Abstract

The aim of the study was to define the composition and methodology for manufacturing laminated composites of polypropylene and continuous fiber reinforcement. These composites are designed with the aim of being integrated into high mechanical performance lightweight parts obtained by high production rate manufacturing processes such as compression molding or the overinjection. The complete cycle of production of the polypropylene textile laminate composites has been analyzed, going from the selection and additivation of raw materials, treatment of the reinforced fibers and fabrication and characterization of the composite laminates. The study has focused on composites based on polypropylene resins and twill 2/2 reinforcements of fiberglass fabric.

Abstract

The use of different stereospecific metallocene catalysts: isotactic (iPP, C2-symmetry) and syndiotactic (sPP, Cs-symmetry) has been investigated in order to improve the mechanical properties of polypropylene/nanoclay nanocomposites obtained by in-situ polymerisation. Stereoregular nanocomposites have been synthetized in the presence of polar comonomers (1-undecenol (R-OH) and acid-undecenoic (R-COOH) for improving the matrix-nanoclay chemical compatibility. An important study of variables: amount of nanoparticles used as co-catalyst support, type of catalyst, type and amount of comonomer have been studied in a full factorial design of experiments in order to identify the main factors that achieve a balance between the stiffness and toughness of the polypropylene nanocomposites.

Important results were found from ANOVA (analysis of variance): the nanoclay has a greater influence on the syndiotactic configuration and, the amount of polar comonomer is the main factor in maximising mechanical properties, irrespective of stereospecificity of the polypropylene nanocomposites.

Abstract

Due to the rapid growth in the use of composite materials, environmental concerns have become an increasingly influential topic, making recyclability of composite materials a key issue. Furthermore, several related European laws have been passed to minimize the environmental impact of composites (EU 2000/53/CE [1], 2000/76/EC [2], 2004/35/EC [3]). Caused by the high energetic requirements and the huge amount of composite materials used in the manufacturing process, recycling supposes a reduction of a 70% in the costs and 98% in the energy demanded [4].

Once the fibers are obtained through pyrolysis, with a high retention of mechanical properties, the next step is the manufacturing process by injection using a thermoplastic polymeric matrix of polypropylene, a polymer widely used in the composite industry. For that purpose, a study of the compatibility of the fiber with the maleic anhydride polypropylene at different relations -10, 20 and 30%- has been carried out.

In order to enhance the mechanical properties, a combination of homopolymer polypropylene, maleic anhydride polypropylene and recycled carbon fibers is studied through the production of a masterbach composed of maleic anhydride polypropylene and carbon fibers, followed by the addition of the homopolymer polypropylene.

Once the pellets are obtained, they are injected. The samples injected are analyzed in terms of fiber distribution by scanning electron microscopy and tomography, thus the mechanical properties are evaluated through tensile, impact and bending tests, to determine the optimum fiber/resin ratio.

Abstract

Modification of polymer matrices has a great insterest in the field of new materials, based on the possibilities offered by the additivation, being able to modulate the properties of the base material depending on the incorporated aggregates. Among the improvements searched include the increase in the mechanical strength of the material or the improvement in the interaction with other materials (adhesion), in addition to providing multifunctionality, combining properties of materials separately in order to obtain a composite with improved properties.

This study focuses on the modification of a polypropylene-ethylene co-polymer by the incorporation of nanoclays and carbon nanotubes (MWCNTs) in low concentrations (0.1% by weight). In order to facilitate the dispersion of the nanomaterials in the matrix by mixing and extrusion, maleic anhydride was used as a compatibilizer. The behavior of these composites was characterized by studying the variation of torque during the compounding, in addition to analize the melt flow index (MFI) and perform an analysis by DSC, TGA and TEM of the composites obtained. Based on the low polarity of polypropylene, the introduction into the matrix of maleic anhydride provides a certain polarity in the composite, so the increase in the surface energy of the different formulations is studied by contact angle measurements (using the OWRK/Fowkes method). The increase in surface energy involves a greater affinity for polar materials, such as polyurethane (PU) or other foams.

Abstract

Polymer-based multifunctional materials reinforced with graphene represent a step forward due to the combination of good structural properties with others of different nature such us electrical conductivity. These new systems are good candidates for applications in the transportation industry provided that the nanofiller is well-dispersed within the matrix and there is a good interaction between the fibre and the polymer. The aim of this work is the study of the nanostructure and the mechanical properties of polymer nanocomposites based on polypropylene (PP) and graphene with concentrations in the range of 0.9 to 2.6 vol.%. The nanostructure of the composites was investigated by wide angle x-ray scattering and the local mechanical properties were assessed by nanoindentation. On the one hand, nanoindentation studies revealed a good distribution of the nanofiller within the polymer matrix. On the other hand, an enhancement of the mechanical properties by the incorporation of graphene was found. This mechanical improvement was attributed to the intrinsic properties of graphene while there were no clear differences in the nanostructure of the nanocomposites compared to that of neat PP. Finally, comparison of the moduli from nanoindentation and tensile testing allowed the understanding of the mechanism of deformation of these materials under external stresses of different nature.

Abstract

The family of polyolefins are materials with a high demand, due to thermoplastics are structurally simpler and economical in their production and processing. Within the polyolefins, the commercial use of polypropylene began with the rise of the catalyzed reactions, in this way it was possible to control its specific conformation and with it, the final properties. In order to improve their properties, these materials are usually reinforced, specially with nanometric loads. So far, three methods have been developed for obtaining nanocomposites: In situ polymerization, melt intercalation and solution mixing. In order to solve the existing problems, in terms of charge dispersion, molecular weight control of the synthesized matrix and the complexity of the immobilization processes of the metallocene catalysts, this research uses In situ polymerization of polypropylene-Sepiolite, using the nanoclay as support of the catalytic system. This study proposes a method of immobilization that contemplates the use of the density of the polar groups that has the surface of Sepiolite, to fix the co-catalyst. In addition, the resulting polymerization process defines the reaction temperature as a variable which will provide a mechanism for controlling the molecular weights of the polypropylene. The proposed method has allowed the polypropylene to be added in its own synthesis process, besides controlling its structure in terms of its stereo-specificity and molecular weight, thus improving its final properties.

Abstract

La fabricación de nuevos materiales sostenibles es clave para satisfacer la creciente demanda sin comprometer el futuro del planeta. Para ello, es esencial reducir el impacto ambiental mediante estrategias como la economía circular. Un ejemplo es el uso de lana de oveja latxa, raza vinculada al queso Idiazabal en el País Vasco. Esta lana presenta propiedades físicas, químicas y mecánicas interesantes, pero carece de aplicaciones industriales. Por tanto, podría utilizarse como refuerzo en la fabricación de composites, lo que también beneficiaría a la economía local.

En este estudio, se ha empleado polipropileno (PP) como matriz, uno de los polímeros termoplásticos más utilizados por su versatilidad, buenas propiedades barrera y resistencia química. Sin embargo, el PP tiene pocos grupos funcionales, lo que limita su interacción con otras sustancias. Esto puede generar una baja adhesión en la interfaz fibra-matriz, afectando la cohesión y las propiedades del composite.

Por ello, se han preparado composites de PP con fibra de lana latxa (PPWF), analizando el efecto de modificar el PP con anhídrido maleico (MAPP) para mejorar la compatibilidad entre matriz y fibra. El MAPP se incorporó en una proporción del 10% respecto a la fibra. Los resultados muestran que añadir un 20% de lana a la matriz modificada mejora significativamente tanto la resistencia como el módulo del PP.

The development of new sustainable materials is key to meeting growing demand without compromising the planet’s future. To achieve this, it is essential to reduce environmental impact through strategies like those of the circular economy. One example is the use of Latxa sheep wool, a breed associated with Idiazabal cheese in the Basque Country. This wool has interesting physical, chemical, and mechanical properties, but currently lacks industrial applications. Therefore, it could be used as reinforcement in composite manufacturing, also supporting the local economy.

In this study, polypropylene (PP) was used as the matrix—one of the most widely used thermoplastic polymers due to its versatility, good barrier properties, and chemical resistance. However, PP has few functional groups, which limits interaction with other materials. This may lead to poor adhesion at the fiber-matrix interface, affecting the cohesion and properties of the composite.

To address this, composites of PP with Latxa wool fiber (PPWF) were prepared, analyzing the effect of modifying the PP with maleic anhydride (MAPP) to enhance compatibility between the matrix and the protein-based fiber. MAPP was added in a proportion of 10% relative to the wool fiber. The results show that adding 20% wool to the modified matrix significantly improves both the strength and modulus of the PP.