Adhesion in composites

Oxane bonds, M—O—Si, are hydroly2ed during prolonged exposure to water but reform when dried. Adhesion in composites is maintained by controlling conditions favorable for equiUbrium oxane formation, ie, maximum initial oxane bonding, minimum penetration of water to the interface, and optimum morphology for retention of silanols at the interface. The inclusion of a hydrophobic silane, such as phenyltrimethoxysilane [2996-92-17, with the organofunctional silane increases thermal stabiUty of the silane and make the bond more water resistant (42). 

Felix, J.M. and Gatenhobn, P. (1991). The nature of adhesion in composites of modified cellulose fibers and polypropylene. Journal of Applied Polymer Science, 42(3), 609-620. 

Herrera-Franco, P.J. and Drzal, L.T. (1992). Comparison of methods for the measurement of fiber/matrix adhesion in composites. Composites, 23, 2-27. 

Lehman WF (1986) Outline of a fast durability test for UF and PF adhesives in composite materials. In Maloney T (ed) Proceedings of the 20th Washington State University Particleboard Symposium, Pullman, Washington, 105-22 Leicester RH (1988) Timber engineering standards for tropical countries. Proceedings of 1988 International Conference of Timber Engineers, Seattle. Forest Products Society, Madison, Wisconsin, Vol. 1 177-85... 

The structure of the filler particle surfaces and of the polymer surface characterised hy their fractal dimensions, affects the interfacial adhesion in composites. To explain the structural effect let us introduce the concept of the accessibility of the sites on these surfaces to form adhesion joints (physical or chemical). As a first approximation the degree of such accessibility may be defined as a difference of the fractal dimensions of two surfaces. The higher is this difference the lower is the accessibility of the surface and the less is the adhesion [21]. Suppose that the filler particle has a very rough surface with dimensions which are close to the Euclidean dimension d = 3 (for example, AI2O3 particles) [33], whereas the polymer surface is very smooth, i.e., dp = d = 2. In this case the contact between two surfaces is possible only at the apexes of the rough surface of the filler and the result could be very low adhesion. In other words, the disparity of the dimensions determines the inaccessibility of the greater part of the filler particle for the formation of adhesion bonds [21]. 

Thus, the adhesive contacts the substrate via a layer of substances that frequently differ from the adhesive in composition. If the cohesion strength of these substances is less than that of the adhesive, this will determine the failure stress of the adhesive-bonded joint. The adhesive, which has the same composition as that of the adhesive in bulk, can form a weak zone in the substrate surface. Adhesives are polymers and the particular nature of a polymer must have effects at all stages of formation and operation of an adhesive-bonded joint. 

Penetrates the top few molecular layers (100 about 10 nm) and modifies the surface, creating a new surface chemistry, enabling improved interfacial adhesion in composites. 

Herrera-Franco PJ, Drzai LT (1992) Comparison methods for the measurement of fibre/matrix adhesion in composites. Composites 23 2-27... 

Juska T D and Puckett P M (1997) Matrix resins and fiber/matrix adhesion, in Composites Engineering Handbook (Ed. Mallick P K) Marcel Dekker Inc., New York, NY, pp. 101-165. 

We considered the effect of the structure of MAPP used on interfacial adhesion in composites. Figure 4 shows the tensile strength of the cellulose composite as a function of the molecular weight of the MAPP used. The tensile strength increases with an increased molecular weight of MAPP. The work is ongoing in our laboratories in order to see whether there are any correlations between the crystalization pattern and interfacial adhesion. 

Measurement methods for fiber-matrix adhesion in composite materials... 

Measurement methods for fiber-tnatrix adhesion in composite materiais... 

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