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Mechanical properties and linear infrared dichroism of thin films of polyurethane nanocomposites

The morphology, mechanical and FTIR dichroic investigations were performed on neat polyurethane (PU) polymer matrix and PU+CaCO3 nanocomposite thin films in order to understand how the nanofiller influences mechanical properties. The measurements were performed on the strips that were cut from the prepared films in parallel and perpendicular direction with respect to the direction of film preparation. Optical microscopy of PU and PU+CaCO3 nanocomposite reveals the strain-induced transition from continuous spherulites morphology to a fiber-like structure. The stress-strain behaviour of neat PU and PU+CaCO3 nanocomposite films shows significant differences at large strain regime. Experimental results suggest that mechanical properties are strongly correlated to the orientational behaviour of separated phases. The orientation of the hard and soft segments is analyzed by the orientation function calculated from the IR absorbances. The correlation between the orientations of segments, tensile properties and hardness of investigated polymer films is established.

polyurethanes; nanocomposites; FT-IR; phase separation

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