Solvent Casting Process Research Articles

Chitosan-Based Membranes as Gentamicin Carriers for Biomedical Applications-Influence of Chitosan Molecular Weight.

Over the past decade, much attention has been paid to chitosan as a potential drug carrier because of its non-toxicity, biocompatibility, biodegradability and antibacterial properties. The effect of various chitosan characteristics on its ability to carry different antibiotics is discussed in the literature. In this work, we evaluated the influence of the different molecular weights of this polymer on its potential as an antibacterial membrane after adding gentamicin (1% w/w). Three types of chitosan membranes without and with antibiotic were prepared using a solvent casting process. Their microstructures were analyzed with a 4K digital microscope, and their chemical bonds were studied using FTIR spectroscopy. Furthermore, cytocompatibility on human osteoblasts and fibroblasts as well as antibacterial activity against Staphylococcus aureus (S. aureus.) and Escherichia coli (E. coli) were assessed. We observed that the membrane prepared from medium-molecular-weight chitosan exhibited the highest contact angle (≈85°) and roughness (10.96 ± 0.21 µm) values, and its antibacterial activity was unfavorable. The maximum tensile strength and Young's modulus of membranes improved and elongation decreased with an increase in the molecular weight of chitosan. Membranes prepared with high-molecular-weight chitosan possessed the best antibacterial activity, but mainly against S. aureus. For E. coli, is not advisable to add gentamicin to the chitosan membrane, or it is suggested to deplete its content. None of the fabricated membranes exhibited a full cytotoxic effect on osteoblastic and fibroblast cells. Based on our results, the most favorable membrane as a gentamicin carrier was obtained from high-molecular-weight chitosan.

Effect of ZrO2 nanoparticles on phosphoric acid-doped poly (Ethylene imine)/Polyvinyl alcohol) membrane for medium-temperature polymer electrolyte membrane fuel cell applications

A high-level research is currently focused on the construction of polymer nanocomposite membranes with high proton conductivity (PC), peak power density (PD), and open circuit voltage (OCV) for polymer electrolyte membrane fuel cells (PEMFC) to substitute the commercial Nafion-211 membrane. The present study deals with the solvent-casting process for producing ZrO2 nanoparticles (1–7 wt %) dispersed on phosphoric acid (PA) doped polyethylene imine and polyvinyl alcohol (PA-PEI/PVA) polymer nanocomposites (PNCs). ZrO2 (5%) dispersed PA-PVA/PEI PNCs showed the highest ion-exchange capacity (IEC) of 2.94 mmol/g−1 at room temperature (RT), and PC of 4.34 10−2 S/cm−1 at 120 °C. Experiments on the PNCs were carried out at 120 °C to evaluate their performance and usability in medium-temperature polymer electrolyte membrane fuel cells (MT-PEMFCs). The results indicate a practical and effective route for the fabrication of a composite membrane that has a semi-interpenetration network structure with abundant active protonated groups, and has future prospects and widespread application in MT-PEMFCs.

Mechanical and Barrier Properties of Cellulosic Nano-Fibers Reinforced Bionanocomposite

Cellulose is one of the most frequently used and generally available materials on Earth and has been utilized for ages in a variety of applications. Numerous researchers have investigated various lignocellulosic sources for the extraction of cellulose and the author has introduced a new source for the extraction of cellulose and cellulosic nanofibers: fruits or seedpods of Delonix Regia (CNF). The solvent casting process is used to create the PVA/CNF composite after the cellulose and CNF have been removed using a mechano-chemical method. SEM, tensile testing, soil burial testing and moisture absorption tests have all been used to examine the morphological, mechanical, biodegradable and moisture absorption capabilities of pure PVA and PVA/CNF composite with 1, 3, 5, 7 and 9 percentages of CNF. According to SEM findings, agglomeration was seen at higher concentrations but uniform and homogenous distribution of nano-fillers was seen at lower percentages of CNF. It is profusely clear from the results of the tensile tests that the percentage elongation initially decreased and then began to increase at higher concentration, while the Young’s modulus and tensile strength initially increased at lower percentages of CNF rapidly and gradually decreased for higher concentration. Pure PVA had the least resistance to degradation in biodegradability test, while the biodegradability test showed that the inclusion of CNF decreased the composite material’s ability to degrade. With the addition of CNF, the rate of moisture absorption decreased, resulting in a PVA/CNF composite material that will last longer and perform better without material degradation.

Graphene nanoplatelet/cellulose acetate film with enhanced antistatic, thermal dissipative and mechanical properties for packaging.

With the increased concern over environment protection, cellulose acetate (CA) has drawn great interests as an alternative for packaging material due to its biodegradability and abundant resources; whereas, the poor antistatic property and thermal conductivity restrict its application in packaging. In this work, we proposed a simple but effective strategy to produce high performance graphene nanoplatelet (GNP)/CA composite films via the consecutive homogenization and solvent casting processes. Relying on the spontaneous absorption of CA during homogenization, the GNP/CA produced shows an excellent dispersibility in the N,N-Dimethylformamide (DMF) solution and many fewer structural defects compared with GNPs alone. As a result, the composite films obtained exhibit simultaneously and significantly enhanced antistatic, heat dissipative and mechanical properties compared with CA. Specifically, the GNP/CA composite with the optimal formula has promising overall performances (namely, surface resistivity of 3.33 × 107Ω/sq, in-plane thermal conductivity of 5.359 , out-of-plane thermal conductivity of 0.785 , and tensile strength of 37.1MPa). Featured by its promising overall properties, simple production processes and biodegradability, the as-prepared GNP/CA composite film shows a great potential for application in packaging. The online version contains supplementary material available at 10.1007/s10570-023-05155-2.

Efficiency of Neat and Quaternized-Cellulose Nanofibril Fillers in Chitosan Membranes for Direct Ethanol Fuel Cells.

In this work, fully polysaccharide based membranes were presented as self-standing, solid polyelectrolytes for application in anion exchange membrane fuel cells (AEMFCs). For this purpose, cellulose nanofibrils (CNFs) were modified successfully with an organosilane reagent, resulting in quaternized CNFs (CNF (D)), as shown by Fourier Transform Infrared Spectroscopy (FTIR), Carbon-13 (C13) nuclear magnetic resonance (13C NMR), Thermogravimetric Analysis (TGA)/Differential Scanning Calorimetry (DSC), and ζ-potential measurements. Both the neat (CNF) and CNF(D) particles were incorporated in situ into the chitosan (CS) membrane during the solvent casting process, resulting in composite membranes that were studied extensively for morphology, potassium hydroxide (KOH) uptake and swelling ratio, ethanol (EtOH) permeability, mechanical properties, ionic conductivity, and cell performance. The results showed higher Young's modulus (119%), tensile strength (91%), ion exchange capacity (177%), and ionic conductivity (33%) of the CS-based membranes compared to the commercial Fumatech membrane. The addition of CNF filler improved the thermal stability of the CS membranes and reduced the overall mass loss. The CNF (D) filler provided the lowest (4.23 × 10-5 cm2 s-1) EtOH permeability of the respective membrane, which is in the same range as that of the commercial membrane (3.47 × 10-5 cm2s-1). The most significant improvement (~78%) in power density at 80 °C was observed for the CS membrane with neat CNF compared to the commercial Fumatech membrane (62.4 mW cm-2 vs. 35.1 mW cm-2). Fuel cell tests showed that all CS-based anion exchange membranes (AEMs) exhibited higher maximum power densities than the commercial AEMs at 25 °C and 60 °C with humidified or non-humidified oxygen, demonstrating their potential for low-temperature direct ethanol fuel cell (DEFC) applications.

Mechanical properties of graphene nanoplatelets reinforced glass/epoxy composites manufactured using resin film infusion process

<abstract> <p>Nanofillers as secondary reinforcement in polymeric composites have shown promising results on improvement of mechanical properties of the polymeric composites. However, due to the in-plane resin path, filtration of the nanofillers through fabric during processing is a major challenge in liquid infusion processes such as resin transfer molding. In resin film infusion process, the resin travels in thickness direction and due the shorter resin path, the possibility of filtration is minimal. In this study, resin film infusion (RFI) process is used to fabricate graphene platelets reinforced glass/epoxy hybrid composites. First, the resin films with 0.4 and 0.8 percent of graphene nanoplatelets (GNPs) were manufactured using solvent casting process. Then, these films were used to fabricate composites using resin film infusion process. Mechanical characterization tests, namely tensile, flexural and short beam, were performed. Tensile strength of the 0.4% and 0.8% GNPs reinforced composites was 36.13% and 22.23% higher, respectively, than that of baseline composites. Flexural strength 0.4% and 0.8% GNPs modified composites was 24.96% higher and 32% lower, respectively, compared to baseline composite. Lastly, minimal change was observed in short beam shear strength due to GNPs reinforcement. Higher void volume fraction of 1.7% and 4.5% as compared to baseline composites observed in 0.4% and 0.8% GNPs modified composites respectively.</p> </abstract>

Properties and characterization of carrot nanocellulose/starch biopolymer nanocomposites

AbstractIn order to produce bio‐nanocomposites for potential food packaging applications, nanocellulose (NC) was extracted from carrot pulp and different weight fractions of NC (5, 7, and 10 wt%) were incorporated into corn starch, either with or without thyme extract, using the solvent casting process. The particle size of the extracted NC (200–300 nm) was determined using the dynamic light scattering test, and field emission scanning electron microscopy confirmed the spherical morphology of the NC, which was successfully extracted from carrot. Fourier transform infrared spectroscopy analysis demonstrated excellent chemical interactions between the starch and NC. According to SEM images of starch‐NC nanocomposites, uniform dispersion of NC into starch was observed for all formulations. Besides, increasing the proportion of NC up to 10 wt% enhanced the tensile strength of starch nanocomposites by 280%. Since the incorporation of NC into starch increased the crystallinity index of the samples, the water absorption capacity and oxygen transmittance rate tests showed that the presence of NC reduced water and oxygen gas diffusion into the starch matrix. Furthermore, thyme‐loaded nanocomposite had remarkable antimicrobial activity, particularly in the case of gram‐positive bacteria (Staphylococcus aureus), as it expanded the bacteria's inhibitory zone by about 10 mm compared with those without an antibacterial agent. Finally, the fabricated bio‐nanocomposites exhibited balanced mechanical characteristics, perfect gas and water barrier properties, as well as promising antibacterial activity for use in the food packaging industry.

Hydrophobicity and Biodegradability of Silane-Treated Nanocellulose in Biopolymer for High-Grade Packaging Applications.

The growing concern about pollution produced by plastic waste and the consequent environmental dangers has led to increased interest in replacing plastics with sustainable and biodegradable alternatives. Biopolymers such as seaweed have been examined for their film-forming characteristics to make edible films for packaging applications. This study aimed to prepare biopolymeric packaging films through a solvent-casting process using natural red seaweed (Kappaphycus alvarezii) and kenaf cellulose nanofiber (CNF), followed by film surface treatment using silane. The hydrophobic properties of the seaweed/CNF biopolymer were examined through water solubility (WS), moisture absorption capacity (MAC), water vapor permeability (WVP), and contact angle (CA) measurements. Fourier transform infra-red (FT-IR) film spectra clearly showed successful modification of the seaweed film (SF) by silane and the incorporation of kenaf CNF over the surface of the seaweed film. The wettability-related analysis showed positive results in determining the modified film’s hydrophobicity properties. Film degradation analysis using the soil burial method showed a lower degradation rate for films with a higher CNF loading. Overall, the characterization results of the seaweed/CNF biopolymer film predicted hydrophobicity properties. The slow degradation rate was improved with surface modification using silane treatment and the incorporation of kenaf CNF filler with the seaweed matrix. As a result, we found that the seaweed/CNF biopolymer film could be used as high-grade packaging material in many potential applications.

Characterisation and Colour Response of Smart Sago Starch-Based Packaging Films Incorporated with Brassica oleracea Anthocyanin.

To meet the need for food products to be safe and fresh, smart food packaging that can monitor and give information about the quality of packaged food has been developed. In this study, pH-sensitive films with sago starch and various anthocyanin concentrations of Brassica oleracea also known as red cabbage anthocyanin (RCA) at 8, 10, 12, and 14% (w/v) were manufactured using the solvent casting process. Investigation of the physicochemical, mechanical, thermal, and morphological characteristics of the films was performed and analysed. The response of these materials against pH changes was evaluated with buffers of different pH. When the films were exposed to a series of pH buffers (pH 3, 5, 9, 11, and 13), the RCA-associated films displayed a spectacular colour response. In addition, the ability of the starch matrix to overcome the leaching and release of anthocyanins was investigated. Higher concentrations of RCA can maintain the colour difference of films after being immersed in a series of buffer solutions ranging from acidic to basic conditions. Other than that, incorporating RCA extracts into the starch formulation increased the thickness whereas the water content, swelling degree, tensile strength, and elongation at break decreased as compared to films without RCA. The immobilisation of anthocyanin into the film was confirmed by the FTIR measurements. The surface patterns of films were heterogeneous and irregular due to the presence of RCA extract aggregates, which increased as the extract concentration enhanced. However, this would not affect the properties of films. An increase in thermal stability was noted for the anthocyanin-containing films at the final stage of degradation in TGA analysis. It is concluded that RCA and sago starch formulation has great potential to be explored for food packaging purposes.

Sugar-Triggered Burst Drug Releasing Poly-Lactic Acid (PLA) Microneedles and Its Fabrication Based on Solvent-Casting Approach.

Microneedles have emerged as a novel transdermal delivery tool that enables the delivery of various products such as drugs, vaccines, or cosmetic ingredients. Although the demand for solid microneedles composed of biocompatible polymer is increasing, the manufacture of microneedles using poly-lactic acid (PLA) with rapid drug-releasing is yet to be established and the process is still in its infancy. Here, we propose a novel strategy for the fabrication of PLA solid microneedles which enable a drug to be burst-released based on a solvent-casting process. This approach offers extreme simplicity, broad geometric capability, cost-effectiveness, and scalability based on high fidelity-replicas. It was verified that microneedles of various heights (250–500 μm) could be fabricated with appropriate mechanical strength to penetrate the stratum corneum layer of skin. By adding sugar in the composition of PLA microneedle, it was observed that both hydrophilic and hydrophobic drugs can be rapidly released within 30 min. Our burst drug-releasing PLA microneedle having both characteristics of solid microneedle and soluble microneedle and its fabrication approach based on solvent-casting will contribute to getting microneedle technology close to commercialization and beyond existing technical limitations.

Fabrication of hydrophobic PLA filaments for additive manufacturing.

There is an ever-greater need for self-cleaning and water-repelling properties of hydrophobic materials at this time in history, mainly due to the coronavirus disease 2019 (COVID-19) pandemic. However, the fabrication processes used to create hydrophobic materials are typically time-consuming and costly. Thus, this study aims to create hydrophobic materials based on low-cost manufacturing. In this study, polylactic acid (PLA) was mixed with various concentrations of hexadecyltrimethoxysilane (HDTMS) and polytetrafluoroethylene (PTFE) with the aid of solvents, chloroform, and acetone, through the solvent casting and melt extrusion process, which is capable of producing hydrophobic PLA filaments suitable for additive manufacturing (AM). Water contact angle (WCA) measurements were performed to verify the improved hydrophobicity of PLA/HDTMS/PTFE filaments. According to the results, it was discovered that the best filament WCAs were achieved with 2 g (10 wt%) of PLA, 0.2 ml of HDTMS, and 1 ml of PTFE (2 g PLA + 0.2 ml HDTMS + 1 ml PTFE), producing an average WCA of 131.6° and the highest WCA of 132.7°. These results indicate that adding HDTMS and PTFE to PLA significantly enhances filament hydrophobicity. Additionally, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) techniques were utilized to characterize the surface morphology, molecular interactions, and thermal decompositions of the prepared PLA/HDTMS/PTFE filaments. This study revealed that compared to 2 g of pure PLA filament, HDTMS and PTFE altered the microstructure of the filament. Its thermal degradation temperature was impacted, but the melting temperature was not. Therefore, the PLA/HDTMS/PTFE filament is good enough to be printed by the fused filament fabrication (FFF) AM process.Graphical abstract

Structural, Thermal, Optical, Mechanical, and Antibacterial Properties of PLA/Nanoclay/TiO2 Nanocomposite Films

In this report, Polylactide/Nanoclay/TiO2 nanocomposite films with two different weight percentages (2wt% and 5wt %) of clay and TiO2 nanoparticles were prepared by a cost-effective approach. A solvent casting process with the help of a cost-effective film applicator was used to prepare nanocomposite films. The surface morphology investigations revealed the agglomeration of fillers at higher weight percentages and uniform mixing of fillers at lower weight percentages. The crystallinity of the prepared films did not alter much with the nanofiller addition. Nanofillers with a 2wt% concentration in the PLA matrix enhanced thermal and mechanical properties significantly. The PLA nanocomposite films have exhibited an intense broad emission band in violet color with a wavelength of ≈420 nm. In addition, the antibacterial activity of polylactic acid nanocomposite films was investigated against Gram-positive S. aureus and Gram-negative E. coli bacteria. The enhanced antibacterial activity is observed for a 5wt% concentration of nanofillers. The results showed that the antibacterial activity increases with nanofiller concentration. This study presents a simple and cost-effective approach to preparing nanocomposite films with tuneable properties of mechanical, thermal, and antibacterial activity.

The Largest Quasicrystalline Tiling with Dodecagonal Symmetry from a Single Pentablock Quarterpolymer of the AB1CB2D Type.

A quasicrystalline tiling pattern with tile size of ca. 60 nm has been discovered in the bulk state of a four-component pentablock polymer molecule of the AS1IS2P type, where A, S, I, and P denote poly(4-vinylbenzyldimethylamine), polystyrene, polyisoprene, and poly(2-vinylpyridine), respectively. The polymer samples used were prepared by anionic polymerizations and have narrow molecular weight distribution. The sample films were obtained by an extremely slow solvent-cast process from dilute solutions of tetrahydrofuran for 14 days. It has been found by TEM observation that the quarterpolymer, AS1IS2P-4 (Mn = 149 kg/mol, ϕA/ϕS1/ϕI/ϕS2/ϕP = 0.12/0.27/0.20/0.29/0.13), reveals two final stable structures, i.e., a 3.3.4.3.4 periodic tiling pattern as a minor component and a quasicrystalline (QC) tiling with dodecagonal symmetry as a major component, where the former includes a triangle/square number ratio of 2 and the latter has one of approximately 2.28, which is close enough to the ideal ratio, 4/ 2.31, for the triangle/square random tiling of the dodecagonal QC tiling (DDQC). Two structures were also clearly proved by SAXS diffraction patterns. Here, it should be noted this QC structure having a tile side length of ca. 60 nm was created with a single block polymer molecule.

Effect of ZnO, SiO<sub>2</sub> and Al<sub>2</sub>O<sub>3</sub> Doped on Morphological, Optical, Structural and Mechanical Properties of Polylactic Acid

In this study, an experimental investigation of the effect of addition of Alumina (Al2O3), Zinc Oxide (ZnO), and Silicon Oxide (SiO2) particles powders on the mechanical behavior and crystallinity of the PLA films was carried. Granulated of Polylactic acid (PLA) and ceramic powders with different concentrations were prepared to form PLA/ZnO and PLA/ZnO-SiO2-Al2O3composites films using a solvent casting process. Morphology of PLA and composite films were examined by optical microscopy, chemical and crystal structures of composites are analyzed by (ATR-FTIR) spectroscopy and XRD techniques. Tensile strength and young modulus are determined by traction test. The obtained result by optical microscopy shows the micrograph of PLA samples with different composition are evenly distributed on the film surface. The intensity of the absorption band located at 754 cm-1which correspond to the crystalline phase of PLA is verified by the ATR-FTIR characterization. The XRD diffraction shows that the ceramic particles influence on the peaks intensity of PLA films localized at 19.5 ° C and 22.5 ° C, which indicate an augmentation in the crystallinity of the composite films. Mechanical tests show Tensile strength and Elasticity modulus are improved after the addition of Oxide Particles to Polylactic acid films.

Lemna minor aqueous extract as a natural ingredient incorporated in poly (vinyl alcohol)-based films for active food packaging systems

An aqueous extract of Lemna minor (LE – 0.5%, dry weight/volume), a wild spontaneous aquatic species, was used as an active agent in poly (vinyl alcohol) (PVA) films at the concentrations of 1, 5, 10, 20 wt%, realized through the solvent casting process. This species was selected after determining a high total phenol content (TPC – 6.7 mg g−1 DW) and antioxidant of its aqueous extract. Transparency, color and morphological studies were considered to define the effect of the LE component on the optical properties of the matrix obtained. In addition, antioxidant, antifungal and antibacterial studies were performed to shed light on the LE effect on the active functional properties of the realized films for multifunctional packaging. The optical characterization of the obtained films revealed that the extract of Lemna minor in PVA films induced some alterations, although its presence determined positive radical scavenging and antimicrobial activity. These results demonstrate the possibility of using these polymeric systems in the food packaging sector.

Morphological, crystallinity and thermal stability characterization of poly(3-hydroxybutyrate-Co-3-hydroxyhexanoate)/zinc oxide nanoparticles bionanocomposites: Effect of filler content

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx)/ZnO-NP nanoparticles bionanocomposites were elaborated by melt compounding in a twin-screw extruder at content ratio of 1.5, 3 and 6 wt.%. Morphology, crystallinity and thermal stability of the PHBHHx-based bionanocomposite samples were investigated by scanning electron microscopy (SEM), wide angle X-ray Diffraction (WAXD) and thermogravimetric analysis (TGA) aiming at evaluating the structure-properties relationships with respect to filler content and to neat PHBHHx. Morphological observations by SEM of the fractured surface of the bionanocomposite samples showed that ZnO-NP was randomly dispersed in PHBHHx matrix, with however a noticeable presence of filler aggregates at 6 wt.%. WAXD patterns displayed an increase in crystallinity of PHBHHx bionanocomposites with increasing ZnO-NP content, whereas TGA data indicated a decrease in thermal stability in comparison with the neat polymer. This result showed that the addition of ZnO-NP promoted the thermal degradation of PHBHHx through a random chain scission mechanism. Moreover, it was found that beyond 3 wt.% of filler content, no significant change was observed in the properties of PHBHHx/ZnO-NP bionanocomposites. The study highlighted the potential use of ZnO-NP at low content, as reinforcement in PHBHHx without necessarily carrying out any filler surface treatment nor solvent casting process.

Development of Antioxidant Packaging Film Based on Chinese Bayberry Tannin Extract and Polyvinyl Alcohol

The current work explores the potential use of commercial Chinese bayberry tannin (BT) to develop antioxidant PVA-based films using solvent casting process for packaging applications. The effect of BT concentration on opacity, water resistance and antioxidant capacity of resulting films was investigated. Properties like tensile strength, thermal behavior, and morphological aspects were also characterized. The experimental results showed that PVA/BT films formed with uniformly brown color and generally good transparency, offering good antioxidant ability. The PVA film containing BT presented slightly higher water resistance according to the results of moisture content and water vapor permeability, especially at low BT content (

Surface-Modifying Effect of Zwitterionic Polyurethane Oligomers Complexed with Metal Ions on Blood Compatibility.

To prevent unsolved problems of medical devices, we hypothesized that combinatorial effects of zwitterionic functional group and anti-bacterial metal ions can reduce effectively the thrombosis and bacterial infection of polymeric biomaterials. In this research, we designed a novel series of zwitterionic polyurethane (zPU) additives to impart anti-thrombotic properties to a polyvinyl chloride (PVC) matrix. We have synthesized zPUs by combination of various components and zPUs complexed with metal ions. Zwitterion group was prepared by reaction with 1,3-propane sultone and Nmethyldiethanolamine and metal ions were incorporated into sulfobetaine chains via molecular complexation. These zPU additives were characterized using FT-IR, 1H-NMR, elemental analysis, and thermal analysis. The PVC film blended with zPU additives were prepared by utilizing a solvent casting and hot melting process. Water contact angle demonstrated that the introduction of zwitterion group has improved hydrophilicity of polyurethanes dramatically. Protein adsorption test resulted in improved anti-fouling effects dependent on additive concentration and decreases in their effects by metal complexation. Platelet adhesion test revealed anti-fouling effects by additive blending but not significant as compared to protein resistance results. With further studies, the synthesized zPUs and zPUs complexed with metal ions are expected to be used as good biomaterials in biomedical fields. Based on our results, we can carefully estimate that the enhanced anti-fouling effect contributed to reduced platelet adhesion. Schematic explanation of the effect of zwitterionic polyurethane additives for blood-compatible and anti-bacterial bulk modification.

Comparative evaluation of cellulose nanocrystals from bagasse and coir agro-wastes for reinforcing PVA-based composites.

In order to increase resilience of planters against climate change and bring additional economic benefits, agro-wastes can be exploited for extracting nanocellulose to produce eco-friendly composites. This paper focused on extracting nanocellulose from sugarcane bagasse and coir (cocos nucifera) using chemical methods including mercerisation, bleaching and acid hydrolysis. Taguchi Design of Experiment showed that the optimum alkaline treatment conditions of bagasse were at 2 wt% NaOH at 90 °C for 16 h. The morphological changes occurring along each treatment stage were observed using Fourier-Transform Infrared spectroscopy and Scanning Electron Microscopy. The differences in the nanoparticles extracted from the two biomass were studied through the determination of crystallinity indexes and particle size. Cellulose nanocrystals (CNCs) from coir exhibited a total crystallinity index (TCI) of 1.03 and an average particle size of 137.3 nm while CNCs extracted from sugarcane bagasse under similar treatment conditions had a TCI of 0.85 and an average particle size of around 48 µm. Dynamic Light Scattering findings showed risks of agglomeration after freeze drying. Bio-nanocomposite films with polyvinyl alcohol (PVA) as matrix were manufactured by the solvent casting process. The highest tensile strength (38.2 MPa) was obtained for CNCs extracted from coir at a CNC/PVA loading of 0.5 wt%, representing a 96.9% increase in the tensile strength as compared to the unreinforced PVA matrix. This study showed that sugarcane bagasse and coir are suitable sources of nanocellulose and can be used to prepare bio-composites with considerably high tensile strengths.

Multilayer photonic films based on interlocked chiral-nematic cellulose nanocrystals in starch/chitosan

In this study, a new approach to employ and control cellulose nanocrystal (CNC) chiral nematic structure as a biodegradable, intelligent material was investigated. Tuned CNC self-assembled films were interlocked between two layers of citric acid, cross-linked starch/chitosan (1:1) films through the solvent casting process. This method increased the mechanical properties of produced films and created a selective reflection band from UV to near-IR depending on the helical pitch of the chiral nematic CNC layer. The features of these intelligent films have potential for different applications, from UV protective packaging to biomedical uses. The water vapor permeability (WVP) of the produced films decreased considerably by adding a CNC layer into the cross-linked starch/chitosan structure. Also, the WVP was different for the different helical pitches of the CNC layer. The starch/chitosan (outer layer) also showed a remarkable antibacterial property against E. coli, P. fluorescens, S. Enteritidis, and S. aureus which could be useful for biomedical applications or antibacterial packaging.