Damien Erre

Compostability of Co-Extruded Starch/Poly(Lactic Acid) Polymeric Material Degradation in an Activated Inert Solid Medium

The aim of this work was to estimate the biodegradation of a co-extruded starch/poly(lactic acid) polymeric material using a vermiculite based inert solid medium which could simulate compost medium and enable us to achieve complete carbon balances. At the end of the test the mineralisation rate was compared to those obtained for co-extruded starch/poly(lactic acid) polymeric material degradation in compost. It was shown that the mineralisation rate after 45 days of degradation was similar in activated vermiculite medium to the one in compost. A protocol for both extraction and quantification of the carbon included in the different degradation by-products was proposed and the carbon balance of the polymer degradation was followed during the test with a satisfactory accuracy. As the non-degraded PLA and starch material had been retrieved during the test, the evolution of the glass transition temperature and the molecular weight of PLA could be followed. A two-step degradation mechanism was highlighted in inert solid medium, showing the fundamental role of abiotic reactions for PLA degradation in compost.

Effect of the formulation of starch-based foam cushions on the morphology and mechanical properties

Cushion foam sheets, made from different blends of wheat starch, were developed with a co-rotating twin-screw extruder machine and compared to commercial plastic foam cushions. An experimental study was developed to identify the effect of three ingredients: glycerol, gluten, and sodium bicarbonate on the bulk expansion, the cellular structure and the mechanical properties of the resulted foams. The experiments showed that the properties of the resulted foams were affected by the formulation. Foams with high level of glycerol and gluten content had lower densities and higher expansion ratio, cell size area, and cell wall thickness than blends with high level of sodium bicarbonate, which had better mechanical strength but less elasticity and shock absorption. The extruded materials had shown their suitability for cushioning use by having comparable physical properties with the commercial plastic foams. The dynamic cushion curve test indicated that the starch-based foam sheets provided good shock absorption properties. They had lower and larger deceleration peak than the expandable polyethylene foams we tested.

X-ray radiography applied to an investigation of thermal diffusion

A laboratory-built x-ray radiography device (combining an x-ray tube as source and a CCD camera as detector) that is simple and easy to use is presented as a complementary analysis tool for the analysis of chemical processes. It allows the in situ acquisition of x-ray absorption images of solid or liquid samples with a lateral resolution of 50 µm and a sensitivity of 10−3 atom per atom. Its main application is in the analysis of liquid ionic solutions such as those met in electrochemical reactions where heavy ions move in a less absorbing medium. Despite a low resolution, a good absorption contrast in images of moving species in a liquid is obtained within a few seconds and the digital format of these images allows quantitative measurements of local concentration changes in solutions. For instance, the system has here been applied to investigate thermal diffusion in a binary solution of potassium iodide KI. X-ray imaging of the solution leads to the determination of the Soret coefficient and to its evolution as a function of the muzzle concentration. These measurements complement existing data on this thermodynamic effect in a scarcely explored concentration field.

Finite Element Simulation of the Strength of Corrugated Board Boxes Under Impact Dynamics

In this study, we propose a model based on the finite element method to study the behavior of corrugated cardboard boxes subjected to shocks. To reduce the preparation of the CAD model and the computational times, we have developed an elastoplastic homogenization model for the corrugated cardboard. The homogenization consists in representing a corrugated cardboard panel by a homogeneous plate. A through-thickness integration on a periodic unit cell containing a flute and two flat linerboards is proposed. Each constituent is considered as an orthotropic elastoplastic material with specific hypotheses for the corrugated medium. The model was implemented in the finite element software ABAQUS. Damage boundary curve (DBC) for corrugated cardboard boxes are defined by experimental testing and finite element simulations using the proposed model. The numerical results obtained are in good agreement with the experimental results.

Experimental Investigations and Finite Element Modelling of the Vibratory Comportment of a Manual Wheelchair

This paper presents the comparison between the numerical results provided by the finite element model of a manual wheelchair and the vibration experiments performed on the same actual wheelchair. Two patients having different corpulence participated in this study while sitting on different types of cushions. The tests were carried out using a vibrating table with white noise as the input, in an attempt to simulate the entire vibration spectrum that the user of the chair could undergo. A numerical approach based on the finite element method has made it possible to create a numerical model of the wheelchair that can then anticipate structural problems resulting from these vibratory constraints. The objective of this work is to characterize the structure of the wheelchair as well as the vibration disturbances suffered by the user according to the daily life tasks. This first study will later allow the development of a design strategy oriented towards patient’s comfort with regard to vibrations and also to develop a new type of wheelchair using an adapted structure guaranteeing a longer material life.

Reproduction of an Actual Transport Packaging Damage Based on Weighted Gaussians Decomposition

Goods transportation across the world is composed of a multitude of phases. These phases are mechanical stresses sources which can damage or destruct the product. To avoid these destructions, it is necessary to simulate the transport in laboratory. Regarding the vibrations, their simulations are performed using a vibration table. These tables are usually controlled from PSD and generate a gaussian acceleration levels signal. However, actual transportation generates ungaussian acceleration levels signal. These actual distributions of accelerations can be decomposed into many weighted gaussian distributions. These different gaussian distributions are associated to several PSD levels. By knowing the adapted Basquin coefficient and the adapted constant of a system made to measure the damage during the actual transport, it is possible to estimate the lifetime of a packaging system and its damage rate from a PSD. However, this damage estimation is adapted to a gaussian distribution usually generated on a vibration table. In this work, the damage calculation is applied to the defined PSDs obtained from a weighted gaussian levels distribution. The total damage generated on a packaging system by the different levels of PSDs are compared to the total damage of an actual transport.

Prediction of the yellowing of styrene-stat-acrylonitrile and acrylonitrile-butadiene-styrene during processing in an internal mixer

Abstract The objective of this study was to build a model that can predict the yellowing of styrene-stat-acrylonitrile (SAN) and acrylonitrile-butadiene-styrene (ABS) during processing in an internal mixer. Considering the change of color of SAN and ABS as they degrade, we correlate the yellowing of SAN and ABS to process parameters. We propose a method to represent the energy of mixing of polymer blends in an internal mixer to understand the complex mixing process of materials under different mixing conditions. Indeed, during processing, the properties of polymers could be affected by both thermal and mechanical degradation leading to several mechanisms of degradation. We presented a simplified model “h” taking into account the contribution of each process parameters applied in the internal mixer. Three process parameters were studied: the temperature T, the rotation speed of the blades V, and the residence time t. Thanks to this method of approach, a good correlation between the yellowing of styrenics and the mixing energy in the internal mixer was described. We validated this equation with two polymers: SAN and ABS, and this model can now predict the yellowing of SAN and ABS as a function of the process parameters in an internal mixer.

Élaboration des Élaboration des plaques de calage issues d’agroressources par extrusion réactive. Optimisation des relations procédés-structures - propriétés

RÉSUMÉ. Les mousses de calage en plastique utilisées dans les emballages sont volumineuses et beaucoup de travaux s’intéressent à limiter leur production et à les remplacer par des matériaux biosourcés et/ou compostables mais avec des propriétés mécaniques comparables aux mousses en plastique pétrochimique. L’un des objectifs de ce travail est de comprendre et d’optimiser le procédé de fabrication des plaques de mousses de calage à base d’amidon afin d’assurer la stabilité et la reproductibilité du procédé. Les mousses présentant les meilleures propriétés de calage ont été caractérisées et leurs performances mécaniques, en termes d’absorption, d’amortissement et de transmission du choc lors du transport, ont été comparées à celles des mousses de calage traditionnelles d’origine pétrochimique. Nous avons étudié le vieillissement et la stabilité des propriétés des mousses à différentes conditions climatiques. Pour améliorer les propriétés et les performances mécaniques des mousses et réduire leur sensibilité à l’humidité, nous avons rajouté des fibres naturelles et des biopolymères à la formulation de base et étudié leurs effets sur les propriétés des mousses résultantes. Les mousses extrudées présentent des propriétés physiques et un pouvoir amortissant comparables aux mousses traditionnelles, type polyéthylène expansé, ce qui permet de les utiliser dans diverses applications dont principalement les calages.