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Abstract This work deals with provision and characterization of the biopolymer-based composites achieved by incorporation of cellulose fibers as the reinforcement within the glycerol plasticized matrix formed by thermoplastic cornstarch biopolymer. The function of starch-based polymers is limited due to poor mechanical properties. However, it is improved with forming a biocomposite of thermoplastic starch (TPS) as matrix and the cellulose fibers (CF) as reinforcement. The surface of cellulose fibers is successfully modified using the air plasma treatment with the aim of improving the matrix/fiber adhesion. The modified fibers are studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The TPS/CF composites are prepared using high friction and hot compression procedure. Tensile test results and SEM images of the fracture surfaces show significant improvement of adhesion between treated cellulose fibers and TPS matrix. Thermogravimetric analysis shows a considerable decomposition at approximately 250–350 °C. XRD proved the significant increase in crystallinity percentage of composites compared to TPS. [ABSTRACT FROM AUTHOR]

Wetting properties and capillary parameters are of first interest for composite and especially bio-composite manufacturing, interface compatibility between reinforcement and matrix, and durability. Few studies have been dedicated in literature to continuous textile fibers and uncured liquid resins wetting properties, and particularly the methods used may be ambiguous, revealing a wide dispersion in results. In this work a reliable method is proposed to determine properly the wetting properties of fibers and some resins commonly used for composite applications. Firstly, a procedure to characterize dispersive and polar components of surface tension for an epoxy and a partially bio-based resin with a tensiometer is proposed. Then a new method was applied on single fibers of semi-synthetic cellulose (viscose), which allows deriving representative values of contact angles from a series of measurements, minimizing the measurement scatter even when using a conventional tensiometer. Resin components and contact angles between cellulose fibers and test liquids, including resins, led to characterize dispersive and polar components of fiber surface energy. [ABSTRACT FROM AUTHOR]

Gelatin biocomposites were successfully manufactured by extrusion followed by injection. The employment of these industrial techniques, which have not been widely used in the case of biopolymers such as gelatins, represents an important advance for the development of gelatin-based biocomposites. Furthermore, the use of a non-enzymatic reaction to cross-link proteins provides a new approach to improve and control some functional properties, such as solubility and swelling. The addition of lactose in the formulations, as well as the heating of injected biocomposites, caused gelatin cross-linking, changing the protein structure towards the formation of pores and thus, solubility, density, and swelling decreased. Additionally, the cross-linked biocomposites showed good mechanical properties. [ABSTRACT FROM AUTHOR]

Fungal dead biomass composite with bentonite (FBC) efficiency was evaluated for the absorption of Ni(II) and Zn(II) from aqueous media. The process variables were optimized and maximum adsorption was achieved at pH 6 (Ni) and 5 (Zn), adsorbent dose 0.05 g, contact time 30 min, initial metal ions concentration 200 mg/L and temperature 51 °C. At optimum conditions, 161 mg/g of Ni(II) and 78.5 mg/g of Zn(II) was removed using FBC. Langmuir, Freundlich and Harkins–Jura isotherms and pseudo-first-order, pseudo-second-order and intraparticle diffusion models were applied to understand the adsorption mechanism. The pseudo-second-order kinetic model and Langmuir isotherm fitted well to the adsorption experimental data. The surfactants and salts (CaCl 2 , KCl, NaCl, CuSO 4 and FeCl 3 ) FBC pre-treatment did not affect the Ni(II) and Zn(II) adsorption. The Δ G °, Δ H ° and Δ S ° values suggest that the adsorption process of Ni(II) and Zn(II) onto FBC was spontaneous and endothermic in nature. NaOH efficiently desorbed Ni(II) and Zn(II) from FBC without compromising the adsorption capacity of composite. Results showed that FBC is efficient for the adsorption of Ni(II) and Zn(II) and is a potential candidate for the adsorption of metal ions from wastewater. [ABSTRACT FROM AUTHOR]

Environmental awareness of the global waste problem has driven the development of new green composites made from either renewable or biodegradable materials. Among the variety of available green composites, natural composites based on poly-lactic acid (PLA) have shown noteworthy performance due to their short degradation time after disposal, good strength, and ease of processing by conventional methods. In particular, green composites manufactured with PLA matrix reinforced with Manicaria Saccifera fabric (MF) display mechanical properties that have shown to be very competitive compared with similar materials. In this study, the tensile properties of a green composite of PLA reinforced with MF are optimized by using a Taguchi method approach. The processing parameters, fabric chemical treatment parameters, compression molding parameters, and fiber content are analyzed simultaneously to yield the optimum biocomposite properties. The predicted optimum parameters are experimentally verified. Tensile tests and scanning electron microscope (SEM) analysis are used. Significant improvements on both the tensile strength (114.2%), and the elastic modulus (120.6%) of the biocomposite are achieved. [ABSTRACT FROM AUTHOR]

This work presents a novel composite hydrogel consisting of silk fibroin (SF) and nanohydroxyapatite (nanoHA) prepared by a new and innovative method using ethanol as gelling agent capable of forming hydrogels in few minutes. The properties of the composite material, such as the microstructure as well as the chemical and physical properties were studied. Moreover in␣vitro studies of osteoblastic citocompatibility were performed. The microporosity and macroporosity obtained combined with interconnected porous structure and a uniform dispersion of nanoHA particles throughout the fibroin matrix makes composite hydrogel suitable for bone regeneration. The compression modulus of composite hydrogels was increased as the nanoHA concentration increased from 10 to 15 wt.% and the water uptake ability of these materials decreased with the incorporation of nanoHA. The metabolic and alkaline phosphatase activities of osteoblastic cells were improved with the incorporation of nanoHA in the SF matrix providing a more promising material for bone tissue engineering. [ABSTRACT FROM AUTHOR]

Abstract: This work describes a truss-core structure made of hemp/epoxy biocomposite based on a topology with auxetic (negative Poisson’s ratio) characteristics. Epoxy-based composites with 25wt.% of hemp yarns have been manufactured and characterized with tensile and flexural tests. Truss-core hexagonal chiral panels with the biocomposite core have been produced using a Resin Transfer Molding technique. The panels have been subjected to standard transverse shear tests, and their properties predicted with a Finite Element nonlinear modeling. The results show that the hexachiral biocomposite truss core exhibits specific shear modulus and strength significantly higher compared to the ones observed in previous demonstrators made of polymeric core. [Copyright &y& Elsevier]

Abstract: Over the last few years, intensive research has been devoted to the exploitation of “green products” based on natural resources for both matrices and as reinforcements in composite systems. The mechanical properties of reinforced biocomposites, such as flax/polylactic acid (PLA), are largely governed by interfacial properties between the two constituents apart from their intrinsic properties. Although many papers indirectly demonstrate the importance of optimising the interface between these two polymers, the exact nature of the interaction between the natural fibre and the polymeric matrix has not been clearly investigated on a fundamental level and is presently a major technological limitation of these materials. This work presents the first direct study of adhesion forces, by colloidal force microscopy, between smooth PLA films representing the polymer matrix, and a microbead of cellulose that mimic the cellulose material in flax fibres. Normalised adhesion force measurements have shown the importance of capillary forces when experiments were carried out under ambient conditions. Experiments, conducted under dry air, allowed for the deduction of the contribution of pure van der Waals forces, and our results, through the calculation of the Hamaker constant, show that these forces, for the PLA/cellulose/air system, were lower than those obtained for the cellulose/cellulose/air system and hence underlined the importance of optimising the interface among these materials. This study demonstrates the capacity of AFM to probe direct interactions in complex systems by adjusting the nature of the surface and the probe to mimic the materials in contact. Furthermore, the technique can be operated in a variety of environments, consistent with composite making and provides particular opportunity for testing and improving the properties of these new classes of composite materials. [Copyright &y& Elsevier]

Abstract: In this work, a starch-based biopolymer was reinforced with flax strands. Composite materials at different fiber content were obtained by means of high-shearing mixing followed by injection molding processing. The evaluation of the mechanical properties gave a significant increase of the strength and stiffness of composites with the percentage of flax strands. The enhancement was analyzed in terms of compatibility and extension of the adhesion at fiber–matrix interface. The intrinsic mechanical properties of the reinforcement were measured and the behavior of the obtained composites was studied in terms of the modified rule of mixtures and the modified Halpin–Tsai equations. [Copyright &y& Elsevier]

Insect cuticle as a natural biocomposite includes many favored microstructures which have been refined over centuries and endow the cuticle eminent mechanical properties. This paper first studies the microstructures of chafer cuticle through SEM observations. Several peculiar fiber configurations and fiber-ply arrangements such as branched fiber, acanth-fiber and helicoid plies are observed. These microstructures are useful for man-made fiber-reinforced composites to improve their mechanical properties. Then, a special configuration of the branched fiber found in chafer cuticle is in details analyzed through a mechanical model and experimental verification. The pullout force of fibers as an index is firstly studied through parameter study. The factors, which can improve the pullout forces, are identified. Finally, the maximal pullout force of the branched fiber is experimentally tested and compared with that of plain straight fiber. It is proved that the maximal pullout force of branched fibers is obviously greater than that of the plain straight fibers. [Copyright &y& Elsevier]