Matrix-filler interactions in a co-ground ecocomposite: surface properties and behaviour in water

Ecocomposites made up of polystyrene and starch were produced by co-grinding. The mechanism by which the composite is formed was identified by following the particle size and morphology. The size reduction of the matrix particles is favoured by the presence of starch which adheres on polystyrene surface, playing the role of agglomeration inhibitor between matrix particles. Thus, the filler is well dispersed in the matrix, permitting a good homogeneity of the composite properties. The hydrophilic behaviour of starch is reduced by co-grinding, resulting of a decrease of the acid and non dispersive components of the surface energies. Consequently the interactions between the initially hydrophobic matrix and hydrophilic filler are enhanced without using a compatibilizer. Thus, the water-resistance of the co-ground composite materials is better compared to blends since blends pellets introduced in water are rapidly disintegrated while an adapted co-grinding time permits to avoid this problem. It was seen that the diffusion coefficient of water in the composite pellets decreases with an increase of the co-grinding time for the lower filler rates, while it is the opposite for high filler rates. Moreover, the diffusion coefficient increases with the filler ratio

Polyimide (PI) films by chemical vapor deposition (CVD): Novel design, experiments and characterization

Polyimide (PI) has been deposited by chemical vapor deposition (CVD) under vacuum over the past 20 years. In the early nineties, studies, experiences and characterization were mostly studied as depositions from the co-evaporation of the dianhydride and diamine monomers. Later on, several studies about its different applications due to its interesting mechanical and electrical properties enhanced its development. Nowadays, not many researches around PI deposition are being carried. This paper presents a PI film deposition research project with an original CVD process design. The deposition is performed under ambient conditions (atmospheric pressure) through a gas flux vector. Design of apparatus, deposition conditions and preliminary characterizations (IR, SEM and surface analyses) are discussed

Effect of the plasticizer on permeability, mechanical resistance and thermal behaviour of composite coating films

Thin layer deposit of a composite material on solid particle surfaces used in the food industry aims to ensure the protection of food powder against aggressive environments such as amoist atmosphere. The layer, having a thickness of a few fractions of millimetre, must have certain physico-chemical properties: it must be compatible with the product, itmust be impermeable to water and oxygen, itmust have goodmechanical strength and good adhesion to the surface of the coated powder. Furthermore the layer must fulfil the regulatory requirements for food ingredients. Film properties like continuity, permeability, and mechanical resistance depend on the choice of the excipients included in the formulation and the operating conditions which can modify the constraints generated at the interface film-powder. As a consequence, the scientific issue consists of combining the local phenomena happening at amicroscopic level on the surface of the particle with the processing technology and the process parameters. In a first step, the attention is focussed on the film and its formulation. For this step, films are prepared separately and they are dried under very smooth conditions. Test samples are taken from the formed composite films and contain hydroxypropyl methylcellulose asmatrix (67% of driedmaterial),micronised stearic acid as hydrophobic filler (20% of driedmaterial) and a plasticizer (13% of driedmaterial). The filmformation procedure and the testmethod are described in detail. The effect of the type of plasticizer (different grades of PEG) onmechanical, thermal and permeability properties of the coating film is studied. The results show that PEG with higher molecular rate provides a better plasticizing effect for the film but increases the water vapour permeability of the film

How to combine a hydrophobic matrix and a hydrophilic filler without adding a compatibilizer – Co-grinding enhances use properties of renewable PLA-starch composites

In order to avoid the use of compatibilizers or plasticizers, co-grinding was performed to produce PLA – starch composite materials. Fragmentation and agglomeration phenomena were analysed to propose a production mechanism. Co-grinding enhances dispersion of the filler in the matrix and interactions between the materials. Consequently while blending the two materials has a negative effect on mechanical properties, co-grinding permits to improve them if optimized operating conditions are applied. Water uptake and diffusion are also controlled by co-grinding conditions. This treatment allows the production of composite materials offering good use properties without any use of a compatibilizer or a plasticizer

Corrosion protection of AA2024 sealed anodic layers using the hydrophobic properties of carboxylic acids

The present study investigates the use of carboxylic acids as a post-treatment for sealed AA2024 anodised in tartaric–sulphuric acid electrolyte. Four monocarboxylic acids with different carbon chain lengths were tested ((CH3–(CH2)n–COOH with n=4, 8, 12 and 16). Hydrophobic surface properties after the posttreatment were characterized by contact angle measurements. Electrochemical impedance spectroscopy (EIS) was performed to assess the ability of the four carboxylic acids to form protective films. It was shown that stearic acid (n=16) used in its pure molten state was the most efficient. The organic film formed very rapidly (under 5 min) and contributed to the enhancement of the protection in terms of corrosion resistance of the sealed anodic layers. EIS measurements showed the presence of the organic films on the specimen surface

Production, by co-grinding in a media mill, of porous biodegradable polylactic acid-apatite composite materials for bone tissue engineering

This paper presents the results of a study of the production of porous biodegradable composite materials by co-grinding, followed by scaffolding. Dry powders of polylactic acid and nanocrystalline carbonated apatite, analogous to bone mineral were co-ground in a tumbling ball mill in order to disperse the mineral filler within the polymer. Porous scaffolds were then made by hot moulding the mixture of the two components along with a pore-forming agent which was subsequently eliminated by washing. The mechanical resistance of the scaffolds was evaluated in order to determine the best operating conditions to produce implants offering optimised properties for use as bone substitutes. It was shown that 30 wt.% of filler and 70 wt.% of pore-forming agent produce scaffolds which are sufficiently porous and resistan

Influence of Moisture on the Electrical Properties of XLPE Insulation

During their operating service, insulated power cables can be exposed to wet environment. The presence of moisture in cables surroundings may affect the properties of the used insulation material for instance, XLPE widely employed in MV and HV power cables insulation and therefore the reliability of the insulated cables. In order to examine the influence of wet aging conditions on the performances of XLPE insulated cables,samples (plates moulded from granules HFDE 4201-EC) of the same insulation material were exposed during 5600 hours to wet environment inside a cell simulating moisture. The XLPE material used in the present investigation is employed as insulation for medium voltage (MV) cables (18 / 30 kV). This work presents the results of the effect of aging under wet conditions on the electrical properties of XLPE. The goal of this paper was to investigate the eventual degradation of XLPE insulation under humidity effect by characterization techniques. For this purpose, measurements of dielectric losses factor, relative permittivity, volume resistivity and dielectric strength were performed

Influence des paramètres de procédés sur les propriétés et éco-composites à base de polylactides

Le travail présenté dans ce manuscrit concerne la fabrication de biomatériaux poreux à base d acide polylactique pour les tissus conjonctifs et calcifiés en utilisant des procédés de chimie verte. Le but de cette thèse est de corréler l influence de certains paramètres de procédés à la structure morphologique et les propriétés des mousses générées. Nous avons étudié, d un côté, les effets de mélange d acide hyaluronique et d acides polylactiques afin d améliorer les propriétés d adhésion de ces biomatériaux. Nos résultats montrent bien une augmentation de l énergie d adhésion mais aussi une diminution de la taille équivalente des pores et de la porosité des biomatériaux poreux après moussage par les fluides supercritiques. D un autre côté, nous avons étudié les effets de mélanges des triphosphates de calcium et d acides polylactiques en tant que substitut osseux. L influence d un ajout de cires en tant qu agent porogène a été discutée et les méthodes de préparation des pastilles (voie sèche ou humide) ont été analysées. Dans cette optique la fabrication semi-industrielle de biomatériaux poreux a été testée en fixant les paramètres du procédé de moussage par le CO2 supercritique (pression, température et temps de saturation, vitesse de dépressurisation) et nous avons contrôlé les mousses de formulations optimisées en termes de porosité et de distribution des pores. En conclusion, ce travail rend possible d adapter les paramètres des procédés de CO2 supercritique et de co-broyage aux propriétés des biomatériaux poreux. En perspective, cette ouvre la voie à de nouvelles recherches à la fois dans les domaines des modèles 3D tumoraux et d ingénierie tissulaire.The work presented in this manuscript concerns the production of scaffolds based polylactides for connective tissues and bone regeneration by adapting green technology. The aim of this thesis was to correlate the influence of different process parameters on the morphological structures and properties of the scaffold generated. On one hand, we studied effect of the blending of hyaluronic acid and polylactides to enhance the surface adhesion properties of scaffolds. Our results relate to an increase in surface properties but a decrease of equivalent pore size and porosity after foaming scaffolds by supercritical process. Calcium Tri-Phosphate On other hand, we studied the effect of the blending of calcium tri-phosphates and polylactides as bone substitute. Influence of adding wax as porogen agent has been discussed and a comparison between wet and dry methods to generate scaffolds has been analyzed. For this purpose, semi-industrial fabrication of porous biomaterials has been tested by blocking supercritical CO2 parameters (saturation pressure, temperature and time, depressurization rate) and you have control the optimized formulation composite scaffold, in term of porosity and distribution of pores. In conclusion, this work made it possible to adapt the process parameters of supercritical CO2 and co-grinding at the properties of scaffolds. In perspective, this research opens new development ways in scaffolds, in both domains of 3D tumoral model and tissue engineering.TOULOUSE-INP (315552154) / SudocSudocFranceF

Production par co-broyage de matériaux composites poreux biodégradables à usage orthopédique

L’article présente les résultats d’une étude sur la production de matériaux composites poreux biodégradables par co-broyage suivi d’une mise en forme. De l’acide polylactique et une apatite nanocristalline carbonatée analogue au minéral osseux, sous forme de poudres, ont été cobroyés dans un broyeur à boulets afin de disperser la charge minérale dans le polymère. Des implants poreux ont ensuite été réalisés en moulant à chaud le mélange des deux constituants et un agent porogène qui a ensuite été éliminé par lessivage. La résistance mécanique des implants a enfin été caractérisée. Il a été montré que des pourcentages de 30 % de charge et 70 % d’agent porogène permettent de produire des implants suffisamment poreux et résistants

Etude des propriétés physico-chimiques de surfaces microstructurées (application à la fabrication de verres organiques ophtalmiques digitaux)

La mise au point d'un verre optique ophtalmique digital est un projet interdisciplinaire révolutionnaire qui fait appel à différentes technologies de microélectronique. Nos premiers travaux ont porté sur l'analyse des matériaux (SU8) et des procédés (photolithographie, sol-gel) utilisés pour la fabrication de microcuves de facteurs de forme différents. Du fait de la dimension micronique des alvéoles, le remplissage est régi par des forces interfaciales et nous avons poursuivi nos travaux en caractérisant les différentes surfaces des microstructures par diverses techniques et en analysant l'avancement progressif de la ligne de contact du liquide sur les surfaces microstructurées. Les multiples procédés de remplissage industriels, qu'ils soient continus (trempage, à la tournette et avec un applicateur "doctor-blade") ou discontinus (jet de matière), ont ensuite été examinés. Les modes de dépôt semi global et ponctuel ont fait l'objet d'une attention particulière, du fait de la résolution potentielle des dépôts et de la gamme des paramètres physico-chimiques des encres. Enfin pour tester le scellement des microstructures, nous avons étudié la solubilité des films acryliques sensibles à la pression PSA en contact avec plusieurs liquides susceptibles d'être introduits dans les microcuves, afin de prédire l'évolution des propriétés adhésives. Quant à la qualité de l'adhérence des films de recouvrement, elle a été caractérisée par pelage et l'analyse des plans d'expériences nous a permis de préciser l'influence de la pollution et du facteur de forme des surfaces microstructurées.The multidisciplinary and revolutionary project of optical ophthalmic digital glasses needs different technologies of microelectronics. First works are concerning analysis of materials (SU8) and process (photolithography, sol-gel) used for manufacturing the microstructures with different form factors. Because of micronic dimension of the cells, the filling is dominated by interfacial forces. Research works are been continued by charactering the different surfaces of microstructures with various techniques then by analysing the liquid contact progress on the micro-structured surface. Multiple filling processes including continuous (dip-coating, spin-coating and applicator doctor-blade ) and discontinuous (ink-jet) depositions had been discussed. Semi-global and punctual depositions by ink jet have been developed due to the high resolution of methods and the large range of physical-chemical parameters of liquids. Finally for testing the microstructures sealing, we have studied the solubility of the pressure sensible acrylic adhesive (PSA) in contact with certain liquids introduced into the micro-cells in order to predict the evolution of sealing properties. As the adhesion quality of the sealing PSA films, several peeling tests have been performed and the analysis of experiment plans has allowed us to precise influences of surface pollution and form factors of the micro-structured surfaces.TOULOUSE-ENSIACET (315552325) / SudocSudocFranceF