No abstract

Blends may be made of pairs of polymers where neither, one, or both components are crystalline. The state of compatibility for such blends may be deduced by x‐ray and light scattering. A survey of recent studies in this laboratory of several binary blends of crystalline and amorphous polymers is presented.

An experimental method is described which allows estimation of remanent polarization and coercive field without assuming functional forms for the capacitive and electrical resistance terms. The method can be used to measure polarization in specimens with voltage-dependent conductivity (often arising from the presence of ions in the specimens), voltage-dependent capacitance, and significant amounts of space charge. It consists of: (1) performing bipolar current/voltage hysteresis loops to allow a steady state of remanent polarization and space charge to build up in the specimen, and (2) following a bipolar loop with two or more unipolar loops in which the polarization changes in the first unipolar loop. Both sinusoidal and linear time-dependent applied voltages may be used. Automatic data processing of hysteresis loops is described for cases in which specimen behavior may be considered to be ideal.

Polyurethane electrostriction was investigated by measuring the tensile electromechanical coupling coefficients of structurally different materials. True values of the strain coefficients M3311, M3322, and M3333 were obtained for four types of polymer: one commercial polyurethane (DOW 2103‐80 AE) and three polyurethanes synthesized at the Naval Surface Warfare Center, including two phase‐separated (PS) materials with molecular weights of 1000 and 2000 and one phase‐mixed (PM) material with a molecular weight of 2000. Measurements were performed at 2 kHz under a bias field of 4 MV/m at room temperature. Measured values of M3333 ranged from −9.4 × 10−18 to −74.6 × 10−18 m2/V2, with the PM material exhibiting the largest coefficient. The electrostatic interaction (Maxwell stress) did not account for more than 15% of the total electromechanical activity in any of the materials. Furthermore, at the macroscopic level, an empirical relationship was established to predict the values of the electrostrictive coefficients from the dielectric constants and the compliance coefficients of the material. Finally, results indicated that, at the microscopic level, the phenomenon of electrostriction in polyurethanes could be best explained by the presence of charges inside the material (space–charge theory). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 399–404, 2003

SYNOPSISNylon-11 polymorphs have been studied by x-ray diffraction and by infrared spectroscopy. A y or y-like phase of Nylon-11 was produced by treating the metastable 6' phase with gaseous HC1 or DC1 and then exposing the resulting complex (amidonium salt) to 100% RH H20 or D20 vapor. An oriented form of the y or y-like phase results from treatment of the oriented 6' phase, but stretching of the unoriented y or y-like phase, obtained by treatment of the unoriented 6' phase, induces a transformation to the a phase stable at room temperature. The use of DCl and D20 produced highly deuterated samples with Fermi resonances indicating the relative strengths of the hydrogen bonds are weakest in the a phase, intermediate in the 6'phase and strongest in the y or y-like phase. 0 1994 John Wiley & Sons, Inc.