Search

Aquesta tesi doctoral i tot el treball experimental s’ha realitzat dintre les línies de treball del grup de recerca, Laboratori d’Enginyeria Paperera i Materials Polímers (LEPAMAP) de l’Escola Politècnica Superior de la Universitat de Girona. Les fibres de reforça amb les que s’ha treballat provenen de la biomassa resultant de la poda de tarongers. Dita biomassa s’ha processat per extreure’n tres tipus de fibres, mecàniques, termomecàniques i químico-termomecàniques. Aquestes fibres s’han usat com a reforç d’una matriu de polipropilè, amb percentatges de fins a un 50% en pes, amb i sense agent compatibilitzador., This doctoral thesis and all experimental work have been done within the lines of the research group, Laboratory of Paper Engineering and Polymeric Materials (LEPAMAP) of the Polytechnic School of the University of Girona. The reinforcing fibres used in this study come from the biomass from orange pruning. The biomass has been processed to remove three types of fibres, mechanical, thermomechanical and chemical-thermomechanical.

The main objective of this study was the management of corn stalk waste as reinforcement for polypropylene (PP) injection moulded composites as an alternative to wood flour and fibers. In the first step, corn stalk waste was subjected to various treatments, and four different corn stalk derivatives (flour and fibers) able to be used as reinforcement of composite materials were prepared and characterized. These derivatives are corn stalk flour, thermo-mechanical, semi-chemical, and chemical fibers. They were characterized in terms of their yield, lignin content, Kappa number, fiber length/diameter ratio, fines, coarseness, viscosity, and the length at the break of a standard sheet of paper. Results showed that the corn stalk derivatives have different physico-chemical properties. In the second step, the prepared flour and fibers were explored as a reinforcing element for PP composites. Coupled and non-coupled PP composites were prepared and tested for tensile properties. For overall trend, with the addition of a coupling agent, tensile properties of composites significantly improved, as compared with non-coupled samples. In addition, a morphological study revealed the positive effect of the coupling agent on the interfacial bonding. The composites prepared with semichemical fiber gave better results in comparison with the rest of the corn stalk derivatives due to its chemical characteristics.

En la primera part del present treball es presenta la investigació duta a terme sobre la reacció d'hidroesterificació d'olefines. S'analitzen els factors que afecten la reactivitat i quimioselectivitat de les reaccions d'hidroesterificació i deuterioesterificació en sistemes catalítics basats en complexes de pal·ladi amb lligands auxiliars de tipus fosfina. Es presenta un estudi detallat del mecanisme catalític a través del qual tenen lloc aquestes reaccions. La determinació del mecanisme de reacció ha estat aplicada a la obtenció d'una versió enantioselectiva de la mateixa. En una segona part del treball s'han analitzat diversos sistemes de modificació superficial de fibres naturals i el seu efecte sobre la compatibilitat fibra - matriu en materials compòsits de matriu poliolefínica. S'han caracteritzat les propietats superficials de fibres de pi químicament modificades. Les fibres naturals modificades s'han utilitzat en la preparació de materials compòsits, les propietats mecàniques, tèrmiques i termomecàniques dels quals han estat caracteritzades i analitzades., The first part of the present work exposes the results obtained during the study of the reactions of hydro and deuterioesterification of acenaphthylene. The different parameters involved in the catalitic system based on palladium complexes with phosphines have been analyzed, allowing the determination of the reaction´s mechanism. This determination has allowed the development of an enantioselective version of this reaction.The second part deals with the chemical modification of natural fibres and their effect on the interface of natural fibre reinforced composites. The surface properties of chemically modified pine fibres have been analyzed throught several techniques. The interface compatibilization provided by such treatments has been analyzed thorough the study of the mechanical, thermal and thermomechanical properties of PP reinforced composites.

One of the most relevant properties of composite materials to be considered is stiffness. Fiberglass has been used traditionally as a fibrous reinforcing element when stiff materials are required. However, natural fibers are been exploited as replacements for synthetic fibers to satisfy environmental concerns. Among the different natural fibers, wood fibers show the combination of relatively high aspect ratio, good specific stiffness and strength, low density, low cost, and less variability than other natural fibers of such those from annual crops. In this work, composites from polypropylene and stone groundwood fibers from softwood were prepared and mechanically characterized under tensile loads. The Young’s moduli of the ensuing composites were analyzed and their micromechanics aspects evaluated. The reinforcing effect of stone groundwood fibers was compared to that of conventional reinforcement such fiberglass. The Halpin-Tsai model with the modification proposed by Tsai-Pagano accounted fairly for the behavior of PP composites reinforced with stone groundwood fibers. It was also demonstrated that the aspect ratio of the reinforcement plays a role in the Young’s modulus of injection molded specimens.

Stone groundwood (SGW) is a fibrous matter commonly prepared in a high yield process, and mainly used for papermaking applications. In this work, the use of SGW fibers is explored as reinforcing element of polypropylene (PP) composites. Due to its chemical and superficial features, the use of coupling agents is needed for a good adhesion and stress transfer across the fiber-matrix interface. The intrinsic strength of the reinforcement is a key parameter to predict the mechanical properties of the composite and to perform an interface analysis. The main objective of the present work was the determination of the intrinsic tensile strength of stone groundwood fibers. Coupled and non-coupled PP composites from stone groundwood fibers were prepared. The influence of the surface morphology and the quality at interface on the final properties of the composite was analyzed and compared to that of fiberglass PP composites. The intrinsic tensile properties of stone groundwood fibers, as well as the fiber orientation factor and the interfacial shear strength of the current composites were determined

At the beginning 11 fibers were prepared by wet and dry cycles (hornification) but only 3 different natural fibers were characterized in order to be put in cement matrix. Biocomposites are finding applications in many fields such as aeronautical industry, automotive industry, or construction industry so we have prepared and characterized such composite. WRV, drying kinetic, fibers diameter, Young's modulus, thermal decomposition, pull-out test were investigated by weight and drying kinetic study, microscopical and SEM study, tensile test study, TGA study, VFRC study respectively. After hornification, WRV test shows a decrease in the water absorption of the water due to a decrease in the average diameter of the fiber (saw by microscopical and SEM study). More of that, tensile test shows an increase in the Young's modulus but a decrease in the maximal strength and in the maximal force. TGA analysis shows an increase of thermal stability of these natural fibers with drying and rewetting cycles. All this test were made to know if fibers can have a benefit impact in a cement matrix. To finish, pull-out shows that the treated fibers need more force to go out of the cement. So to increase the fiber-matrix adhesion, the fibers must be treated by wet and dry cycles before.