence the final properties of the nanocomposites were studied. A better CNC dispersion within PLA was obtained when using solution casting method, whereas the formation of CNC agglomerates was observed in the melt‐processed nanocomposites. The rheological results confirmed that a solid network was formed at the CNC content of around 3 wt% in the solution‐casted samples. The PLA crystallization could also be enhanced differently in the presence of CNC nanoparticles through various preparation routes. Moreover, the CNC incorporation noticeably enhanced the storage modulus of PLA beyond its glass transition temperature. The oxygen permeability of PLA was also remarkably reduced with CNC by employing both methods.

Plant cell wall inspired xyloglucan/cellulose nanocrystals aerogels produced by freeze-casting

Cellulose nanocrystals (CNC) and xyloglucan (XG) were used to construct new aerogels inspired by the hierarchical organization of wood tissue, i.e., anisotropic porous cellular solid with pore walls containing oriented and stiff cellulose nanorods embedded in hemicellulose matrix. Aerogels with oriented or disordered pores were prepared by directional and non-directional freeze-casting from colloidal dispersions of XG and CNC at different ratios. XG addition induced a clear improvement of the mechanical properties compared to the CNC aerogel, as indicated by the Young modulus increase from 138 kPa to 610 kPa. The addition of XG changed the pore morphology from lamellar to alveolar and it also decreased the CNC orientation (the Hermans’ orientation factor was 0.52 for CNC vs 0.36−0.40 for CNC-XG). The aerogels that contained the highest proportion of XG also retained their structural integrity in water without any chemical modification. These results open the route to biobased water-resistant materials by an easy and green strategy based on polymer adsorption rather than chemical crosslinking.

Preliminary Screening and Formulation of New Generation Nanoparticles for Stable Pickering Emulsion in Cold and Hot Heavy-Oil Recovery

Summary Injecting water with chemicals to generate emulsions in the reservoir is a promising method in the enhancement of heavy-oil recovery because the formation of oil-in-water (O/W) emulsions significantly reduces oil viscosity. Nanoparticles (NPs) (Pickering emulsions) can be used for this purpose as a cost-effective alternative to expensive surfactants; however, such Pickering emulsions need to be stable for successful applications. The objective of this study is to screen the effective emulsifier for O/W emulsions from a broad range of solid NPs and identify suitable Pickering emulsifying agents (e.g., adjusting pH or salt concentration) that can render emulsions stable at relevant conditions, and to investigate how a range of physical parameters, such as particle concentration, water/oil ratio (WOR), and temperature affect emulsion stability. Five NPs—including cellulose nanocrystals (CNCs), silica, alumina, magnetite, and zirconia—were tested on their capabilities of stabilizing O/W emulsions through glass vial screening tests under various pH and salinity conditions. The screening results showed that the CNC could become an effective emulsifier by either adjusting pH or salinity. In addition, zeta potential measurements were conducted to explain the observations. The stabilization mechanisms of CNCs were studied through an epifluorescent transmitted microscope showing that the formation of a dense particle layer around the oil droplets, as well as a network in the continuous phase, were the two main mechanisms accounting for the high stability of the emulsions stabilized by CNCs. The effects of particle concentrations on the emulsion stability were studied quantitatively by analyzing the droplet-size distributions calculated by the open-source ImageJ software, with the results showing a sharp decrease in droplet size, followed by a smooth change as the particle concentration increased. For the WOR effect, phase inversion from O/W to water-in-oil (W/O) emulsions was observed when the oil content was more than 0.6. The thermal stability of emulsions was studied both macroscopically by glass bottle tests and microscopically through a microscope, both of which show that the CNC-stabilized emulsions remained thermally stable up to 100°C. The rheological properties of both aqueous dispersions of CNCs and the corresponding O/W emulsions were also measured under various salinity conditions. The results showed that the salinity had a great impact on the viscosity of the CNC suspension and the typical shear-thinning behavior of Pickering emulsions. This study provides an option to enhance emulsion stability without surfactants, which will reduce the costs and facilitate field applications of emulsion flooding in heavy-oil recovery.

Implementation of High Gas Barrier Laminated Films Based on Cellulose Nanocrystals for Food Flexible Packaging

In this work, three types of cellulose nanocrystals (CNCs) were used: CNCSO3H extracted from wood pulp by sulfuric acid (H2SO4), CNCCOOH extracted from cotton linters by ammonium persulfate (APS) and CNCCOOR obtained by esterification of the previous two CNCCOOH and CNCSO3H. For a comparative assessment of gas barrier performance, plastic films such as PLA, PET, PE, PP, OPP and OPA were selected, coated with the three types of CNCs and finally laminated with a solvent-based polyurethanic adhesive. First, all dispersed CNCs were characterized by apparent hydrodynamic diameter and Z potential by means of dynamic light scattering (DLS) and electrophoretic light scattering (ELS) techniques, respectively, followed by the crystallinity index (XRD), thermogravimetric analysis (TGA) and evaluation of Fourier-transform infrared spectroscopy (FTIR), as well as the charges density. The surface chemistry of coated plastics (CNCs-P) was assessed by the Z potential through the electrokinetic technique (streaming potential method) and the optical contact angle (OCA). Lastly, laminated films (P-CNC-P) were evaluated by gas permeability measurements at 23 °C and 50–80% RH. It is worth noting that improvements between 90% and 100% of oxygen barrier were achieved after the lamination. This paper provides insights on the choice of cellulosic nanomaterials for the design and development of advanced and sustainable food packaging materials.

Experimental evaluation of glass fiber composite reinforced with cellulose nanoparticles

This study aims to improve the mechanical properties such as tensile strength, flexural strength, impact energy and fracture toughness of a Glass Fiber Reinforced Polymer (GFRP) composite laminate by reinforcing it with Cellulose Nano-Crystals (CNC) for the application of stow bin and the sub floor box on the fuselage of the aircraft. The epoxy matrix of the GFRP composite was reinforced with Cellulose Nano Crystals by the sonication process, SEM images were taken to study the mixing characteristics of CNC with GFRP laminate. Three specimens have been prepared with varying quantities of CNC dispersion in the matrix. The specimen with the code (GE) was not reinforced with CNC. Whereas the specimen (CGECNC-1) and the specimen (CGECNC-2) was reinforced with 10% wt. And 20% wt. of CNC in its matrix, respectively. The experimental results have been obtained from the load–displacement plot from each test. These results revealed that the specimen reinforced with 10% wt. CNC had improved tensile strength, flexural strength, impact energy and fracture toughness when compared to the other two specimens. The mechanical properties improved with 10% wt. CNC whereas it decreased with the reinforcement of 20% wt. CNC. In 20% wt. The excess amount of CNC tends to decreases the density of resin which induces the poor bonding between fiber and resin. The elasticity of the material decreases with an increase in the CNC.

Surface graft polymerization of lactic acid from the surface of cellulose nanocrystals and applications in chloroprene rubber film composites

Cellulose nanocrystals (CNCs) have been modified through surface graft polymerization of (l)-lactide for the purpose of improving dispersion and reducing aggregation of CNCs into chloroprene rubber (CR). Statistically designed experiments have been carried out to study the effects of polymerization conditions (temperature, and catalyst and monomer concentrations) on water contact angle, solvent dispersibility, and particle size distribution of the produced mCNCs. The effects of catalyst concentration and interaction of monomer-catalyst concentrations were found to be significant. Dry films produced from mCNCs exhibited surface hydrophobicity as evidenced by very high water contact angles (> 90°). In addition, mCNCs in powder form exhibited very good water/latex dispersibility. Blending of mCNCs with CR latex resulted in well-dispersed modified CNC/CR composites based on microscopy observations. The tensile properties of cast films produced from CNC/CR and mCNC/CR composites have been evaluated and it has been found that increasing the CNC and mCNC content increases tensile strength and modulus while maintaining elongation at break close to that of the unfilled CR. Composites containing 3 wt% of mCNCs exhibited the best properties with tensile strength and modulus improving by about 200% and 450%, respectively. These results are very promising and suggest that these mCNC/CR composites could find applications in the manufacturing of cut/fat resistant medical gloves, balloons, catheters, and other biomedical devices.

Effect of Cellulose Nanocrystals Extracted from Oil Palm Empty Fruit Bunch as Green Admixture for Mortar

This paper aims to examine the effect of cellulose nanocrystals (CNCs) derived from oil palm empty fruit bunch fiber (EFB) incorporating cement mortar on its structural performances. Cellulose nanocrystals (CNCs) were extracted from α-cellulose extracted from EFB using an acid hydrolysis process with a concentration of acid used was 64% w/v under the temperature of 45 °C for 60 minutes. The Cellulose nanocrystals (CNCs) were mixed into the cement mortar ranging from 0 to 0.8% w/w and its mechanical properties were determined. The developed CNCs mortar was characterized for their compressive and flexural properties as well as microstructure. The influence of CNCs concentration, curing method, dispersion of CNCs on mortar’s mechanical performance was thoroughly examined to find out the optimum condition. Overall results revealed that an addition of 0.4% cellulose nanocrystals has shown to increase the compressive and flexural strength to 46% and 20%, respectively cured under the wrapping method. The hydration of cementitious composites also improved significantly with the addition of CNCs by the formation of highly crystalline of portlandite observed under the XRD test. This present work demonstrates the importance of palm oil empty fruit bunch waste as a sustainable resource of cellulose nanocrystals admixture to achieve structural strength of cement mortar and promotes green technologies in construction.

Amidation of TEMPO-oxidized cellulose nanocrystals using aromatic aminated molecules

In this study, the grafting of 1-methyl-3-phenylpropylamine (1-M-3-PP) on cellulose nanocrystals (CNCs) via a two-step reaction route was investigated and compared with physico-chemical surface adsorption. The first step involved subjecting CNCs to a 2,2,6,6-Tetramethyl-1-piperidinyloxy (TEMPO)-mediated oxidation. The carboxylic groups present on recovered oxidized TEMPO-CNC were quantified by several characterization methods (conductometric titration, elemental analysis, and X-ray photoelectron spectroscopy), and a degree of oxidation close to 0.2 was found. The second step was an amidation reaction carried out in an aqueous medium under mild conditions and in the presence of N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (EDC)/N-hydroxysuccinimide (NHS) as catalyst. The recovered modified CNCs after amidation reaction with 1-M-3-PP (CNC-1-M-3-PP) were extensively washed and then characterized. The amount of grafted molecules was determined by several techniques like X-ray photoelectron spectroscopy (XPS), and the calculated degree of substitution was found to be close to 0.05 with respect to the bulk CNC. This low amount is sufficient to enhance the modified CNC dispersion and their colloidal stabilization in organic solvents, allowing the preparation of nanocomposites. Furthermore, such CNC-1-M-3-PP units with aromatic molecules attached to it can find applications in barrier materials in which the sorption of aromatic molecules can be very useful.

Valorization of pineapple peel waste and sisal fiber: Study of cellulose nanocrystals on polypropylene nanocomposites

AbstractThe present study focuses on the isolation and characterization of the cellulose nanocrystals (CNCs) from the pineapple peel waste (PPW) (agro‐waste) and sisal fiber (SiF) (natural fiber) employing the acid hydrolysis method, and its comparison with the commercially available CNCs (CNC‐C). Furthermore, the CNCs from PPW, SiF, and CNC‐C were subjected to transmission electron microscopy (TEM), Fourier transform electron microscopy, X‐ray diffraction, particle size distribution, and zeta potential analysis. The studied properties of the isolated CNCs are considerably different from the PPW and SiF. The CNCs so formed have been estimated by TEM to be around 10–40 nm wide and length of several micrometers. Fourier transform electron microscopy studies described the removal of the noncellulosic components like lignin, hemicellulose, and pectin substances from the base materials in both the cases by employing acid hydrolysis method. Additionally, nanocomposites of CNC isolated from PPW along with polypropylene (PP) matrix were fabricated using melt blending method followed by injection molding. Maleic anhydride grafted PP (MAPP) acts as a compatibilizer for improving the dispersibility of hydrophilic CNC within the nonpolar PP matrix. The addition of CNC (3 wt%) along with MAPP at 5 wt% showed optimum tensile strength and modulus to the tune of 10.39 and 25.53%, respectively, when compared to their counterparts without MAPP. Dynamic mechanical analysis revealed an increased stiffness of PP in its nanocomposite system due to the addition of CNC. Scanning electron microscopy studies revealed uniform distribution of CNC within the nonpolar PP matrix in the presence of MAPP.

Adhesive properties of bio-based epoxy resin reinforced by cellulose nanocrystal additives

Abstract The adhesive properties of a self-prepared bio-based epoxy resin with native cellulose nanocrystals (CNCs) are evaluated in this article. The porosity of actual CNCs is high. The most promising finding is the acquisition of high tensile modulus. The addition of CNC composites significantly increased the tensile modulus at lower wt.%, and the maximum crystallinity of CNCs was obtained. Bearing in mind the advantages of CNCs, scanning electron microscopy (SEM) showed a uniform distribution of concentrated CNCs. Clusters were formed at higher CNCs ratios, and the composite matrix content with high CNCs produced good expansion, low crystallinity, and increased elongation. Our analysis showed that the original CNCs were more evenly distributed in the self-prepared bio-based epoxy resin, which enhanced transformation, supported by improved dispersion of native CNCs. The presence of native CNCs greatly improved and enhanced the bonding performance of the bio-based epoxy resin in the interface area. Enhancing the mechanical properties of native CNCs has broad application prospects in environmental areas. This suggests that the widespread use of native CNCs in environmental engineering applications is feasible, especially in terms of adhesives properties.

Role of solvent exchange in dispersion of cellulose nanocrystals and their esterification using fatty acids as solvents

The recent emergence of bio-based nanocomposites makes perfect sense from a technical and environmental point of view. Cellulose nanocrystals (CNCs) are novel bio-based nanomaterials with a wide range of beneficial properties. Their biodegradability, crystallinity, high surface area, and mechanical strength, as well as their highly reactive surface, make them ideal materials as nanofillers in polymeric matrices. However, most the bio-based polymers are hydrophobic, and the hydrophilicity of CNC is therefore a challenge to their incorporation in such matrices. In this study, a new procedure for surface modification of CNC with long aliphatic chains [lauric acid (12 carbons) and stearic acid (18 carbons)] was developed that limits the use of petro-chemicals and facilitates their potential recycling. A study of the dispersion state of CNC in acetone was performed first. Then, grafting efficiency was highlighted by several techniques and quantification of the amount of grafted fatty chains was investigated. Degrees of substitution on the bulk and on the surface of the CNC were calculated between 0.1 and 0.3, which provided enough grafted functions to confer hydrophobic behavior to modified CNCs, as highlighted by the increasing of contact angle from 65° for neat CNC to 80° after modification. Finally, conservation of CNC crystalline structure and morphology was proved by both X-ray diffraction and transmission electron microscopy analyses. Modified CNCs exhibit a crystallinity index close to 86% and length of approximately 350 nm. Thus, crystalline hydrophobic cellulosic nanomaterials were prepared using a more environmentally friendly procedure than those classically found in the literature.

Effects of molecular weight and crystallizability of polylactide on the cellulose nanocrystal dispersion quality in their nanocomposites

This study investigated how cellulose nanocrystals (CNC) dispersion quality and its percolation network formation could be influenced when using polylactide (PLA) with various molecular weights and crystallizability. In this context, systematic rheological experiments were conducted on PLA/CNC nanocomposites prepared through solution casting method using dimethylformamide (DMF) as the solvent. It was found that lower CNC percolation concentrations could be obtained when a PLA matrix possesses lower molecular weight as the shorter chains and CNCs interpenetration could be facilitated during their dissolution in the solvent. On the other hand, the CNC percolation concentration was further lowered when the PLA with higher crystallizability was used. During the solvent evaporation step that occurred at 85 °C, the isothermal heterogeneous crystallization of PLA around the dispersed CNCs could prevent the driving force of the CNCs towards their re-agglomeration. Therefore, the finest CNC dispersion was appeared in the highly crystallizable low molecular weight PLA through which the rheological properties were dramatically improved and the thermal stability was significantly extended to higher temperatures. The crystallization behavior of the prepared nanocomposites was also analyzed using differential scanning calorimeter and X-ray diffractometer. The thermal degradation behavior of the PLA/CNC nanocomposites were examined through thermogravimetric and rheological analysis.

Reinforcement of rubber nanocomposite thin sheets by percolation of pristine cellulose nanocrystals

Research on the use of bio-based material rather than fossil fuel-based synthetic polymers is of considerable value due to the increasing interest in biodegradable and ecofriendly products. This paper describes an in-depth analysis of the effect of cellulose nanocrystals (CNC), a promising nanomaterial filler derived from cellulosic biomass, on the mechanical properties of rubber latex thin sheets. Sheets of styrene butadiene rubber (SBR) and its bio-based alternative, natural rubber (NR) were tested and compared. Percolation of CNC was studied within the rubber matrices, where the tear strength, water permeability, and water absorption increased due to the formation of a continuous network of CNC within the polymer thin sheets. The rubber nanocomposites were resistant to tear propagation, caused by increased tortuosity along the tear path brought about by CNC dispersion and filler network formation. The CNC reinforcement yielded thin sheets that were much stronger and more durable than their non-reinforced counterparts. Additionally, the increased water uptake of the sheets could aid in the biodegradation of the polymer. Thus, CNC is found to be an excellent functional filler in rubber sheets, where its formation of a percolating network significantly improved their properties.

Exploiting Supramolecular Interactions from Polymeric Colloids for Strong Anisotropic Adhesion between Solid Surfaces.

Adhesion occurs by covalent bonding, as in reactive structural adhesives, or through noncovalent interactions, which are nearly ubiquitous in nature. A classic example of the latter is gecko feet, where hierarchical features enhance friction across the contact area. Biomimicry of such structured adhesion is regularly achieved by top-down lithography, which allows for direction-dependent detachment. However, bottom-up approaches remain elusive given the scarcity of building blocks that yield strong, cohesive, self-assembly across multiple length scales. Herein, an exception is introduced, namely, aqueous dispersions of cellulose nanocrystals (CNCs) that form superstructured, adherent layers between solid surfaces upon confined evaporation-induced self-assembly (C-EISA). The inherently strong CNCs (EA > 140 GPa) align into rigid, nematically ordered lamellae across multiple length scales as a result of the stresses associated with confined evaporation. This long-range order produces remarkable anisotropic adhesive strength when comparing in-plane (≈7 MPa) and out-of-plane (≤0.08 MPa) directions. These adhesive attributes, resulting from self-assembly, substantially outperform previous biomimetic adhesives obtained by top-down microfabrication (dry adhesives, friction driven), and represent a unique fluid (aqueous)-based system with significant anisotropy of adhesion. By using C-EISA, new emergent properties will be closely tied with the nature of colloids and their hierarchical assemblies.

Linking Film Structure and Mechanical Properties in Nanocomposite Films Formed from Dispersions of Cellulose Nanocrystals and Acrylic Latexes.

Cellulose nanocrystals (CNCs) are unique, lightweight materials that possess high elastic modulus and tensile strength, making them of great interest in the formation of nanocomposite materials. However, efficient design of the composite material is essential in translating the mechanical properties of the individual CNCs into the nanocomposite film. In this work, we demonstrate the formation of structured CNC/acrylic dispersions by physical blending of the anionic CNCs with charged acrylic latex particles. By blending with large cationic latex particles, the CNCs adsorbed onto the acrylic latex surface while blending with small latex particles led to the inverse structure. Films were cast from these dispersions and the physical properties were compared with the aim of understanding the influence of the initial structure of the hybrid dispersion on the structure of the final film. A significant difference in the mechanical properties was observed based on the position of the CNCs in the initial dispersion. Adsorption of latex particles onto the CNC surface led to a random distribution of nonconnected CNCs, which contributed little to improving the Young's modulus, while adsorption of CNC onto the latex led to a honeycomb CNC network and a large increase in the Young's modulus. This work underlines the importance of particle structure on the structure and mechanical properties of nanostructured films.

Sonication amplitude and processing time influence the cellulose nanocrystals morphology and dispersion

The application of bio-based materials is becoming impellent owing to the increasing demand for alternatives to petroleum-based analogs. In this regard, cellulose nanocrystals (CNCs) with unique properties have received a significant interest, while their hydrophilic character poses a challenge to their commercial applications. Ultrasonication treatment is one of the most commonly used methods to improve CNCs’ dispersion in different solvents and polymer matrices. In this work, the effectiveness of ultrasonication treatment in the dispersion of CNCs in a water-soluble polymer (polyvinyl alcohol, PVA) was studied. An aqueous suspension of polyvinyl alcohol and CNCs was prepared using different ultrasonication times and amplitudes. The morphology, particle size and dispersion of CNCs were studied using X-ray diffraction, transmission electron microscopy, and dynamic light scattering. The results indicated that with increase in the sonication amplitude, there was a substantial decrease in nanoparticle length, while long sonication times gently affected the nanoparticle length. Furthermore, improved dispersion was observed in samples prepared using longer sonication time.

Characterization of size and aggregation for cellulose nanocrystal dispersions separated by asymmetrical-flow field-flow fractionation

Cellulose nanocrystals (CNCs) derived from various types of cellulose biomass have significant potential for applications that take advantage of their availability from renewable natural resources and their high mechanical strength, biocompatibility and ease of modification. However, their high polydispersity and irregular rod-like shape present challenges for the quantitative dimensional determinations that are required for quality control of CNC production processes. Here we have fractionated a CNC certified reference material using a previously reported asymmetrical-flow field-flow fractionation (AF4) method and characterized selected fractions by atomic force microscopy (AFM) and transmission electron microscopy. This work was aimed at addressing discrepancies in length between fractionated and unfractionated CNC and obtaining less polydisperse samples with fewer aggregates to facilitate microscopy dimensional measurements. The results demonstrate that early fractions obtained from an analytical scale AF4 separation contain predominantly individual CNCs. The number of laterally aggregated "dimers" and clusters containing 3 or more particles increases with increasing fraction number. Size analysis of individual particles by AFM for the early fractions demonstrates that the measured CNC length increases with increasing fraction number, in good agreement with the rod length calculated from the AF4 multi-angle light scattering data. The ability to minimize aggregation and polydispersity for CNC samples has important implications for correlating data from different sizing methods.

Using cellulose nanocrystals as sustainable additive to enhance mechanical and shape memory properties of PLA/ENR thermoplastic vulcanizates

Cellulose nanocrystals (CNC) show great potential in polymers due to their sustainability and excellent mechanical properties, etc. Herein, we used CNC as sustainable additive to improve mechanical and shape memory properties of polylactide (PLA)/epoxidized natural rubber (ENR) thermoplastic vulcanizates (TPVs). A method of combining latex mixing and melt mixing was used to achieve homogeneous dispersion of CNC. With only 5 phr (relative to ENR) CNC, tensile strength, Young’s modulus and dynamic storage modulus at 20 ℃ increased by 22 %, 64 % and 78 % compared with unfilled sample. The shape recovery behavior also improved with the incorporation of CNC, which increased from 87.4 % of unfilled TPV to 91.7 % of sample with 5 phr CNC. Moreover, the decline of Rr in the subsequent cycles also reduced with incorporation of CNC. These results indicate that the enhanced cross-linked rubber network and increased crystallinity of PLA contributed to the enhanced properties.