Electrostrictive Graft Elastomers and Applications
- PDF / 817,981 Bytes
- 6 Pages / 417.6 x 639 pts Page_size
- 30 Downloads / 187 Views
131 Mat. Res. Soc. Symp. Proc. Vol. 600 0 2000 Materials Research Society
(a) Figure 1.
(b) Structure and morphology of the graft elastomer.
The graft elastomer films were prepared by solution casting. Five grams of graft elastomer powder was added to N,N-dimethylformamide ( as received from Aldrich ) and was heated to 60 °C while stirring for 2 hours to make a 5 wt% solution. The solution was cooled to room temperature and cast on glass substrates and placed in a vacuum chamber. After drying overnight under vacuum, at room temperature, 20 micrometer thick films of the graft elastomer films were obtained. Gold electrodes were sputtered on opposing sides of the films using a plasma deposition device (Hummer III, Technics). Dynamic mechanical and piezoelectric properties of the graft elastomer films were measured as a function of temperature and frequency using a Rheovibron DDV-II-C mechanical analyzer that has been modified to collect electric charge data as a function of applied stress. Dielectric data of the films was measured as a function of temperature and frequency using an HP4192A Impedance Analyzer. The electric field induced strain was tested as a function of the applied electric field. The deflection of a bilayer bending actuator was measured and the strain was calculated using the relationship
-SL = 2 ST = 2d(1/R) = 4dL/(L 2+12)
(1)
where SL is the longitudinal strain of the active elastomer layer, ST is the strain of the active layer in the transversal direction, 1/R is the bending curvature of the actuator, d is the distance between the central layers of active and non-active films, and the L and I are the deflection of the tip of the actuator in in-surface and off-surface directions.[6,7] The low temperature response of the bending actuator was tested in a Satec TCS 1200 temperature controller with cryovac chamber (Satec Systems Inc.). Voltage was applied using a Trek 10/10A amplifier. Deflection was measured as a function of temperature (-55 °C to 25 °C) and voltage (up to 2.75 kV) using a Sony XC-55 progressive scan CCD and IMAQ 1407 PCI image acquisition board (national Instruments) controlled by LabView software (National Instruments). The results of the x-ray diffraction (XRD) test of the films showed that the crystallinity is about 22%. Since the graft elastomer contains 30 wt% of the graft polymer, approximately, 70% of the graft polymer crystallized for the present processing condition. Differential scanning calorimetry (DSC) analysis showed that the melting temperature of the graft elastomer is about 160 TC with a melting range from 145 TC to 185 °C. DSC results also indicate that a glass transition occurs around 50 TC (from 40 TC to 60 'C). This transition should be the secondary glass transition, which is related to the cross linking grafted units.
132
RESULTS AND DISCUSSION Figure 2 shows the relationship between the electric field induced longitudinal strain, S, and the applied electric field at room temperature. The strain exhibits a quadratic dependence with the applied electri
Data Loading...
