Crosslink Density Changes during the Hydrolysis of Tridimensional Polyesters

The hydrolysis of almost ideal networks based on macrodiols of average molar mass about 2 kg mol 1, with L¼18 ester groups per chain is studied. Tensile testing is used to evaluate the crosslink density through the statistical theory of rubber elasticity at two temperatures and three values of relative humidity. A kinetic model for ester consumption including an autocatalysis term is proposed and combined with two original approaches for modeling the crosslink density changes. This allows kinetic parameters of hydrolysis to be determined, and very good predictions are obtained for the variations of crosslink density (or elastic modulus) in the three aging conditions considered. The initial curvature of elastic modulus versus time is predicted positive for weak autocatalysis and negative for strong autocatalysis. The obtained conversion ratio at degelation is found to decrease sharply with the number of esters per elastically active chaincontrat de recherche SAFRAN - ART

Dynamic Behaviour of Polycarbonate/Polyurethane Multi-Layer for Transparent Armor

This paper deals with the study of the dynamic behaviour of layered Polycarbonate (PC)/Polyurethane (PU) polymers used in lightweight transparent armor bilayer concept. In fact, dimensioning and optimizing this armor concepts need a determination and an understanding of behaviour not only of the multi-layer but also of each component (PC and PU). Thus after an adaptation of dynamic compressive tests in different configurations, it appears that the initial multi-axial prestress of PU is one of the most important parameter for material and layered response. A numerical approach carried out with a monodimensional finite difference code is made to analyze more accurately the system response.L'objectif de ce travail est d'étudier le comportement dynamique des feuilletages de Polycarbonate (PC)/Polyuréthanne (PU) utilisés en face arrière de concept de blindages légers transparents bicouche. En effet, le dimensionnement de ces concepts et leur optimisation passe par une détermination et compréhension du comportement non seulement du feuilletage, mais aussi de chacun des constituants (PC et PU). Ainsi après avoir adapté des essais dynamiques de compression et testé diverses configurations, il apparaît que l'état de précontrainte multi-axiale du PU modifie considérablement son comportement et celui de l'assemblage. Une approche numérique menée à l'aide d'un code monodimensionnel en différences finies permet d'analyser plus finement la réponse de l'ensemble

Memoriale an eine hoch-löbliche Reichs-Versammlung zu Regenspurg

von dem Residenten des Staats der vereinigten Niderlanden, die schweizerische Unruhen betreffen

Fireproofing of polyurethane elastomers by reactive organophosphonates

International audienc

New Phosphonated Methacrylates: Synthesis, Photocuring and Study of their Thermal and Flame-Retardant Properties

International audienc

Fireproofing of polyurethane by organophosphonates

International audienc

Thermal degradation and fire performance of newphosphonate polyurethanes

International audienc