Dynamic mechanical properties of oral mucosa: comparison with polymeric soft denture liners.

The purpose of this work was to characterize the viscoelastic behaviour of oral mucosa and compare it with the dynamic mechanical properties of different soft liners. For this purpose, a sample of pig oral mucosa and six commercialized soft liner samples have been investigated. A comparison was also carried with the first suitable hard rubber for dental prosthetics: vulcanite. Creep recovery (CR) and dynamic mechanical analysis (DMA)have been used to determine the mechanical modulus of oral mucosa and soft liners respectively. The Poisson ratio is used to compare mucosa bulk modulus and soft liner shear modulus. The biomechanical concept of conventional complete dentures needs a good adjustment of dynamic mechanical impedance between the base and oral mucosa. The viscoelastic mechanical property of the oral mucosa as a referent biopolymer has been confirmed in vitro. The modulus value, adjusted for old patients in physiological conditions, is in the order of 3 MPa. This study underlines the plasticization effect of absorbed water on the mechanical properties of the underlying tissue. This study allows us to define some characteristics of the most adapted biomaterial according to the clinical exigency. The required biomaterial must display the following properties: compatibility and chemical resistance with biological environment perpetuated mechanical properties during physiological conditions and clinical use, good adjustment of dynamic mechanical impedance with supporting mucosa and easy sample processing

Changes in the physical structure and chain dynamics of elastin network in homocysteine-cultured arteries

The thermal and dielectric properties of the elastin network were investigated in arteries cultured with physiological and pathological concentrations of homocysteine, an aminoacid responsible of histological impairments in human arteries. The physical structure of this amorphous protein was investigated by differential scanning calorimetry (DSC). To explore the molecular dynamics of the elastin network in the nanometer range, we used thermally stimulated currents (TSC), a dielectric technique running at low frequency, and measuring the dipolar reorientations in proteins subjected to a static electrical field. Combining DSC and TSC experiments reveals the molecular mobility of the proteins, both in the glassy state and in the liquid state. Significant differences are evidenced in the physical structure and relaxation behavior of elastin network in cultured arteries (physiological and pathological concentrations of homocysteine) and discussed

Influence of homocysteine on the physical structure and molecular mobility of elastin network in cultured arteries

The thermal and dielectric properties of the elastin network were investigated in arteries cultured with physiological and pathological concentrations of homocysteine, an aminoacid responsible of histological impairments in human arteries. The glass transition of this amorphous protein was investigated by Differential Scanning Calorimetry (DSC). To explore the molecular dynamics of the elastin network in the nanometer range, we used Thermally Stimulated Currents (TSC), a dielectric technique running at low frequency and measuring the dipolar reorientations in proteins subjected to a static electrical field. Combining TSC and DSC experiments with determination of the activation parameters of relaxation times reveals the molecular mobility of the proteins. The major differences in the relaxation behavior of elastin between arteries cultured with physiological and pathological concentrations of homocysteine are discussed

Mechanical and thermal behaviour of bamboo flour-reinforced XLPE composites

In the present work, the influence of natural fillers (bamboo flour/BF) on crosslinked polyethylene (XLPE) has been discussed. The main difficulty for the preparation of the composites is to establish adhesion between hydrophilic natural fillers and hydrophobic matrix. Consequently, coupling agent (CA) as silane must be added to promote interface. In this work, different amounts of tetraethyl orthosilicate (TEOS) were used as coupling agent and SEM images allow us to control the quality of the interface. Differential scanning calorimetry (DSC) shows that the XLPE crystallinity is unmodified upon the introduction of BF. The absence of transcrystallinity is important for preserving the ductility of composites. The dynamic mechanical analyses (DMA) highlight an optimum of shear modulus for a TEOS content of 5 mass% (CA5). Above this amount, the mechanical properties are reduced. These results were confirmed by the SEM observations which highlighted the decrease in the interface between the XLPE and BF. Furthermore, neither the introduction of BF nor the treatment with TEOS exerts an influence on the relaxation temperature: there is no plasticization. The combination of DSC/DMA allows us to show that higher viscoelasticity favouring impact strength is observed in XLPE/BF CA5 composites

Physical structure and mechanical properties of polyamide/bamboo composites

The main objective of this work is to process innovative bamboo flour (BF)-reinforced polymer composites.In this context, polyamide 11 (PA 11) is used as technical matrix. Moreover, BF is treated with tetraethyl orthosilicate (TEOS) playing the role of coupling agent. SEM observations show no influence of TEOS on the affinity. The composites were analysed by DSC and DMA, in comparison with neat PA 11. DSC analyses of PA 11/BF highlight that there is no significant modification of the percentage of crystallinity upon introduction of BF whatever the treatment is. Concerning the amorphous phase, only a slight shift of the glass transition of PA 11 from 35°C (PA 11) to 38°C (PA 11/BF composites) is recorded. This shift can be explained by physical bonds at the interface PA 11/BF. DMA analyses allow us to explore the role of BF fillers onto the properties of PA 11/BF composites. The first observation is a slight improvement of the shear modulus G0 when the concentration in TEOS increases. The b relaxation at -80°C is associated with the mobility of the complexes free amide groups/water molecules. There is no shift of the peak due to the presence of BF fillers. The magnitude and width of the relaxation increase with BF and also with TEOS treatment. These observations highlight the increase of hydrogen-bonded water in various sites of the vitreous state. The a relaxation is associated with the anelastic mobility liberated at the glass transition. For PA 11/BF composites, it is constituted by two components: the lower-temperature one due to neat polyamide and a higher-temperature one associated with PA 11/BF amorphous domains with a lower thermal conductivit

Thermal and mechanical performances of bamboo strip

Bamboo strips extracted from Phyllostachys viridiglaucescens, grown in Europe, were analysed to assess their thermal and mechanical properties for composites application. Thermal stability of the European bamboo was studied by Thermogravimetric Analysis (TGA) and compared to the one of species grown in Oceania. An evolution of the chemical composition along the radial direction of the Phyllostachys bamboo was identified by TGA. The inner part of culms shows a higher proportion of hemicelluloses, while the percentage of crystalline cellulose is higher in the outer portion. This evolution of the composition was used to interpret the original data recorded by Dynamic Mechanical Analysis (DMA) of the strips. Glassy tensile modulus founded by DMA increases from the inner part of the culm (6.8 GPa) to the outer part (9.9 GPa). The variation of the cellulose content along the radius of the bamboo culm is related to this increase and shows a good correlation with thermal behaviour. The dynamic relaxations in the shear mode reveal the existence of two secondary relaxation modes sensitive to water. In the order of increasing temperatures, they have been assigned to the mobility of methylol groups and to heterogeneities of the polymeric matrix. By combining Differential Scanning Calorimetry (DSC) and DMA, the response of the viscoelastic transition of bamboo strips, at 210 °C, was evidenced for the first time. Bamboo strips behave as a unidirectional composite reinforced by technical fibres; its particularly high shear glassy modulus (2.3 GPa) deserves to be emphasised

Continuous Bamboo Fibers/Fire-Retardant Polyamide 11: Dynamic Mechanical Behavior of the Biobased Composite

A biobased composite was generated from bamboo fibers (BF) and a polyamide 11 (PA11) matrix. In order to fulfill security requirements, a PA11 already containing a flame retardant (FR) was chosen: This matrix is referred as PA11-FR. In this work, the effects of flame retardant (melamine cyanurate) on the composite properties were considered. In the calorimetric study, the glass transition and melting temperatures of PA11-FR were the same as those of PA11. The melamine cyanurate (MC) had no influence on these parameters. Thermogravimetric analysis revealed that PA11-FR was less stable than PA11. The presence of MC facilitated thermal decomposition regardless of the analysis atmosphere used. It is important to note that the presence of FR did not influence processing conditions (especially the viscosity parameter) for the biosourced composite. Continuous BF-reinforced PA 11-FR composites, single ply, with 60% of fibers were processed and analyzed using dynamic mechanical analysis. In shear mode, comparative data recorded for BF/PA11-FR composite and the PA11-FR matrix demonstrated that the shear glassy modulus was significantly improved: multiplied by a factor of 1.6 due to the presence of fibers. This result reflected hydrogen bonding between reinforcing fibers and the matrix, resulting in a significant transfer of stress. In tensile mode, the conservative modulus of BF/PA11-FR reached E’ = 8.91 GPa. Upon BF introduction, the matrix tensile modulus was multiplied by 5.7. It can be compared with values of a single bamboo fiber recorded under the same experimental conditions: 31.58 GPa. The difference is partly explained by the elementary fibers’ lack of alignment in the composit

Application et analyse de GNSS dans l'industrie forestière

La localisation est un problème qui affecte beaucoup d’industries. Comme l’automatisation devient de plus en plus importante, la localisation doit aussi devenir de plus en plus précise pour assurer une bonne efficacité des opérations et pour assurer la sécurité des employés qui vont devoir travailler avec cette automatisation. Notre étude se concentre sur la problématique de la localisation, appliquée à l’industrie forestière. Comme cela demande l’automatisation de machinerie lourde et la manipulation de l’inventaire, il est important d’avoir une localisation précise sur une échelle du décimètre. Une solution possible pour la localisation de précision est via les récepteurs Global Navigation Satellite System (GNSS) Real Time Kinematic (RTK), qui permettent de faire la localisation à une dizaine de centimètres près. Par contre, l’industrie forestière travaille dans des environnements divers qui peuvent causer des difficultés pour ces récepteurs GNSS. Par exemple dans des forêts denses ou près de bâtiments qui peuvent cacher des satellites pour la localisation. Comme l’environnement du récepteur et la qualité de la réception sont mesurables, nous avons aussi développé une méthode permettant de faire une relation entre les deux. Ce mémoire tentera d’expliquer la problématique de l’application et l’analyse de GNSS pour faire la localisation dans des environnements divers. Ensuite, le mémoire va montrer comment les récepteurs GNSS sont affectés par divers environnements en montrant des résultats d’expériences dans ces derniers. Le tout sera démontré dans le chapitre 1 et la section 4.1 Comme l’environnement est important pour estimer son influence sur les receveurs GNSS, la génération de carte 3D est importante. Cette génération est expliquée dans le chapitre 2 et la section 4.2. Une plate-forme de récolte de données que nous avons conçue sera expliquée en grand détail dans le chapitre 3. Ensuite, nous avons fait une estimation de la qualité de la visibilité de satellite avec un article scientifique dans le chapitre 5. Les résultats y montrent que notre méthode obtient une bonne relation entre l’environnement et la performance des récepteurs GNSS. Ces résultats sont tirés d’expériences réalisées dans divers environnements

Multifinality in geoheritage inventories: a cross-cutting approach of geotourism and geoconservation issues in the “Causses du Quercy” Regional Natural Park (Lot, SW France)

Geotourism and geoconservation are the main management issues of geoheritage inventories. In France, the INPG (National Inventory of Geological Heritage) constitutes a good basis for the definition of future protected areas and the further promotion of geoheritage. However, methodological adjustments are often necessary to fit with the different finalities of the inventory. The aim of this paper is to propose a cross-cutting approach of geotourism and geoconservation issues in the “Causses-du-Quercy” Regional Natural Park (PNRCQ), a rural territory typified by a rich geoheritage with a predominance of palaeontological and karstic sites. This geoheritage is currently the subject of protection measures (creation of a National Nature Reserve of geological interest, RNNg) and promotion actions (project of Geopark application). Because numerous geosites of the Regional Park are not managed, the PNRCQ aims to develop a substantive, integrated geoheritage project well beyond the limits of the reserve and extended to the whole PNR territory. To achieve this, two parallel studies (geoconservation and geotourism) were launched in 2013-2014. On one hand, a qualitative approach with cyndinic assessment – inspired by experience in risk evaluation – was proposed for the definition of a geoconservation strategy applied to karstic sites. On the other hand, a semi-quantitative method of geosite assessment – based on multi-criteria analysis adapted to geotourism purposes – met the need to define a ranking or priority-based classification of geosites of geotouristic interest, in accordance with the Regional Park management policy and the geoconservation issues. As a whole, this integrated work constitutes a solid, prospective basis for consolidating the project of Geopark application