Biopolymer composites from high-cellulose pulps and/or nanocellulose

Increasingly our society seeks an economy based on renewable resources (bio-based economy) with the goal of providing materials of high value and from renewable resources. One popular renewable resource is cellulose, or forest products in general. In this study, cellulose derivatives will be combined together with bio-plastics to produce granules of thermoplastic nano-biocomposites by melt processing. The intention is to get bio-based materials with highly advanced properties that can be shaped into complex geometries using widely used industrial melt-processes such as extrusion or injection molding. The challenges in this study deal with production technologies for the realization of nanocomposites for large-scale industrial use. In a biobased society, it is important to better utilize the intrinsic potential of wood cellulose, beyond paper and board products. Although nanocellulose is a large research area, and many companies have pilot-scale production units, there are no commercial biocomposites based on nanocellulose. One reason is the challenges associated with the mixing of thermoplastics with nanoparticles. Here, the hypothesis is that pulp fibers can be chemically pretreated and then disintegrated in the mixing extruder, so that a high-performance biocomposite with well-dispersed nanofibers is obtained. If this works, it may inspire the development of a new generation of thermoplastic biocomposites, where the forest industry could have a competetive advantage. These biocomposites may have superior properties to regular biocomposites in terms of mechanical performance, including toughness. Therefore, the value chain of the project comprises pulping companies, for chemical modification of pulp, compounding technologies and polymer compound development, and the end user using the material in different final applications. In this study, chemical pulp of high cellulose content is being used as reinforcing material of selected biomatrices. Parameters such as the level of microfibrillation of wood fibers, different compounding strategies, as well as interface compatibility and anisotropy effects are studied. The combination of research and technology challenges provide interesting aspects to both academia and industrial sectors

Nanopaper-Based Organic Inkjet-Printed Diodes

AbstractThe rise of internet of things (IoTs) applications has led to the development of a new generation of light‐weight, flexible, and cost‐effective electronics. These devices and sensors have to be simultaneously easily replaceable and disposable while being environmentally sustainable. Thus, the introduction of new functionalized materials with mechanical flexibility that can be processed using large‐area and facile fabrication methods (as, for example, printing technologies) has become a matter of great interest in the scientific community. In this context, cellulose nanofibers (CNFs) are renewable, affordable, robust, and nontoxic materials that are rapidly emerging as components for eco‐friendly electronics. Their combination with conductive polymers (CPs) to obtain conductive nanopapers (CNPs) allows moving their functionality from just substrates to active components of the device. In this work, a route for the inkjet‐printing of organic diodes is outlined. The proposed strategy is based on the use of CNPs as both substrates and bottom electrodes onto which insulator and organic semiconducting layers are deposited to fabricate novel diode structures. Remarkable rectification ratios of up to 1.2 × 103 at |3 V| and a current density up to 5.1 µA cm−2 are achieved. As a proof‐of‐concept of the potentiality of the approach for versatile, low‐temperature, and disposable sensing applications, an NO2 gas sensor is presented

Biocomposites from Rice Straw Nanofibers: Morphology, Thermal and Mechanical Properties

Agricultural residues are major potential resources for biomass and for material production. In this work, rice straw residues were used to isolate cellulose nanofibers of different degree of oxidation. Firstly, bleached rice fibers were produced from the rice straw residues following chemical extraction and bleaching processes. Oxidation of rice fibers mediated by radical 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) at pH 10 was then applied to extract rice cellulose nanofibers, with diameters of 3-11 nm from morphological analysis. The strengthening capacity of rice nanofibers was tested by casting nanocomposite films with poly(vinyl alcohol) polymer. The same formulations with eucalyptus nanofibers were produced as comparison. Their thermal and mechanical performance was evaluated using thermogravimetry, differential scanning calorimetry, dynamic mechanical analysis and tensile testing. The glass transition of nanocomposites was shifted to higher temperatures with respect to the pure polymer by the addition of rice cellulose nanofibers. Rice nanofibers also acted as a nucleating agent for the polymer matrix. More flexible eucalyptus nanofibers did not show these two phenomena on the matrix. Instead, both types of nanofibers gave similar stiffening (as Young\u27s modulus) to the matrix reinforced up to 5 wt.%. The ultimate tensile strength of nanocomposite films revealed significant enhancing capacity for rice nanofibers, although this effect was somehow higher for eucalyptus nanofibers

Bacterial Cellulose Network from Kombucha Fermentation Impregnated with Emulsion-Polymerized Poly(methyl methacrylate) to Form Nanocomposite

The use of bio-based residues is one of the key indicators towards sustainable development goals. In this work, bacterial cellulose, a residue from the fermentation of kombucha tea, was tested as a reinforcing nanofiber network in an emulsion-polymerized poly(methyl methacrylate) (PMMA) matrix. The use of the nanofiber network is facilitating the formation of nanocomposites with well-dispersed nanofibers without using organic solvents or expensive methodologies. Moreover, the bacterial cellulose network structure can serve as a template for the emulsion polymerization of PMMA. The morphology, size, crystallinity, water uptake, and mechanical properties of the kombucha bacterial cellulose (KBC) network were studied. The results showed that KBC nanofibril diameters were ranging between 20-40 nm and the KBC was highly crystalline, >90%. The 3D network was lightweight and porous material, having a density of only 0.014 g/cm(3). Furthermore, the compressed KBC network had very good mechanical properties, the E-modulus was 8 GPa, and the tensile strength was 172 MPa. The prepared nanocomposites with a KBC concentration of 8 wt.% were translucent with uniform structure confirmed with scanning electron microscopy study, and furthermore, the KBC network was homogeneously impregnated with the PMMA matrix. The mechanical testing of the nanocomposite showed high stiffness compared to the neat PMMA. A simple simulation of the tensile strength was used to understand the limited strain and strength given by the bacterial cellulose network. The excellent properties of the final material demonstrate the capability of a residue of kombucha fermentation as an excellent nanofiber template for use in polymer nanocomposites

Geometric figures and mobile technology for numerical relations as a way to teach and learn in the XXI century

Les relacions numèriques actuals, com a part de les matemàtiques, utilitzen dibuixos, signes i codis, així com mètodes manuals que no han variat gaire durant centenars d'anys. Avui en dia, la irrupció dels dispositius mòbils ho desafia. Aquest nou enfocament capacita tant als estudiants com a persones amb discapacitat numèrica per aprendre relacions numèriques. S'obre un munt de noves possibilitats perquè la comprensió és més ràpida, la desconnexió cerebral és més curta .... La tecnologia MNT (Mobile Numbers Technology) amb figures geomètriques amplia la base de l'usuari.Postprint (author's final draft

Valorization of Hemp Core Residues: Impact of NaOH Treatment on the Flexural Strength of PP Composites and Intrinsic Flexural Strength of Hemp Core Fibers

Hemp core is a lignocellulosic residue in the production chain of hemp strands. Huge amounts of hemp core are gathered annually in Europe (43,000 tons) with no major application end. Such lignocellulosic wastes have potential as filling or reinforcing material to replace synthetic fibers and wood fibers in polymer composites. In this study, hemp core biomass was treated under different NaOH concentrations and then defibrated by means of Sprout Waldron equipment to obtain single fibers. Polypropylene matrix was reinforced up to 50 wt.% and the resulting hemp core fibers and the flexural properties were investigated. The results show that the flexural strength of composites increased with the intensity of NaOH treatment. The effect of NaOH was attributed to the removal of extractives and lignin in the fiber cell wall leading to improved interfacial adhesion characteristics. Besides, a methodology was established for the estimation of the intrinsic flexural strength of hemp core fibers. The intrinsic flexural strength of hemp core fibers was calculated to be 940 MPa for fibers treated at 10 wt.% of NaOH. In addition, a relationship between the lignin content and the intrinsic strength of the fibers was established

Feasibility of Barley Straw Fibers as Reinforcement in Fully Biobased Polyethylene Composites: Macro and Micro Mechanics of the Flexural Strength

Awareness on deforestation, forest degradation, and its impact on biodiversity and global warming, is giving rise to the use of alternative fiber sources in replacement of wood feedstock for some applications such as composite materials and energy production. In this category, barley straw is an important agricultural crop, due to its abundance and availability. In the current investigation, the residue was submitted to thermomechanical process for fiber extraction and individualization. The high content of holocellulose combined with their relatively high aspect ratio inspires the potential use of these fibers as reinforcement in plastic composites. Therefore, fully biobased composites were fabricated using barley fibers and a biobased polyethylene (BioPE) as polymer matrix. BioPE is completely biobased and 100% recyclable. As for material performance, the flexural properties of the materials were studied. A good dispersion of the reinforcement inside the plastic was achieved contributing to the elevate increments in the flexural strength. At a 45 wt.% of reinforcement, an increment in the flexural strength of about 147% was attained. The mean contribution of the fibers to the flexural strength was assessed by means of a fiber flexural strength factor, reaching a value of 91.4. The micromechanical analysis allowed the prediction of the intrinsic flexural strength of the fibers, arriving up to around 700 MPa, and coupling factors between 0.18 and 0.19, which are in line with other natural fiber composites. Overall, the investigation brightness on the potential use of barley straw residues as reinforcement in fully biobased polymer composites

Macro and micro-mechanics behavior of stifness in alkaline treated hemp core fibres polypropylene-based composites

[EN] Traditionally, glass fibre has been used as plastic reinforcement whenever mechanical properties of a matrix, like stiffness, do not meet the specifications. However, current tendencies try to replace glass fibres by more sustainable fibres to obtain eco-friendlier products. Natural fibres show comparatively good physical and mechanical properties and, unlike glass fibres, come from renewable resources and are recyclable and sustainable. In this work, hemp straw discarded from hemp manufacturing was used as reinforcement in polypropylene composites. One drawback associated to hemp straw is its high lignin content that reduces its reinforcing potential. Therefore, a soft alkaline treatment was employed to adjust the lignin contents. In this work, the evolution of the Young's modulus with the NaOH treatment is assessed and discussed. Intrinsic Young's moduli of hemp straw fibres at different alkaline conditions were determined by Hirsch model. Finally, Tsai-Pagano and Halpin-Tsai equations allowed the prediction of the theoretical Young's modulus of the composites. The results showed the competitiveness of a by-product reinforced composite in front of commodity materials.Vilaseca, F.; Rey Tormos, RMD.; Serrat, R.; Alba Fernández, J.; Mutje, P.; Espinach, FX. (2018). Macro and micro-mechanics behavior of stifness in alkaline treated hemp core fibres polypropylene-based composites. Composites Part B Engineering. 144:118-125. doi:10.1016/j.compositesb.2018.02.029S11812514

Water-assisted melt processing of cellulose biocomposites with poly(ε-caprolactone) or poly(ethylene-acrylic acid) for the production of carton screw caps

Composites in 25 kg batches were compounded of cellulose nanocrystals (CNC) and thermomechanical pulp (TMP) and shaped into caps at industrial facilities on a pilot-plant scale. Some of the material was also injection molded into plaques to compare the effect of laboratory-scale and pilot-scale compounding of poly(ethylene-co-acrylic acid) (EAA7) and poly(caprolactone) composites reinforced with 10\ua0wt% CNC and TMP. The materials compounded under laboratory-scale conditions showed a different morphology, improved mechanical properties, and a higher viscosity, than the materials compounded on a pilot-scale. In some cases, the rheological properties of the melts indicated the presence of a relatively strong percolating cellulosic network, and the interphase region between the cellulose and the matrix appears to be important for the mechanical performance of the composites. After the compounding on a pilot scale, both the length and width of the pulp fibers was reduced. The TMP provided better reinforcement than the CNC possibly due to the higher aspect ratio

Effect of NaOH treatment on the flexural modulus of hemp core reinforced composites and on the intrinsic flexural moduli of the fibers

This paper describes the potential of using hemp core waste in the composite industry. These lignocellulosic residues can be used to produce environmentally friendly and economically viable composites and improve the overall value chain of hemp production. To this purpose, hemp core residues were alkaline treated at different NaOH concentrations and then mechanically defibrated. Hemp core fibers were mixed with polypropylene and injection molded to obtain testing specimens. The effect of sodium hydroxide on the flexural modulus of composites was studied from macro and micro mechanical viewpoints. Results showed remarkable improvements in the flexural modulus due to the presence of hemp core fibers in the composites. At a 50 wt % of reinforcement content, increments around 239%, 250% and 257% were obtained for composites containing fibers treated at a 5, 7.5 and 10 wt % of NaOH, respectively. These results were comparable to those of wood composites, displaying the potential of hemp core residues. The intrinsic flexural modulus of the hemp core fibers was computed by means of micromechanical analysis and was calculated using the ratios between a fiber flexural modulus factor and a fiber tensile modulus factor. The results agreed with those obtained by using models such as Hirsch and Tsai-Pagano. Other micromechanical parameters were studied to fully understand the contribution of the phases. The relationship between the fibers\u27 intrinsic flexural and Young\u27s moduli was studied, and the differences between properties were attributed to stress distribution and materials\u27 anisotropy