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Interpenetrating polymer networks (IPNs) are materials composed of two or more crosslinked polymers permanently and intimately intertwined on a molecular level. The resulting distribution of microenvironments can result in a material with a high mechanical loss in the glass-rubber relaxation, that is shifted in temperature and broadened over that of either constituent polymer. Several series of polyurethane/epoxy IPNs have been prepared for evaluation as possible broad band damping materials. Dynamic mechanical analysis and differential scanning calorimetry revealed that the temperature of the loss peak could be varied widely with sample formulation. Flexible epoxy components and plasticizers were incorporated. This resulted in materials with relatively low Young's and shear moduli, with losses that were broadened in the temperature regime. Simply supported beam assemblies were used to measure damping of three layer constrained structures. Comparison of measured temperature and frequency dependent viscoelastic behavior in constrained layer structures is analyzed in terms of the Ross-Kerwin-Ungar model for coated beams, and correlated to polymer composition and morphology.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. |
