Adhesion loss moisture absorption

The major drawback of cellulose fibers in the present context resides in their highly polar and hydrophilic character, which make them both poorly compatible with commonly used non-polar matrices, such as polyolefins, and subject to loss of mechanical properties upon atmospheric moisture absorption. That is why they should be submitted to specific surface modifications in order to obtain an efficient hydrophobic barrier and to minimize their interfacial energy with the often nonpolar polymer matrix, and thus generate optimum adhesion. Further improvement of this interfacial strength, which is a basic requirement for the optimized mechanical performance of any composite, is attained by chain entanglement between the matrix macromolecules and the long chains appended to the fiber surface (brushes) or, better still, by the establishment of a continuity of covalent bonds at the interface between the two components of the composite. 

A 121"C cure toughened cyanate ester film adhesive formulated for use in specific applications where low moisture absorption and/or low dielectric constant/low loss are of utmost importance. The system s strength and toughness when bonding solid, honeycomb or foam core structures, is a>mparable and often greater than high performance epoxy adhesives, particularly at elevated temperatures. 

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