Towards more sustainable material formulations: a comparative assessment of PA11-SGW flexural performance versus oil-based composites

The replacement of commodity polyolefin, reinforced with glass fiber (GF), by greener alternatives has been a topic of research in recent years. Cellulose fibers have shown, under certain conditions, enough tensile capacities to replace GF, achieving competitive mechanical properties. However, if the objective is the production of environmentally friendlier composites, it is necessary to replace oil-derived polymer matrices by bio-based or biodegradable ones, depending on the application. Polyamide 11 (PA11) is a totally bio-based polyamide that can be reinforced with cellulosic fibers. Composites based on this polymer have demonstrated enough tensile strength, as well as stiffness, to replace GF-reinforced polypropylene (PP). However, flexural properties are of high interest for engineering applications. Due to the specific character of short-fiber-reinforced composites, significant differences are expected between the tensile and flexural properties. These differences encourage the study of the flexural properties of a material prior to the design or development of a new product. Despite the importance of the flexural strength, there are few works devoted to its study in the case of PA11-based composites. In this work, an in-depth study of the flexural strength of PA11 composites, reinforced with Stoneground wood (SGW) from softwood, is presented. Additionally, the results are compared with those of PP-based composites. The results showed that the SGW fibers had lower strengthening capacity reinforcing PA11 than PP. Moreover, the flexural strength of PA11-SGW composites was similar to that of PP-GF compositesPostprint (published version

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

Maleic anhydride polylactic acid coupling agent prepared from solvent reaction: synthesis, characterization and composite performance

In the present work, a functionalization of polylactic acid (PLA) has been carried out to anchor maleic anhydride onto the main polymer chain to promote improvement in the compatibility of this polymer matrix with cellulose fibres. Low-molecular-weight PLA has been reacted with maleic anhydride following different procedures: a bulk reaction in an internal mixer and a solution reaction. The presence of oxygen during bulk processing did not allow for functionalization, guiding the reaction towards a decrease in the molecular weight of the material. On the contrary, a controlled reaction under an inert atmosphere in the presence of dioxane as the solvent, at reflux temperature, led to the functionalization of the polymer reaching different yields depending on the percentage of radical initiator and maleic anhydride added and reaction time. The yield of functionalization has been monitored by acid number titration as well as 1H NMR, with optimal yield values of functionalization being up to 3.5%. The PLA-functionalized formula has been used to make commercial PLA compatible with cellulose fibres derived from a thermomechanical treatment. The addition of 10% w/w of fibres to PLA increases the ultimate tensile strength (UTS) of PLA by up to 15%. The incorporation of 4 w/w of the already-functionalized coupling agent to the composite produces improvements in UTS of up to 24% regarding PLA, which confirms the functionalization from a performance point of view.Peer ReviewedPostprint (published version

Simulated environmental conditioning of PHB composites reinforced with barley fibres to determine the viability of their use as plastics for the agriculture sector

Nowadays, the search for new materials with a sustainable character to reduce the production of residues is under continuous research. In this sense, fully biodegradable composites based on polyhydroxybutyrate and different pretreated fibres coming from barley straw have been fabricated, and their resistance to environmental controlled conditions have been characterized. The materials were already compounded in a kinetic mixer and injection-moulded as specimens for tensile assay to be aged in a Xenotest chamber so as to simulate environmental conditioning. The samples, after accelerated aging, were characterized thus: mechanical characterization (tensile assay), water uptake (immersion and contact angle), and surface observation (optical and SEM microscopy). The incorporation of the fibres helps the composite to keep its structure for a longer time. On the other hand, the presence of the fibres increases the water uptake capacity to allow water permeation in the composite, which allows final degradation, characterised by a significant drop in properties after one month of exposure to simulated environmental conditions.Peer ReviewedPostprint (published version

THE ARCHITECTURE OF SCARCITY: THE LOW-COST HOUSING OF SANT CUGAT DE SALT IN 1956

[EN] The low-cost housing that began to be constructed in the middle of the 20th century in post-war Spain was characterised by its simple construction. Our objective is to demonstrate the relationship between the lack of materials available in post-war Spain (1940- 1960) and the spatial, urbanistic and architectural qualities of these houses. Above all, our objective is to research the constructive possibilities of the vaulted ceiling. This study¿s methodology is both theoretical and practical. Collecting planimetric information on the urban complex and the existing building typologies has allowed us to understand, first hand, the houses¿ architectural characteristics. The system of construction employed to build the houses stands out for its use of vaulted hollow brick ceilings braced with cables. This design makes the houses inexpensive to build, accommodates a range of compositional possibilities and has proven durable. This echnology has gained respect for the structural integrity created by the complex of this grid of structural spaces.[ES] Las casas baratas de la posguerra española son grupos de viviendas sociales que se construyeron, a partir de mediados del siglo XX, con una gran simplicidad constructiva. Nuestro objetivo es demostrar la relación entre la carencia de materiales durante la postguerra española (1940-1960) y la calidad espacial, urbanística y arquitectónica, de muchas de ellas, y sobre todo investigar las posibilidades constructivas de la bóveda vaída. La metodología de trabajo ha sido teórica y práctica a la vez. El levantamiento planimétrico del conjunto urbanístico y las topologías edificatorias actuales nos ha dado la posibilidad de conocer, de primera mano, sus características arquitectónicas. Sobresale la utilización del sistema constructivo de las bóvedas vaídas de mahón atirantadas con cables, de bajo coste de construcción, de grandes posibilidades compositivas y de una durabilidad contrastada. Una tecnología que ha obligado a respetar la integridad del conjunto de esta parrilla de espacios estructurales.Ripoll Masferrer, R.; Julián Pérez, F.; Espinach Orus, X.; Verdaguer Pujadas, N. (2012). LA ARQUITECTURA DE LA ESCASEZ. LAS CASAS BARATAS DE SANT CUGAT DE SALT DE 1956. EGA. Revista de Expresión Gráfica Arquitectónica. 17(19):262-269. doi:10.4995/ega.2012.1378SWORD2622691719Bosch, I., 1956. Planos del Archivo del Colegio de Arquitectos de Catalu-a. Demarcación de Girona.Cabrera, A., Sala, M. y Jordi, C., 2005. Les voltes de quatre punts. Estudi constructiu i estructural de les cases barates. Girona: Colegio de aparejadores y arquitectos técnicos de Girona, p. 89.Gelada, J. M., 1977. La volta de Quatre punts. Revista La Punxa, nº. 25. Colegio Oficial de aparejadores y Arquitectos Técnicos de Girona, pp.44-49.Gómez, M. L., 2006. La intención administrativa en la vivienda en Espa-a. 1938-2005. Madrid: Editorial Montecorvo, pp.8-20.Gulli, R., 1994. La memoria delle tecniche. Le Corbusier e la volta catalana. Ancona: Clua Edizioni, p.28/p.32.Ripoll, R., 2006. 50 anys del barri de Sant Cugat. Les Cases barates de Salt. Girona: Diputación de Girona y Ayuntamiento de Salt, pp.20-29

Polyhydroxy-3-Butyrate (PHB)-based composite materials reinforced with cellulosic fibers, obtained from barley waste straw, to produce pieces for agriculture applications: production, characterization and scale-up analysis

Cellulosic fibers obtained from Barley straw were utilized to reinforce PHB. Four different processed fibers were employed as reinforcing material: sawdust (SW), defibered (DFBF), delignified (DBF), and bleached (BBF) fibers. The composite was processed from two different perspectives: a discontinuous (bach) and an intensification process (extrusion). Once processed and transformed into final shape specimens, the materials were characterized by mechanical testing (tensile mode), scanning electron microscopy, and theoretical simulations by finite elements analysis (FEA). In terms of mechanical properties, only the elastic moduli (Et) exhibited results ranging from 37% to 170%, depending on the reinforcement composition. Conversely, strengths at break, under both tensile and bending tests, tended to decrease, indicating poor affinity between the components. Due to the mechanical treatment applied on the fiber, DFBF emerged as the most promising filler, with mechanical properties closest to those of neat PHB. DFBF-based composites were subsequently produced through process intensification using a twin-screw extruder, and molded into flowerpots. Mechanical results showed almost identical properties between the discontinuous and intensification processes. The suitability of the material for agriculture flowerpots was demonstrated through finite analysis simulation (FEA), which revealed that the maximum von Mises stresses (5.38 × 105 N/m2) and deformations (0.048 mm) were well below the limits of the composite materialsThis research was funded by Interreg program (POCTEFA 2014–2020), grant number Bioplast-EF 253/16. APC was funded by UdG. Dr. Oliver-Ortega acknowledges the funding of the research group TECTEX (2021 SGR 01056) from the Department de Recerca i Universitats de la Generalitat de CatalunyaPostprint (published version