Chemical and structural characterisation of DGEBA-based epoxies by time of flight secondary ion mass spectrometry (ToF-SIMS) as a preliminary to polymer interphase characterisation

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has become a powerful tool in the field of surface analysis since it provides information about the top few monolayers of a sample, i.e. on the chemical composition of the sample surface. Thus, the general question arises whether a surface-sensitive technique like ToF-SIMS would be appropriate to detect systematic chemical and/or structural changes in organic bulk polymers caused by varying a chemical content of the initial components or by tracking, e.g. curing processes in such materials. It is shown that careful sample preparation and the use of multivariate methods permit the quantitative acquisition of chemical and structural information about bulk polymers from the secondary ion signals. The hardener concentration and a cross-linking coefficient in diglycidyl ether of bisphenol A based epoxies were determined by ToF-SIMS measurements on samples with different resin to hardener ratio and varying curing time. In future work, we will use the developed method to investigate the local composition of adhesively bonded joints. In particular, the mapping of the chemical and structural properties in the so-called interphase will then be of interest.