Entity

Time filter

Source Type

Rapid City, SD, United States

Trademark
Distar Inc. and Bsc Inc. | Date: 1986-09-23

COMPUTER PROGRAMS AND USER MANUALS SUPPLIED THEREWITH.


Bendler J.T.,BSC Inc. | Fontanella J.J.,U.S. Naval Academy | Shlesinger M.F.,U.S. Naval Academy | Shlesinger M.F.,U.S. Navy | Wintersgill M.C.,U.S. Naval Academy
Journal of Non-Crystalline Solids | Year: 2011

Four topics are treated within the framework of the defect diffusion model (DDM). First, it is shown how the relationship between EV*/H* (ratio of the apparent isochoric activation energy to the isobaric activation enthalpy) and monomer volume for polymers that has been pointed out by Floudas and co-workers [G. Floudas, K. Mpoukouvalas and P. Papadopoulos, J. Chem. Phys. 124 (2006) 074905] is predicted. Next, it is shown that in the DDM, scaling arises because the critical temperature can be represented approximately by a power law. Consequently, in the DDM scaling is always approximate and significant departures from scaling, as is observed in the case of hydrogen bonded materials for example, are matters of degree. It is also shown how the connection of scaling with EV*/H* is a natural consequence of the DDM. Finally, DDM calculations of the defect correlation length are carried out and compared with experimental dynamical correlation lengths measured using the 4D3CP solid state NMR method. © 2010 Elsevier B.V.All rights reserved. Source


Bendler J.T.,BSC Inc. | Boyles D.A.,South Dakota School of Mines and Technology | Edmondson C.A.,U.S. Naval Academy | Filipova T.,South Dakota School of Mines and Technology | And 3 more authors.
Macromolecules | Year: 2013

The relative permittivity and dielectric strength have been determined for a bisphenol A polycarbonate (BPA-PC), in which a cyanoethyl group has been substituted for one of the geminal dimethyl groups. The new material (CN-PC) has a glass transition temperature that is 19 K higher than that for BPA-PC. In addition, the dielectric strength of CN-PC, 405 V/μm, is somewhat smaller than that for BPA-PC, 620 V/μm. The relative permittivity was determined from 10 to 105 Hz over a wide temperature range and at pressures up to 0.25 GPa. While the real part of the relative permittivity at 103 Hz and room temperature for BPA-PC is about 3, that for CN-PC is found to be greater than 4. Correspondingly, the γ relaxation region in CN-PC is very strong. For the γ relaxation, a strong increase in peak height as temperature increases and a strong decrease in peak height as pressure increases are observed. A relaxation is found at temperatures higher than the γ relaxation. This process is labeled as the β relaxation because it appears to be related to the β relaxation in BPA-PC in that the strength and position depend on the history of the material. The effects of pressure on the γ relaxation for both CN-PC and BPA-PC are quite large and similar to those previously seen for the γ relaxation in a fluorinated tetraaryl bisphenol A polycarbonate (DiF p-TABPA-PC). In fact, the activation volume is found to be approximately the same for all three BPA-PC-based materials despite wide variations in both peak position and peak height. Finally, computer studies of the model compounds, 4,4′-diphenylpentanenitrile and diphenyl carbonate, were carried out. Both provide insight into the nature of the γ relaxation with the latter yielding an activation volume in approximate agreement with the experimental values. © 2013 American Chemical Society. Source


Bendler J.T.,BSC Inc. | Edmondson C.A.,U.S. Naval Academy | Wintersgill M.C.,U.S. Naval Academy | Boyles D.A.,South Dakota School of Mines and Technology | And 2 more authors.
European Polymer Journal | Year: 2012

The relative permittivity, loss and dielectric strength have been measured for a polycarbonate-based material, tetraaryl bisphenol A polycarbonate, that has been fluorine substituted (DiF p-TABPA-PC). The new material has a glass transition temperature, T g = 489 K, that is higher than that for either conventional bisphenol A polycarbonate (BPA-PC) for which T g = 421 K or for a copolymer of tetraaryl bisphenol A (TABPA) and bisphenol A (BPA) (TABPA-BPA-PC) for which T g = 464 K. In addition, the dielectric strength of DiF p-TABPA-PC is almost identical to that for purified BPA-PC and slightly larger than the value for TABPA-BPA-PC. The relative permittivity and loss measurements were carried out from 10 to 10 5 Hz over a wide temperature range and at pressures up to 0.25 GPa. Variable temperature results for the α relaxation and both temperature and pressure results for the γ relaxation regions are reported. The α relaxation exhibits standard behavior. The γ relaxation exhibits unusual characteristics such as a strong increase in peak height as temperature increases and a strong decrease in peak height with increasing pressure. The data for the γ relaxation have been analyzed using several formulations. Expressions for the peak height and peak position based on a two state (inequivalent well) model and the resulting parameters are discussed in terms of the insight they provide into the molecular mechanisms responsible for the sub-T g relaxation. Ab initio SCF results for a related model compound are presented. Finally, the real part of the relative permittivity for the new polymer is about 10% higher than for BPA-PC. © 2012 Elsevier Ltd. All rights reserved. Source


Fontanella J.J.,U.S. Naval Academy | Boyles D.A.,South Dakota School of Mines and Technology | Filipova T.S.,South Dakota School of Mines and Technology | Awwad S.,South Dakota School of Mines and Technology | And 5 more authors.
Journal of Polymer Science, Part B: Polymer Physics | Year: 2012

The relative permittivity, loss, and breakdown strength are reported for a commercial sample of bisphenol A-polycarbonate (comm-BPA-PC) and a purified sample of the same polymer (rp-BPA-PC) as well as for two new polycarbonates having low molecular cross-sectional areas, namely a copolymer of tetraaryl polycarbonate and BPA-PC (TABPA-BPA-PC) and a triaryl polycarbonate homopolymer (TriBPA-PC). The glass transition temperatures of the new polymers are higher than the T g of BPA-PC (187 and 191 °C vs. 148 °C). Relative permittivity and loss measurements were carried out from 10 to 10 5 Hz over a wide temperature range, and results for the α- and γ-relaxation regions are discussed in detail. For the α-relaxation, the isochronal peak position, T α, scales approximately with T g. On the other hand, the peak temperature for the γ-relaxation is approximately constant, independent of T g. Also, in contrast to what is observed for α, γ exhibits a strong increase in peak height as temperature/frequency increases and a significant difference is found between Arrhenius plots determined from isochronal and isothermal data analyses. Next, the γ-relaxation region for comm-BPA-PC and associated activation parameters show strong history/purity effects. The activation parameters also depend on the method of data analysis. The results shed light on discrepancies that exist in the literature for BPA-PC. The shapes of the γ loss peaks and hence glassy-state motions for all the polymers are very similar. However, the intensities of the TriBPA-PC and TABPA-BPA-PC γ peaks are reduced by an amount that closely matches the reduced volume fraction of carbonate units in the two new polymers. Finally, for comm-BPA-PC, the breakdown strength is strongly affected by sample history and this is assumed to be related to volatile components in the material. It is found that the breakdown strengths for TriBPA-PC and TABPA-BPA-PC are relatively close to that for rp-BPA-PC with the value for TriBPA-PC being slightly larger than that for rp-BPA-PC or the value usually reported for typical capacitor grade polycarbonate. Finally, it is shown that the real part of the relative permittivity remains relatively constant from low temperatures to T g. Consequently, based on the dielectric properties, TriBPA-PC and TABPA-BPA-PC should be usable in capacitors to at least 50 °C higher than BPA-PC. © 2011 Wiley Periodicals, Inc. Source

Discover hidden collaborations