Epoxy and Hydroxyl Content

Next to viscosity, epoxy content and hydroxyl content are the prime properties of importance in formulating epoxy-based adhesive systems. Epoxy content allows one to determine the correct amount of curing agent to use. With certain curing agents it may also be important to know the hydroxyl content. These values determine the reactivity of the system. [Pg.440]

Epoxy content is generally determined by wet analytical techniques. ASTM D 1652 is widely used. The most common method is based on the addition of hydrogen halide (e.g., hydrogen chloride, hydrogen bromide, or hydrogen iodide) to the epoxy group. The difference between the amount of acid added and the amount unconsumed, determined by titration with standard base, is a measure of the epoxy content. There are numerous epoxy assay methods based on this technique. The specific method used depends on the resin type being analyzed as well as on the extent to which side reactions can occur. [Pg.440]

The hydroxyl equivalent weight of epoxy resins can be determined by several methods. The most common is esterification with acids, reaction with acetyl chloride, and reaction with lithium aluminum hydride. Infrared spectroscopy may also be used. [Pg.440]

The hydroxyl content is of importance in estimating average molecular weight. To an extent, it also determines system functionality since the hydroxyl groups could be reactive sites. Certain curing agents may preferentially react with the hydroxyl groups. [Pg.440]

When a polymeric resin is stored for a considerable time, physical and chemical changes may occur within the material that will affect its performance as an adhesive or sealant. [Pg.440]