Feasibility study of replacement of glass fiber reinforced panels with bio-based thermoset resin and natural fiber

The purpose of this thesis is to develop the production of bio-based thermoset fiber reinforced composites. In particular, this study investigates the feasibility of replacing traditional fossil-based epoxy resins and curing agents with bio-based ones and traditional glass fibers with natural fibers in order to obtain innovative materials for the automotive sector. Many trials were carried-out with different types of resins and hardeners to select the best one in terms of thermo-mechanical proprieties. The most promising formulation was used to produce natural fiber composites through vacuum bagging process. Characterization of both resins and natural fibers was done through mechanical and thermal tests, also comparing them with petro-based resins and glass fiber used as reference. The final mechanical proprieties of the composites were evaluated by tensile and bending tests and their morphology was investigated by SEM analysis

Investigation of Novel Flax Fiber/Epoxy Composites with Increased Biobased Content

: Currently, biobased epoxy resins derived from plant oils and natural fibers are available on the market and are a promising substitute for fossil-based products. The purpose of this work is to investigate novel lightweight thermoset fiber-reinforced composites with extremely high biobased content. Paying attention to the biobased content, following a cascade pathway, many trials were carried out with different types of resins and hardeners to select the best ones. The most promising formulations were then used to produce flax fiber reinforced composites by vacuum bagging process. The main biocomposite properties such as tensile, bending, and impact properties as well as the individuation of their glass transition temperatures (by DSC) were assessed. Three biocomposite systems were investigated with biobased content ranging from 60 to 91%, obtaining an elastic modulus that varied from 2.7 to 6.3 GPa, a flexural strength from 23 to 108.5 MPa, and Charpy impact strength from 11.9 to 12.2 kJ/m2. The properties reached by the new biocomposites are very encouraging; in fact, their stiffness vs. lightweight (calculated by the E/ρ3 ratio) is comparable to some typical epoxy-glass composites

Sustainable 3D printed poly (lactic acid) (PLA)/Hazelnut shell powder bio composites for design applications

In the context of seeking sustainable solutions for developing innovative materials and products by an efficient use of natural resources and recycling waste, with an increasing focus on circular economy and mitigating environmental impact, the presents research aims to use biomass and agricultural residues as raw materials for bio composite production. Specifically, valorizing European hazelnut waste presents a unique opportunity to devise innovative formulations for 3D printing, leveraging both the mechanical properties and aesthetic appeal of lignocellulosic bio composites. In detail, this work aimed at the investigation of new poly(lactic acid) (PLA)/Hazelnut Shell Powder formulations for 3D printing design applications exploiting the woody aesthetic effect of these bio composites. A pellet 3D printer was used to bypass the filament production. Three different Hazelnut Shell Powder content (from 10 up to 30 wt%) were investigated and a design of experiment was carried out to generate response surfaces able to identify the best printing conditions to optimize flexural, tensile and impact properties. Finally, the effect of three different raster angles (0°, ±45° and 90°) on the mechanical properties was investigated. The best configuration was: 220 °C of nozzle temperature, 25 mm/s of printing speed and ±45° of raster angle. With this configuration, prototypes of ornamental pots, jewellery and home furniture were produced as demonstrators

Tearing fracture of poly(lactic acid) (PLA)/ poly(butylene succinate-co-adipate) (PBSA) cast extruded films: Effect of the PBSA content

The development of bio-based film formulations that show mechanical properties comparable to current fossil films is a challenging technological goal. Poly(lactic acid) (PLA) is the most attractive bio-based polymer; however, its poor ductility limits its use for film application. To overcome this issue, in this work PLA was blended with a ductile poly(butylene succinate-coadipate) (PBSA) bio-based polymer, and cast extruded PLA/PBSA films were produced with differing PBSA amounts (20, 30 and 40 wt%). The mechanical properties of the film were evaluated both in machine and cross direction. The tearing resistance of the produced film was implemented with the essential work of fracture approach to explore the mode III out-of-plane fracture resistance

Pathology of Salmonella enterica subspecies enterica serotype Typhimurium infection in chinchillas (Chinchilla lanigera)

Septicaemia is the main pathological manifestation of Salmonella infection in chinchillas (Chinchilla lanigera), although information on its pathology is limited. We now describe the gross, histological and immunohistochemical features of Salmonella enterica subspecies enterica serotype Typhimurium (S. Typhimurium) infection in ranched chinchillas. Eighty-five adult pregnant chinchillas had anorexia, prostration, weight loss, hyperthermia and abortion. Necropsy of 13 animals revealed splenomegaly, hepatomegaly, mesenteric lymphadenomegaly, prominent Peyer’s patches, pulmonary oedema, white pinpoint lesions in multiple organs and petechiae in the urinary bladder. In all cases, histological lesions were consistent with septicaemia, characterized by acute necrotizing hepatitis, splenitis, lymphadenitis, cystitis, pneumonia, enterocolitis, gastritis and/or nephritis. Immunohistochemistry for Salmonella spp on seven cases revealed intralesional immunolabelling in all affected organs. Salmonella sp was isolated from liver, spleen, intestinal contents and blood of 10 chinchillas. Isolates of four animals were identified as S. Typhimurium

Resumos concluídos - Saúde Coletiva

Resumos concluídos - Saúde Coletiv