1312
V . I . KLENIlffe$ al.
9. M. KANTOV, Fraktsionirovaniye polimerov (Fraetionation of Polymers). Mir, 1971 10. J. R. MARTIN, g. E. SOHNSON and A. R. COOPER, J. Macromolec. Sci. C8: 57, 1972
11. P. J. FLORY, J. Amer. Chem. Soc. 67: 2048, 1943; P. J. FLORY, Industr. and Engng. Chem. 38: 417, 1945 12. A. P. PAULAUSKAS, R. D. LEPARSKITE and S. A. GRIGALYUNENE, Zh. prikl. khimii 41: 2329, 1968 13. Ye. V. BYSTRITSKAYA, V. I. GOL'DENBERG, G. B. PARITSKII, L. V. SAMSONOVA
and V. Ya. SHLYAPINTOKH, Vysokomol. soyed. A14: 1727, 1972 (Translated in Polymer Sci. U.S.S.R. 14: 8, 1931, 1972) 14. C. H. DE PUY and R. W. KING, Chem. Revs. 60: 431, 1960
STUDY OF THE STRUCTURE OF INTERPENETRATING POLYMER SYSTEMS USING T H E TURBIDITY SPECTRUM AND X-RAY DIFFRACTOMETRY * V. I. KLENII~, M. Yu. PROZOROVA, L. S. AI~DRIAI~OVA,YU. V. BRESTKIN, G. P. BELOI~OVSKAYAa n d S. YA. FRENKEL' Institute of High Molecular Weight Compounds, U.S.S.R. Academy of Sciences N. G. Chernyshevskii State University, Saratov (Received 1 November 1976)
A study was made of tile mierostructural heterogeneity of interpenetrating polymer systems (IPS) prepared using hexamethylenodi-isocyanato (HMDI)-ethylenesulphide (ES) and 2,4-toluylenedi-isoeyanate (2,4-TDI)-propylenesulphide (PrS) by methods involving the turbidity spectrum and X-ray diffractometery. Methodical problems of using the turbidity spectrum to characterize IPS were described. It was shown that IPS are amorphous heterogeneous systems of colloidal level of heterogeneity. The degree of heterogeneity decreases markedly on increasing polyalkylenesulphide content which, apparently, reflects the type of micro-separation in HMDI-ES and 2,4-TDI-PrS systems.
ANIONIC p o l y m e r i z a t i o n of di-isocyanate m i x t u r e s M 1 with polar m o n o m e r s M S t a k e s place in t w o stages [1]. Di-isocyanates are first h o m o p o l y m e r i z e d to form a t h r e e dimensional structure, which swells in m e d i u m M 2 a n d t h e n p o l y m e r i z e s t o M S. I n t e r p e n e t r a t i n g p o l y m e r s y s t e m s (IPS) are f o r m e d as a result, in which microregions of t h e linear p o l y m e r are d i s t r i b u t e d in t h e di-isocyanate m a t r i x (network). A c c o r d i n g t o t h e M 1 : M 2 ratio I P S are t r a n s p a r e n t plastics of increased h e a t stability or reinforced r u b b e r s in m a n y cases. * Vysokomol. soyed. A19: No. 5, 1138-1142, 1977.
Study of structure of interpenetrating polymer systems
1313
The specific structure of IPS considerably complicates the study of structure and without explaining the quantitative agreement between structure and properties it is difficult to depend on the effective control of properties of these systems. This paper is concerned with possibilities ofl~red by methods of the turbidity spectrum and X-ray diffractometry for the quantitative description of IPS structure using di-isocyanates and alkylcne sulphides. The method of t u r b id it y spectrum has been successfully used previously [2, 3] for the study of initial stages of forming three dimensional polyurethanes. The authors examined the structure of the reaction system after reaching a given degree of conversion (up to 70-90%) and then converted it into a homogeneous solution by the addition of an excess a m o u n t (95~o) of solvent. I n this study we analysed the possibilities of the method of turbidity spectrum to examine the structure of fully solidified I P S type systems, excluding at the same time possible structural disturbances due to the addition of excess solvent. I t is natural t h a t with a positive solution of the problem I P S structure m ay also be studied a t intermediate stages of formation. COMPOSITIO~
IPS
OF I N T E R P E N E T R A T I : N G P O L Y M E R
I
Component ratio (molar) IPS
I ]
Component ratio (molar)
~
SYSTE51:
ES : HMDI
0.2 : 1
0.5 : 1"
1 : 1
I
1.5 : 1
l PS : 2-4-TDI 2:1
2:1
2:1
4 : 1 1 6 : 1 18: 11, 1 0 : 1 4 1"!6 1" 1 8
2 : 1
i
2.5 : 1"
I 10:1!15:1 20:1 15 1" 20 1"
* Samples o f I P S o f an independent series o f synthesis.
I P S prepared using 2,4-toluylenedi-isocyanate (2,4-TDI) and propylene sulphide (P,'S), hexamethylenedi-isocyanate (HMDI) and ethylenesulphide (ES) was synthesized in ampoutes or hermetic cells in dry argon [1]. Di-isocyanates, alkylenesulphides and tertiary amine Ral~" (catalyst) were agitated to achieve gel formation; subsequent stages of the reaction took place under static conditions. Amine concentration varied according to the M~ : M~ ratio. After solidification I P S were heated under given temperature conditions. Compox)ents of I P S and their molar composition are tabulated. I-Iomopolymers--components of I P S have the following characteristics [1]. Network: P o l y T I ) I and p o l y H D I are amorphous plastics with Tsoit ~ 300 ° and ~ 200 °, respectively. Linear polymer: polypropylenesulphide (PPrS)--amorphous, soluble. T g = - 50 °. Polyethylenesulphide-- crystalline, insoluble, Tmelt =: 205- 210 °. No t more t h a n 5o/o P P r S is e x tr a c t e d with hot benzene using a T D I - P S I P S with a ratio of M 1 : Me of up to I : 5; on increasing the proportion of M2 the amount of PPrS extracted increases. X - r a y photographs were taken using an URS-55 device with CuK~ radiation. X - r a y photographs with two rings diffuse in the radial direction were obtained in every case. The intensity ratio of rings depends on the composition of IPS. A typical X - r ay photograph is shown in Fig. 1. X - r a y photographs indicate t h a t I PS studied are amorphous (Table). Fine sections of I P S were observed with an MBI-1 microscope (magnification: 120). Microtomes could not be used due to the mechanical properties of samples (brittleness o r hardness combined with elasticity). Sections more or less satisfying requirements of light microscopy, could be obtained using the blade of a safe razor. A typical microphotograph°
]314
V. I, KLENISTet al.
,shown in Fig. 2 indicates a marked heterogeneity of IPS. However, no q u a n t i t a t i v e infor-
mati~)n could be obtained from these microphotographs about the dimensions of heterogeneities, especially as the photograph reflects not so much the true regions of heterogeneity, as the system of diffraction rings of these regions, the dimensions of which remain outside £he limits of the resolving power of the microscope.
FIG. 1. X - r a y diffraction p a t te r n of I P S of 2,4-TDI-PrS (molar ratio 1 : 2).
Samples of IPS were transparent or to some extent opalescent (according to the composition and thickness of the sample) blocks. Some samples of IPS were yellow brown in colour. To find the "turbidity openings" (absence of absorption),
FIG. 2. Microphotograph of the section of I P S of 2,4-TDI-PrS (molar ratio 1 : 20) ( × 120).
optical density D of IPS was measured in a wide range of wave lengths ,~ using a n SF-5 spectrophotometer. To measure D in a suitable range of magnitudes :samples of different thicknesses with plane parallel edges were cut from samples of IPS; these samples were polished with abrasive dust, diamond paste and then with chamois leather. Figure 3 shows an example of the spectrum D = D (4) on a double logarithmic scale. The linear section determines the relation D=B~-"
(l)
Study of structure of interpenetrating polymer systems
1315
This smooth spectrum D = D (2) (step function) in a comparatively large range of 2 values proves the absence of absorption bands from this range, which show a much more complex dependence on 2, as observed for IPS in the short and long wave range of the spectrum. The marked absorption in the short wave range of 2 is due to the colour of IPS.
log).
,A,nrn
2.8
T-Z
~6
0"17
,~.gog 2.gDg
-
\ z~
700~ 2"MO
2"700 -5g0 ~
'
2" 600
v
z5
0
\\~a. \\ " ~
~ [
I
Z.g
I
f.~
I
[
7:7
[
[
g.z
FIa. 3. Log D-log 2 for IPS of HMDI-ES (molar ratio 1 : 2.5) (1) and 2,4.TDI-PrS (] : 2) (2).
On the other hand, the turbidity of the system T is generally expressed b y a step function 2 [4-11] which agrees with'formula (1) with an accuracy of up to the pre-exponential factor, since ~ is proportional to D (~--2.3.D/I; 1 is the thickness of the sample). Exponent n in formula (1) is the function of the dimensions and the relative refractive index of heterogeneity ranges which are distributed at random in the matrix m=y/po , where p and P0 are the refractive indices of heterogeneity ranges and the matrix, respectively. Exponent n has already been used to describe the micro-structure of solids [6, 7], structurally complex polymer solutions [9-11] and as noted previously, systems obtained b y the synthesis of crosslinked polyurethanes [2, 3]. Dimensions of heterogeneity ranges were determined previously [7] in terms of the correlation function of density fluctuations and later in terms of colloid optics [2, 3, 9-11]: supermolecular particles are particles of the dispersed phase and a polymer solution subjected to molecular dispersion is the dispersion medium. Although these approaches are more or less equivalent, to characterize the microstructure of a single component polymer, a description in terms of correlation functions is more appropriate. The "colloid" terminology is more descriptive for two component solid polymers. The evaluation of m for IPS prepared using 2,4-TDI-PrS and H M D I - E S
V . I . KLENZ~ et al.
1316
i n v o l v e d considerable difficulties in v i e w of the i m p o s s i b i l i t y o f a n i n d e p e n d e n t d e t e r m i n a t i o n o f # a n d /~0 o f c o m p o n e n t s . T h e r e f r a c t i v e i n d e x of P P r S could o n l y b e d e t e r m i n e d f r o m t h e r e f r a c t i v e i n d e x i n c r e m e n t of benzene solutions m e a s u r e d using a n I R F - 2 3 r e f r a c t o m e t e r : ~l~/~c=O.11 cm3/g; t e m p e r a t u r e 25 °, ,l---5461/~. A s s u m i n g t h a t t h e G l a d s t o n e - D y l e rule is v a l i d a n d b e a r i n g in m i n d t h e d e n s i t y o f P P r S [12] it was f o u n d t h a t ppprs ~ 1.626. P o l y e t h y l e n e s u l p h i d e d o e s n o t dissolve a t r o o m t e m p e r a t u r e in organic solvents [12]. T 7 cm -~
1"2f O"q
El
1~
o
i7
Z'O 3"0f 1"0 r~~um 1"5 Z'O 1"0I 1"63 7"61 I'M
i~.
TM
NTCm-3 70 7o
I I I
70 9 70 a
1"57
/0 7 1"55
l'SJ 1"51
10 s I
I
I
20
l
l
qO
i
I
El?
FIa. 4
I
t
80
70 5
|
ES,mole%
100
I
ZO
I
I
qO
I
(
60
I
f
GO
[
100
E8 , °1o P S ~ °Io
FIG. 5
FIG. 4. Relation between the refractive index P~PSof HMDI-ES and ES content. Dark and light triangles refer to IPS of independent series of synthesis. Fie. 5. Parameters of the microstructure of IPS of HMDI-ES (1) and 2,4-TDI-PS (2), according to the content of polyalkylenesulphide, mol. %: a--turbidity z when 2 ~ 740 nm; b--exponent n: c--average size of heterogeneities ~ and d--numerical concentration _N (logarithmic scale) (dark and light signs refer to IPS of independent series of synthesis). I t s h o u l d b e n o t e d t h a t e x p o n e n t n m a y be a s e m i q u a n t i t a t i v e c h a r a c t e r i s t i c o f t h e degree o f m i c r o h e t e r o g e n e i t y e v e n for p o o r l y d e t e r m i n e d s y s t e m s since t h e v a l u e o f n decreases in a p r a c t i c a l l y i m p o r t a n t d i m e n s i o n a l r a n g e o f p a r t i c l e s
Study of structure of interpenetrating polymer systems
1317
both when increasing dimensions and increasing m which may, in the general case, be treated as an increase of the degree of heterogeneity. Furthermore, n is independent of m in the range of 2 , 4 ~ n ~ 4 [8], which removes the need for independent determination and considerably increases the validity of information concerning the dimensions of particles of the heterogeneous medium. In this study we evaluated m b y determining the refractive index of samples of IPS of different compositions using an IRF-22 refractometer. Samples of I P S with polished edges (see above) were used for these measurements. As shown b y results in Fig. 4, a direct proportionality was detected between the refractive index of IPS #' and composition for the H M D I - E S system. Assuming t h a t additivity #' is valid in the entire range of composition, the value of #' was extrapolated to 100% contents of polydi-isocyanate and polyalkylcnc sulphide, thus evaluating the refractive indices of individual components of IPS: p ~ 1.630 and #0 ~ 1.52; hence m ~ ~ 1-07. We did not have at our disposal IPS based on 2,4-TDIPrS in the same range of composition, however, #' values with a high PrS content were arranged near the extrapolation curve #' (Fig. 4). Furthermore, the refractive index of polyethylene sulphide, according to extrapolation (1-630), is close to #PPrs from increment (1-626), which enabled us to assume that m ~ 1-07 for I P S of T D I : PrS. The uncertainty of the value of m for the 2,4-TDI-PS system is offset to a certain extent b y the significant range of variation of n, high values of which are contained in the universal range of 2 . 4 ~ n ~ 4 . For I P S it is natural to accept di-isocyanates as the dispersion medium (matrix). On the other hand, a component of lower concentration is normally used as dispersed phase. Then, in the 2,4-TDI-PrS system m ~ 0.935~ 1. However, for the interpretation of effects of light scattering of systems with m ~ 1, t h e sign of deviation from 1 [5] is of no significance, all calculations were therefore carried out for m : l . 0 7 , since the value o f n was calibrated for m ~ l [6, 8, 10, 11]. Calibration of n in relation to ~ : 2 7 : r x p o / ) . was used in this study, for m~--l-07 [11] where )~-740 nm, fx is the average :radius of equivalent spherical particles of the same volume. This value of ~ is the average complex particle size which depends on n [11, 13]. It was shown [11] that when n ~ 2 fx is close to the weight average particle radius r w, when n ~ 0 is the average surface value of r s which only differs b y 25~o from fw (fr~fw) even for a system of maximum polydispersion. The numerical concentration of heterogeneities N was evaluated b y the formula [ 14] N~50.4
• ~ao (m-- 1)2 )2Kp2
'
where T is the turbidity with wave length ~ (in vacuum, cm) and p : 2 g ( m - - l ) . The coefficient of scattering in the formula was determined b y calibration o f K-----K (a) for m----1.07 [11].
1318
V . I . l r ~ E ~ i ~ et al.
I t should be noted in connection with the type of object studied with commensurate concentrations of the dispersed phase and dispersion medium t h a t e x p o n e n t n is of comparatively low sensitivity in relation to the effect of repeated light scattering [15]. Judging b y the fact t h a t turbidity is not reduced markedly for IPS on changing composition (Fig. 5a) (which would indicate first of all repeated scattering), this effect is, apparently,, negligible in this case, as it is most probably due to the low value of m. Furthermore, in view of the low geometrical thickness the optical thickness of objects d does not exceed the value of 2. Results show t h a t IPS based on di-isocyanates and al]rylenesulphides are amorphous heterogeneous systems of colloidal level of heterogeneity (Fig. 5). A marked reduction in the degree of heterogeneity of IPS on increasing polyalkylene sulphide content is significant. This fact, apparently, reflects the t y p e of micro-separation in H M D I - E S and 2,4-TDI-PrS systems, which is recorded or modified to some extent in subsequent processes of polymerization. A high degree of heterogeneity of fully solidified three dimensional polyuret h a n e was established [16] by a method using a molecular sonde. I t is therefore fully justified and recommended to use the method of turbidity spectrum in search of methods describing structurally complex polymer systems such as three dimensional polyurethanes and interpenetrating systems according to results obtained previously [2, 3] and in this study. Translated by E. SEMERE REFERENCES 1. G. P. BF~0NOVSI~LYA, L. S. ~ T D R I ~ T O V A , L. A. KOROTNE~A, Zh. D. CHERNOYA
and B. A. DOLGOPLOSK, Dokl. AN SSSR 212: 615, 1973 2. A. Ye. NESTEROV, T. E. LIPATOV'A, S. A. ZUBKO and Yu. S. LIPATOV, Vysokomol. soycd. A12: 2252, 1970 (Translated in Polymer Sei. U.S.S.R. 12: 10, 2553, 1970) 3. A. Ye. NESTEROV, T. E. LIPATOVA, S. A. ZUBKO and Yu. S. LIPATOV, Vysokomol. soyed. B13: 346, 1971 (Not translated in Polymer Sci. U.S.S.R.) 4. K. S. SHIFRIN, Rasseyaniye sveta v mutnoi srede (Light Scattering in Turbid Medimn), GITTL, 1951 5. G. VAN DE HULST, Rasseyaniye sveta malymi chastitsami (Light Scattering by Small Particles). Izd. inostr, lit., 1961 6. A. I. SLUTSKER and V. A. MARIKHIN, Optika i spektroskopiya 10: 512, 1961 7. P. DEBYE and A. M. BUECHE, J. Appl. Phys. 26: 518, 1949; J. J. KEANE and S. R. STEIN, J. Polymer Sci. 20: 327, 1956; H. W. STARKWEATHER; J. Polymer Sci. B2: 499, 1964 8. W. HELLER, H. L. BHATNAGAR and M. NAKAGAKI, J. Chem. Phys. 36: 1163, 1962 9. V. I. KLENIN, O. V. KLENINA and V. V. (~ALAKTIONOV,Vysokomol. soyed. 8: 1574, 1966 (Translated in Polymer Sci. U.S.S.R. 8: 9, 1734, 1966) 10. S. Yu. SHCHEGOLEV and V. I. KLENIN, Vysokomol. soyed. A13: 2809, 1971 11. V. I. KLENIN, S. Yu. SHCHEGOLEV and V. I. LAVRUSHIN, Kharak~eristicheskiye funktsii svetorasseyaniya dispersnykh sistem (Characteristic Functions of Light Scattering of Dispersed Systems). Izd. Saratovskogo un~ta, 1977 12. L. L. STOTSKAYA, Polialkilensulfidy, Entsikopediya polimerov (Polyalkylene SuN phides, Encyclopaedia of Polymers). vol. 2, Sovetskaya Entsikopediya, 1974
Effect of ozone on breakdown of polyvinylchloride
1319~
13. S. Yu. SHCHEGOLEV and V. I. ] ( ~ , Optika i spektroskopiya ~1: 794, 1971 14. V. I. KLENIN and S. Yu. SHCHEGOLEV, Vysokomol. soyed. A13: 1919, 1971 (Translated in Polymer Sci. U.S.S.R. 13: 8, 2161, 1971) 15. V. I. KLENIN, S. Yu. SHCHEGOLEV and L. G. LEBEDEVA, Optika i spektroskopiya 35: 1161, 1973 16. T. E. LIPATOVA, Ye. G. MOISYA, S. A. ZUBKO and G. M. SEMENOVICH, Vysokomol. soyed. AI4: 287, 1972 (Translated in Polymer Sci. U.S.S.R. 14: 2, 319, 1972)
E F F E C T OF OZONE ON T H E B R E A K D O W N POLYVINYLCHLORIDE *
OF
~/[. I. ABDULLII~, R. F. GATAULLIN, K. S. MIlqSKER, A. A. KEFELI,
S. D. RAZUMOVSKIIand G. YE. ZAIKOV State University of the 40-th Anniversary of October, Bashkir Institute of Chemical Physics, U.S.S.R. Academy of Sciences (Received 9 November 1976)
A study was made of kinetic relations of hydrogen chloride liberation from PVC and the formation of peroxide compounds in the polymer during thermal decomposition of PVC in the presence of ozone. Rate constants of corresponding processes were determined. Ozone markedly intensifies the separation of HCl from PVC macromolecules; gross dehydrochlorination of the polymer in ozone mainly takes place by the statistical elimination of HCI, the process of forming polyconjugated systems being practically fully inhibited. By the action of ozone on PVC 03 rapidly interacts with internal and terminal double bonds > C = C ( and slow reaction takes place with saturated polymer structures. It was shown that labile groups containing oxygen, formed during the attack of saturated macromolecular sections of PVC by ozone reduce polymer stability to a greater extent than structures formed during the reaction of ~}:~ with ) C = C ( bonds.
THERE are a few papers in t h e literature concerning the effect of ozone o:1 ~he b r e a k d o w n of PVC [1-4]. L i q u i d phase o z o n i z a t i o n of PVC is used for the q u a n t i t a t i v e d e f o r m a t i o n of internal b o n d s \/ C --- C \/ in macromolecules a n d for the e v a l u a t i o n o f kinetic c o n s t a n t s of statistical d e h y d r o c h l o r i n a t i o n of P V C [5]. P V C m a y be exposed to the effect o f ozone d u r ! n g o p e r a t i o n u n d e r a t m o s p h e r i c conditions, or u n d e r conditions of artificial irradiation. I t was therefore interesting to s t u d y t h e kinetic effect of ozone on t h e b r e a k d o w n c f PVC a n d on t h e r e a c t i o n of ozone with PVC considering t w o t y p e s of interaction: i n t e r a c t i o n with u n s a t u r a t e d } C = C ( a n d with s a t u r a t e d b o n d s in p o l y m e r macromolecules. * Vysokomol. soyed. A19: No. 5, 1143-1149, 1977.