AbstractMicrocrazing in the struts of flexible polyurethane foams was discovered during compressive deformation and observed directly in the scanning electron microscope. Attributed to this phenomena was the decrease in stress at maximum compression and the intensity of acoustic emission during compressive cycling. The higher content of styrene–acrylonitrile (SAN) copolymer in these foams resulted in higher modulus, more severe microcrazing, an increase in acoustic emission activity, and a decrease in the stress at maximum compression as cycling progresse
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