Preparations And Properties Of Electrostrictive Polyurethane Elastomers

Electrostriction is one of the electromechanical coupling effects of materials; it exits in any dielectric materials. The strain induced by electrostriction that called electrostrictive-strain is proportional to the square of the driving electric field, which means the strain has nothing to do with the direction of the electric field. Electrostriction has very stable electric-strain and time-strain relationships. For their good repeatability, quick respondences, low driving voltages, excellent temperature and time stabilities, electrostrictive materials have been widely utilized in transducers, sensors and actuators. Polyurethane that is named by the group–NH-COO- in its main molecular chains is a kind of polymer with special properties and many uses. In this thesis, series of polyurethane elastomers and barium titanate/polyurethane composite elastomers were prepared and characterized.Polyurethane elastomers were synthesis by step-reaction-polymerization with polyester polyol, 2,4-toluene diisocyanate, 1,4-butanediol and 1,1,1-trimethanol propane. The characterization of properties indicated that the hardnesses and densities of polyurethane elastomers increased with the increase of crosslink-degree of elastomers; the glass transition temperatures of polyurethane elastomers also increased with the increase of crosslink-degree of elastomers; the dielectric constants of polyurethanes decreased with the increase of crosslink-degree of elastomers.The introduction of barium titanate into polyurethane elastomer could increase both hardnesses and densities of composite materials. The increase of the contents of barium titanate in the composite materials could raise their glass transition temperatures and the dielectric properties of composite materials.The electrostrictive strain of polyurethane was measured by the DSCM(Digital Speckle Correlation Method).Through the on-and-off of high voltage, the electrostrictive strains of polyurethanes appeared the corresponding shrink and recovery. The electrostrictive coefficient of polyurethane increased with the introduction of barium titanate into polyurethane, but the electrostrictive coefficient of the composite materials decreased with the increase of content of barium titanate.