Biomedical subjects

Patrice Dole

Publications and source records attributed to Patrice Dole.

5 recordsLinked to original sources

PubMed2006

Thermoplastic starch-waxy maize starch nanocrystals nanocomposites.

Waxy maize starch nanocrystals obtained by hydrolysis of native granules were used as a reinforcing agent in a thermoplastic waxy maize starch matrix plasticized with glycerol. Compared to our previous studies on starch nanocrystals reinforced natural rubber (NR) [Macromolecules 2005, 38, 3783; 2005, 38, 9161], the present system presents two particularities: (i) thermoplastic starch is a polar matrix, contrarily to NR, and (ii) the chemical structures of the matrix and the filler are similar. The influence of the glycerol content, filler content, and aging on the reinforcing properties of waxy maize starch nanocrystals (tensile tests, DMA) and crystalline structure (X-ray diffraction) of materials were studied. It was shown that the reinforcing effect of starch nanocrystals can be attributed to strong filler/filler and filler/matrix interactions due to the establishment of hydrogen bonding. The presence of starch nanocrystals leads to a slowing down of the recrystallization of the matrix during aging in humid atmosphere.

Crystallization↗

PubMed2006

Typical diffusion behaviour in packaging polymers - application to functional barriers.

When plastics are collected for recycling, possibly contaminated articles might be recycled into food packaging, and thus the contaminants might subsequently migrate into the food. Multilayer functional barriers may be used to delay and to reduce such migration. The contribution of the work reported here is to establish reference values (at 40 degrees C) of diffusion coefficients and of activation energies to predict the functional barrier efficiency of a broad range of polymers (polyolefins, polystyrene, polyamide, PVC, PET, PVDC, [ethylene vinyl alcohol copolymer], polyacrylonitrile and [ethylene vinyl acetate copolymer]). Diffusion coefficients (D) and activation energies (Ea) were measured and were compiled together with literature data. This allowed identification of new trends for the log D=f(molecular weight) relationships. The slopes were a function of the barrier efficiency of the polymer and temperature. The apparent activation energy of diffusion displayed two domains of variation with molecular weight (M). For low M (gases), there was little variation of Ea. Focusing on larger molecules, high barrier polymers displayed a larger dependence of Ea with M. The apparent activation energy decreased with T. These results suggest a discontinuity between rubbery and glassy polymers.

Acrylic Resins↗

PubMed2004

Stabilization of aroma compounds through sorption-release by packaging polymers.

Plastic packaging materials are often associated to aroma losses and to a decrease of the organoleptic quality of foods. This work defines situations where, on the contrary, plastics play a regulating role on the concentration of reactive aroma compounds in foods. These systems can be described by a two step mechanism; first, aroma is sorbed in the polymer, while the fraction in solution degrades quickly; in a second step, as the concentration is close to zero in the solution, the polymer liberates progressively the sorbed aroma back to the food. A simple numerical model is proposed, describing competitive processes of aroma degradation in solution and sorption by a polymer in contact with a homogeneous aqueous food. The classical limonene/low density polyethylene (LDPE) system is studied experimentally for the validation of the model: in an acidic medium, limonene both degrades quickly and is sorbed quickly, with a large solubility in LDPE. To define which aroma packaging systems could also display this interesting behavior, all types of possible interactions, using thermodynamic and kinetic parameters describing most practical situations, are simulated. For that purpose, 35 values of reference diffusion coefficients and 35 partition coefficients of usual aroma compounds between polymers and water have been measured and combined with the few available data from literature. The situations where polymers regulate the aroma concentration in food correspond to large partition coefficients (above 10), large diffusion coefficients (>10(-9) cm2 x s(-1)), and large degradation constants.

Adsorption↗

PubMed2002

Using transgenic poplars to elucidate the relationship between the structure and the thermal properties of lignins.

In an attempt to draw relationships between the molecular structure and the thermal behavior of lignins, thermomechanical analyses were run on six milled wood and enzyme poplar lignin fractions prepared from genetically modified and control woods. All the lignin samples displayed similar thermal profiles with a clear inflection point assigned to the glass transition point. The temperature (T(g)) at which this transition occurs showed large variations from 170 to 190 degrees C, depending both on the genetic modification and on the age of the tree. These variations were found to be closely related to the condensation degree of lignins evaluated by thioacidolysis.

Alcohol Oxidoreductases↗

PubMedDate not supplied

Lignin-polymer blends: evaluation of compatibility by image analysis.

This paper opens onto a general discussion on the development of new polymeric materials obtained from lignin blends. The aim is (i) to look for good polymer candidates to obtain a good compatibility with lignins (that is among semi polar polymers), and (ii) to look for good lignin candidates to obtain a good compatibility with polymers showing extreme behaviours (very polar, e.g. starch, or apolar, e.g. polypropylene). The compatibility is simply assessed through the blend morphology, as studied by visible microscopy. The morphology of the blends obtained from semi polar polymers is very sensitive to the variation of the solubility parameters. In a low range of polymer solubility parameters (delta delta = 1 cal cm(-3)), both heterogeneous and homogeneous systems are obtained. These blends could be easily improved by a careful choice in the polymer structure (particularly in the family of biodegradable polyesters); it could be possible also to take advantage of lignin variability to improve the compatibility. Only low molecular weight lignins are compatible with apolar and very polar matrixes. These compounds induce interesting specific properties, and original methods have to be looked for in order to improve their production.

Lignin↗