Spruce Bark-Extracted Lignin and Tannin-Based Bioresin-Adhesives: Effect of Curing Temperatures on the Thermal Properties of the Resins.

In this study, formaldehyde-free bioresin adhesives were synthesised from lignin and tannin, which were obtained from softwood bark. The extraction was done via organosolv treatment and hot water extraction, respectively. A non-volatile, non-toxic aldehyde, glyoxal, was used as a substitute for formaldehyde in order to modify the chemical structure of both the lignin and tannin. The glyoxal modification reaction was confirmed by ATR-FTIR spectroscopy. Three different resin formulations were prepared using modified lignin along with the modified tannin. The thermal properties of the modified lignin, tannin, and the bioresins were assessed by DSC and TGA. When the bioresins were cured at a high temperature (200 °C) by compression moulding, they exhibited higher thermal stability as well as an enhanced degree of cross-linking compared to the low temperature-cured bioresins. The thermal properties of the resins were strongly affected by the compositions of the resins as well as the curing temperatures.

All-Cellulose Composites: A Review of Recent Studies on Structure, Properties and Applications.

Nowadays, there is greater demand for greener materials in societies due to environmental consciousness, depleting fossil fuels and growing ecological concerns. Within the foreseeable future, industries and suppliers will be required to be more aware of challenges faced due to the availability of resources and use more sustainable and renewable raw materials. In this context, cellulose can be expected to become a vital resource for materials owing to its abundance, versatility as a biopolymer, several different forms and potential applications. Thus, all-cellulose composites (ACCs) have gained significant research interest in recent years. ACC is a class of biocomposites in which the matrix is a dissolved and regenerated cellulose, while the reinforcement is undissolved or partly dissolved cellulose. This review paper is intended to provide a brief outline of works that cover recent progress in the manufacturing and processing techniques for ACCs, various cellulose sources, solvents and antisolvents, as well as their properties.

Hybrid Polymer Composites of Bio-Based Bast Fibers with Glass, Carbon and Basalt Fibers for Automotive Applications-A Review.

Composites with reinforcements based on bast fibers such as flax, hemp and kenaf offer many advantages such as weight reduction, improved specific impact, flexural, acoustic properties, and balanced performance to cost that can be achieved by properly designing the material composition. Their position is well established, especially in the nonstructural automotive applications. However, in structural applications of composites, their mechanical property profile is not comparable to the dominant reinforcements such as glass and carbon fibers. The low mechanical properties of these composites could be improved by hybridization that involves adding high-performance fibers to the bast fiber composites that could improve the low mechanical performance of the bast fiber composites. The review presented in this article provides an overview of the developments in the field of hybrid polymer composites composed of bio-based bast fibers with glass, carbon, and basalt fibers. The focus areas are the composite manufacturing methods, the influence of hybridization on the mechanical properties, and the applications of hybrid composites.

Textile-Friendly Interconnection between Wearable Measurement Instrumentation and Sensorized Garments-Initial Performance Evaluation for Electrocardiogram Recordings.

The interconnection between hard electronics and soft textiles remains a noteworthy challenge in regard to the mass production of textile-electronic integrated products such as sensorized garments. The current solutions for this challenge usually have problems with size, flexibility, cost, or complexity of assembly. In this paper, we present a solution with a stretchable and conductive carbon nanotube (CNT)-based paste for screen printing on a textile substrate to produce interconnectors between electronic instrumentation and a sensorized garment. The prototype connectors were evaluated via electrocardiogram (ECG) recordings using a sensorized textile with integrated textile electrodes. The ECG recordings obtained using the connectors were evaluated for signal quality and heart rate detection performance in comparison to ECG recordings obtained with standard pre-gelled Ag/AgCl electrodes and direct cable connection to the ECG amplifier. The results suggest that the ECG recordings obtained with the CNT paste connector are of equivalent quality to those recorded using a silver paste connector or a direct cable and are suitable for the purpose of heart rate detection.

3D printing of polypropylene reinforced with hemp fibers: Mechanical, water absorption and morphological properties.

The aim of this study was to develop and additively manufacture polypropylene-hemp fiber (PPHF) composites, which were composed of polypropylene (PP) and hemp fibers (HF) in various percentages (5%, 10%, and 20%). The objective was to examine the mechanical properties and water absorption behaviors of extruded PP, conventional filament PP and PPHF composites. The findings of the flexural and tensile tests provided important valuable information. In comparison to the other materials examined, extruded PP had the highest flexural modulus and strength, but filament PP had the lowest mechanical properties. The results showed that the 5% hemp PP composite exhibited the highest tensile strength, and the 20% hemp PP composite showed the highest Young's modulus. These results highlight how crucial hemp fiber content is in modifying the mechanical characteristics of a polymeric material to obtain the material with desirable properties for specific industry requirements.

Influence of the Manufacturing Method (3D Printing and Injection Molding) on Water Absorption and Mechanical and Thermal Properties of Polymer Composites Based on Poly(lactic acid).

The manufacturing method influences the properties of the produced components. This work investigates the influence of manufacturing methods, such as fused deposition modeling (3D printing) and injection molding, on the water absorption and mechanical and thermal properties of the specimens produced from neat bio-based poly(lactic acid) (PLA) polymer and poly(lactic acid)/wood composites. Acrylonitrile butadiene styrene (ABS) acts as the reference material due to its low water absorption and good functional properties. The printing layer thickness is one of the factors that affects the properties of a 3D-printed specimen. The investigation includes two different layer thicknesses (0.2 mm and 0.3 mm) while maintaining uniform overall thickness of the specimens across two manufacturing methods. 3D-printed specimens absorb significantly higher amounts of water than the injection-molded specimens, and the increase in the layer thickness of the 3D-printed specimens contributes to further increased water absorption. However, the swelling due to water absorption in 3D-printed specimens decreases upon increased layer thickness. The tensile, flexural, and impact properties of all of the specimens decrease after water absorption, while the properties improve upon decreasing the layer thickness. Higher porosity upon increasing the layer thickness is the predominant factor. The results from dynamic mechanical analysis and microscopy validate the outcomes. The results from this experimental study highlight the limitations of additive manufacturing.

Production and Characterization of Melt-Spun Poly(3-hydroxybutyrate)/Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) Blend Monofilaments.

We investigated the melt-spinning potential of a poly(3-hydroxybutyrate)/poly(3-hydroxybutyrate-co-4-hydroxybutyrate) blend using a piston spinning machine with two different spinneret diameters (0.2 and 0.5 mm). Results from the differential scanning calorimetry, dynamic mechanical thermal analysis, and tensile testing showed distinct filament properties depending on the monofilaments' cross-sectional area. Finer filaments possessed different melting behaviors compared to the coarser filaments and the neat polymer, indicating the formation of a different type of polymer crystal. Additionally, the mechanical properties of the finer filament (tensile strength: 21.5 MPa and elongation at break: 341%) differed markedly from the coarser filament (tensile strength: 11.7 MPa, elongation at break: 12.3%). The hydrolytic stability of the filaments was evaluated for 7 weeks in a phosphate-buffered saline solution and showed a considerably reduced elongation at break of the thinner filaments. Overall, the results indicate considerable potential for further filament improvements to facilitate textile processing.

Mechanical Properties of Bio-Based Sandwich Composites Containing Recycled Polymer Textiles.

In this paper, sandwich composites were produced by compression moulding techniques, and they consisted of regenerated cellulose fabric (rayon) and bio-based polypropylene (PP) to form facings, while virgin and recycled polyamide (PA) textiles were used as core materials. To compare the mechanical performance between sandwich composites and typical composite designs, a control composite was produced to deliver the same weight and fiber mass fraction from rayon and PP. To evaluate the influence of recycled textile on the mechanical properties of the composites, a series of flexural, low velocity impact (LVI) and tensile tests were performed. It was found that the incorporation of thicker PA textile enhanced the bending stiffness by two times and the peak flexural force by 70% as compared to those of control. Substitution of a layer of recycled textile for two layers of rayon provided a good level of impact energy absorption capacity (~28 J) and maximum force (~4893-5229 N). The tensile strength of the four sandwich composites was reported to be in the range of 34.20 MPa and 46.80 MPa. This value was 91.90 for the control composite. The 2D cross-section slices of the composite specimens did not show any evidence of fiber tow debonding, fiber bundle splitting, or delamination.

Enhancing Sustainability: Jute Fiber-Reinforced Bio-Based Sandwich Composites for Use in Battery Boxes.

The rising industrial demand for environmentally friendly and sustainable materials has shifted the attention from synthetic to natural fibers. Natural fibers provide advantages like affordability, lightweight nature, and renewability. Jute fibers' substantial production potential and cost-efficiency have propelled current research in this field. In this study, the mechanical behavior (tensile, flexural, and interlaminar shear properties) of plasma-treated jute composite laminates and the flexural behavior of jute fabric-reinforced sandwich composites were investigated. Non-woven mat fiber (MFC), jute fiber (JFC), dried jute fiber (DJFC), and plasma-treated jute fiber (TJFC) composite laminates, as well as sandwich composites consisting of jute fabric bio-based unsaturated polyester (UPE) composite as facing material and polyethylene terephthalate (PET70 and PET100) and polyvinyl chloride (PVC) as core materials were fabricated to compare their functional properties. Plasma treatment of jute composite laminate had a positive effect on some of the mechanical properties, which led to an improvement in Young's modulus (7.17 GPa) and tensile strength (53.61 MPa) of 14% and 8.5%, respectively, as well as, in flexural strength (93.71 MPa) and flexural modulus (5.20 GPa) of 24% and 35%, respectively, compared to those of JFC. In addition, the results demonstrated that the flexural properties of jute sandwich composites can be significantly enhanced by incorporating PET100 foams as core materials.

Mechanical and Thermal Properties of Wood-Fiber-Based All-Cellulose Composites and Cellulose-Polypropylene Biocomposites.

This article explores wood-fiber-based fabrics containing Lyocell yarn in the warp and Spinnova-Lyocell (60%/40%) yarn in the weft, which are used to form unidirectional all-cellulose composites (ACC) through partial dilution in a NaOH-urea solution. The aim is to investigate the role of the yarn orientation in composites, which was conducted by measuring the tensile properties in both the 0° and 90° directions. As a reference, thermoplastic biocomposites were prepared from the same fabrics, with biobased polypropylene (PP) as the matrix. We also compared the mechanical and thermal properties of the ACC and PP biocomposites. The following experiments were carried out: tensile test, TGA, DSC, DMA, water absorption test and SEM. The study found no significant difference in tensile strength regarding the Spinnova-Lyocell orientation between ACC and PP biocomposites, while the composite tensile strength was clearly higher in the warp (Lyocell) direction for both composite variants. Elongation at break doubled in ACC in the Lyocell direction compared with the other samples. Thermal analysis showed that mass reduction started at a lower temperature for ACC, but the thermal stability was higher compared with the PP biocomposites. Maximum thermal degradation temperature was measured as being 352 °C for ACC and 466 °C for neat PP, and the PP biocomposites had two peaks in the same temperature range (340-474 °C) as ACC and neat PP combined. ACCs absorbed 93% of their own dry weight in water in just one hour, whereas the PP biocomposites BC2 and BC4 absorbed only 10% and 6%, respectively. The study highlights the different properties of ACC and PP reference biocomposites that could lead to further development and research of commercial applications for ACC.

All-Cellulose Composite Laminates Made from Wood-Based Textiles: Effects of Process Conditions and the Addition of TEMPO-Oxidized Nanocellulose.

All-cellulose composites (ACCs) are manufactured using only cellulose as a raw material. Biobased materials are more sustainable alternatives to the petroleum-based composites that are used in many technical and life-science applications. In this study, an aquatic NaOH-urea solvent system was used to produce sustainable ACCs from wood-based woven textiles with and without the addition of TEMPO-oxidized nanocellulose (at 1 wt.-%). This study investigated the effects of dissolution time, temperature during hot press, and the addition of TEMPO-oxidized nanocellulose on the mechanical and thermal properties of the composites. The results showed a significant change in the tensile properties of the layered textile composite at dissolution times of 30 s and 1 min, while ACC elongation was the highest after 2 and 5 min. Changes in hot press temperature from 70 °C to 150 °C had a significant effect: with an increase in hot press temperature, the tensile strength increased and the elongation at break decreased. Incorporating TEMPO-oxidized nanocellulose into the interface of textile layers before partial dissolution improved tensile strength and, even more markedly, the elongation at break. According to thermal analyses, textile-based ACCs have a higher storage modulus (0.6 GPa) and thermal stabilization than ACCs with nanocellulose additives. This study highlights the important roles of process conditions and raw material characteristics on the structure and properties of ACCs.

Fabrication: Mechanical Testing and Structural Simulation of Regenerated Cellulose Fabric Elium® Thermoplastic Composite System.

Regenerated cellulose fibres are an important part of the forest industry, and they can be used in the form of fabrics as reinforcement materials. Similar to the natural fibres (NFs), such as flax, hemp and jute, that are widely used in the automotive industry, these fibres possess good potential to be used for semi-structural applications. In this work, the mechanical properties of regenerated cellulose fabric-reinforced poly methyl methacrylate (PMMA) (Elium®) composite were investigated and compared with those of its natural fibre composite counterparts. The developed composite demonstrated higher tensile strength and ductility, as well as comparable flexural properties with those of NF-reinforced epoxy and Elium® composite systems, whereas the Young's modulus was lower. The glass transition temperature demonstrated a value competitive (107.7 °C) with that of other NF composites. Then, the behavior of the bio-composite under bending and loading was simulated, and a materials model was used to simulate the behavior of a car door panel in a flexural scenario. Modelling can contribute to predicting the structural behavior of the bio-based thermoplastic composite for secondary applications, which is the aim of this work. Finite element simulations were performed to assess the deflection and force transfer mechanism for the car door interior.

The promiscuous potential of cellulase in degradation of polylactic acid and its jute composite.

It has been suggested that cellulolytic enzymes can be effective on the degradation of PLA samples. The idea was investigated by examining the impact of cellulase on degradation of PLA and PLA-jute (64/36) composite in an aqueous medium. The obtained results demonstrated 55% and 61% thickness reduction in PLA and PLA-jute specimens after four months of treatment, respectively. Gel permeation chromatography (GPC) showed significant decline in the number average molecular weight (Mn) approximately equal to 85% and 80% for PLA and PLA-jute in comparison with their control. The poly dispersity index (PDI) of PLA and PLA-jute declined 41% and 49% that disclosed more homogenous distribution in molecular weight of the polymer after treatment with cellulase. The cellulase promiscuity effect on PLA degradation was further revealed by Fourier-transform infrared spectroscopy (FT-IR) analysis where substantial decrease in the peak intensities of the polymer related functional groups were observed. In addition, PLA biodegradation was studied in more detail by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) of control and cellulase treated specimens. The obtained results confirmed the promiscuous function of cellulase in the presence or the absence of jute as the specific substrate of cellulase. This can be considered as a major breakthrough to develop effective biodegradation processes for PLA products at the end of their life cycle.

Effect of ceramic filler content on the mechanical and thermal behaviour of poly-L-lactic acid and poly-L-lactic-co-glycolic acid composites for medical applications.

One main application of resorbable poly-L-lactic acid (PLLA) and poly-L-lactic-co-glycolic acid (PLGA) based materials is in medical implants. In this study composites were made from PLLA and PLGA with hydroxyapatite (HAp) respective beta-tricalcium phosphate (beta-TCP) fillers. The filler content and particle size were varied, and the thermal properties as well as the mechanical strength of the composites were investigated. The composites were made by an extrusion compounding process giving 2-2.5 mm diameter sized profiles. The results verified that the thermal stability of the composites was reasonable during the optimized compounding conditions. Scanning electron microscopy revealed that the fillers were well dispersed in the polymer matrices. The mechanical properties were improved by the addition of the fillers. The optimum mechanical properties for the extruded profiles were obtained with the HAp fillers. The E-modulus was increased from 3.3 to 4.6 GPa by addition of filler particles (30 wt%) whereas the flexural strength was reduced from 133 to 106 MPa.

Synthesis and Properties of Thermosets from Tung Oil and Furfuryl Methacrylate.

This work focuses on the development of cross-linked polymer from a highly unsaturated vegetable oil, tung oil (TO) and a bio-based acrylate, furfuryl methacrylate (FMA). The presence of a high degree of unsaturated carbon-carbon bonding in TO makes it a suitable precursor for polymer synthesis. Using this advantage of TO, in this work, we have synthesised a cross-linked polymer from TO and FMA through free radical polymerisation followed by Diels-Alder (DA) reaction. Successful incorporation of both of the raw materials and the two chemical reactions was shown using Fourier-transform infrared (FTIR) and Raman spectroscopy. The development of cross-linked structure was analysed through thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA).

Hydrophobic Shape-Memory Biocomposites from Tung-Oil-Based Bioresin and Onion-Skin-Derived Nanocellulose Networks.

The fabrication of smart biocomposites from sustainable resources that could replace today's petroleum-derived polymer materials is a growing field of research. Here, we report preparation of novel biocomposites using nanocellulose networks extracted from food residue (onion skin) and a vegetable oil-based bioresin. The resin was synthesized via the Diels-Alder reaction between furfuryl methacrylate and tung oil at various ratios of the components. The onion-skin-extracted cellulose nanofiber and cellulose nanocrystal networks were then impregnated with the resins yielding biocomposites that exhibited improved mechanical strength and higher storage modulus values. The properties of the resins, as well as biocomposites, were affected by the resin compositions. A 190-240-fold increase in mechanical strength was observed in the cellulose nanofiber (CNF) and cellulose nanocrystal (CNC)-reinforced biocomposites with low furfuryl methacrylate content. The biocomposites exhibited interesting shape-memory behavior with 80-96% shape recovery being observed after 7 creep cycles.

Melt rheology and extrudate swell properties of talc filled polyethylene compounds.

An experimental study of high-density polyethylene (HDPE) composites filled with talc (0-15 wt.%) was carried out to investigate the rheological properties. The apparent melt viscosity, melt density, and die-swell ratio (B) of the composites were measured at constant shear stress and constant shear rate by using a melt flow indexer and capillary rheometer. The experimental conditions were set to a temperature range from 190 to 220 °C for both apparatuses whereas a load range from 5 to 12.16 kg was selected for melt flow indexer and shear rate range from 1 to 10000 s-1 for capillary rheometer. The initial study showed that the talc particulates did not influence the melt viscosity compared with the neat HDPE but decreased the elasticity of the polymer system. The HDPE/talc systems obeyed power-law model in shear stress-shear rate variations and were shear thinning, meanwhile, the die-swell increased with an increased wall shear rate and shear stress. The melt density of the composites increased linearly with an increase of the filler weight fraction and decreased with the increase of the testing temperature. The talc-HDPE composites showed compressible in the molten state.

Green Conducting Cellulose Yarns for Machine-Sewn Electronic Textiles.

The emergence of "green" electronics is a response to the pressing global situation where conventional electronics contribute to resource depletion and a global build-up of waste. For wearable applications, green electronic textile (e-textile) materials present an opportunity to unobtrusively incorporate sensing, energy harvesting, and other functionality into the clothes we wear. Here, we demonstrate electrically conducting wood-based yarns produced by a roll-to-roll coating process with an ink based on the biocompatible polymer:polyelectrolyte complex poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The developed e-textile yarns display a, for cellulose yarns, record-high bulk conductivity of 36 Scm-1, which could be further increased to 181 Scm-1 by adding silver nanowires. The PEDOT:PSS-coated yarn could be machine washed at least five times without loss in conductivity. We demonstrate the electrochemical functionality of the yarn through incorporation into organic electrochemical transistors (OECTs). Moreover, by using a household sewing machine, we have manufactured an out-of-plane thermoelectric textile device, which can produce 0.2 µW at a temperature gradient of 37 K.

Osteogenic Differentiation of Human Mesenchymal Stem cells in a 3D Woven Scaffold.

Fiber-based scaffolds produced by textile manufacturing technology offer versatile materials for tissue engineering applications since a wide range of crucial scaffold parameters, including porosity, pore size and interconnectivity, can be accurately controlled using 3D weaving. In this study, we developed a weavable, bioactive biodegradable composite fiber from poly (lactic acid) (PLA) and hydroxyapatite powder by melt spinning. Subsequently, scaffolds of these fibers were fabricated by 3D weaving. The differentiation of human mesenchymal stem cells (hMSCs) in vitro was studied on the 3D scaffolds and compared with differentiation on 2D substrates having the same material composition. Our data showed that the 3D woven scaffolds have a major impact on hMSCs proliferation and activation. The 3D architecture supports the differentiation of the hMSCs into osteoblast cells and enhances the production of mineralized bone matrix. The present study further confirms that a 3D scaffold promotes hMSCs differentiation into the osteoblast-lineage and bone mineralization.

Dendritic copolymers and particulate filler composites for dental applications: degree of conversion and thermal properties.

OBJECTIVES: The aim of this study was to determine the degree of double bond conversion and thermal properties of photopolymerized dendritic copolymers and particulate filler composites that may be used as dental restorative materials. METHODS: The resins consisted of a multifunctional dendritic monomer, methyl methacrylate and varying proportions of acetoacetoxyethyl methacrylate. In addition, one of the composites contained 1,4-butanediol dimethacrylate. Camphorquinone and 2-(N,N-dimethylamino)ethyl methacrylate were used as the light-activated initiation system. The degree of conversion was determined with Fourier transform infrared spectroscopy and the thermal properties with differential scanning calorimetry. RESULTS: The degree of conversion of copolymers varied from 52 to 60% and increased with increasing concentration of acetoacetoxyethyl methacrylate. The values for the composites were 32-44%. Reaction exotherms of 0.2-9.6J/g were measured for the photopolymerized experimental materials indicating residual reactivity that increased with increasing concentration of acetoacetoxyethyl methacrylate. The residual reactivity trend seemed counter intuitive to the degree of conversion. The glass transition temperatures for the completely polymerized copolymers containing acetoacetoxyethyl methacrylate were 112-116 degrees C and for the particulate filler composites 84-87 degrees C. SIGNIFICANCE: The addition of acetoacetoxyethyl methacrylate increased the degree of conversion. The polymerization characteristics of the experimental materials were comparable to those of control materials.