Neuere Entwicklungen auf dem Gebiete der lösungsmittelfreien Lacksysteme auf Basis von Epoxyharzen

Abstract

The past five years have shown a gradual advance of solvent-free epoxy resin systems. As is well-known, these systems possess the following advantages:

1. Considerable saving in time and expenses, it being possible to apply the desired layer thickness in one operation.
2. No loss of solvents.
3. Absence of offensive smell, fire risk reduced to a minimum, no danger of explosion.
4. Less deformation during curing of the film: as a result of the curing reaction a shrinkage of only 0.5 to 2 % by volume is expectable.

In the beginning difficulties were experienced in formulating systems suitable for actual practice, and the methods of application were not yet sufficiently advanced. At present a wide range of resins, hardeners, diluents and cheaper additives are available, while new methods of application have also been developed.
In this lecture the available componends and their influence on the properties of the layers are discusste. In selecting components due allowance should be made for the field and method of application. Hardeners will determine the curing rate and the minimum curing temperature. Diluents are required for obtaining a sufficiently low viscosity; they need not be bonded to the cross-linked macromolecule, but are sometimes physico- chemically bound or chemically built into the molecule as so-called reactive diluents. The proportioning of monofunctional epoxies as reactive diluents is discussed in some detail. Pigmenting, e.g. with leafing pigments or with graded sand and quartz flour is of great importance for special purposes.
The method of application by means of airless spraying at high pressure has lately been developed to such an extent that it can now successfully be used in practice. Details of experience gained in this field are given.