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).

The bridge desc ribed is capable of measurin g t he p arallel capacitance and resista nce of dielectric specim e ns ill t he fr eque ncy r a nge of 0.008 to 200 cps. It employs no ear thing device a nd is directly con nected to a t hree termin al oscillator. The su bstit ut ion m ethod is employed. The capabilities of the bridge ar e experime ntall y tested by measure men ts upon known capacitors a nd resistors and by co mpa riso n with results obtained usin g a Schering bridge near 100 cps. Th e apparatus is capable of acc uracies previously unattained at these Jow frequcnci es. Cap acita nces between zero a nd 100 pf may bc measured to an acc uracy of ± (0.05 %+ 0.00 2 pf) at frequencies " bove 5 cps. Below 5 cps t he acc uracy becomes ± [0.05 %+ (0.002 + 2 X 10 5 /jR n)pf], wh ere f is the freque ncy i n cps a nd RD is the equi valent resistance in o h ill S ac ross the detcctor te rmin a ls. Co ndu ctances between 10-9 a nd 10-15 mh os m ay be measured to an accuracy of abo ut ± (1 %+ 3f X 10-15 mhos) when J~O.l cps. \Vhen f < O.l cps the accu racy is abo ut ± (l %+ 2 X lO-IO mhos). The dielect ric constant « ') of a spec im e n m ay be determined to an acc uracy proportio nal to that of capacitance measu re me nts. The loss ind ex «") may be determin ed to a n accuracy of about ± (1 % + 5 X 10-4 /C ,) when f ~0.1 cps and ± (1 %+ 3 X 1O-5/jC ,) when .r< 0.1 cps. H 1'e C , is t he vacuum capacita nce of t he specimen ex prcssed i n picofarads. Th e eff cct.s of stray impedances shunting the bridge ratio a nns, a rc investigated. Useful modi fi cations of Lho bridge are disc ussed.

No abstract

The bridge desc ribed is capable of measurin g t he p arallel capacitance and resista nce of dielectric specim e ns ill t he fr eque ncy r a nge of 0.008 to 200 cps. It employs no ear thing device a nd is directly con nected to a t hree termin al oscillator. The su bstit ut ion m ethod is employed. The capabilities of the bridge ar e experime ntall y tested by measure men ts upon known capacitors a nd resistors and by co mpa riso n with results obtained usin g a Schering bridge near 100 cps. Th e apparatus is capable of acc uracies previously unattained at these Jow frequcnci es. Cap acita nces between zero a nd 100 pf may bc measured to an acc uracy of ± (0.05 %+ 0.00 2 pf) at frequencies " bove 5 cps. Below 5 cps t he acc uracy becomes ± [0.05 %+ (0.002 + 2 X 10 5 /jR n)pf], wh ere f is the freque ncy i n cps a nd RD is the equi valent resistance in o h ill S ac ross the detcctor te rmin a ls. Co ndu ctances between 10-9 a nd 10-15 mh os m ay be measured to an accuracy of abo ut ± (1 %+ 3f X 10-15 mhos) when J~O.l cps. \Vhen f < O.l cps the accu racy is abo ut ± (l %+ 2 X lO-IO mhos). The dielect ric constant « ') of a spec im e n m ay be determined to an acc uracy proportio nal to that of capacitance measu re me nts. The loss ind ex «") may be determin ed to a n accuracy of about ± (1 % + 5 X 10-4 /C ,) when f ~0.1 cps and ± (1 %+ 3 X 1O-5/jC ,) when .r< 0.1 cps. H 1'e C , is t he vacuum capacita nce of t he specimen ex prcssed i n picofarads. Th e eff cct.s of stray impedances shunting the bridge ratio a nns, a rc investigated. Useful modi fi cations of Lho bridge are disc ussed.

The effect of absorbed water upon the dielectric properties of polymethylmethacrylate, polyethylmethacrylate, and polyethylacrylate is experimentally investigated over a temperature range from 70°C to —195°C and at frequencies between 100 cps and 200 kc. It is found in each case that the absorbed water gives rise to a discernible loss index peak in the low-temperature region (0° to —100°C). The 2.1% water absorbed in a specimen of polyethylacrylate acts as a plasticizer, apparently lowering the glass transition by 5C°. The facts that the apparent activation energy and the temperature location of the water induced peak changes with variations in the polymeric structure indicate that the induced loss peak is not to be identified with the loss peak found in ice, and furthermore suggests that the dielectric method can be employed to learn more about the water—polymer complex which is formed when water is absorbed into a polymer.