The successful application of glue all depends on timing. Pot life, open time, time for minor adjustments, curing time or time to reach maximum bonding strength—are terms used to describe the properties of glues and to give guidance for their use, and they all have to fit together to create a successful glue product. For example, depending on the method used to apply the glue, the open time needs to be adjusted to avoid curing before the parts have been joined.
A rheometer is an essential tool to characterize not only the uncured glue but the curing process itself. Whether you’re investigating a drying glue, a two-component system, a thermally curing glue, or a UV-curing glue, rheometers are the perfect tools to characterize glue curing behavior.
Still, rheological methods have a limitation; a rheometer can only tell us what happens during the curing process but it does not tell us why. The “why” becomes especially important when we want to understand why a batch of the glue shows properties other than the expected ones, or when we want to develop glue for a new application. To overcome this limitation, the rheological data needs to be combined with data from another analytical method that is able to detect what happens on the molecular scale. A perfect match is FTIR spectroscopy, a technology able to identify and quantify different chemical groups in a substance or mixture of substances.
The disadvantage of running tests on two separate instruments is the extra effort it takes to prepare two different samples and following different procedures for each method. Plus, this approach makes it virtually impossible to collect both sets of data on two identical samples under exactly the same conditions. To combine rheological tests with FTIR spectroscopy while avoiding these disadvantages, a rheometer module has been developed that can be combined with an FTIR spectrometer to simultaneously record, on the same sample, what happens during the curing process and why it happens on a molecular level. This significantly reduces the sample preparation and analysis time and excludes uncertainties about different sample composition or sample treatment when running both analyses separately. This unique combination of methods not only increases the quality of the data collected but also increases the time and cost efficiency of an analysis.
Next, read about a test method for monitoring the curing of the acrylate glue with rheology and simultaneous FTIR.
Read Curing of an Acrylate Glue – Rheology with Simultaneous FTIR Spectroscopy for a more in-depth description of the test including the resulting figures and spectra.