Cellulose nanopaper as reinforcement for sustainable polymer composites

The use of cellulose nanopapers as reinforcement to produce high performance polymer composites is investigated in this thesis. Cellulose nanopapers are dense networks of nanofibrils that uses the hydrogen bonding ability of cellulose nanofibres. Both microbially synthesised cellulose nanofibres (known as bacterial cellulose or BC) and wood derived cellulose nanofibrils (CNF), were used in this work. This thesis starts with the investigation of the influence of test specimen geometries on the measured tensile properties of both CNF and BC nanopapers is investigated. Miniaturised specimens are often used for the tensile testing of cellulose nanopapers as there are no standardised test geometries to evaluate their tensile properties Four test specimen geometries were studied: (i) miniaturised dog bone specimen with 2 mm width, (ii) miniaturised rectangular specimen with 5 mm width, (iii) standard dog bone specimen with 5 mm width and (iv) standard rectangular specimen with 15 mm width. It was found that the tensile moduli of both CNF and BC nanopapers were not significantly influenced by the test specimen geometries if an independent strain measurement system (video extensometer) was employed. The average tensile strength of the cellulose nanopapers is also influenced by test specimen geometries. It was observed that the smaller the test specimen width, the higher the average tensile strength of the cellulose nanopapers. This can be described by the weakest link theory, whereby the probability of defects present in the cellulose nanopapers increases with increasing test specimen width. The Poisson’s ratio and fracture resistance of nanopapers are also discussed. The use of (ultra-)low grammage nanopaper as polymer reinforcement is also investigated. Bacterial cellulose (BC) nanopapers of 5, 10, 25 and 50 g m-2 were manufactured. Vacuum filtration to produce a 5 g m-2 nanopaper was found to be 3 times faster than that of a 50 g m-2. Low grammage nanopapers possessed a tensile modulus and strength as low as 2.4 GPa and 31 MPa respectively, against 11.8 GPa and 111 MPa for the 50 g m-2. Laminated composites containing 10, 5, 2 and 1 layer(s) of 5, 10, 25 and 50 g m-2 nanopapers were produced using a polylactide (PLLA) matrix. With a fibre loading fractions of vf ≥ 39%, the manufactured composites all possessed a tensile modulus and strength of ~10 GPa and ~100 MPa, respectively. The porosity of the nanopapers increased from 48% to 78% from 50 g m-2 to 5 g m-2. The porosity of the composites was ~10% independently of the layup. Finally, SEM images of the fracture surfaces of the composites revealed a layered morphology with little or no impregnation. The mechanical response of PLLA reinforced with multiple layers of BC nanopaper is then discussed. Laminated composites consisting of 1, 3, 6 and 12 sheet(s) of BC nanopaper were produced. It was observed that increasing the number of BC nanopaper led to an increase in the porosity of the resulting BC nanopaper-reinforced PLLA laminated composites. The tensile moduli of the laminated composites were found to be ~12.5 – 13.5 GPa, insensitive to the number of sheets of BC nanopaper in the composites but the tensile strength of the laminated composites decreased by up to 25% (from 121 MPa to 95 MPa) when the number of reinforcing BC nanopaper increased from 1 to 12 sheets. This was attributed to the presence and severity of the scale-induced defects increased with increasing number of sheets of BC nanopaper in the PLLA laminated composites. Finally, the environmental impacts of BC- and CNF-reinforced epoxy composites were evaluated using life cycle assessment (LCA). Neat polylactide (PLA) and 30% randomly oriented glass fibre-reinforced polypropylene (GF/PP) composites were used as benchmark materials for comparison. A cradle-to-gate LCA showed that BC- and CNF-reinforced epoxy composites have higher global warming potential (GWP) and abiotic depletion potential of fossil fuels (ADf) compared to neat PLA and GF/PP even though the specific tensile moduli of the nanocellulose-reinforced epoxy composites are higher than neat PLA and GF/PP. However, when the use phase and the end-of-life of nanocellulose-reinforced epoxy composites are considered, their “green credentials” are comparable to that of neat PLA and GF/PP composites. The life cycle scenario analysis showed that the cradle-to-grave GWP and ADf of BC- and CNF-reinforced epoxy composites could be lower than neat PLA when the composites contains more than 60 vol.-% nanocellulose. The LCA model suggests that nanocellulose-reinforced epoxy composites with high nanocellulose loading is desired to produce materials with “greener credentials” than the best performing commercially available bio-derived polymer.Open Acces

Outil d’analyse automatique de profils de plage

Les côtes basses sableuses sont des écosystèmes côtiers dynamiques jouant un rôle deprotection face aux risques d’érosion côtière et de submersion marine. L’observation dela dynamique de ces systèmes est un préalable pour améliorer la compréhension desprocessus environnementaux et pour adapter les stratégies et méthodes de gestion de labande côtière. La mesure de l’altimétrie littorale par l’acquisition de profils de plage estune méthode courante pour observer l’évolution des systèmes plage-dune. En région Paysde la Loire, les acquisitions et le traitement des données sont réalisés par une multiplicitéd’opérateurs mobilisant divers moyens techniques. Au regard des pratiques en région etdes outils d’analyse de profils de plage existant à ce jour, il manque un service en ligneet libre d’accès dédié à l’analyse automatisée de séries de profils de plage. Cet articlepropose la création d’un tel outil et présente d’une part sa conception et d’autre part lespremiers résultats issus de l’exploitation des données topographiques disponibles sur lesite du Pays de Monts

Thinner and better: (Ultra-)low grammage bacterial cellulose nanopaper-reinforced polylactide composite laminates

One of the rate-limiting steps in the large-scale production of cellulose nanopaper-reinforced polymer composites is the time consuming dewatering step to produce the reinforcing cellulose nanopapers. In this work, we show that the dewatering time of bacterial cellulose (BC)-in-water suspension can be reduced by reducing the grammage of BC nanopaper to be produced. The influence of BC nanopaper grammage on the tensile properties of BC nanopaper-reinforced polylactide (PLLA) composites is also investigated in this work. BC nanopaper with grammages of 5, 10, 25 and 50 g m−2 were produced and it was found that reducing the grammage of BC nanopaper from 50 g m−2 to 5 g m−2 led to a three-fold reduction in the dewatering time of BC-in-water suspension. The porosity of the BC nanopapers, however, increased with decreasing BC nanopaper grammage. While the tensile properties of BC nanopapers were found to decrease with decreasing BC nanopaper grammage, no significant difference in the reinforcing ability of BC nanopaper with different grammages for PLLA was observed. All PLLA composite laminates reinforced with BC nanopapers possessed similar tensile modulus of 10.5–11.8 GPa and tensile strength of 95–111 MPa, respectively, at a BC loading fraction vf,BC = 39–53 vol.-%, independent of the grammage and tensile properties of the reinforcing BC nanopaper

Spring habitats of small pelagic fish communities in the Bay of Biscay

Mapping habitats of species communities helps to inform on the ecological processes which drive their distribution. This information is critical to identify suitable areas for spatial management, aimed at preserving biodiversity, ecosystem functions or essential habitats. While demersal fish have been extensively studied at the community scale, small pelagic fish have mainly been characterised at the population scale. This paper presents a community-based approach on the biodiversity of small pelagic fish, with the aim to: (i) define small pelagic fish communities, (ii) characterise their spatial and interannual dynamics, and (iii) assess their habitats. We present a Multiple Factor Analysis (MFA)-based method that characterises the spatio-temporal variability in a series of multivariate maps. The main components of variability in these maps are identified to define “characteristic areas” displaying contrasting conditions in both MFA ordination and geographical spaces. Characteristic habitats of fish communities were defined by the correlation between the main components of variability from MFAs applied to maps containing fish information on one hand, and on hydrographic variables on the other hand. The analysis of the long term PELGAS survey series of fish biomass and hydrological indices maps resulted in the characterisation of mesoscale latitudinal gradients and coarse to mesoscale onshore-offshore gradients in both fish and hydrology datasets. A community with anchovy (E. encrasicolus) and chub mackerel (S. colias) as indicator species was consistently distributed in southeast Biscay. This area was associated with higher bottom temperatures, which likely affected the fish community through physiological processes. A second community with small clupeiforms as indicator species was found in coastal spawning habitats. These habitats were typically characterised by low salinity, a probable proxy for high productivity and good feeding grounds for those species. Mapping the habitats of small pelagic fish communities may inform marine spatial management, aimed at preserving biodiversity, ecosystem structure and function. In addition, it may help in achieving maximum sustainable yields of these commercially important species, and contribute to achieving and maintaining good environmental status of shelf seas ecosystems

Supplementary Material: Supporting analytical data from Better together: synergy in nanocellulose blends

TEM image TEMPO CNF, results of Mw determination of (r-)BC and conductometric titration, FT-IR spectra of pulp and TEMPO-CNF, all single results of BC nanopaper tensile tests and a schemactic of freacture toughness samples as well as a photograph of actual samples

The impact of intraoperative autologous blood transfusion during type III radical hysterectomy for early-stage cervical cancer

Objective: The aim of this study was to determine the effects on transfusion rates, perioperative complications, and survival of using intraoperative autologous blood transfusions for patients undergoing type III radical hysterectomy and lymphadenectomy. Study Design: A retrospective analysis was conducted on 156 patients treated with type III radical hysterectomy and lymphadenectomy at the University of Miami School of Medicine from 1990 to 1997. One group of patients (n = 50) had intraoperative autologous blood transfusions and the other (n = 106) did not. Results: The group that received intraoperative autologous blood transfusion had a significant reduction in homologous blood transfusions (12% vs 30%; P = .02). Patient demographic data, histologic parameters, and operative factors were similar between the 2 groups. There was a higher percentage of patients with positive pelvic lymph nodes in the group that did not receive intraoperative autologous blood transfusion (10% vs 30%; P = .02). Seven patients in the intraoperative autologous blood transfusion group (14%) died with disease present and all the recurrences in this group were local. Conclusion: The use of intraoperative autologous blood transfusions during type III radical hysterectomy and lymphadenectomy appears to be safe and effective without compromising rates and patterns of recurrence. (Am J Obstet Gynecol 1999;181:1310-6.

Un nouvel indicateur de prédisposition au risque d’érosion côtière, application en Manche et en Vendée (France)

Low sandy coasts are small and constrained spaces very sensitive to coastal hazards. The settlement of human activities next to the coastline sets up at-risk territories. The identification of territories exposed to coastal erosion is one of the objectives of the French national strategy for integrated coastal management initiated by the French Ministry of Ecology. This national strategy relies on the network of regional coastal observatories. This paper proposes a common geomatics approach of two of these regional observatories aimed at spatializing a new coastal erosion risk indicator. The partnership between the "Réseau d’observation du littoral de Normandie et des Hauts-de-France" and the "Observatoire régional des risques côtiers en Pays de la Loire", aims at applying this indicator along the sandy coasts of western Manche and northern Vendée, France. The indicator is composed of the combination of 3 variables into spatial units (“boxes”): (i) the historical shoreline change, (ii) the distance between the shoreline and the buildings, roads and campsites located in the 100-m coastal strip and (iii) the presence/absence of coastal protections. The computation of the indicator for each stake, at the scale of the territories, allows the ranking of the erosion risk territorie