No abstract

The adsorption of several prehydrolyzed alkoxysilanes onto the surface of cellulosic fibers in ethanol/ water mixtures has been studied quantitatively. The corresponding isotherms show the formation of a monolayer followed by further adsorption. The nature of the fourth substituent on the silane plays a specific role on the features of this association. Whereas at room temperature only dispersive and polar attractive interactions occur, heating above 100 °C produces condensation reactions resulting in covalent bonding between the substrate and the silane forming the monolayer. As a result of this investigation, the possibility of calling upon this surface modification in order to compatibilize cellulosic fibers with polyolefinic matrixes for the elaboration of composite materials seems to be a promising strategy.

No abstract

Unsaturated polyester and epoxy resin matrices were filled with silane-treated cellulose fibers and the ensuing composites were tested in terms of mechanical properties before and after accelerated aging consisting of their immersion into water. The coupling agents used were ␥-aminopropyltriethoxysilane (APS), ␥-methacrylopropyltrimethoxysilane (MPS), hexadecytrimethoxysilane, and ␥-mercaptopropyltrimethoxysilane (MRPS) and those containing reactive functions capable of reacting at one end with the fibers and at the other with the matrix, namely, APS, MPS, and MRPS, were more efficient in improving the mechanical properties of the composites. The immersion into water induced a drastic loss of mechanical properties of the materials. The water uptake of the composites was also studied and showed that the silane treatment was poorly efficient in preventing cellulose from water absorption. The fracture surfaces were inspected by scanning electron microscopy, which confirmed the quality of the interface. These observations were in agreement with the results obtained from the dynamic mechanical characterization.