Preparations And Properties Of Novel Thermoplastic Polyurethane And Their BaTiO₃ Composite Elastomers

Polyurethane (PU) elastomer is a kind of polymer between normal rubber and rigid plastic; it was used widely because of the special structure of soft and hard segment. Since the discovery of significant electrostrictive deformation of PU, the measurement of electrostriction and the basic principles about it were reported recently. A series of thermopolyurethane (TPU) and their composites with barium titanate (BT) were prepared and characterized. The electrostrictive strain of polyurethane was measured by the DSCM (Digital Speckle Correlation Method), some factors that effect the electrostrictive property of PUE were studied.Firstly, several chain extenders were prepared by Williamson Reaction, and polyester polyols with pendant methyl were synthesized with adipic acid, 1,4-butanediol and 2,2-dimethy-1,3-propanediol. A series of TPU with different kind of the chain extenders were polymerized from polyester diol, 4,4′-methylenebis(phenyl isocyanate) and the chain extenders by solution moulding. TPU with different NCO:OH ratio were also polymerized from polyester diol, 4,4′-methylenebis(phenyl isocyanate) and hydroquinone bis(2-hydroxyethy)ether. The study on their physical property, electrical property and electrostrictive property indicated that their properties were signicantly related with the structure of the hard segment. However the influence is relatively little when the ratio of NCO:OH is changed in a small range.Next, several kinds of polyurethane/BaTiO3 composite elastomers were prepared from polyester diol, 4,4′-methylenebis(phenyl isocyanate) and the chain extender with BaTiO3 nanoparticles. The structure, compression moduls,permittivity and electrostrictive strain of polyurethane/BaTiO3 composite elastomers were researched with ATR-FTIR, SEM, DMTA et al. The results indicated that the hardness, the permittivity of the composite elastomers increased with the increase of the content of BaTiO3, whereas the compression moduls increased slightly when the content of BaTiO3 above 24wt%. The glass transition temperature of the composite elastomers decreased as compared with pure polyurethane elastomers. Through the on-and-off of high voltage, the electrostrictive strains of the composite elastomers appeared the corresponding shrink and recovery. Along with the increase of BaTiO3 nanoparticles in the composite elastomers, the electrostrictive coefficient of PU firstly ascended and then descended.