An ultra low frequency bridge for dielectric measurements

Scheiber, Donald J.

doi:10.6028/jres.065c.004

Cited by 21 publications

(15 citation statements)

References 4 publications

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“…5 pr?per tles of P CTFE and oth er polym en c matenals, a number of probl ems relatin o' to a,pparfl,tus and measurement techniqu es were" encoun tered a nd solved. D oub tless ma,ny of t hese problems were noted an d adequately dealt wi th in vario~l s wfI,Ys by ot her investiga,tors, bu t t he [act remalns t ha,t such usef ul deta,ils are rfl,rely publi s hed.…”

Section: Summary Of Results Of Analysis Of DI Polar J'elaxa Tion and mentioning

confidence: 99%

“…The extension of the frequency range down to 0.1 cis is made possible by the use of a low-frequency bridge described in detail elsewhere [5]. Nakajima and Saito [6] have reported measurements of the dielectric properties of POTFE in the frequency range of 0.1 to 10 6 cis in which a bridge of rather similar capabilities was used.…”

Section: Hoffman and Weeksmentioning

confidence: 99%

“…One may then write for the degree of crystallinity at 23 DC X 0. 48175 -V 23 0.0242 (5) Using this formula, X can be simply determined from the value of V 23.…”

Section: Determination Of Xmentioning

confidence: 99%

“…A slio'ht modification described later ~Y whi ch t he holder m ay be operated 1Il a three-ternu nal man ner makes it poss ible to. extend the freque ncy at t he lower end to 0.01 cis uSll1 g a. t hree-term in allow-Crequ ency bl'idge [5] .…”

Section: 2 Micrometer Specimen Holder O Design Requirementsmentioning

confidence: 99%

“…A graph of th e mechaniealloss data of McCrum, plotted as logarithmic decrement (~7r tan 0) versus temperature, also at 1 e/s, for samples of various degrees of crystallinity is shown in figure 16b. 7 The degree of crystallinity was calculated from sp ecific volume data using eq (5).…”

Section: A the Intermediate-temperature Processmentioning

confidence: 99%

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Dielectric properties of semicrystalline polychlorotrifluoroethylene

Scott¹,

Scheiber²,

Curtis³

et al. 1962

J. RES. NATL. BUR. STAN. SECT. A.

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The di electric pt"Oper t ies of polyc hlorotrifluoroethylene ( '1' m= 224°C, T g = 52°C) h ave been meas ured at temperatures between -50 and + 250 °C, and at frequ encies between 0.1 cis a nd 8.6 kMc/s. Specim ens of known crystallinit ies, ra nging from x = 0.80 to x = O.OO (pure liquid) were studied . Co mpre hens ive ta bles of data a rc prese nted. The experimental techniques e mplo.ved to measure the dielectric properties over these wide r'anges of temperature, fr equency, phys ical sta te, and sa mple type (di s ks, cylinders, and t hin film s), are disc ussed. The operation a nd calibrat ion of the s pecimen holder, bridges, r eson a nt circuits, a nd waveg uide a ppamt us used are di scussed in detail.When t he dielectric loss index, , ", at 1 cis is plotted as a fun ction of temperature for a hig hly crystallin e sp ecimen (x = 0.80), where the crystallini ty co ns ists la rgely of la mellar spheruli tes, Llu-ee distin ct loss peaks a re readily a pparent. These peaks occ ur at abo ut -40°C (low-te mperaL ure process), 95°C (i nterm edi ate-Le mperat ure process), and 150°C (hig h-temperature pt'ocess) . The di electri c data a re co mpa red with t he m ec ha ni cal loss data obtained at 1 cis by McCrum. Mech a nical loss p caks at temp eratures vir t ua lly iden t ical to Lhose in t he , " ve r~u s T plot a re fo und .Th e high-tempemtuTe process is attri b uted to the presence of well-form ed cha in-folded lamella r sph erulites. Some ev idence poin ts to the surfaces of t he la mellae as the site of the loss}mec ha nis m. The high-temperature loss peak docs no t a ppear in resol ved form in n011-spheruli t ic s peci mens even when the cr ystalli nity is hi gh. The intermediate-tem pemture process or'igin 'ttes in the norm al s upe rcooled a morp ho us phase, a nd is du e to t he co mplex dipol e relaxatio n effects involving mot ions of la rge numbers of poly mer cha in seg me nts t hat a re assoc iated wi th t he onset of the glass transition at T g = .52 °C. As de termined by i7 -T da.ta, the glass trnns it ion te mpemture at T g = 52°C t hat is associated wi t ll t his r elaxation eff ect docs not s hift appreciably wit h increas ing crys tallini ty. The low-tem perature dielecLri e loss process, wh ich is acL ive fa r belo w T " or igin ntes principa lly in t Ile s up ercooled a morphous regions, and ev iden t ly corres ponds to a fa irly simple motion invo lvin g a s mall number of cha in segments. This process t ends to ex hibi t a noma lous behavior in h ig hly crystalline s pecimens, pctrLicula.rly at 101V te mperatures.A la rge dipo la r contribu t ion of the crys tals to the static di electric cons tan t was obser ved. This co nLribu t ion increased with in creas in g temperature, an d co r respo nded to a very r a pid dipole reori e ntation process ( T~10-rr sec at 23°C).

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Section: Summary Of Results Of Analysis Of DI Polar J'elaxa Tion and mentioning

confidence: 99%

Section: Hoffman and Weeksmentioning

confidence: 99%

“…One may then write for the degree of crystallinity at 23 DC X 0. 48175 -V 23 0.0242 (5) Using this formula, X can be simply determined from the value of V 23.…”

Section: Determination Of Xmentioning

confidence: 99%

Section: 2 Micrometer Specimen Holder O Design Requirementsmentioning

confidence: 99%

Section: A the Intermediate-temperature Processmentioning

confidence: 99%

See 3 more Smart Citations

Dielectric properties of semicrystalline polychlorotrifluoroethylene

Scott¹,

Scheiber²,

Curtis³

et al. 1962

J. RES. NATL. BUR. STAN. SECT. A.

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Dielectric properties of solid polymers

Curtis

1962

Polymer Engineering & Sci

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Dielectric Relaxation in Segmented Polyurethanes

Dev

North

Reid

1972

Dielectric Properties of Polymers

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Dielectric measurements between 10-5 and 10+ 6 Hz have been made on one commercial (B. F. Goodrich Estane 5702 F1) polyurethane, and on polyethylene oxide and polypropylene oxide methylene bis phenyl diisocyanate polyurethanes. Four loss processes are observed and are ascribed to bulk conductance, interfacial polarization at the electrodes, Maxwe11-Wagner-Si11ars polarization of an occluded phase, and orientation polarization of the flexible chain segments. The processes due to migration of charge carriers give rise to large complex dielectric constants at very low frequencies. These processes are enhanced by the absorption of water. The orientation process in the polyether polyurethanes is compared with the same process in pure po1yethers and is equivalent to 'normal' movement of a reduced number of the possible ether groups per chain segment. The temperature dependence of this process has been examined using a simple free volume model. For polyethylene oxide polyurethanes the ratio of critical volume to volume occupied at a reference temperature is estimated to be 0.6, compared with 0.4 in pure po1yether.A procedure is described for the evaluation of the low frequency complex dielectric constant from d.c. transient measurements. The technique fits a series of overlapping curves (parabo1ae or exponentials) to arbitrarily spaced data, so permitting evaluation of the Fourier transform without the inaccuracies introduced by the more conventional use of event1y spaced data. 217F. E. Karasz (ed.), Dielectric Properties of Polymers

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An ultra low frequency bridge for dielectric measurements

Cited by 21 publications

References 4 publications

Dielectric properties of semicrystalline polychlorotrifluoroethylene

Dielectric properties of semicrystalline polychlorotrifluoroethylene

Dielectric properties of solid polymers

Dielectric Relaxation in Segmented Polyurethanes

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