Dielectric Spectroscopy of Bisphenol-A Polycarbonate and Some of Its

Chapter 10

Dielectric Spectroscopy of Bisphenol-A Polycarbonate and Some of Its Blends 1

2

G. J. Pratt and M. J. A. Smith Downloaded by OHIO STATE UNIV LIBRARIES on October 14, 2014 | http://pubs.acs.org Publication Date: January 28, 1999 | doi: 10.1021/bk-1998-0710.ch010

1

Department of Mechanical and Manufacturing Engineering, University of Melbourne, Parkville 3052, Australia Department of Physics,Universityof Warwick, Coventry CV4 7AL, United Kingdom

2

Dielectric spectroscopy has been applied to the study of commercial bisphenol-A polycarbonate and some of i t s blends and to their susceptibility to environmental factors. The m u l t i p l i c i t y of overlapping absorptions i s consistent with the high impact strength of polycarbonate over an extended temperature range. Two intermediatetemperature losses are differentiated and delineated; their origins and reason for diminution by annealing are examined. Dielectric spectroscopy is seen as a particularly sensitive means for detecting and possibly characterizing radiation-induced changes in polymers before significant deterioration of other properties has occurred. For impact-modified PC/PBT and PC/PET blends evidence i s provided for p a r t i a l m i s c i b i l i t y of the component polymers and for a two-phase morphology with a polyester-rich dispersed phase in a continuous matrix r i c h in polycarbonate. The high impact strength, dimensional s t a b i l i t y and optical c l a r i t y (low c r y s t a l l i n i t y ) of bisphenol-A polycarbonate (PC) together with i t s low d i e l e c t r i c loss have led to a range of applications embracing optical components, CD-ROMs, film capacitors and safety-related products. Subsequent market demands for enhanced physical properties has stimulated the development of a range of commercial blends of which rubber-modified bisphenol-A polycarbonate (PC) with polybutylene terephthalate (PBT) or polyethylene terephthalate (PET) are amongst the more successful.

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©1998 American Chemical Society In Structure and Properties of Glassy Polymers; Tant, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1999.

Downloaded by OHIO STATE UNIV LIBRARIES on October 14, 2014 | http://pubs.acs.org Publication Date: January 28, 1999 | doi: 10.1021/bk-1998-0710.ch010

145 Dielectric spectroscopy is concerned with the dependence of complex p e r m i t t i v i t y on temperature and frequency. The r e l a t i v e l y low l e v e l of d.c. conduction i n polycarbonate ensures t h a t the p r i n c i p a l relaxations a s s o c i a t e d with polycarbonate's a c t i v e C=0 d i p o l e can be observed over a u s e f u l range of frequency and temperature. In multi-phase or multi-component polymers charge accumulation a t the s u b - s t r u c t u r e i n t e r f a c e s leads to Maxwell-Wagner-Sillars (MWS) c o n t r i b u t i o n s t o the o v e r a l l polarization. The s e n s i t i v i t y of d i e l e c t r i c spectrometry i s such t h a t i t may be used with polymers t o study how molecular motion i s i n f l u e n c e d by low molecular weight a d d i t i v e s , crosslinking, branching, i n t e r - and i n t r a - molecular i n t e r a c t i o n s , b l e n d i n g , c o p o l y m e r i z a t i o n , and degradation. D i e l e c t r i c data can complement t h a t obtained u s i n g dynamic mechanical analysis, d i f f e r e n t i a l scanning c a l o r i m e t r y , spectrophotometry, e l e c t r o n s p i n resonance, or n u c l e a r magnetic resonance. Much of the useful dielectric information on polymeric materials is provided by observations w i t h i n the frequency range 10" Hz t o 10 Hz. The present paper reviews the application of dielectric spectroscopy t o an i n t e g r a t e d study of commercial bisphenol-A polycarbonate and some of i t s blends [2-3] including its susceptibility to environmental f a c t o r s such as u.v. r a d i a t i o n [4,5] and humidity [6]. 3

e

Experimental The clear polycarbonate m a t e r i a l s i n v e s t i g a t e d were General E l e c t r i c LEXAN 141, a medium v i s c o s i t y grade containing a small amount of phosphite p r o c e s s i n g stabilizer, the corresponding u . v . - r e s i s t a n t compound (143), and an a d d i t i v e - f r e e grade (145). The blends i n v e s t i g a t e d were a PC/PET blend (XL1339) from GE P l a s t i c s Europe, a 5:4 melt blend of LEXAN 145 PC and VALOX 315 PBT containing a transesterification inhibitor (as used i n the production of commercial XENOY m a t e r i a l s ) , and a s i m i l a r composition c o n t a i n i n g 10% of added rubber (impact m o d i f i e r ) . XL1339 contains 68.5% PC, 21.0% PET and 7.0% impact m o d i f i e r . Sample p r e p a r a t i o n and measurement techniques have been d e s c r i b e d p r e v i o u s l y [2,7]. Apart from some samples of LEXAN 141 which were d e l i b e r a t e l y exposed t o the l a b o r a t o r y atmosphere f o r a t l e a s t one month, each sample was e q u i l i b r a t e d i n dry n i t r o g e n a t 30 t o 35°C f o r a t l e a s t 24 hours p r i o r t o i n v e s t i g a t i o n . The d i e l e c t r i c data was obtained over the ranges 0.1 Hz t o 3 MHz and -190°C t o +195°C u s i n g the wide-band capacitative-T p e r m i t t i v i t y bridge of P r a t t and Smith [ 7 ] . For each material a single sample o f approximate dimensions 25 χ 20 χ 0.4 mm was s u f f i c i e n t t o cover the experimental range without a change of apparatus o r technique and without r e s o r t t o F o u r i e r transform a n a l y s i s . Temperature c o n t r o l In Structure and Properties of Glassy Polymers; Tant, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1999.

146 was achieved u s i n g a b a f f l e d flow of dry n i t r o g e n gas a t the d e s i r e d temperature. For the i n v e s t i g a t i o n i n t o the i n f l u e n c e of u.v. r a d i a t i o n on the d i e l e c t r i c p r o p e r t i e s of polycarbonate, pressed sheets of the m a t e r i a l were i r r a d i a t e d a t room temperature i n a i r by a standard Hanovia mercury lamp. The lamp provided a spectrum o f wavelengths w i t h i n the range 254 t o 546 nm and sample i n t e n s i t i e s of 2.47 mW cm and 0.91 mW cm" r e s p e c t i v e l y a t the p r i n c i p a l wavelengths o f 365 nm and 254 nm. A v o l t a g e - s t a b i l i z e d power supply a s s i s t e d c o n s i s t e n c y of s p e c t r a l output. Immediately p r i o r t o a d i e l e c t r i c measurement, a Keithley Instruments 602 electrometer was used to determine the guasi-d.c. c o n d u c t i v i t y of the sample after a l l o w i n g time, t y p i c a l l y up t o an hour, f o r the decay of c u r r e n t t r a n s i e n t s . The e q u i v a l e n t imaginary p e r m i t t i v i t y caused by the quasi-d.c. c o n d u c t i v i t y was s u b t r a c t e d from the measured t o t a l p e r m i t t i v i t y . -2


2

R e s u l t s and D i s c u s s i o n Bisphenol-A carbonate has been widely studied by dielectric [8-26], dynamic mechanical [27-32] and thermally stimulated depolarization (TSD) [20-23,32-35] techniques. However, d i f f e r e n c e s i n the compositions of the m a t e r i a l s s t u d i e d , and i n t h e i r thermal h i s t o r y and pretreatment, have l e d t o apparently c o n f l i c t i n g r e s u l t s being r e p o r t e d i n the l i t e r a t u r e , as d i s c u s s e d i n d e t a i l i n a r e c e n t paper [6]. In the present study contour maps of complex r e l a t i v e p e r m i t t i v i t y f o r both b a s i c and u . v . - r e s i s t a n t grades of LEXAN have been obtained over an extended range of experimental c o n d i t i o n s using a s i n g l e apparatus, with each grade of m a t e r i a l s u b j e c t t o the same thermal h i s t o r y . U n i r r a d i a t e d Polycarbonate Homopolymers. Dielectric spectroscopy has i d e n t i f i e d e i g h t d i s t i n c t absorption and d i s p e r s i o n regions i n n i t r o g e n - e q u i l i b r a t e d commercial bisphenol-A polycarbonate [ 2 ] . A c l e a r correspondence i s found between the temperature-frequency regimes i n which changes occur i n s' and ε as expected from the KramersKronig r e l a t i o n s . Increases i n ε' c o i n c i d e with peak maxima f o r ε" as seen, f o r example, i n F i g u r e s 1 and 2. Μ

High- and Low-Temperature R e l a x a t i o n s . A p a r t i c u l a r l y sharp and prominent l o s s peak i n the ε contour map f o r u n i r r a d i a t e d LEXAN 141, 143 o r 145 i s attributed to the primary (a) r e l a x a t i o n which i s a s s o c i a t e d with gross motions of the polymer c h a i n i n the r e g i o n of Tg. The widths of the α peaks for each of the t h r e e m a t e r i a l s are comparable with t h a t shown i n Figure 3 f o r u n e q u i l i b r a t e d LEXAN 141 and suggest a s i m i l a r , low degree of c r y s t a l l i n i t y [27]. The most e x t e n s i v e f e a t u r e i n each ε'· map i s a broad ppeak i n a r e g i o n where ε' changes g r a d u a l l y . Deconvolution Μ

In Structure and Properties of Glassy Polymers; Tant, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1999.


147

-200

0

200°C

Figure 1: P l o t s o f the temperature-variation of r e a l r e l a t i v e p e r m i t t i v i t y ε' o f u n e q u i l i b r a t e d LEXAN 141 polycarbonate a t half-decade frequencies from 0.1 Hz t o 3 MHz. The s c a l e markings on the v e r t i c a l axes r e f e r t o ε' values f o r 3 MHz, 10 kHz, 30 Hz and 0.1 Hz r e s p e c t i v e l y , as i n d i c a t e d .



148

F i g u r e 2: P l o t s o f the temperature-variation o f imaginary relative permittivity ε of u n e q u i l i b r a t e d LEXAN 141 polycarbonate a t half-decade frequencies from 0.1 Hz t o 3 MHz. The s c a l e markings on the v e r t i c a l axes r e f e r t o s values f o r 3 MHz, 10 kHz, 30 Hz and 0.1 Kz r e s p e c t i v e l y , as i n d i c a t e d . Μ

M



149

Figure 4: 3-D r e p r e s e n t a t i o n showing the temperaturefrequency v a r i a t i o n of imaginary r e l a t i v e p e r m i t t i v i t y s" f o r u n e q u i l i b r a t e d LEXAN 141 polycarbonate.



150 of the peak i n d i c a t e s t h a t a range of segmental motions contribute to i t s breadth and shape [36]· At lower temperatures the phenyl groups are immobile and l o c a l i z e d segmental motion i s hindered by adjacent phenyl r i n g s d e s p i t e the open packing of the polymer chains i n g l a s s y PC. At higher temperatures the m o b i l i t y of the phenyl groups f a c i l i t a t e s t i g h t l y - c o u p l e d combined motion of carbonate and phenyl groups. In u n e q u i l i b r a t e d LEXAN 141 the presence of an a d d i t i o n a l l o s s r e g i o n above -40°C is indicated by the i n c r e a s e of slope above 30 kHz i n the Arrhenius p l o t (Figure 5) f o r the o v e r a l l p-peak which does not occur f o r the m a t e r i a l e q u i l i b r a t e d i n dry n i t r o g e n . The higher activation energy of t h i s water-related relaxation r e l a t i v e t o the fundamantal ρ-process i s c o n s i s t e n t with the e x i s t e n c e of hydrogen-bonding, o r some other form of i n t e r - m o l e c u l a r i n t e r a c t i o n which hinders the cooperative movements of adjacent carbonyl and phenyl groups. Both LEXAN 141 and 143 [2] show a d i s t i n c t i v e l o s s of s i m i l a r i n t e n s i t y i n the range -120°C t o -130°C below 3 Hz which i s not observed i n LEXAN 145 [ 3 ] . I t i s concluded t h a t the low temperature process below 3 Hz is a consequence of the presence of the phosphite p r o c e s s i n g s t a b i l i z e r i n the former which i s absent i n LEXAN 145. Exceedingly l a r g e l o s s e s a t low frequencies above 150°C are a t t r i b u t e d t o Maxwell-Wagner-Sillars (MWS) p o l a r i z a t i o n s a r i s i n g from conduction mismatches a t the structural interfaces between a continuous matrix o f amorphous polycarbonate and a c r y s t a l l i n e or d e n s i f i e d second phase. Provided t h a t the discontinuous phase tends towards a two-dimensional aspect and has a c o n d u c t i v i t y l e s s than t h a t of the matrix, theory p r e d i c t s s u b s t a n t i a l NWS l o s s e s even with a low c o n c e n t r a t i o n of the d i s c o n t i n o u s phase [37]. Intermediate - Temperature R e l a x a t i o n s . Secondary relaxations in the glassy state at temperatures intermediate between those of the a- and P- r e l a x a t i o n s have been reported, but workers disagree as t o t h e i r nature, l o c a t i o n and o r i g i n . Confusion a r i s e s i n p a r t from a f a i l u r e t o recognize the existence of two separate processes. Krum and MUller [19] observed an intermediate relaxation only f o r injection-moulded or cold-drawn polycarbonate samples. Since the magnitude was diminished by annealing and the l o s s was not detected i n f u l l y annealed samples, they concluded t h a t the intermediate process i s a non-equilibrium e f f e c t a s s o c i a t e d with residual stresses. In the present work two separate intermediate r e l a x a t i o n s are observed and d e f i n e d i n the g l a s s y s t a t e a t temperatures above ambient i n a l l LEXAN grades which have been i n v e s t i g a t e d , whether e q u i l i b r a t e d [1,3] or unequilibrated [ 6 ] , u . v . - i r r a d i a t e d [4] or u n i r r a d i a t e d [1,3,6]. The f i r s t ( i i ) appears i n F i g u r e s 3 and 4, f o r example, as a shoulder from about 105°C a t 0.1 Hz to


6

f

4

62 kJ ιποΓ

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1

-

33

log


151

2

-

-

1^43

-

0

1

3

1

I

5

I

7

10^ F i g u r e 5: Arrhenius p l o t s of the logarithm of the frequency l o c a t i o n o f the p-peak vs. reciprocal temperature f o r e q u i l i b r a t e d ( © ) and unequilibrated ( Λ ) LEXAN 141. E q u i l i b r a t e d samples were stored i n dry N a t 30-35°C f o r 24 hours p r i o r t o t e s t i n g . 2


152 140°C a t 300 Hz. T h i s a b s o r p t i o n cannot be d i s c e r n e d above 1 kHz, and corresponds c l o s e l y with t h a t r e p o r t e d by Watts and Perry [26] f o r LEXAN 101. The second ( i ) persists throughout the frequency range covered by the present work, and most probably corresponds with t h a t reported by MUller and co-workers [28-29], Sacher [23-25] and others [8-9,28-29,38-39]. At low frequencies the i absorption e x i s t s as a separate peak a t moderate temperatures (Figure 4) which a t higher f r e q u e n c i e s g r a d u a l l y merges with the α-peak t o become a shoulder a t about 160°C a t 3 MHz. On balance, the i i r e l a x a t i o n process i s now regarded as i n v o l v i n g p a r t i a l l y - c o r r e l a t e d motion of a moderate number of molecular segments or repeat u n i t s as precursor to the cooperative but uncorrelated micro-Brownian motion which occurs above Tg. It i s p o s t u l a t e d t h a t the o r i g i n of the i - a b s o r p t i o n i s a r e l a x a t i o n process i n which the phenyl groups undergo 180° f l i p s as might a r i s e when adjacent carbonyl groups interchange between cis-trans and trans-trans conformations [40-42]. Annealing reduces the a v a i l a b l e free-volume, thereby i n h i b i t i n g the r i n g - f l i p process. Rather than the r e l i e f of f r o z e n - i n s t r e s s e s , t h i s r e d u c t i o n i n f r e e volume i s considered t o be the u n d e r l y i n g cause of the diminution by annealing of the intermediate relaxations· 2


2

a

I n f l u e n c e o f U.V. R a d i a t i o n . Above 180°C the values of ε', ε" and tan 6 r i s e s i g n i f i c a n t l y more r a p i d l y f o r the u.v.r e s i s t a n t LEXAN 143 than f o r e i t h e r 141 or 145 and i n a manner which seems t o be independent of frequency [1]. I t i s p o s t u l a t e d t h a t u . v . - p r o t e c t i o n i n the 143 m a t e r i a l i s c o n f e r r e d by i n t i m a t e a s s o c i a t i o n of the b e n z o t r i a z o l e a d d i t i v e with the polymer molecules, and t h a t above 180°C t h i s a d d i t i v e i s l i b e r a t e d from the polymer molecules, f r e e i n g a d d i t i o n a l p o l a r i z a b l e groups which c o n t r i b u t e t o the observed i n c r e a s e i n ε', ε and tan £· For the u n s t a b i l i z e d LEXAN 141 exposed t o u.v. r a d i a t i o n , a d d i t i o n a l d i s p e r s i o n s appear as a r e s u l t of new p o l a r groups c r e a t e d by the i r r a d i a t i o n (Figure 6b). Continuation of irradiation causes the additional d i s p e r s i o n s t o move t o lower temperature and frequency (Figure 6c) i n a manner which i s broadly c o n s i s t e n t with a sequence of p h o t o - F r i e s r e a c t i o n s and subsequent photoo x i d a t i o n [4]. Using polycarbonate samples c o n t a i n i n g identifiable photo-products, in particular phenyl salicylate, some progress has been made towards establishing specific c o r r e l a t i o n s between r a d i a t i o n induced absorptions and expected products of photodegradation or photo-oxidation [ 5 ] . Moreover, an i n d i c a t i o n of photo-degradation can be obtained a t an early stage before significant deterioration of p r o p e r t i e s has occurred. For the s t a b i l i z e d polycarbonate there i s evidence t h a t the b e n z o t r i a z o l e imparts p a r t i a l u.v. s t a b i l i z a t i o n Μ



Ο 100

(b)

200°C

(c)

F i g u r e 6: P a r t i a l contour maps o f l o s s tangent t a n 6 f o r GE LEXAN 141 polycarbonate, (a) u n i r r a d i a t e d , (b) a f t e r 2 hours u.v., (c) after 5 hours u.v.-irradiation.

(a)


154


by a mechanism of p r e f e r e n t i a l u.v. absorption u n t i l the a d d i t i v e i s i t s e l f consumed [ 5 ] . Polycarbonate / P o l y e s t e r Blends. Contour maps of the temperature-frequency variation of complex relative p e r m i t t i v i t y have been obtained f o r impact-modified PC/PBT and PC/PET blends [3,43] and for their constituent polycarbonate [3], PBT [44] and PET [45] homopolymers. In the impact-modified PC/PBT blend (Figure 7 ) , as i n each of the blends, a s i n g l e broad p-absorption i s observed but the separate α-absorptions of the c o n s t i t u e n t s p e r s i s t . The p e r s i s t e n c e of the g l a s s t r a n s i t i o n temperatures of the component polymers i n each of the blends, and the l a c k of a t h i r d Tg peak a t an intermediate temperature (see, f o r example, F i g u r e 8 ) , confirms t h a t the blends c o n t a i n two phases. The temperature s h i f t i n each Tg i s a consequence of the p a r t i a l m i s c i b i l i t y of the component polymers i n the melt. The very s l i g h t i n c r e a s e i n the Tg of PBT and PET in the PC/PBT and PC/PET blends respectively i n d i c a t e s t h a t the p o l y e s t e r - r i c h phase c o n t a i n s only a s m a l l amount of polycarbonate, whereas the s i g n i f i c a n t decrease i n Tg i n the PC component of the blends suggests the presence of s u b s t a n t i a l p r o p o r t i o n s of PBT or PET r e s p e c t i v e l y i n the phase c o n s i s t i n g predominantly of polycarbonate. A reason f o r b l e n d i n g PBT with PC i s t o overcome the comparatively poor s o l v e n t r e s i s t a n c e of polycarbonate. The enhanced s o l v e n t r e s i s t a n c e of the blend would be expected i f PBT was the continuous matrix phase i n the blend, as suggested by Hobbs e t a l [46-47]. However, the o b s e r v a t i o n t h a t the d.c. c o n d u c t i v i t y of polycarbonate and i t s blends i s orders of magnitude l e s s than t h a t of PBT and PET over a s u b s t a n t i a l temperature range i n d i c a t e s unambiguously t h a t the P C - r i c h phase forms the continuous matrix i n each of the blends i n v e s t i g a t e d here. I t would seem t h a t the enhanced s o l v e n t r e s i s t a n c e i n PC/PBT blends can only a r i s e from the substantial p r o p o r t i o n of e v e n l y - d i s t r i b u t e d PBT which i s contained i n the matrix. Conclusions. E i g h t d i s t i n c t a b s o r p t i o n regions are identified in n i t r o g e n - e q u i l i b r a t e d polycarbonate, with bound water causing a f u r t h e r absorption i n the u n e q u i l i b r a t e d m a t e r i a l . The m u l t i p l i c i t y of o v e r l a p p i n g absorptions i s consistent with the high impact strength of polycarbonate over an extended temperature range. Two intermediate-temperature l o s s e s are d i f f e r e n t i a t e d and delineated; t h e i r o r i g i n s and reason f o r diminution by annealing are examined. Rather than the r e l i e f of f r o z e n - i n s t r e s s e s , the a s s o c i a t e d reduction i n free volume i s considered t o be the u n d e r l y i n g cause o f the diminution by annealing of the intermediate r e l a x a t i o n s .



155

Figure 7: Contour map of imaginary relative permittivity ε f o r an impact-modified polycarbonate /PBT blend, [adapted from ref. 3] Μ

7

_J

26

I

L_

30

Figure 8: Arrhenius p l o t s of the logarithm o f the frequency o f maximum l o s s v s . r e c i p r o c a l temperature f o r the d i e l e c t r i c α-relaxations i n GE LEXAN 145 PC ( · ) , VALOX 315 PBT ( • ) , a 5:4 PC/PBT blend (ψ) and a 5:4 PC/PBT blend c o n t a i n i n g 10% impact m o d i f i e r ( φ ) , [adapted from ref. 48]



156 Dielectric spectroscopy i s a p a r t i c u l a r l y s e n s i t i v e means f o r d e t e c t i n g r a d i a t i o n - i n d u c e d changes i n polymers before s i g n i f i c a n t d e t e r i o r a t i o n o f other p r o p e r t i e s has occurred. For u . v . - i r r a d i a t e d polycarbonate the d i e l e c t r i c data i s broadly c o n s i s t e n t with a sequence o f p h o t o - F r i e s r e a c t i o n s and subsequent photo-oxidation. Changes i n t h e a d d i t i o n a l r e g i o n observed a t h i g h temperatures i n t h e u . v . - r e s i s t a n t polycarbonate imply t h a t the b e n z o t r i a z o l e imparts p a r t i a l u.v. s t a b i l i z a t i o n by a mechanism o f p r e f e r e n t i a l u.v. a b s o r p t i o n . Some progress has been made towards establishing specific correlations between r a d i a t i o n - i n d u c e d absorptions and expected products o f photodegradation o r photo-oxidation. For impact-modified PC/PBT and PC/PET blends evidence has been presented for partial miscibility of the component polymers and f o r a two-phase blend morphology with a p o l y e s t e r - r i c h d i s p e r s e d phase i n a continuous matrix r i c h i n polycarbonate. Other absorptions a r e attributed respectively t o MWS i n t e r f a c i a l p o l a r i z a t i o n , to t h e presence o f t h e impact m o d i f i e r and t o a phosphite processing s t a b i l i z e r .

Literature Cited 1. P r a t t , G . J . ; Smith,M.J.A. Brit.Polym.J. 1986, 18, 105 2. P r a t t , G . J . ; Smith,M.J.A. Polymer 1989, 30, 1113 3. P r a t t , G . J . ; Smith,M.J.A. Plastics, Rubber and Composites Processing and Applications 1991, 16, 67 4. P r a t t , G . J . ; Smith,M.J.A. Polym.Degr.Stab. 1989, 25, 2671 5. P r a t t , G . J . ; Smith,M.J.A. Polym. Degr.Stab. 1997, 56, 197 6. P r a t t , G . J . ; Smith,M.J.A. Polym.Internatl. 1996, 40, 239 7. P r a t t , G . J . ; Smith,M.J.A. J.Phys.E:Sci.Instrum. 1982, 15, 927 8. A l l e n , G . ; McAinsh,J.; Jeffs,G.M. Polymer 1971, 12, 85 9. A l l e n , G . ; Morley,D.C.W.; Williams,T. J.Mater.Sci. 1973, 8, 1449 10. Aoki,Y.; B r i t t a i n , J . O . J. Polym. Sci.; Polym. Phys. Ed. 1976, 14, 1297 11. Aoki,Y.; B r i t t a i n , J . O . J.Appl.Polym.Sci. 1976, 20, 2879 12. Aoki,Y.; B r i t t a i n , J . Ο . J.Appl.Polym.Sci. 1977, 21, 199 13. Hong,J.; B r i t t a i n , J . O . J.Appl.Polym.Sci. 1981, 26, 2459 & 2471 14. B a i r , H . E . ; J o h n s o n , G . Ε . ; Merriweather,R. J.Appl.Phys. 1978, 49, 4976 15. I t o , E . ; Hatakeyama,T. J.Polym.Sci.;Polym.Phys.Ed. 1974, 12, 1477 16. I t o , E . ; Hatakeyama,T. J.Polym.Sci.;Polym.Phys.Ed. 1975, 13, 2313 17. Matsuoka,S.; Ishida,Y. J. Polym.Sci.,C 1966, 14, 247 18. M ü l l e r , F . H . ; Huff,K. Kolloid Z. 1959, 164, 34 19. Krum,F.; M ü l l e r , F . H . Kolloid Z. 1959, 164, 81



157 20. Pochan,J.M.; Hinman,D.F.; Turner,S.R. J.Appl.Phys. 1976, 47, 4245 21. Pochan,J.M.; Gibson,H.W.; F r o i x , M . F . ; Hinman,D.F. Macromolecules 1978, 11, 165 22. Pochan,J.M.; Gibson,H.W.; Pochan,D.L.F. Macromolecules 1982, 15, 1368 23. Sacher,E. J.Macromol.Sci.-Phys. 1974, B9, 163 24. Sacher,E. J.Macromol.Sci.-Phys. 1974, B1O, 319 25. Sacher,E. J.Macromol.Sci.-Phys. 1975, B22, 403 26. Watts,D.C.; Perry,E.P. Polymer 1978, 19, 248 27. Chung,C.I.; Sauer,J.A. J.Polym.Sci.,A-2 1971, 9, 1097 28. I l l e r s , K . H . ; Breuer,H. Kolloid Z. 1961, 176, 11 29. I l l e r s , K . H . ; Breuer,H. J.Colloid Sci. 1963, 18, 1 30. L o c a t i , G . ; Tobolsky,A.V. Adv.Mol.Relax.Proc. 1970, 1, 375 31. Reding,F.P.; Faucher,J.A.; Whitman,R.D. J.Polym.Sci. 1961, 54, S56 32. J a i n , K . ; Agarwal,J.P.; Mehendru,P.C. I1 Nouva Cimento 1980, 55B, 123 33. Mehendru,P.C.; J a i n , K . ; Agarwal,J.P. J.Phys.D;Appl. Phys. 1980, 13, 1497 34. Linkens,A.; Vanderschueren,J. Polym.Letters 1977, 15, 41 35. Vanderschueren,J.; Linkens,A.; Haas,B.; D e l l i c o u r , J . J.Macromol.Sci.-Phys. 1978, B15, 449 36. P r a t t , G . J . ; Smith,M.J.A. Polymers at Low Temperatures (Proceedings), PRI: London, 1987; pp. 9/1-10 37. van Beek,L.K.H. in Progress in Dielectrics; Birks,J.B.; H a r t , J . , E d s . ; Heywood: London, 1967; pp.7 & 69 38. Heijboer,J. J.Polym.Sci.,C 1968, 16, 3755 39. Bussink,J.; Heijboer,J. Proc.Intern.Conf.IUPAC, Delft, 1964 40. Jones,A.A. Macromolecules 1985, 18, 902 41. O ' G a r a , J . F . ; J o n e s , Α . Α . ; Hung C.-C.; Inglefield,P.T. Macromolecules 1985, 18, 1117 42. C o n n o l l y , J . J . ; I n g l e f i e l d , P . T . ; Jones,A.A. J.Chem. Phys. 1987, 86, 6602 43. P r a t t , G . J . ; Smith,M.J.A. Electrical, Optical and Acoustic Properties of Polymers - EOA III, PRI: London, 1992; pp.13/1-8. 44. P r a t t , G . J . ; Smith,M.J.A. J.Mater.Sci. 1990, 25, 477 45. P r a t t , G . J . ; Smith,M.J.A. Electrical, Optical and Acoustic Properties of Polymers - EOA II, PRI: London, 1990; pp.P9/l-4 46. Hobbs,S.Y.; Dekkers,M.E.J.; Watkins,V.H. J.Mater.Sci. 1988, 23, 1219 47. Hobbs,S.Y.; Dekkers,M.E.J.; Watkins,V.H. Polym.Bull. 1987, 17, 341 48. P r a t t , G . J . ; Smith,M.J.A. Polym.Internat1., 1997, 43, 137


Dielectric Spectroscopy of Bisphenol-A Polycarbonate and Some of Its

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