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Spilled oil in seas has a direct impact on the environment and biodiversity. Moreover, there is no clear relationship between the amount of oil in the aquatic environment and its impact, since it mainly depends on the time and season that the oil is spilled. Nowadays, there are several techniques to clean up and recover oil from the sea, including the use of microorganisms, chemicals, controlled burning, dispersants and solidifiers, among others. Sometimes, unfortunately, the best option is to watch and wait for natural attenuation. Cellulose nanofibers have potential environmental applications due to their availability, light weight, mechanical and optical properties, and renewability. Several studies have dealt with modification of their hydrophilic character through silanation and acetylation. Both treatments, despite having a significant impact on the environment, are not plausible on a large scale because of the cost of chemicals and complexity of the modification. In this sense, the present work aims to develop hydrophobic nanocellulose-based aerogels from bleached kraft eucalyptus fibers modified with alkyl ketene dimers. For this, an experimental batch of 24 aerogels was prepared, including three types of CNF (TEMPO-oxidized, enzymatically hydrolyzed and mechanical) and eight modification degrees. The obtained aerogels were characterized in terms of morphology, hydrophilicity and water–oil absorption capacity under static and dynamic conditions, as well as their suitability for recycling and reuse for selective oil removal. The results showed that it is possible to obtain 3D-structured aerogels with a high oil absorption capacity by a simple and presumably low-cost methodology.

The textile industry generates a large amount of byproducts that must be treated before being recycled or disposed of. The treatments to extract the dyeing agents are mandatory, and involve costs and interaction with toxic reagents. A relevant amount of such byproducts are short cotton dyed fibers. Cotton fibers are high-quality cellulosic fibers and can be used as composite reinforcement. In this paper, dyed cotton fibers were used to formulate, obtain and tensile test composite materials. The impact of the presence of dyes was studied and such dyes enhanced the interphase between the matrix and the reinforcement. On the other hand, when a coupling agent was incorporated to the formulation of the composites, the dyes hindered the chemical interactions between the maleic acid and the OH groups of the cellulosic fibers. Nonetheless, the composite materials showed competitive mechanical properties that were better than other natural fiber-reinforced composites and comparable to some glass fiber-based ones. Dyed cotton fibers can be used as reinforcement without further treatment, increasing the value chain of the textile industry and decreasing the chemical treatments necessary to recycle or dispose of dyed textile fibers. © The Author(s) 2018.

Increasing environmental concern in developed countries has supported the search for greener building materials. In this regard, using materials from renewable resources is of great interest, including the case of wood-plastic composites in replacement of fiberglass-reinforced composites. Since in the Mediterranean regions annual plants are more abundant than wood forests, in the present work, agroforestry wastes were used as reinforcing elements in composites. Specifically, rapeseed wastes were used to produce polypropylene copolymer based composites. The mechanical behavior of the resulting composites was studied, as well as the influence of a coupling agent in the formulation. From the results, rapeseed sawdust exhibited reinforcing capacity and was considered a plausible substitute for wood-plastic composites in certain uses. The stiffness of the composites was affected by the coupling agent, as the Young’s Moduli progressed from 3.2 to 4 GPa for the formulation containing 50wt% of rapeseed sawdust. Micromechanical analysis was used to identify the contribution of each phase by means of a modified rule of mixtures and Halpin-Tsai equations. The micromechanical study confirmed the competitive stiffening capability of rapeseed sawdust in composite materials.

In this work, starch-based composites reinforced with jute strands were obtained by injection moulding procedure. The influence of the degree of adhesion at fibre–matrix interface to the mechanical properties of the composites was evaluated. For this purpose, partial delignification of jute strands by means of NaOH treatment was carried out and the mechanical properties of the corresponding composites determined. The alkali treatment resulted in an increase of the strength and stiffness of the jute strand/starch composites. The enhancement was analysed in terms of compatibility and extension of the adhesion at fibre–matrix interface. The application of a blocking reaction to the surface hydroxyl groups of jute strands corroborated the influence of the mechanical properties to the extension of the interfacial adhesion. Thus, higher extension of the hydrogen bonds at fibre–matrix interface gave higher strength and stiffness of the jute strand/starch-based composites.

Hemp strands as natural lignocellulosic fibers are used to reinforce polypropylene composites obtained by injection molding. The aim of this work is to improve the final mechanical properties using simple and cheap treatments. Therefore, a refining process is applied to increase the specific surface and the fibrillation of hemp strands resulting in a better mechanical anchoring and adhesion with the matrix. The hydrophilic nature of the hemp strands is diminished by surface chemical treatment with alkyl ketene dimmer (AKD) in aqueous media. Final mechanical properties of hemp composites are studied and compared to those of glass fiber reinforced polypropylene composites. The fiber length and diameter of fiber reinforcement during processing are also analyzed. The results thus obtained show that the specific mechanical properties at yield of hemp composites may increase 80% of the mechanical properties of glass fiber composites.

The main objective of this research was to study the feasibility of incorporating organosolv semi-chemical triticale fibers as the reinforcing element in recycled high density polyethylene (HDPE). In the first step, triticale fibers were characterized in terms of chemical composition and compared with other biomass species (wheat, rye, softwood, and hardwood). Then, organosolv semi-chemical triticale fibers were prepared by the ethanolamine process. These fibers were characterized in terms of its yield, kappa number, fiber length/diameter ratio, fines, and viscosity; the obtained results were compared with those of eucalypt kraft pulp. In the second step, the prepared fibers were examined as a reinforcing element for recycled HDPE composites. Coupled and non-coupled HDPE composites were prepared and tested for tensile properties. Results showed that with the addition of the coupling agent maleated polyethylene (MAPE), the tensile properties of composites were significantly improved, as compared to non-coupled samples and the plain matrix. Furthermore, the influence of MAPE on the interfacial shear strength (IFSS) was studied. The contributions of both fibers and matrix to the composite strength were also studied. This was possible by the use of a numerical iterative method based on the Bowyer-Bader and Kelly-Tyson equations.

The stiffness of a material has high impact when its industrial use is considered. Moreover, this property has interest in the case of short fiber reinforced materials due to its dependence on the orientation of the fibers against the loads. Due to nowadays-environmental concerns, greener alternatives to oil-based composites are under study and development showing some promising results. In this work, a polyamide 11 reinforced with lignocellulosic fiber composite is evaluated as such sustainable alternative. Previous works showed the suitability of PA11-based composites to replace glass fiber reinforced polypropylene. Nonetheless, there is a lack of information about the flexural modulus behavior of these composites. This is of interest because, under some conditions, flexural modulus is more representative of a material behavior than Young's modulus. The flexural moduli of these composites were analyzed under a three point bending test and the results were evaluated from macro and micromechanical points of view. The increment of the modulus with the fiber contents implied a good dispersion of the reinforcements. Nonetheless, the results were lower than those observed for the tensile modulus. This was unexpected due to the anisotropy of the bending test. The micromechanics analysis showed a lower performance of the fiber during the flexural test. These lower results were related with a non-optimal interface or with the non-adequate compression of the fibers. Additionally, the calculus of the void volume showed low void contents.

Two of the drawbacks of using natural-based composites in industrial applications are thermal instability and water uptake capacity. In this work, mechanical wood pulp was used to reinforce polypropylene at a level of 20 to 50 wt. %. Composites were mixed by means of a Brabender internal mixer for both non-coupled and coupled formulations. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to determine the thermal properties of the composites. The water uptake behavior was evaluated by immersion of the composites in water until an equilibrium state was reached. Results of water absorption tests revealed that the amount of water absorption was clearly dependent upon the fiber content. The coupled composites showed lower water absorption compared to the uncoupled composites. The incorporation of mechanical wood pulp into the polypropylene matrix produced a clear nucleating effect by increasing the crystallinity degree of the polymer and also increasing the temperature of polymer degradation. The maximum degradation temperature for stone ground wood pulp–reinforced composites was in the range of 330 to 345 oC.