- Email: [email protected]
Effect of γ-neutron pulse radiation on permittivity of polymethylmethacrylate
3108
V.V. ZUBOV et al. CONCLUSIONS
(1) I t is pointed out t h a t bands at 437 and 1343 cm -1 are crystalline and the band at 502 cm -1 is "amorphous". ( 2 ) The specific volume of the amorphous fraction was determined Va= (0"764i0'001) cm3/g. (3) The crystalline fraction content of unoriented P E T P fibres was determined; it changes from 22 to 57% in accordance with heat treatment conditions. (4) Formulae are derived to determine the crystalline fraction content from absorption at the maximum of the absorption bands at 437, 1343 and 502 cm -1. Translated by E. SE~F~E REFERENCES
1. I. I. NOVAK, Vysokomol. soyed. 5: 1945, 1963 2. V. N. NIKITIN and Ye. I. POKROVSKII, Dokl. AN SSSR 95: 109, !954 3. I. I. RESHINA, I. L. SAKIN and I. I. NOVAK. Optiko-mekhanieh. prom-st', No. 11, 18, 1954 4. J. E. JOHNSON, J. Appl. Polymer Sci. 42: 205, 1959 5. C. Y. LIANG and S. KRIMM, J. Molec. spectr. 3: 554, 1959 6. R. P. de DAUBENY and C. W. BUNN, Proc. Roy. Soc. A226: 531, 1954
E F F E C T OF 7 - N E U T R O N P U L S E R A D I A T I O N ON P E R M I T T I V I T Y OF P O L Y M E T H Y L M E T H A C R Y L A T E * V. V: ZUBOV, V. F. KHOKHRYAKOVand Yu. F. TUTU~OV (Received 25 January 1967)
A SIGNIFICANT number" of papers have been published in recent years dealing with the properties cf dielectric materials in t h e field of high energy radiation-~-radiation, neutron, etc. Normally the objects investigated were irradiated in these studies by stationary sources and reactors and macroscopic characteristics such as electrical conductivity, mechanical and dielectric properties of insulating materials studied. Several studies have also been published in foreign literature on the effect of ?-neutron pulse radiation on the electrical conductivity of materials [1-3]. This paper deals with methods of measuring permittivity and the tangent of the dielectric loss angle of insulating materials during irradiation with a 7-neutron pulse flow and with experimental results obtained from an investigation of the effdct of 7-neutron pulse radiation on the permittivity of polymethylmethacrylate (PMMA). * Vysokomol. soyed. A9: No. 12, 2746-2750, 1967.
y-Neutron radiation effect on permittivity of polymethylmethacrylate
3109
EXPERIMENTAL PMMA specimens were irradiated with bell-shaped y-neutron pulses of half-width ranging from 50 microsec to 1-2 msee. The m a x i m u m intensity of neutron and g a m m a components in the pulse did not exceed 2 × 1018 n/cm2/sec, 109 r/see, respectively. The energy spectrum of the neutrons was close to the dividing spectrum. The PMMA specimens were discs of 110 m m diameter and 1 m m thickness. A. triode connection system was used. The electrodes were applied by vacuum spraying of copper on the specimen. The initial capacitance of the specimens was 100 pF. The specimens were placed in a hermetically sealed flask containing a drying agent. P e r m i t t i v i t y variation was measured by a device based on the following principle. The signal which repeats the shape of the radiation pulse was fixed simultaneously with the recording of Je/e0 (a two-beam cathode oscillograph was used for recording). The measuring device was situated outside the zone of irradiation and was connected to the specimens by cables of 20 m length. Methods of measurements. The measurement of p e r m i t t i v i t y and the tangent of the loss angle in irradiation of materials by a y-neutron pulse flow involves several difficulties. These are: 1. The measuring apparatus cannot be arranged in the direct proximity of the specimen and is connected to it by cables, the length of which sometimes reaches several scores of meters. At the same time the capacitance of the cables and their insulation resistance m a y v a r y during the experiment. 2. The variations of the parameters studied are rapidly alternating in nature. 3. Coinciding with the radiation pulse electromagnetic interferences are observed in the conducting cables, the range of which is close to t h a t of the values measured. Thus, the measuring apparatus should eliminate: 1) the effect of varying cable parameters; 2) electromagnetic interference and 3) be sufficiently rapid in operation. Existing devices used for measuring 8 and tan 5 do not meet these requirements. This paper deals with a remote method of measurement of e and tan ~ and the variations of these values at frequencies f<
zo
E EJznmt FIG. 1. Theoretical measurement network. The method proposed is essentially a variety of bridge methods of measurement and differs by a somewhat unusual ratio of arms, which makes it possible, within a given range of accuracy, to exclude the effect of varying cable parameters on experimental results.
3110
V . V . ZuBov et a/.
Theoretical and equivalent networks of measurement arc shown in Figs. 1 and 2. I t can be pointed out that if the oscillatory circuit formed b y the inductance of an auxiliary bridge arm (zs) and capacitance (zl) connected in series with the specimen, develops resonance with the frequency of the oscillator (the network in the standard capacitor circuit, which is
1
L
!
l
R2~
~~slnwt Fro. 2. Equivalent measurement network• identical to the first, is t u n e d similarly), the condition of bridge balance, in the case when the effect of network resistance, inductance and cable conductor resistance can be disregarded and the internal resistance of the oscillator assumed to be zero and the i n p u t resistance of the indicator infinite, will be given by the following conventional relation
z~zy=zdz s ,
or
zx=zo .
(1)
l~elation (1) is independent of capacitance and cable insulation resistance. The variation in the capacitance of the specimen studied is determined from the variation of the modulus of the voltage Ua in relation to the modulus of the voltage U4 and the increment of the tangent of loss angle, from the phase difference between them. The calculations lead to the following expressions:
IU,I-IU,I=Eoc~ '~% • --,
cl
~8--~.A~
t g ~z,
(2)
CxD
and the inertia of the network-- Ti if % <
will be
T i = 3 - - S x 2/¢-OZClkrl (1-~- ~lk) •
(3a)
A prototype was made with the foUowing technical parameters: 1) operating frequency 100 ke/s; 2) capacitance range measured 50-150 pF; 3) basis error of measuring initial capacitance -4-3°/o~0"5 pF/cx0; 4) basic error in the measurement of capacitance increase not
7-Neutron radiation effect on permittivity of polymothylmethacrylat,e
3111
exceeding 3% (without considering the error of the recording instrument); 5) range of measurement of initial values of the tangent of loss angle 0"01 -- 0"1; 6 ) basic error in the meas urement of initial values of the tangent of loss angle -t-5--10%±8 × 10-3; 7) basic error in the measurement of the increase of tangent of loss angle :t: 5-~ 10% ± 2 × 10-3; 8) inertia of the system on changing increments Aej:/ezo, A tan 5x, ~ 25-30 microsee. The above errors were calculated and determined experimentally by connecting the specimens to the network with an RK-19 type cable, 20 m long, the relative variation of capacitance ziClk/Clk being 20%. As mentioned previously at the moment of the radiation pulse, electromagnetic induction is observed in the connecting cables on a frequency spectrum, similar to the spectrum of the signals to be recorded. Several experiments were carried out which indicate that the amplitude of electromagnetic induction depends to a great extent on the resistance with which the cable is loaded. In the measuring network studied the conducting cable ends were loaded with resistances, which enabled the amplitude of electromagnetic induction to be reduced to a level below the threshold of response of the device. EXPERIMENTAL RESULTS
Two series of m e a s u r e m e n t s were made. I n the first series of e x p e r i m e n t s the specimen was situated directly at the radiation source. The distance f r o m specimen to source was fixed a n d u n c h a n g e d d u r i n g the whole cycle of irradiation b y pulses of differing half-width and intensity. T y p i c a l oscillograms indicating t h e v a r i a t i o n of PMMA p e r m i t t i v i t y , superimposed on oscillograms of t h e r a d i a t i o n pulse, are shown in Fig. 3, a-c. I t can be seen in the oscillogram t h a t the n a t u r e of p e r m i t t i v i t y v a r i a t i o n is complex and depends not only on the intensity, b u t also on the half-width of t h e r a d i a t i o n pulse. I t was revealed t h a t a) during irradiation of a specimen with pulses of halfw i d t h Ti>~250 microsec, the m a x i m u m v a r i a t i o n of ~ ( p e r m i t t i v i t y increased) ivith t i m e agrees with the m a x i m u m value of i n t e n s i t y in t h e pulse; b) with half-widths of 7-neutron pulses in t h e range of 180>~Tt~>70 microsec, a slight a n d t h e n an increasing displacement with time of the m a x i m u m v a r i a t i o n of e is observed in relation to the m a x i m u m of r a d i a t i o n intensity; c) with halfwidths of 70 t> vii> 50 microsec a b r e a k appears on the f r o n t of the p e r m i t t i v i t y v a r i a t i o n which deforms the curve into a d o u b l e - h u m p e d curve with increase of intensity; m a x i m u m increase in p e r m i t t i v i t y is observed in practice at t h e final m o m e n t of the r a d i a t i o n pulse. The v a r i a t i o n of PMMA p e r m i t t i v i t y is, a p p a r e n t l y , related to two processes which occur at different intensities a n d h a v e t y p i c a l r e l a x a t i o n times, which differ considerably. T h e first is the process of increasing e, which has a t y p i c a l r e l a x a t i o n t i m e in the range of 120-160 microsec, a n d the second is a process of r e d u c t i o n of ~ from ~ p ~ 5 0 microsec. I n the second series of e x p e r i m e n t s the specimens were i r r a d i a t e d b y pulses of a p p r o x i m a t e l y identical half-width (v~ ~ 50-60 microsec) and intensity. T h e i n t e n s i t y of the 7-neutron flow t r a n s m i t t e d to the specimen was recorded b y t h e v a r i a t i o n of the distance from the specimen to the radiation source. As in the first case, during irradiation of the specimen with pulses of half-widths T , ~ 7 0
3112
V.V. Z~fnov et
al.
FIG. 3. Oscillograms showing the variation of e--As/e0 during irradiation. Lower curves show the shape of the radiation pulse: a - In=2×101~ n/cm~.sec, I ~ 1 " 4 × 107 r/sec, v~:280 microsec; b --I,~2×1017 n/em2"sec, Iv=1"4×108 r/sec, r1:70 microsec; c -- I , : 4 × 1017 n/cm2"sec,I v : 3 × l0 s r/sec, v~:60 microsec. microsec, the variation of E had the character of a double-hump curve. Maxim u m increase of e was observed at the final moment of the pulses, and the depth of dip increased with higher radiation intensity. I t was also noted t h a t the duration of the drop Ae/e0 to 1/2-level from ACmax/Eo increased with the increase of 7-neutron flow. For a qualitative explanation o f the effects observed several models can be used; however, the experimental data available so far are insufficient to enable preference to be given to one of them. The relative variations of g--~gmax/g0 are tabulated. Finally, the authors express their deep gratitude to V. A. K h r a m o v for experimentally testing the possibilities of measuring the tangent of the loss angle by methods described in this paper, I. S. Pogrebov for his assistance in carrying out the measurements in the reactor and Yu. A. Zysin for his constant interest in the study.
Low angle scattering of polarized light by polymer fibres
3113
R E L A T I V E VARIATIONS OF e - - Z J e m a x / e 0 OF P O L Y M E T H Y L M E T H A C R Y L A T E IN y - N E U T R O N PI~LSE IRRADIATION
Half-width of the radiation pulse, v~ mierosec
Maximum intensity of neutrons in the pulse, I n, H/em2see
280 140 70 60 50
2× 101e=l=20% 7 X 101e=t=20% 2 × 101v±20% 4 × 1017:J=20% 5× 1017=[=20%
Maximum dose rate of 7-quanta I v, r/see
i
l'4x 5x 1"4 × 3x 3.5×
107-4-20% 107±20% 108±20% 108±20% 108±20%
Relative variation of permittivity ~emax ,% e0 4!0"6 9=[=0"8 9"54-0"8 114-1 llil
CONCLUSIONS
A description is given of a method for the measurement of permittivity and the tangent of the loss angle of dielectric materials during irradiation with a 7-neutron pulse flow. Experimental data are given on the effect of ?-neutron pulse radiation on the permittivity of polyniethylmethacrylate. Translated by E. SEMERE REFERENCES 1. N. W. WIEKLEIN, H. NUTLEY and J. M. FERRY, I E E E Trans. on Nucl. Sci. NS-I0: 131, 1963 2. S. E. HARRISON, F. N. COPPAGE and A. W. SHYDER, I E E E Trans. on Nucl. Sei. NS-10: 118, 1963 3. D. M. COMPTON, G. T. CHENEY and R. A. POLL, J. Appl. Phys. 36: 234, 1965
LOW ANGLE SCATTERING OF POLARIZED LIGHT BY POLYMER FIBRES* T. I. VOLKOV Institute of High-Molecular Weight Compounds, U.S.S.R. Academy of Sciences
(Received 23 February 1967)
THE polarization diffractometric method of investigating various types and stages of supermolecular order and corresponding structural processes has in recent years found wide application in the study of both solid [1] and liquid [2] polymer systems. When solving general theoretical problems of formation of oriented order in polymers and more practical problems of fibre formation, * Vysokomol. soyed. A9: No. 12, 2751-2753, 1967.
V.V. ZUBOV et al. CONCLUSIONS
(1) I t is pointed out t h a t bands at 437 and 1343 cm -1 are crystalline and the band at 502 cm -1 is "amorphous". ( 2 ) The specific volume of the amorphous fraction was determined Va= (0"764i0'001) cm3/g. (3) The crystalline fraction content of unoriented P E T P fibres was determined; it changes from 22 to 57% in accordance with heat treatment conditions. (4) Formulae are derived to determine the crystalline fraction content from absorption at the maximum of the absorption bands at 437, 1343 and 502 cm -1. Translated by E. SE~F~E REFERENCES
1. I. I. NOVAK, Vysokomol. soyed. 5: 1945, 1963 2. V. N. NIKITIN and Ye. I. POKROVSKII, Dokl. AN SSSR 95: 109, !954 3. I. I. RESHINA, I. L. SAKIN and I. I. NOVAK. Optiko-mekhanieh. prom-st', No. 11, 18, 1954 4. J. E. JOHNSON, J. Appl. Polymer Sci. 42: 205, 1959 5. C. Y. LIANG and S. KRIMM, J. Molec. spectr. 3: 554, 1959 6. R. P. de DAUBENY and C. W. BUNN, Proc. Roy. Soc. A226: 531, 1954
E F F E C T OF 7 - N E U T R O N P U L S E R A D I A T I O N ON P E R M I T T I V I T Y OF P O L Y M E T H Y L M E T H A C R Y L A T E * V. V: ZUBOV, V. F. KHOKHRYAKOVand Yu. F. TUTU~OV (Received 25 January 1967)
A SIGNIFICANT number" of papers have been published in recent years dealing with the properties cf dielectric materials in t h e field of high energy radiation-~-radiation, neutron, etc. Normally the objects investigated were irradiated in these studies by stationary sources and reactors and macroscopic characteristics such as electrical conductivity, mechanical and dielectric properties of insulating materials studied. Several studies have also been published in foreign literature on the effect of ?-neutron pulse radiation on the electrical conductivity of materials [1-3]. This paper deals with methods of measuring permittivity and the tangent of the dielectric loss angle of insulating materials during irradiation with a 7-neutron pulse flow and with experimental results obtained from an investigation of the effdct of 7-neutron pulse radiation on the permittivity of polymethylmethacrylate (PMMA). * Vysokomol. soyed. A9: No. 12, 2746-2750, 1967.
y-Neutron radiation effect on permittivity of polymethylmethacrylate
3109
EXPERIMENTAL PMMA specimens were irradiated with bell-shaped y-neutron pulses of half-width ranging from 50 microsec to 1-2 msee. The m a x i m u m intensity of neutron and g a m m a components in the pulse did not exceed 2 × 1018 n/cm2/sec, 109 r/see, respectively. The energy spectrum of the neutrons was close to the dividing spectrum. The PMMA specimens were discs of 110 m m diameter and 1 m m thickness. A. triode connection system was used. The electrodes were applied by vacuum spraying of copper on the specimen. The initial capacitance of the specimens was 100 pF. The specimens were placed in a hermetically sealed flask containing a drying agent. P e r m i t t i v i t y variation was measured by a device based on the following principle. The signal which repeats the shape of the radiation pulse was fixed simultaneously with the recording of Je/e0 (a two-beam cathode oscillograph was used for recording). The measuring device was situated outside the zone of irradiation and was connected to the specimens by cables of 20 m length. Methods of measurements. The measurement of p e r m i t t i v i t y and the tangent of the loss angle in irradiation of materials by a y-neutron pulse flow involves several difficulties. These are: 1. The measuring apparatus cannot be arranged in the direct proximity of the specimen and is connected to it by cables, the length of which sometimes reaches several scores of meters. At the same time the capacitance of the cables and their insulation resistance m a y v a r y during the experiment. 2. The variations of the parameters studied are rapidly alternating in nature. 3. Coinciding with the radiation pulse electromagnetic interferences are observed in the conducting cables, the range of which is close to t h a t of the values measured. Thus, the measuring apparatus should eliminate: 1) the effect of varying cable parameters; 2) electromagnetic interference and 3) be sufficiently rapid in operation. Existing devices used for measuring 8 and tan 5 do not meet these requirements. This paper deals with a remote method of measurement of e and tan ~ and the variations of these values at frequencies f<
zo
E EJznmt FIG. 1. Theoretical measurement network. The method proposed is essentially a variety of bridge methods of measurement and differs by a somewhat unusual ratio of arms, which makes it possible, within a given range of accuracy, to exclude the effect of varying cable parameters on experimental results.
3110
V . V . ZuBov et a/.
Theoretical and equivalent networks of measurement arc shown in Figs. 1 and 2. I t can be pointed out that if the oscillatory circuit formed b y the inductance of an auxiliary bridge arm (zs) and capacitance (zl) connected in series with the specimen, develops resonance with the frequency of the oscillator (the network in the standard capacitor circuit, which is
1
L
!
l
R2~
~~slnwt Fro. 2. Equivalent measurement network• identical to the first, is t u n e d similarly), the condition of bridge balance, in the case when the effect of network resistance, inductance and cable conductor resistance can be disregarded and the internal resistance of the oscillator assumed to be zero and the i n p u t resistance of the indicator infinite, will be given by the following conventional relation
z~zy=zdz s ,
or
zx=zo .
(1)
l~elation (1) is independent of capacitance and cable insulation resistance. The variation in the capacitance of the specimen studied is determined from the variation of the modulus of the voltage Ua in relation to the modulus of the voltage U4 and the increment of the tangent of loss angle, from the phase difference between them. The calculations lead to the following expressions:
IU,I-IU,I=Eoc~ '~% • --,
cl
~8--~.A~
t g ~z,
(2)
CxD
and the inertia of the network-- Ti if % <
will be
T i = 3 - - S x 2/¢-OZClkrl (1-~- ~lk) •
(3a)
A prototype was made with the foUowing technical parameters: 1) operating frequency 100 ke/s; 2) capacitance range measured 50-150 pF; 3) basis error of measuring initial capacitance -4-3°/o~0"5 pF/cx0; 4) basic error in the measurement of capacitance increase not
7-Neutron radiation effect on permittivity of polymothylmethacrylat,e
3111
exceeding 3% (without considering the error of the recording instrument); 5) range of measurement of initial values of the tangent of loss angle 0"01 -- 0"1; 6 ) basic error in the meas urement of initial values of the tangent of loss angle -t-5--10%±8 × 10-3; 7) basic error in the measurement of the increase of tangent of loss angle :t: 5-~ 10% ± 2 × 10-3; 8) inertia of the system on changing increments Aej:/ezo, A tan 5x, ~ 25-30 microsee. The above errors were calculated and determined experimentally by connecting the specimens to the network with an RK-19 type cable, 20 m long, the relative variation of capacitance ziClk/Clk being 20%. As mentioned previously at the moment of the radiation pulse, electromagnetic induction is observed in the connecting cables on a frequency spectrum, similar to the spectrum of the signals to be recorded. Several experiments were carried out which indicate that the amplitude of electromagnetic induction depends to a great extent on the resistance with which the cable is loaded. In the measuring network studied the conducting cable ends were loaded with resistances, which enabled the amplitude of electromagnetic induction to be reduced to a level below the threshold of response of the device. EXPERIMENTAL RESULTS
Two series of m e a s u r e m e n t s were made. I n the first series of e x p e r i m e n t s the specimen was situated directly at the radiation source. The distance f r o m specimen to source was fixed a n d u n c h a n g e d d u r i n g the whole cycle of irradiation b y pulses of differing half-width and intensity. T y p i c a l oscillograms indicating t h e v a r i a t i o n of PMMA p e r m i t t i v i t y , superimposed on oscillograms of t h e r a d i a t i o n pulse, are shown in Fig. 3, a-c. I t can be seen in the oscillogram t h a t the n a t u r e of p e r m i t t i v i t y v a r i a t i o n is complex and depends not only on the intensity, b u t also on the half-width of t h e r a d i a t i o n pulse. I t was revealed t h a t a) during irradiation of a specimen with pulses of halfw i d t h Ti>~250 microsec, the m a x i m u m v a r i a t i o n of ~ ( p e r m i t t i v i t y increased) ivith t i m e agrees with the m a x i m u m value of i n t e n s i t y in t h e pulse; b) with half-widths of 7-neutron pulses in t h e range of 180>~Tt~>70 microsec, a slight a n d t h e n an increasing displacement with time of the m a x i m u m v a r i a t i o n of e is observed in relation to the m a x i m u m of r a d i a t i o n intensity; c) with halfwidths of 70 t> vii> 50 microsec a b r e a k appears on the f r o n t of the p e r m i t t i v i t y v a r i a t i o n which deforms the curve into a d o u b l e - h u m p e d curve with increase of intensity; m a x i m u m increase in p e r m i t t i v i t y is observed in practice at t h e final m o m e n t of the r a d i a t i o n pulse. The v a r i a t i o n of PMMA p e r m i t t i v i t y is, a p p a r e n t l y , related to two processes which occur at different intensities a n d h a v e t y p i c a l r e l a x a t i o n times, which differ considerably. T h e first is the process of increasing e, which has a t y p i c a l r e l a x a t i o n t i m e in the range of 120-160 microsec, a n d the second is a process of r e d u c t i o n of ~ from ~ p ~ 5 0 microsec. I n the second series of e x p e r i m e n t s the specimens were i r r a d i a t e d b y pulses of a p p r o x i m a t e l y identical half-width (v~ ~ 50-60 microsec) and intensity. T h e i n t e n s i t y of the 7-neutron flow t r a n s m i t t e d to the specimen was recorded b y t h e v a r i a t i o n of the distance from the specimen to the radiation source. As in the first case, during irradiation of the specimen with pulses of half-widths T , ~ 7 0
3112
V.V. Z~fnov et
al.
FIG. 3. Oscillograms showing the variation of e--As/e0 during irradiation. Lower curves show the shape of the radiation pulse: a - In=2×101~ n/cm~.sec, I ~ 1 " 4 × 107 r/sec, v~:280 microsec; b --I,~2×1017 n/em2"sec, Iv=1"4×108 r/sec, r1:70 microsec; c -- I , : 4 × 1017 n/cm2"sec,I v : 3 × l0 s r/sec, v~:60 microsec. microsec, the variation of E had the character of a double-hump curve. Maxim u m increase of e was observed at the final moment of the pulses, and the depth of dip increased with higher radiation intensity. I t was also noted t h a t the duration of the drop Ae/e0 to 1/2-level from ACmax/Eo increased with the increase of 7-neutron flow. For a qualitative explanation o f the effects observed several models can be used; however, the experimental data available so far are insufficient to enable preference to be given to one of them. The relative variations of g--~gmax/g0 are tabulated. Finally, the authors express their deep gratitude to V. A. K h r a m o v for experimentally testing the possibilities of measuring the tangent of the loss angle by methods described in this paper, I. S. Pogrebov for his assistance in carrying out the measurements in the reactor and Yu. A. Zysin for his constant interest in the study.
Low angle scattering of polarized light by polymer fibres
3113
R E L A T I V E VARIATIONS OF e - - Z J e m a x / e 0 OF P O L Y M E T H Y L M E T H A C R Y L A T E IN y - N E U T R O N PI~LSE IRRADIATION
Half-width of the radiation pulse, v~ mierosec
Maximum intensity of neutrons in the pulse, I n, H/em2see
280 140 70 60 50
2× 101e=l=20% 7 X 101e=t=20% 2 × 101v±20% 4 × 1017:J=20% 5× 1017=[=20%
Maximum dose rate of 7-quanta I v, r/see
i
l'4x 5x 1"4 × 3x 3.5×
107-4-20% 107±20% 108±20% 108±20% 108±20%
Relative variation of permittivity ~emax ,% e0 4!0"6 9=[=0"8 9"54-0"8 114-1 llil
CONCLUSIONS
A description is given of a method for the measurement of permittivity and the tangent of the loss angle of dielectric materials during irradiation with a 7-neutron pulse flow. Experimental data are given on the effect of ?-neutron pulse radiation on the permittivity of polyniethylmethacrylate. Translated by E. SEMERE REFERENCES 1. N. W. WIEKLEIN, H. NUTLEY and J. M. FERRY, I E E E Trans. on Nucl. Sci. NS-I0: 131, 1963 2. S. E. HARRISON, F. N. COPPAGE and A. W. SHYDER, I E E E Trans. on Nucl. Sei. NS-10: 118, 1963 3. D. M. COMPTON, G. T. CHENEY and R. A. POLL, J. Appl. Phys. 36: 234, 1965
LOW ANGLE SCATTERING OF POLARIZED LIGHT BY POLYMER FIBRES* T. I. VOLKOV Institute of High-Molecular Weight Compounds, U.S.S.R. Academy of Sciences
(Received 23 February 1967)
THE polarization diffractometric method of investigating various types and stages of supermolecular order and corresponding structural processes has in recent years found wide application in the study of both solid [1] and liquid [2] polymer systems. When solving general theoretical problems of formation of oriented order in polymers and more practical problems of fibre formation, * Vysokomol. soyed. A9: No. 12, 2751-2753, 1967.