JOURNAL OF MATERIALS SCIENCE 40 (2 0 0 5 ) 2759 – 2760 LETTERS On the hybrid character of glass fibres surface networks P. ZINCK, J. F. GERARD ∗ Laboratoire des Mat ´ eriaux Macromol ´ eculaires, UMR CNRS 5627, Institut National des Sciences Appliquees de Lyon, France The structure of organomineral coatings on glass fi- bres surface is a function of numerous parameters. Among them, the molecular parameters of organosi- lane coupling agents in aqueous solution are of great importance [1]. The understanding of hydrolysis and condensation mechanisms, the influence of the pH, temperature, concentration and the nature of the or- ganic ligand are keys for the control of the structure [2–4]. It is now well accepted that the structure result- ing from the deposition from an aqueous solution of 1,4 γ -aminopropyltriethoxysilane consists in a three- dimensional graded cross-linked network [5, 6]. The crosslinking density increases as the glass surface is reached and the outer layers are thought to be ph- ysisorbed. The situation still remains uncertain in the case of more complex industrial sizings, although it is assumed that the silane migrates to the interface pro- viding an interfacial region which is similar to that ob- tained from the pure coupling agents solutions [7]. The silane may act as a surfactant for the colloidal poly- mer particles in the sizing emulsion. The evolution of the structure in the course of a thermohydrolytic treat- ment has not been discussed so far, although changes in the mechanical behaviour of the fibres [8–10] and in the mechanical properties and the structure of in- terfacial zones in composites materials [11, 12] have been reported. The first steps of interfacial zones for- mation can be described by the dissolution of the outer physisorbed layers of the structure in the reacting co- monomers, and the consecutive diffusion in the pre- formed inorganic–organic network [3]. An attempt to apply general concepts from the chemistry of hybrid materials to the formation and properties of glass-fibers sizings and glass fibers-polymer interfaces can thus be proposed by considering the simultaneous reactions of organic and inorganic components. Apart from an anal- ogy between the sizing treatment of glass fibers and the strengthening of silica glass by means of hybrid inorganic–organic coatings [13], the application of con- cepts from the chemistry of hybrid materials in the field of glass fibers sizings and their interfaces with a poly- mer has remained to our knowledge purely conceptual, suffering from a lack of experimental data. In fact, due to the geometry of these systems, the dimensions in- volved and the necessity to perform in situ measure- ments, the experimentation still remains difficult. In the early eighties, Miller [l4] developped a technique based on dynamical mechanical analysis which enables to characterize coatings directly on glass fibers strands. ∗ Author to whom all correspondence should be addressed. Using this technique, we report here an experimental observation of the hybrid character of glass fibers siz- ings via the evolution of their structure in the course of a thermo-hydrolytic treatment. The loss factor was computed on a Rheometrics RSAII apparatus every 2 degrees between −150 and 200 ◦ C. Three different kinds of E-glass fibers from Vetrotex Co. differing by their surface treatments have been considered: – a water-based sizing treatment corresponding to the deposition of an aqueous solution of an anti-static agent only, – a silane-based treatment corresponding to the deposition of γ -aminopropyltriethoxy-silane from a 1 wt.% aqueous solution of silane, – an industrial sizing referred to as P122 by Vetrotex Co., known as an universal sizing. The coupling agent included in the sizing formulation is the γ -APS. Other components such as lubricant and film-former were also included. Figure 1 Loss factor of γ -APS (a) and P122 (b) sized E-glass fibers de- termined by dynamical mechanical analysis in bending at l Hz. Untreated glass fibers loss factor in grey. 0022–2461 C  2005 Springer Science + Business Media, Inc. 2759