Molecular intermixing tends to broaden the glass transition regions of some IPN materials compared to their component polymers. This unique characteristic provides excellent mechanical damping properties over a wide range of temperatures and frequencies due to a relatively constant and high phase angle. In IPNs composed of both rubbery and glassy polymers, considerable toughening is observed compared to the constituent polymers. When the glassy component forms a discrete, discontinuous phase, the elastomeric nature of the continuous rubbery phase can be preserved while increasing the overall toughness of the material and its elongation at break. On the other hand, when the glassy polymer forms a bicontinuous phase within the rubbery network, the IPN material can behave like an impact-resistant plastic.