Understanding the main factors affecting TD-NMR data on tyre products: MDOE and data compression index.

Time Domain – Nuclear Magnetic Resonance (TD-NMR) is a non-destructive analytical technique increasingly used in the analysis of tyre and rubber products. Its greater use is due to the nature of the signal obtained by this technique. Indeed, a decay over time is obtained which is strongly correlated with the polymeric mobility of the materials analyzed. Therefore, any factor that affects polymeric mobility will also affect the signal obtained, such as the temperature of the sample analyzed, the compound formulation and the curing or not of the compound. It is therefore essential for the daily use of this technique to know the impact of these factors. To the aim, a Design of Experiment (DoE) strategy was applied in which the effect of the following three factors was evaluated: 1. Temperature of the sample → Three levels (coded as: -1, 0, +1) 2. Ratio between the amount of component A and component B → Two levels (coded as: -1, +1) 3. Curing or not curing → Two levels (coded as: -1, +1) For each level of temperature, all compounds obtained by combining the second and third factor levels were analysed at TD-NMR (1H-20 MHz applying Carr Purcell Meiboom Gill sequence). On the obtained dataset, a strategy of data compression was applied in order to obtain a parameter which holds all the information contained in the data. In this regards, several parameters were studied. The most promising one is the time at which a specific intensity is reached by the signal. The strategy DoE + data compression index allows to obtain response surfaces that are an indication of how the parameter, and subsequently the signal, vary with the variation of the factors analysed. Through this approach, interesting information can be obtained which may allow a more conscious use of the analytical technique.