Impact properties and water uptake behavior of old newspaper recycled fibers-reinforced polypropylene composites

Natural fiber-reinforced thermoplastic composites can be an alternative to mineral fiber-based composites, especially when economic and environment concerns are included under the material selection criteria. In recent years, the literature has shown how lignocellulosic fiber-reinforced composites can be used for a variety of applications. Nonetheless, the impact strength and the water uptake behavior of such materials have been seen as drawbacks. In this work, the impact strength and the water uptake of composites made of polypropylene reinforced with fibers from recycled newspaper have been researched. The results show how the impact strength decreases with the percentage of reinforcement in a similar manner to that of glass fiber-reinforced polypropylene composites as a result of adding a fragile phase to the material. It was found that the water uptake increased with the increasing percentages of lignocellulosic fibers due to the hydrophilic nature of such reinforcements. The diffusion behavior was found to be Fickian. A maleic anhydride was added as a coupling agent in order to increase the strength of the interface between the matrix and the reinforcements. It was found that the presence of such a coupling agent increased the impact strength of the composites and decreased the water uptake. Impact strengths of 21.3 kJ/m3 were obtained for a coupled composite with 30 wt % reinforcement contents, which is a value higher than that obtained for glass fiber-based materials. The obtained composites reinforced with recycled fibers showed competitive impact strength and water uptake behaviors in comparison with materials reinforced with raw lignocellulosic fibers. The article increases the knowledge on newspaper fiber-reinforced polyolefin composite properties, showing the competitiveness of waste-based materialsPostprint (published version

Topography of the interfacial shear strength and the mean intrinsic tensile strength of hemp fibers as a reinforcement of polypropylene

The strength of the interphase between the reinforcements and the matrix has a major role in the mechanical properties of natural ¿ber reinforced polyole¿n composites. The creation of strong interphases is hindered by the hydrophobic and hydrophilic natures of the matrix and the reinforcements, respectively. Adding coupling agents has been a common strategy to solve this problem. Nonetheless, a correct dosage of such coupling agents is important to, on the one hand guarantee strong interphases and high tensile strengths, and on the other hand ensure a full exploitation of the strengthening capabilities of the reinforcements. The paper proposes using topographic pro¿le techniques to represent the e¿ect of reinforcement and coupling agent contents of the strength of the interphase and the exploitation of the reinforcements. This representation allowed identifying the areas that are more or less sensitive to coupling agent content. The research also helped by ¿nding that an excess of coupling agent had less impact than a lack of this componentPostprint (published version

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

Suitability of wheat straw semichemical pulp for the fabrication of lignocellulosic nanofibres and their application to papermaking slurries

The present work studies the feasibility of wheat soda pulp as a raw material for the fabrication of cellulose nanofibres and their application as an additive in papermaking. Wheat straws were cooked under alkaline conditions and the resulting pulp was used as a raw material for the production of lignocellulosic nanofibres (LCNF). Nanofibres were fabricated by intense mechanical beating followed by highpressure homogenization. The produced LCNF were characterized and applied to papermaking slurry based also on wheat straw soda pulp. Paper sheets made thereof were analysed for their physical and mechanical properties. The results indicated that paper strength was improved after addition of LCNF, whereas density increased and porosity was reduced. These improvements in properties (except the Tear Index) are significant because they were achieved using LCNF with lower fibrillation degree compared to previous works where chemically pre-treated LCNF were used as reinforcement

Comparison between two different pretreatment technologies of rice straw fibers prior to fiberboard manufacturing: Twin-screw extrusion and digestion plus defibration

The present work compares two different pretreatment technologies, i.e. twin-screw extrusion, and steaming digestion plus defibration, for producing a thermo-mechanical pulp from rice straw for fiberboard manufacturing. Five liquid/solid ratios from 0.43 to 1.02 were tested for twin-screw extrusion pretreatment, while liquid/solid ratios from 4 to 6 were used for digestion pretreatment. Energy consumption, and characteristics of the extrudates (twin-screw extrusion) and pulps (digestion) (including fiber morphology, chemical composition, thermal properties, apparent and tapped densities, as well as color) were the analyzed parameters for the resulting lignocellulosic fibers. The results showed that liquid/solid ratio had influence on energy consumption of the equipment for both defibrating methods For the twin-screw extrusion method, a lower liquid/solid ratio required more energy while for the digestion plus defibration the effect was the opposite. The corresponding total specific energy consumption ranged from 0.668 kW h/kg to 0.946 kW h/kg dry matter for twin-screw extrusion, and from 6.176 kW h/kg to 8.52 kW h/kg dry matter for digestion plus defibration. Thus, the pulping method consumed about nine times more energy than that of the twin-screw extrusion. In addition, for twin-screw extrusion, the liquid/solid ratio did not have a substantial effect on fiber characteristics with similar chemical compositions and thermal properties. For twin-screw extrusion, the energy consumption was 37% reduced when the liquid/solid ratio was increased from 0.43 to 1.02. Instead, for digestion plus defibration, the energy increase was 38% when the liquid/solid ratio increased from 4 to 6

On the path to a new generation of cement-based composites through the use of lignocellulosic micro/nanofibers

Due to its high biocompatibility, bio-degradability, and low cost, cellulose finds application in disparate areas of research. Here we focus our attention on the potential applications of cellulose nanofiber in cement-basedmaterials for the building sector. We first describe the chemical/morphological composition of cellulose fibers, their process and treatment, the characterization of cement-based composites, and their flexural strengthPeer ReviewedPostprint (published version

Avocado Pruning Residues for the Formulation of Bio-Based Polyethylene/Fiber-Based Biocomposites for Sustainable Food Packaging

The extensive use of non-biodegradable bioplastics and fossil-based plastics in food packaging presents a significant environmental challenge. Consequently, there has been a growing interest in exploring agricultural biomass as a potential source for formulating biocomposites for packaging due to the substantial amount of lignocellulosic residue generated. This study explores the utilization of avocado pruning residue (APR) for isolating lignocellulose fibers and their application as replacement and reinforcement material for bio-based polyethylene (BioPE) composites. The results obtained reveal that a concentration of 9% (w/w) of maleic anhydride-grafted-polyethylene (MAPE) shows the most effective fiber–polymer interaction, resulting in a significant improvement of 25.47% in the mechanical properties. Biocomposites with varying fiber concentrations, ranging from 10% to 40% (w/w), are prepared and assessed for their macro- and micromechanical properties. The results demonstrate a substantial 49% increase in tensile strength and a remarkable 325% enhancement in Young's modulus for biocomposites containing 40% (w/w) fiber content. Furthermore, micromechanical analysis provides insights into the intrinsic strength and modulus of avocado fibers, with values of ≈437 MPa and 33 GPa, respectively. This research contributes to the development of sustainable and eco-friendly alternatives for food packaging, reducing the reliance on fossil-based plastics, and promoting the utilization of agricultural waste

Leather Waste to Enhance Mechanical Performance of High-Density Polyethylene

Leather buffing dust (BF) is a waste from tannery which is usually disposed on landfills. The interest in using wastes as fillers or reinforcements for composites has raised recently due to environmental concerns. This study investigates the potential use of BF waste as filler for a high density polyethylene matrix (HDPE). A series of HDPE-BF composites, containing filler concentrations ranging from 20 to 50wt%, were formulated, injection molded and tested. The effect of filler contents on the mechanical properties of the composites were evaluated and discussed. Composites with BF contents up to 30wt% improved the tensile strength and Young's modulus of the matrix, achieving similar mechanical properties to polypropylene (PP). In the case of flexural strength, it was found to be proportionally enhanced by increasing reinforcement content, maintaining high impact strength. These composites present great opportunities for PP application areas that require higher impact resistance. The materials were submitted to a series of closed-loop recycling cycles in order to assess their recyclability, being able to maintain better tensile strength than virgin HDPE after 5 cycles. The study develops new low-cost and sustainable composites by using a waste as composite filler

Valorization Strategy for Leather Waste as Filler for High-Density Polyethylene Composites: Analysis of the Thermal Stability, Insulation Properties and Chromium Leaching.

Leather waste (BF) and high-density polyethylene (HDPE) were compounded in a lab scale internal mixer and processed by means of injection molding. In this study, leather waste and HDPE composites were characterized by instrumental techniques such as differential scanning calorimetry (DSC), thermo-gravimetric Analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). Physical integrity of composites against chemical exposure and chromium-leaching properties of the composites were also investigated. This study shows that the incorporation of 30% leather waste fiber into HDPE composites decreases the thermal conductivity of the composite samples by 17% in comparison to that of neat HDPE samples. Composites showed no thermal degradation during processing cycle. Strong interfacial bonding between leather waste and polymer results in comparable low-leachate levels to maximum allowed concentration for nonhazardous waste, and good chemical resistance properties. The BF/HDPE composites could be a promising low-cost alternative in industrial application areas of HDPE, where high-mechanical strength and low-thermal conductivity is required.This research was funded by the Spanish Ministry of Science and Innovation, project KAIROS-BIOCIR (PID2019-104925RB-C32