Jean Marc Saiter

Diffusion and permeation of water through unsaturated polyester resins—influence of resin curing

Abstract The diffusion and permeation properties of liquid water through an isophthalic-maleic acid-propanediol-based copolyester resin were studied with a highly sensitive permeameter. The value of the parameters of the exponential dependence of the diffusion coefficient on the water concentration decreases with the curing extent, except that of the plasticization coefficient, which decreases after a post-curing at 120°C. Infrared-spectrophotometric and calorimetric data show that the curing involves mainly a polymerization of styrene during the curing at 25°C, and a crosslinking by the opening of the double bonds on the polyester chains in the subsequent curing step at 80°C. The water sorption by the resin results in a 20°C-decrease in the glass transition temperature of the water saturated resin, leading to the diffusivity enhancement by the plasticization effect.

Study of Wheat-Flour-Based Agropolymers: Influence of Plasticizers on Structure and Aging Behavior

ABSTRACTWheat-flour-based agropolymers are prepared using an extrusion method. The morphology of the native and extruded wheat flours are analyzed by scanning electron micrography (SEM). During plasticization using water (9%, w/w) and glycerol (12.8%, w/w), a change in morphology of native wheat flour occurs. The structure of these materials was investigated by X-ray diffraction (XRD) with special reference to the amount of plasticizers used, such as water and glycerol molecules. The introduction of these plasticizers decreases the crystallinity rate and also increases the average distance between chains in the remaining vitreous phase of the extruded wheat flour. Replacing water molecules with glycerol reduces the crystalline phase and diminishes the average size of crystalline structures. The plasticization effects were confirmed by mechanical investigations. Indeed, increasing the amount of glycerol from 12.8 to 20% decreases the stress at failure and the tensile modulus, while the strain at failure in...

Thermal behavior of chemically treated and untreated sisal fiber reinforced composites fabricated by resin transfer molding

Using thermogravimetric analysis (TGA), the thermal behavior of sisal fibers and sisal/polyester composites, fabricated by resin transfer molding (RTM), has been followed. Chemical treatments have been found to increase the thermal stability, which has been attributed to the resultant physical and chemical changes. Scanning electron microscopy (SEM) and infrared (FT-IR) studies were also performed to study the structural changes and morphology in the sisal fiber during the treatment. The kinetic studies of thermal degradation of untreated and treated sisal fibers have been performed using Broido method. In the composites, as the fiber content increases, the thermal stability of the matrix decreases. The treated fiber reinforced composites have been found to be thermally more stable than the untreated derivatives. The increased thermal stability and reduced moisture behavior of treated composites have been correlated with fiber/matrix adhesion.

Viscoelastic and thermal properties of eco-friendly composites fabricated by resin transfer molding

This article reports the result of the effect of banana fiber on the dynamic mechanical and thermal properties of polyester composites. Composites were prepared using resin transfer molding by varying the fiber content (20, 30, 40, and 50 vol.%). Studies revealed that increase in the fiber content will increase the storage modulus (E′) and the maximum is given by the composites having a fiber loading of 40 vol.% at all temperature ranges. The peak height of loss modulus (E″) and damping curves (tan δ) were lowered with respect to the fiber content. Glass transition temperature (Tg) calculated from the E″ and tan δ shifted toward high temperature with the addition of fiber. An attempt has been made to correlate the experimental and theoretical values of storage modulus and tan δ. Thermogravimetric analysis showed that incorporation of fiber to the matrix will affect the thermal stability of the composites.

Effect of mercerization of flax fibers on wheat flour/flax fiber biocomposite with respect to thermal and tensile properties

New composites materials, 100% ecofriendly based on modified wheat flour as matrix and flax fiber as fillers have been obtained by means of an extrusion process. The wheat flour matrix contains non-toxic plasticizers and is mixed well with natural fibers. One sample series without specific fiber surface treatment and a second series with a mercerization surface treatment have been prepared. The content of fillers varies from 0% w/w to 20% w/w. In this work the performances of these new composites in term of thermal stability, mechanical behaviours are compared and discussed in regard to the fiber treatment efficiency and composition. We observe an interesting behaviour: the efficiency is found the best for a fiber composition close to 10% w/w.

Are 100% Green Composites and Green Thermoplastics the New Materials for the Future?

A review of the history of the evolution of material science and material technology shows us that one tendency for the future could be the use of agriculture resources. In this work, we review the performances of one of these resources, that is, wheat flour. We show that it is possible to get thermoplastic films with properties quasiequivalent to what is obtained for expensive pure starch. By adding natural fibres, composites are also obtained. These composites exhibit performances which allow their use only for short duration.

Design of a Compliant Underactuated Robotic Finger With Coordinated Stiffness

In this paper, we propose an underactuated robotic finger whose grasp behavior is modulated by the design of its superelastic joints. Using shape-memory alloy, the finger joints can be given specific stiffness and pre-form shapes such that a single-cable actuation rather than opposing-pair actuation can be used; this also allows the grasping motions of the phalanges to be synchronized in the free phase and then adaptive once contact is made. A default-closed pre-tensioned configuration allows grasp forces to be maximal for larger objects and still keeps control components such as tendons out of the grasp workspace. The simplicity of the design lends itself to the possibility of integrated joint angle and surface pressure sensing on the finger itself. The details of design, prototyping and testing are described.© 2013 ASME