Correlating thermal properties of polyurethane/clay nanocomposite coatings with processing

Phase morphology of polyurethane (PU) and its nanocomposites with Bentone 38 (B38) nano clay additive has been investigated and its effect on the thermal degradation behaviour has been evaluated. Two processing schemes were used to reinforce B38 into the matrix of PU in three different weight percentages (1, 2 and 3 wt%). The nanocomposite coatings show different formations (pyramid, sheet stacks etc.) of clay on the surface of the PU nanocomposite samples. The variable intensity of the key peaks in Fourier transform infrared spectroscopy (FTIR) confirms changes in the chemical interface between B38 clay-PU chains due to different processing schemes. The FTIR data was quantitatively derived to calculate the degree of phase separation (DPS) and the degree of phase mixing (DPM) and analyse the effect of this variation. Cure index calculations from differential scanning calorimetry (DSC) were used to analyse the cure state of the nanocomposites. The morphological studies through X-ray diffraction (XRD), atomic force microscopy (AFM) and optical microscopy (OM) highlight the variation in structures due to modified processing schemes. An improvement of around 34% (89 degrees C) is seen in the 20% weight loss temperature (T-g20) at a loading of just 1 wt% B38. DSC scans also show improved thermal properties. A shift of 14 degrees C (2 wt% B38) and 46 degrees C (1 wt% B38) respectively is observed in the degradation temperature from the heat flow scans w.r.t. the pristine PU. These results indicate that even at low clay loadings, properties can be significantly enhanced just by tweaking the processing scheme, thereby indicating the great sensitivity nanocomposites have to processing schemes.

Automated summary

This study investigates the phase morphology of polyurethane and its nanocomposites with B38 nano clay additive, and evaluates its effect on thermal degradation behavior. The results show that even at low clay loadings, properties can be significantly enhanced by adjusting the processing scheme.