Effect Of Soft Segment Control On The Structure And Dielectric Properties Of Polyurethane Elastomer

Dielectric elastomers are widely used as artificial muscles,actuators and generators.The polyurethanes have a advantage of esay adjusting strucure via altering the monomers of hard and soft segments.The contents of this thesis are composite of four parts as following:(1)Polyester polyurethane elastomer(PU)was synthesized by using polyester polyol as soft segment.The influence of soft segment structure on the microphase separated and performances of PUs were considered.The results showed that the degree of soft segment crystallinity order in PUs was showed as polycaprolactone diol(PCL)<Poly(butylene adipate ester glycol)(PBA)<Poly(hexanediol adipate ester glycol)(PHA),and the microphase separation of PUs was suppresed by crystallization of soft segment.The elongation at break,elastic recovery rate,dielectric constant and actuated area strain of PUs were slightly decreased,whereas the young's modulus and breakdown field strength increased greatly when the soft segment having larger crystallinity.(2)The influence of hard segment components in polyurethane elastomer on its structure and character was discussed.The results showed that the microphase separated structure of PU is improved and the size of hard domains is became to larger when increase of the hard segment content from 20%to 40%,accordingly,the Young's modulus and breakdown field strength were increased,whereas the elongation at break,elastic recovery rate,dielectric constant and actuated area strain were slightly reduced.(3)The effect of Polydimethylsiloxane(PDMS)content on the microphase separated and properties of PUs with bi-soft segment of PDMS and PCL were investigated.The results showed that incoporation of PDMS can improve the the microphase separation of hard segment and PCL.The dielectric constant of PUs with PDMS and PCL was decreased slightly with increase of PDMS content,wehreas the breakdown strength was increased obviously.The breakdown strength of PU with PDMS and PCL can be reached to 90.9 kV mm-1 when containing 5wt%of PDMS.(4)It was discussed how the structure and performances of PUs microphase separation were affected by the PCL-410 content.The results showed that incorporation of PCL-410 can significantly reduce the crystallinity of soft segment and the young's modulus of PUs.When the PCL-410 content was 40%,the young's modulus of PUs with PCL and PCL-410 was 1.5MPa,which was 89%lower than that of PU without containg PCL-410.The dielectric constant and actuated area strain were increased as increase of PCL-410 content.The dielectric constant of PU was showed 8.0 at 1 kHz when incorporating 40%of PCL-410 in soft segment.Our results can provide the new insight into understanding the mechanisms of soft segment structure inflences on microphase separation and properties of PUs.