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In this study, the effects of two environmentally-friendly pulping methods along with two different reactive compatibilization methods on the foamability of poly (lactic acid) (PLA)/rice straw (RS) biocomposites have been investigated. RS as an annually renewable agricultural waste is low-cost and available. Melt-compounding and melt-foaming processes were performed through a twin-screw extrusion processing. The correlations between processing and microstructure were studied. The findings show that the RS pulping with sodium bicarbonate (SB) solution leads to the lignocellulosic particles with a porous structure. The structure causes the filler/matrix mechanical engagement and improves the interfacial adhesion and rheological properties, hence forming smaller cells with the narrowest cell size distribution. In contrast, applying ultrasound waves on the RS pulp brings the particles to very smooth surfaces. These surfaces have the highest activity at the cell nucleation stage and considerably increase the foam's cell density. The reactive compatibilizers based on epoxy and maleic anhydride groups show opposing effects on the biocomposite microstructure, depending on the RS pulp type. The use of the reactive compatibilizers in the PLA/RS pulp treated with SB led to lighter foams with larger cells and higher cell densities and void fractions. Whereas the incorporation of the compatibilizers into the biocomposites containing RS pulp treated with SB and ultrasonic waves resulted in noticeably lower cell density and larger foam density. The extruded biocomposite foams with closed-cell microstructure can be used in insulation and packaging applications. [ABSTRACT FROM AUTHOR]

Over hundreds of millions of years, organisms have evolved architected structures via precise control over hierarchically assembled components, including the integration of dissimilar materials. One such example is found in the radula system of chitons, intertidal mollusks that feed on algae growing on the rock. Their radula consists of multiple rows of ultrahard teeth, each integrated with a foldable belt-like substrate via a stiff, yet flexible stylus, which is essential for efficient rasping during the feeding process. Here, we investigate the nano and micro-scale components and architectures as well as regional mechanical properties of the stylus, and their subsequent role during the rasping of Cryptochiton stelleri. Three important factors were determined to contribute to the regio-specific stiffness of the stylus: the presence of mineral components, highly oriented chitinous fibers, and a chemically cross-linked protein matrix. All these factors are varied throughout the stylus. There is a high mineral content on the trailing edge close to the tooth and a cross-linked matrix on the leading edge, both with orientational specific oriented chitin fibers that provide force transduction to the tooth. Conversely, there is a significant lack of mineral or cross-linked matrix in the proximal end as well as a low degree of fiber orientation, resulting in a flexible region that can accommodate torsion and flexure during rasping. Understanding the graded composite structure of the stylus and applying this unique design to various engineering fields such as soft robotics, biotechnology, and the medical industry, can inspire the production of high-performance materials. Graphical Abstract [ABSTRACT FROM AUTHOR]

The purpose of this study is to evaluate in detail the usability of new cellulosic fibers extracted from the stem of the plant Strelitzia reginae, as a potential reinforcement for polymer composites. The morphological, physical, thermal, and mechanical properties of fibers were addressed for the first time in this paper. Both untreated and alkali-treated fibers were characterized, using scanning electron microscopy (SEM), Fourier-transform infrared, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), optical microscope, and X-ray diffraction (XRD) and applying tensile test for determining the mechanical behavior. For both fiber treated at one hour (T1H) and at four hours (T4H), the stem anatomy and fiber SEM micrographs showed a strong presence of fiber cells. Thermogravimetry and DSC showed that the fiber was thermally stable up to 233°C for untreated fiber, 254 and 240°C, respectively, In single-fiber tensile tests, it was observed that the fibers extracted from the stem of Strelitzia reginae were strong. The mean values of Young's modulus exhibited by untreated fibers and treated (T1H) and (T4H) are, respectively, 9.89 GPa, 12.08, and 18.39 GPa. Also mean values of tensile strength are 271.79, 306.23, and 421.39 MPa. The XRD reveals the presence of cellulose with a Crystallinity Index of 70% for raw fiber and 72% for the treated one. Fourier-transform infrared analysis well demonstrated the effect of chemical treatment. It can be concluded from the results of all above experiments that the Strelitzia reginae fibers (SR) could serve as a possible reinforcement in composite materials. [ABSTRACT FROM AUTHOR]

This study deal with the development and investigation of a novel hybrid nano-shell plant fiber biocomposite. Nano-calcium carbonate CaCO3 ranging from 1 to 5 wt% and 20 wt% banana fiber-filled hybrid biocomposite were prepared using a hand lay-up process followed by applying load on a closed mold. Nano-CaCO3 of near-uniform size and shape was synthesized from Achatina Fulica through a mechanochemical technique. The effect loading fiber of uniform 30 mm size on the mechanical, physical, thermal properties of greenpoxy composite was investigated. The influence of nano-CaCO3 loading (1 to 5 wt%) on banana fiber-filled greenpoxy composite, dynamic mechanical properties, tensile, flexural, impact strength was further investigated. The result showed that the loading of banana fiber improved mechanical properties and negatively affected temperature dependence storage modulus, loss modulus, and tan δ. Better load carrying and stress distribution capacity of the fiber within the biocomposites can be attributed to the high strength and stiffness observed for these series. The poor thermal properties of banana fiber can be ascribed to a decrease in the temperature dependence properties. The loading of nano-CaCO3 improved most of the banana-filled greenpoxy biocomposite, and hybrid composite with 2 wt% nano-CaCO3 offered superior properties. Uniform dispersion, excellent matrix/nano-CaCO3/banana fiber adhesion provided a strong structure, resulting in improved mechanical and temperature-dependant properties. [ABSTRACT FROM AUTHOR]

This paper reports the effect of lignocellulosic flour and talc powder on the thermal degradation behavior of poly (lactic acid) (PLA) by thermogravimetric analysis (TGA). Lignocellulosic flour was obtained by grinding Opuntia Ficus Indica cladodes. PLA/talc/ Opuntia Ficus Indica flour (OFI-F) biocomposites were prepared by melt processing and characterized using Wide-angle X-ray scattering (WAXS) and Scanning Electron Microscope (SEM). The thermal degradation of neat PLA and its biocomposites can be identified quantitatively by solid-state kinetics models. Thermal degradation results on biocomposites compared to neat PLA show that talc particles at 10 wt % into the PLA matrix have a minor impact on the thermal stability of biocomposites. Loading OFI-F and Talc/OFI-F mixture into the PLA matrix results in a decrease in the maximum degradation temperature, which means that the biocomposites have lower thermal stability. The activation energies (Ea) calculated by the Flynn Wall Ozawa (FWO) and Kissinger Akahira Sunose (KAS) model-free approaches and by model-fitting (Kissinger method and Coats-Redfern method) are in good agreement with one another. In addition, in this work, the degradation mechanism of biocomposites is proposed using Coats-Redfern and Criado methods. [ABSTRACT FROM AUTHOR]

Jute woven fabrics in as-received and alkali-treated conditions were respectively combined with polylactic acid resin to fabricate completely biodegradable composites by compression molding in one step. Scanning electron microscopy and differential scanning calorimetry and tensile tests were conducted to estimate the surface morphology, thermal, and mechanical properties of jute fabrics and the composites manufactured. The formability of the composites was evaluated by a thermal-stamping experiment. The results demonstrate that alkali treatment removes the surface impurities of fabrics and refine the fiber structures, lifting the thermal property of composites. As for the mechanical properties, the strength of the fabrics and composites declines while the modulus increases after alkali treatment of fabrics. Although some defects occur, the thermal-stamping experiments confirm the possibility of shaping jute/polylactic acid composite into complicated geometries. And the formability of the composites is influenced by many factors including sample sizes, the holding time of temperature, layup sequence, and so on while the number of layer makes no obvious difference to it. [ABSTRACT FROM AUTHOR]

The main objective of this work was to explore for the first time the potential of the co-grinding process using a high-energy vibrated ball mill to prepare poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/wheat straw fibers biocomposites. Grinding conditions of virgin PHBV pellets were examined by focusing on the evolution of particle size, morphology, crystallinity, and molecular weight. Temperature and grinding duration were demonstrated to be the key parameters affecting PHBV milling. In a second step, mechanical properties of biocomposites prepared by cryo-co-grinding were discussed in relation to the processing conditions and the resulting structure of materials. Comparing to virgin PHBV, the reinforcing effect of wheat straw fibers was very poor, regardless of the good dispersion of fibers within the polymer matrix induced by co-grinding. The increased brittleness and decreased toughness of biocomposites were attributed to (a) a poor interfacial compatibility between wheat straw fibers and PHBV and (b) the degradation of PHBV during processing, as revealed by the decrease in molecular weight. [ABSTRACT FROM AUTHOR]

In this study, crystalline cellulose was prepared through hydrolysis of jute fiber and was used as reinforcement of gelatin-based biocomposite film. The effects of crystalline celluloses loading on the morphology, mechanical properties and water sensitivity of the biocomposite were investigated by means of Scanning electron microscopy, tensile strength testing and water absorption testing. The developed biocomposite film showed homogeneous dispersion of crystalline celluloses within the gelatin matrix and strong interfacial adherence between matrix and reinforcement. A significant increase in tensile strength and E Modulus was also found (tensile strength was 25.4 MPa for pure gelatin and 48.2 MPa for 2% crystalline celluloses/gelatin film at 45% relative humidity), which was further induced by gamma radiation. The resulting biocomposite film also showed a higher water resistance and excellent biocompatibility. Therefore, crystalline celluloses played an important role in improving the mechanical properties as well as water resistance of the biocomposite film. [ABSTRACT FROM AUTHOR]

The potential of flax fabric in the production of ‘green’ composites based on polypropylene (PP) was evaluated. The laminate composites were prepared by compression molding of flax fabric (with and without treatment) and PP films (using different formulations of PP). The morphology and crystallization of the PP/flax composites were characterized using scanning electron microscope, X-ray diffraction, and differential scanning calorimetry. The mechanical performance of the composites was also evaluated. The results demonstrate that fiber treatment and PP formulation play important roles on the performance of composites. This study proved that the addition of the coupling agent maleic anhydride grafted PP to the composites improves the interfacial adhesion between hydrophilic flax fibers and the hydrophobic PP matrix and thus the mechanical properties. The combination of the coupling agent and reactive additive provides superior strength, modulus and brings further fire resistance to the PP/flax composites. [ABSTRACT FROM AUTHOR]

The main aim of this study was the modification of jute fibres with stearic acid using new route called azide method. The surface changes after modification process were characterized by attenuated total reflectance – Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy analyses. It was shown that the stearic acid was bonded to JF using azide method and the surface modification through azide method did not deteriorate the surface properties of JF. Representative JF containing low-density polyethylene-based composites were also prepared and characterized by tensile testing, dynamical mechanical analysis and differential scanning calorimeter. According to mechanical test results, the tensile strength and elastic modulus were increased using stearic acid modified JF through azide method. According to differential scanning calorimeter results, surface modification with stearoyl azide reduced the degree of crystallinity with respect to alkaline treated one. [ABSTRACT FROM AUTHOR]

Chicken feathers waste from poultry industry was incorporated in poly(lactic acid) matrix to obtain an environmental friendly biocomposite taking advantage of the unique properties of chicken feathers, such as low density, biodegradability and good thermal and acoustic properties, and of the biodegradability of the poly(lactic acid). The effect of manufacturing conditions on the final properties of the composite and on the matrix–fiber compatibility was studied. Optimal manufacturing conditions, in order to obtain the best mechanical results, were found at a temperature of 170–180℃ for a processing time of 5 min and a speed of mixing of 50 r/min. Young’s modulus was not very affected by the chicken feather’s content showing a maximal variation of less than 8%, indicating that is possible to include chicken feathers in a composite maintaining its stiffness. However, tensile strength and elongation decreased up to 58 and 12%, respectively, when chicken feather content was 25% because of the restraining effect of the fibers. Moreover, dimensional stability was negatively affected with the inclusion of chicken feathers. Infrared spectroscopy and scanning electron microscopy studies show that fiber–matrix interaction exists but it is weak. [ABSTRACT FROM AUTHOR]

Bamboo fiber was considered a good candidate for the reinforcement of green composites. The applications of bamboo fibers as reinforcements in fabric or structural forms to constitute composites have been widely investigated. This study conducted the process from the bamboo strips to the fibers that were compounded with the polylactide to form the composite pellets for the following injection molding process. Alkali treatment of bamboo fiber at 100℃ for 12 h could properly delignify the bamboo fiber strips, resulting in required bamboo fibers. After compounded with polylactide in a banbury mixer to form composite pellets, the injection molding process was used to make composites with improved mechanical properties, including the tensile strength, tensile modulus, flexural strength, flexural modulus, and impact strength. The reinforced effect of the bamboo fiber on polylactide was quite apparent in our experiments. A simple rule of mixture was used to approximate the tensile strength and modulus of the bamboo fiber/polylactide composite. The fire safety improvement of the biocomposite was also investigated by adding fire retardant. [ABSTRACT FROM AUTHOR]

In this study, novel acrylated epoxidized hemp oil bioresin was used in the manufacturing of jute fibre reinforced biocomposites. The 100% biocomposite laminates were characterised in terms of mechanical properties (tensile, flexural, Charpy impact and interlaminar shear), thermo-mechanical properties (glass transition temperature, storage modulus and crosslink density) and water absorption properties (saturation moisture level and diffusion coefficient). Comparisons with the equivalent synthetic vinylester resin based jute fibre reinforced biocomposite panels were performed. Scanning electron microscopic analysis confirmed panel samples containing acrylated epoxidized hemp oil to display improved fibre–matrix interfacial adhesion compared with the vinylester resin based samples. Furthermore in terms of mechanical properties acrylated epoxidized hemp oil based biocomposites compared favourably with those manufactured from vinylester resin synthetic resin. Dynamic mechanical analysis found acrylated epoxidized hemp oil based biocomposites to have lower glass transition temperature, storage modulus and crosslink density than vinylester resin based samples. Increasing acrylated epoxidized hemp oil content resulted in a marginal increase in saturation moisture content and diffusion coefficient. [ABSTRACT FROM PUBLISHER]

Novel biocomposites made of an acrylated epoxidized hemp oil based bioresin reinforced with random hemp fiber mat were manufactured by the vacuum infusion technique. Mechanical properties (tensile, flexural, Charpy impact and interlaminar shear), dynamic mechanical properties (glass transition temperature, storage modulus and crosslink density) and moisture absorption properties (saturation moisture level and diffusion coefficient) were investigated and compared with samples manufactured under the same conditions but using a commercial synthetic vinylester resin as the polymeric matrix. Results showed that the 100% biocomposites mechanical performance is comparable to that of the hybrid composites made with the synthetic resin. Moisture absorption tests showed that acrylated epoxidized hemp oil based samples displayed both higher diffusion coefficient and saturation moisture content; however, fiber reinforcement was the dominant transfer mechanism. Vinyl ester based samples were found to have higher storage modulus, glass transition temperature and crosslink density than acrylated epoxidized hemp oil samples. [ABSTRACT FROM AUTHOR]

The present work describes a biocomposite with thermal and acoustic insulating properties from agricultural or forestry residues using a steam injection molding technique. The biocomposites showed reasonable thermal insulation properties as judged based on their thermal conductivity, thermal diffusivity, and thermal stability data. The biocomposites had also good sound absorption properties. The dimensional stability of the biocomposites under accelerated weathering conditions was almost ideal. Although the flame retardancy of the biocomposites had rating acceptable to building products, it was yet concluded that for the biocomposites to have a wider market share, their flame-retardant capacity should be improved. [ABSTRACT FROM AUTHOR]