Evaluation by MOIT of organic coating oxidation degree and degradation activity through thermogravimentry

Abstract The work relates to the study of the chemical and chemical-physical properties of artificially aged organic films, compared with those of the materials naturally aged (atmosphere exposure). The first objective of this study is the selection and validation of the most suitable instrumental methods to highlight the consequences of the degradative action due to photo-oxidation and/or weathering agents on protective coatings applied on wood substrates. With the MOIT term we indicated the Modified Oxidation Induction Time parameter that results from the instrumental analysis we used. It appears very sensible to property of materials and may be useful for the ageing assessment. The technique involves a double weight loss analysis (TG) instead of the calorimetric analysis (as recommended in the standard method) on a sample of the film: the first being carried out in a nitrogen atmosphere and the second in an air atmosphere. In both cases the analysis is carried out under the same conditions, i.e. with a thermal profile which provides a heating ramp. At fixed time and temperature, the sample weights, determined under a nitrogen atmosphere, were subtracted from the sample weights homolog in air. The values obtained allow the determination of the "Δ", parameters and its evolution with temperature/time, from which it is possible to determine both the oxidation entity and the oxidation induction time. In this paper the authors illustrate the method referring to one acrylic resin used for coating