Reactive Adhesives - Fundamentals

For reasons of clarity, the following issues have to be explained  

Applied Adhesive Bonding A Practical Guide for Flawless Results. Gerd Habenicht Copyright 2009 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 978-3-527-32014-1 

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While the chemistry of radiation curable hot melt adhesives is the same as that used in liquid (syrup) adhesives and coatings discussed elsewhere in this volume, there is a fundamental difference between the objectives of reaction in the two types of systems. Syrups consist largely or entirely of reactive monomeric and/or oligomeric materials. Radiation is used to initiate the polymerization of virtually the entire mass. In contrast, hot melts generally contain polymers initially, and these polymers are capable of reaction via radiation to produce chain extension and... 

If in the case of aluminized silicone we were able to evidence a drastic difference between sputtering and evaporation, it happens not to be the case for aluminized PET (13). Our preliminary results on this latter polymer indeed show no marked differences between the two deposition processes, both giving strong chemical interaction. By contrast we have also observed that with noble metals such as Au, no chemical interaction is taking place with silicone substrate with both deposition processes. This tells us that the nature of the polymer substrate and of the metal are most important for the interfacial and adhesive properties. The fundamental parameter seems to be the reactivity of both constituents of the interface. It has been confirmed by Pireaux et al. that the carboxylic function is one of the most reactive surface entity (14) and indeed for PET, the adsorption site for the Al atoms is found to be the carboxylic function (13). During this interaction, Al is oxidized and the diffusion of O into the Al film can occur. 

The surface coverage achieved in PEG immobilization determines the NSA of proteins as well as cell adhesion [54-57]. Thus, precise control of the modification reactions is also desirable also in this context. This control is directly linked to the detailed study of the relevant surface reactions, and in particular to a fundamental understanding of the relation of structure, local order, local surface properties on the one hand to the reaction kinetics, the activation energies and transition state parameters on the other hand. As previously mentioned, systematic studies of such confined reactions on soUd supports have been scarce to date [36,37,58]. In particular, the direct assessment of the relation of local, nanometer-scale structiue and surface properties to chemical reactivity in wet chemical siuface reactions has been hampered by instrumental and analytical limitations so far. 

Fundamentals, Properties, and Testing). Generally speaking, aliphatic amines provide fast cures and are effective at room temperature, whereas aromatic amines are somewhat less reactive but give products with higher heat-distortion temperatures. Polyfunctional amines are widely used in adhesive, casting, and laminating applications. 

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