Thermoplastic based composites containing different weight fractions of molybdenumdisulfide (MoS2) solid lubricant were developed by injection molding.Polymethyl methacrylate (PMMA) and polycarbonate (PC) were chosen for the thermoplasticmatrices. In order to characterize the interfacial adhesion between the matrices and thefiller, we observed the fracture morphologies of selected composites. Micrographs of thefractured surfaces showed removal of MoS2 particles by microcraking as well asthe presence of voids in the case of PMMA/MoS2 composites. These observationswere confirmed by complementary images obtained using the X-ray tomography. The additionof an appropriate coupling agent may improve the adhesion between the MoS2particles and the polymer matrix. Tribological behavior of the composites was alsoinvestigated using a ball-on-flat microtribometer with a high chromium steel ballantagonist. It was found that the addition of MoS2 particles didn’t improve thetribological performance of the composite in the case of PMMA matrix unlike the case of PCmatrix where the friction coefficient was considerably reduced.

The accuracy of a range of immobilisation systems for head and neck radiotherapy has been measured. Two types of vacuum-formed shells, and eight thermoplastic systems have been evaluated. For each system, a mask was made for the same volunteer. A non-invasive optical system, using a scanning laser digitiser, was used to measure the displacement of a fiducial marker. The volunteer was asked to move a maximum comfortable distance in each of the superior, inferior, left and right directions, and a scan was taken at each location. Standard deviations, calculated from the maximum range of movements, were in the range of 1.7–2.9mm in the right–left direction, and 0.9–3.0mm in the superior–inferior direction. The smallest movements were measured for the Medtec S-frame, with nine-point fixation. A laser-scanning camera can assess the movement potential for a subject inside an immobilisation device with good accuracy and precision. Because ionising radiation is not used as part of the imaging process, the same subject can be used for several mask systems to assess which is the best one.

Dans un premier temps, les phénomènes à l'origine des contraintes résiduelles en injection de thermoplastique sont décrits, avec les spécificités liées aux polymères renforcés de fibres. Le refroidissement hétérogène associé à une variation de comportement mécanique conduit aux contraintes d'origine thermique, auxquelles il faut ajouter les contraintes dues à la pression dans la phase fluide figée par la solidification. Les fibres de renfort introduisent une hétérogénéité et une anisotropie de comportement mécanique et de retrait. Dans un deuxième temps, une méthode de mesure des contraintes résiduelles basée sur l'enlèvement de couches et la mesure des moments de flexion est présentée. Elle permet la mesure des contraintes résiduelles pour des matériaux anisotropes comme les thermoplastiques renforcés de fibres. En général, on obtient des contraintes de traction en cœur, et de compression en peau. L'effet du fraisage pour enlever les couches est évalué. La pression et le temps de maintien, la température de régulation du moule, le taux de fibres influencent les profils de contraintes.