Polyurea resins having excellent mechanical properties and high heat resistance can be prepared by the reaction of an aromatic polyamine component and an aliphatic polyisocyanate component, in which the aromatic polyamine component is a combination of a first aromatic polyamine compound which is typically a polyoxyalkylene-bis(aminobenzoate) compound and a second aromatic polyamine compound selected from various classes of aromatic polyamine compounds different from the first aromatic polyamine compound, in a specified weight proportion. The polyurea resin can be imparted with further improved heat resistance when the aliphatic polyisocyanate component is a combination of an aliphatic diisocyanate compound and a cyclic trimer of an aliphatic polyisocyanate compound in a specified weight proportion.
An etched dielectric film for use in a hard disk drive. The dielectric film has a thickness of about 25 &mgr;m or greater when it is attached to a supporting metal substrate, and is subsequently etched to a thickness of about 20 &mgr;m or less.
An etched dielectric film for use in microfluidic devices. Channels, recesses, and other features can be etched into the films to make them suitable for use in microfluidic devices.