CC BY
23
UDC678
K. S. Minsker, M. I. Artsis, G. E. Zaikov
ACHIEVEMENTS AND RESEARCH TASKS FOR POLY(VINYL CHLORIDE)
AGEING AND STABILIZATION
Key-words: Labile groups; chemical, structural-physical, solvatational, and "echo " stabilization; non-toxic chemical-additives,
ceolites, modified clays.
Perspectives ofPVC manufacture, not containing of labile groups in a backbone are considered. It will provide drastic increase of an intrinsic stability of polymeric products, possibility of PVC processing with the minimal contents or in total absence of stabilizers and other chemicals - additives and opportunity of creation of materials and products on a PVC basis with the essentially increased service life-time. Presented data allow to create rigid, semi-rigid and flexible (plasticized) materials and products with the minimal contents of chemicals - additives and increased life-time of their service at exploitation in natural and special conditions.
Ключевые слова: лабильные группы; химическая, структурно-физическая, сольватационная и "эхо" стабилизация; нетоксичные химические добавки, цеолиты, модифицированные глины.
Рассматриваются перспективы производства ПВХ, не содержащего лабильных групп. Это обеспечит резкое повышение внутренней стабильности полимерных продуктов, возможность переработки ПВХ с минимальным содержанием или при полном отсутствии стабилизаторов и других химических веществ - добавок и возможность создания материалов и изделий на основе ПВХ с существенно увеличенным сроком службы. Представленные данные позволяют создать жесткие, полужесткие и гибкие (пластифицированные) материалы и изделия с минимальным содержанием химических веществ - добавок и увеличить срок службы при эксплуатации в естественных и специальных условиях.
1. Introduction
Poly(vinyl chloride) (PVC) is one of the most known multi-tonnage and practically important polymeric products. Thousand of rigid, semi-flexible, and flexible (plasticized) materials and products based on PVC widely used practically in all spheres of a national economy and everyday life. PVC was synthesized first by E. Baumann in 1872, but it's industrial manufacture had begun much later - since 1935 in Germany according to the literature data and in 1930 in the USA according to the data of the DuPont company.
The global PVC production is impressed: 220 thousand ton in 1950, about 1.5 million ton in 1960, more than 3 million ton in 1965, more than 5 million ton in 1970; now its production is estimated for more than 25 million ton.
The basic PVC problem is its low stability. Under action of heat, UV-light, oxygen, radiations etc. it easily disintegrates under the law of transformation of framing groups with elimination of hydrogen chloride and formation of sequential double carbon-carbon bonds in macromolecules with appearance of undesirable coloration (from yellow up to black). Therefore, it is necessary to apply set of methods leading to its increased stability to action of the various factors at a storage, processing and exploitation of PVC as well as at the synthesis, storage and the use of materials and products on its basis.
It is logical to assume that among many aspects causing low stability of PVC and rather short life-time of materials and products on its basis, the primary importance has a knowledge of the reasons of abnormally high rates of disintegration of its macromolecules compare to low-molecular weight models. This problem has appeared to be rather complex for understanding of the experts involved to synthesis and processing of PVC
and, on - essence, is still being discussed now. The researchers of industrial centers of the different countries to the present time can't find the general point of view concerning identification of a weak site in structure of the PVC macromolecule, which determines its abnormal low stability. However, sometimes it is believed that it is done on purposely, though it is not so clear - what for?
2. Who is responsible for low stability of PVC?
The low PVC stability used to be connected to possible presence of labile groups at the macromolecules' structure, which activate polymer's disintegration. These labile groups are distinct from sequences of regular vinyl chloride repeating units ~CH2CHCl-CH2-CHCl-CH2-CHCl~. The overwhelming majority of the researchers believe that such groupings are: a) chlorine atoms bonded to tertiary atoms of the carbon C-Cl (At); b) vicinal chlorine atoms in the macromolecule's structure ~CH2-CHCl-CHCl-CH2~ (Av); c) unsaturated end-groups such as ~CH=CH2 and/or ~CCl=CH2; d) p-chloroallyl groups ~CH2-CH=CH-CHCl~ (Ac); e) oxygen-containing hydroxy- and peroxy groups (A0) [1-8]. Meanwhile, even after brief consideration of the process of PVC disintegration it becomes obvious that, on - essence, there are much less amount of labile groups (which can be considered as the cause of low PVC stability) in the macromolecules, because at PVC dehydrochlorination tertiary chlorine (At) and vicinal (Av) groups turn into the p-chloroallyl ones and the hydroperoxide groups transform in to carbonyl groups:
Cl
~H2C C OH2" CH3
H H _~H2C—C—C—CH2~
I I
- h2o
~H2C-
H
-C—C-
-CH2~
Ao
HH -C^=C-CHCl~
- HCl
HHHH ~H2C—c^C—c^=c-
Besides, the world practice of PVC research has shown that initial (freshly synthesized) PVC macromol-ecules (which are processed in materials and products) do not contain di - (A2), tri - (A3) and/or polyene (Ap) groups [2, 3, 9 - 14]. Internal peroxide groups ~CH2-CHCl-O-O-CH2-CHCl~ are not found as well, since if they are formed at PVC synthesis they would quickly collapse in result of hydrolysis and/or homolytic break of 0-0 bond. There are reliable experimental results, including ones received at study of thermal destruction of fractioned PVC, showing that although unsaturated end-groups are present at structure of polymeric molecules, they do not affect on PVC's disintegration rate [10, 13 - 15].
Thus, the process of gross - dehydrochlorination of PVC (VHCl) with sufficient proximity can be described by the Scheme 1, where a0 - the contents of regular vinyl chloride ~CH2-CHCl~ groups, and KCl, Kt, Kv, Kc, Kp - rate constant of the appropriate dehydrochlorination reactions of PVC; Ktr - rate constant of destruction of polyenes' growth reaction.
Following from the scheme, VHCl - KCla0 + KcAc + KpAp with real values of: Ka = 10-8 - 10-7 s-1 and
ci ■ 10-4 s-1
a0 = 1 mol/mol PVC; Kt = mol/mol PVC; Kc = 10-4 - 10-5 s mol/mol PVC; Kv = 10-3-10-4 s-1 mol/mol PVC; Kp = 10-2 s-1 (448 K).
and [At] = 10-3 and [Ac] = 10-4 and [Av] = 10-5
Av
Kp><AP
a0"
A2
Ar Kt
kA*
Scheme 1
It's obvious that the Scheme 1 assumes the concept of P-chloroallyl activated disintegration of PVC accepted by the majority of the researchers, but without the serious proofs [1 - 5]. However, this postulate is in the contradiction with many experimental facts [16, 17]. In particular:
1). Calculated values of VHCl drastically differ from the experimental ones;
2). The P-chloroallyl activation of PVC disintegration assumes an auto-acceleration of PVC gross -dehydrochlorination process in time [16 - 18]. The linear dependence is observed experimentally (Fig.
[HC11*103, mol/mol PVC 100
Fig. 1 - Kinetic curves of PVC dehydrochlorination. p-chloroallyl activation: 1 - calculated data, 2 - experimental data, (448 K, 10-2 Pa)
A gross-rate constant of PVC disintegration, according to experimental data and Fig. 1 at Kc = 10-4 -10-5 s-1 should contain the expression with Kp = 10-2 s-1 (at 448 K) from the very beginning of PVC thermodestruction. However, according to the data on thermo-disintegration of low molecular weight model compounds [19 - 21] this is observed only at destruction of the model compounds containing a chlorine atom in a p-position to conjugated (C=C)n bonds (at n>2) [19-21], i.e. at occurrence of the effect of the adjacent group of the long-range order (Table 1).
Table 1 - Dehydrochlorination rate constant at thermo-destruction of low molecular weight model compounds
Temperature area where
№ Compound the compounds start to degrade with a noticeable rate, K Groups' index Decomposition's rate constant, K, s-1
1 2,4-dichloro-pentane 563 - 593 a0 2.6*10-9
2 meso-2,4-di-chloropentane 563 - 593 a0 1.9*10-9
3 3-ethyl-3-chloropentane 488 - 553 At 7.9* 10-6
4 4- chlorohexene-2 433 - 463 Ac 5.1*10-4
5 4- chlorodecene-2 438 - 468 Ac 5.0*10-5
6 7-chloronona-diene-3,5 343 - 369 Ap 3.4*10-2
7 6-chloroocta-diene-2,4 360 - 386 Ap 2.6*10-2
Thus, even the primary analysis of experimental results concerning the concept of P-chloroallyl activation of the PVC dehydrochlorination, does not sustain criticism and has no right on existence. It is the erroneous point of view.
It has to be noted that on the basis of theoretical consideration of PVC thermal degradation in view of all available experimental data following can be concluded: even if internal P-chloroallyl groups (as well as tertiary chlorides and vicinal ones) are present in the macromolecules' structure, they do not contribute much
A
A
Cl Cl
O
OOH Cl
Cl
HC
CHCl
A
A
p
K
Cl
A
c
to the process of PVC gross-dehydrochlorination due to of their sufficient relative stability. It was assumed and then proved that such a group is an oxovinylen (carbonylallyl) conjugated dienophile group, at which the unsaturated bond is activated by the adjacent elec-trophilic group C=O (-C(O)-CH=CHCl-CH2-) which, apparently, comprises in PVC macromolecules in rather small amounts y = 10-4 mol/mol PVC, but disintegrates with the rather high rate (Kp =10-2 s-1) with HCl elimination [14, 17, 22 - 24].
It is extremely important to emphasize that the concept of oxovinylene activation of PVC disintegration does not contradict to any of known (up to date) experimental facts. Meantime, new (including the original ones) proofs of existence of the basic groups in the structure of PVC macromolecules have received recently. In particular, oxovinylene groups which are included into a PVC macromolecules, are easily (in mild conditions) splited at alkaline hydrolysis (5 % aqueous solution KOH, 5 % solution of PVC in cyclohexanone) [13, 14] - a characteristic reaction for a, P-unsaturated ketones [25].
Reaction 1:
V*10«, HCI/(mol PVC*s)
~CH=CH-C(O)~
H2O
KOH
yO <
+ H3C-
Using this reaction it's easy to estimate contents of labile oxovinylene groups in the macromolecules' structure (y0) by a decrease of PVC's viscosity-average molecular weight [13 - 17].
3. How can we identify carbonylallyl groups?
It's important to specify that both P-chloroallyl and polyene groups are inert to an alkaline hydrolysis but easily decomposed at oxidizing (at presence of hydrogen peroxide) ozonolysis [13]. The ozonolysis method allows to estimate a complete amount of internal unsaturated (P-chloroallyl, chloropolyenyl, and oxovinylene) groups in the PVC macromolecules' structure by a decrease of PVC molecular weight. Thus, it's experimentally shown that practically all internal unsaturated groups included in PVC's initial macromolecules are oxovinylene ones and PVC dehydrochlorination rate linearly connected to the contents of the internal labile oxovinylene groups in polymeric molecules [14, 26], determined by a method of alkaline hydrolysis (Fig. 2).
It is characteristic that the polymeric products synthesized in an absence of oxygen, always were noticeable more stable than PVC received in the industry due to the presence in the first case of stable enough internal P-chloroallyl (not oxovinylene) groups (oxidative ozonolysis) in PVC macromolecules' structure. As a whole, the real process of HCl elimination at PVC disintegration on reaction of transformation of framing groups is complex, since generally this or that contribution is brought in by all abnormal groups contained in the macromolecules' structure. However, apparently, the contribution of different reactions to this process varies and in a number of cases some of them can be neglected.
1.4 1,8
Yo*10\ mol/mol PVC
Fig. 2 - Dependence of PVC dehydrochlorination rate of the contents of carbonylallyl groups in the polymer molecules (448 K, 10-2 Pa)
The kinetic analysis taking in account the real contents of characteristic (including abnormal) groups in PVC and rate constants of their disintegration (Table 2) has precisely shown [14, 17, 24, 27] that the ratio of the appropriate reaction rate constants KCl:Kc:Kt:Kp = 1:100:100:100000 and for this reason PVC's own thermal stability, on - essence, is determined by an effect of the adjacent group of the long-range order (conjugation effect) and for this reason the total elimination rate of HCl from PVC is described by the simple equation with sufficient accuracy:
VHc, = = Kcla0 + Ky = Vcl + Vp (1)
Table 2 - Rate constants of dehydrochlorination of characteristic groupings and their contents in the initial PVC structure
Contents in PVC Rate constant
№ of degradation at 448 K
Index Amount Authors In d Val ue, Authors
mol/mol e s-1
PVC x
1 Yc ~10-4 K.Minsker, K 10- K.Minsker
1978 p 1- , 1977
E.Sorvik, 10-2 W.Starnes
1984 , 1985
G.Zimmerman,
1984
2 Aci0 o K.Minsker, K 10- Z.Meyer,
1978 Cl 5- 1971
G.Zimmerman, 10-4 B.Troitsky
1984 , 1973 W.Starnes , 1983
3 At0 ~10-3 E.Sorvik, 1984 A.Caraculaku, 1981 V.Zegelman, 1985 K t 10-4 W.Starnes , 1983 Z.Meyer, 1971
4 Ap o K.Minsker, K ~10 Z.Meyer,
1976 p 1971
K.Minsker , 1984
5 ao 1 K Cl 107 10-8 Z.Meyer, 1971 K.Minsker , 1972
1) ~CO-CH=CH-CHCl~; 2) (~CH2)CCl-CH2-< CH2Cl~ ;
3) -CCI-CH2CH2CI; 4) ~CH2-(CH=CH)n>i-CHCl;
5) ~CH2-CHCl-CH2- CHCl~
0
Even at the account of PVC disintegration with participation of tertiary chloride (At) and p-chloroallyl (Ac) groups the contribution of the expression Vp = Kpy comprises of about 90 % and more of total gross - rate of PVC dehydrochlorination, that precisely concludes about oxovinylene (not p-chloroallyl) activation of the gross - process of PVC thermal disintegration.
The development of the concept of oxovinylene activation of PVC thermodestruction appeared to be an important mark in the theory and practice of PVC chemistry and objectively defines necessity of the new specific approach to study of various aspects of destruction and stabilization of PVC.
In particular, new characteristic reactions with unsaturated ketones, confirming the presence of oxyvinylene groups in PVC structure, are the interaction of ~C(O)-CH=CH-CHCl~ groups with organic phosphites P(OR)3 [29 - 33] and dienes [34, 35].
4. Principal ways for stabilization of PVC
Organic phosphites in mild conditions (290 -330 K) easily react with oxovinylene groups at the presence of the proton donors with formation of stable ketophosphonates:
Reaction 2:
CHCl~
~C-C=C-CH~ + p(or)3
0=P(OR)s
Reaction kinetics of interaction of organic phosphites with oxovinylene groups are shown on Fig. 3.
Yo*10\ mol/mol PVC 1,6
Time, h
Fig. 3 - A change of the ~C(O)-CH=CH~ groups contents in PVC at interaction with tri-(2-ethylhexyl)phosphite (1-3) (Co = 10-2 mol/mol PVC): 1 - 289; 2 - 298; 3 - 448 K
The formation of ketophosphonate structures according to the reaction (2) results in disappearance of internal unsaturated C=C bonds in PVC structure. As a result, neither, oxidizing ozonolysis of a polymeric product, nor especially alkaline hydrolysis, do not result to degradation of macromolecules and decrease of PVC's molecular weight.
It's important to specify that organic phosphites do not react with P-chloroallyl groups that is confirmed by a method of competing reactions of organic phosphites (trialkty-, arylalkyl- and triarylphosphites) with a mixture (1:1 mol/mol) of methylvinylketone (model of an oxovinylene group) and 4-chloropentene-2 (model of a P-chloroallyl group) at 353 K. An organic phosphite selectively, practically quantitatively (regarding to a proton donors) reacts with methylvinylketone, while 4-chloropentene-2 is practically quantitatively allocated after realization of reaction, excluding of some (less than 7 wt. %) amount of products of its dehydrochlorination. The CH3-C(O)-CH2-CH2-P(OR)2 is the main reaction product (up to 75 wt. %). In this reaction trialkyl- and alkylarylphosphites are more active than triarylphosphites.
Dienophylic oxovinylene groups react with conjugated dienes according to the Diels-Alder reaction: Reaction 3:
HC-
r
CH
H
RHC \
HC
/ \
CC
CHCl~ CHR-
I
CH
It is new not known earlier reaction for PVC proceeds in mild conditions (353 K) with cyclopentadiene, piperylene, isoprene, 5-methylheptatriene-1,3,6 etc. and results (see Reaction 3) in liquidation of internal unsaturated C = C groups in PVC chains similarly to organic phosphites.
PVC stabilization, i.e. a complex of methods used with the purpose of increase of the polymer's stability to action of the various factors (such as heat, light, oxygen etc.) in terms of storage, processing and exploitation is closely connected to a level of development of PVC degradation theory. Therefore, it is clear that significant change of theoretical developments about the reasons of PVC's thermal instability (a presence of oxovinylene groups in the backbone), mechanism of the process (fundamental influence of the adjacent groups of the long-range order) and kinetics of their disintegration, have shown a necessity and have enabled a new look at determination of new effective ways of PVC stabilization at thermal and other influences.
According to the equation (2) it is impossible (and is not necessary) to increase stability of PVC mac-romolecules due to reduction of rate VCl since this process is rather slow. According to the experimental data, the rate of PVC statistical (law of randomness) dehydrochlorination VCl does not depend on how polymer was synthesized and its molecular weight and is constant. Hence, it is the fundamental characteristic of PVC, showing that all parts in clusters ~BXBXBX~ participate similarly in process of HCl elimination under the law of a randomness, whereas the rate of formation of the conjugated systems (Vp) can noticeable differ, since it linearly depends on the contents of oxovinylene groups in initial macromolecules of PVC (y0) (Fig. 2).
Thus, the basis of effective PVC stabilization which determines both operational properties and durability of rigid materials and products from PVC, is a principle of increased self-stability of PVC macromole-
O
O
CHCl~ +
O
Cl
CHCl
cules [17, 40 - 43]. This can be reached first of all due to of a chemical stabilization of PVC - destruction of labile oxovinylene groups whose are present in initial PVC macromolecules on specific polymer-analogous reactions with either of the reaction centers (1) - (3):
2
~C-CH=CH-CH~ 111 13
O Cl
The conjugation ~C(O)CH=CH~ has to be destroyed and/or labile chlorine atom has to be replaced with a more stable framing group at interaction with the appropriate chemicals - additives (stabilizers). This principle underlies stabilization of PVC in real formulations at manufacture of rigid materials and products. 1). Polymer-analogous reactions on >C=O fragments of oxovinylenchloride groups:
R3SiH
R3GeH R3-
O II O /\ 'R-HC — CH-R"
~C-CH=CH-CHCl~
OH OH 1 |
R'-CH-CH-R"
~CH-CH=CH-CHCl~
I
-Si
G.A.Razuvaev et al, 1969 [5]
~C-CH=CH-CHCl~ /\
0 O
1 I
R'-CH-CH-R"
K.S.Minsker, S.R.Ivanova, 1978 [36]
2). Polymer-analogous reactions on >C=C< fragments of oxovinylene groups:
P(OR)3
~C-CH2-CH-CHCl~ ~/ \
II I and/or O VH CHCl~
O . P(OR)3 ON p/CH-CHCl
R'-CH=CH-CH=CH-R"
HC=CH / \
K.S.Minsker, N.A.Mukmeneva et al., 1979 [31-33]
- CH-CH / \
'R-HC^ CH-R" K.S.Minsker, S.V.Kolesov, 1980 [34, 35] HC = CH
O C|H K.S.Minsker, S.V.Kolesov, 1983 [37, 38] .CH-CHCl~
~HC.
3). Polymer-analogous reactions on labile >C-Cl
groups:
R2Sn(COCR)2
Cd(COCR)2 Zn(COCR)2, etc.
O /\
~CO)CH=CHHCH2-OCO)R
Classic reaction, [16, 17]
'R-HC—CHR"^ ~CO)CH-CHCH- K.S.Minsker, S.V.Kolesov, S.RIvanova, 1982 [39]
(ZnCl2)
O-CHRCHCR"
This method is called "chemical stabilization" of PVC [17, 40, 41].
It is important that the concept of oxovinylene activation of macromolecules' disintegration at PVC destruction has allowed to reveal new unexpected possibilities of effective not only thermal, but also light-stabilization of this polymer. This also allows to use for its stabilization previously unknown classes of chemical compounds, in particular, conjugated diene hydrocarbons, adducts of Diels-Alder reaction, protonic acids, a, P - dicarbonic comcpounds, etc. [34 - 38, 44 - 46]. It also has enabled to reveal new real reactions proceeding at PVC chemical stabilization, including at application of known chemicals - additives to PVC, which are used
for a long time for PVC stabilization (for instance, organic phosphites, epoxy compounds, proton-donating compounds, etc.), and on this basis to manage PVC aging process more effectively (Scheme 2). The connection between chemical structure of chemicals - additives and their efficiency as stabilizers for PVC determines an opportunity of scientific - based and economically expedient selection of the appropriate stabilizers and their synergistic combinations at creation of rigid materials based on PVC.
5. Light stabilization of PVC
Polymer-analogous transformations of oxovinylene groups in PVC macromolecules at its chemical stabilization with the appropriate chemicals -additives lead not only to increased self-stability of PVC and inhibition of macromolecules cross- linking, but also to a noticeable increase of PVC's color stability.
The transformation of oxovinylene groups in result of polymer-analogous transformations with chemicals - additives in keto-phosphonate-, cyclohexan-, dioxolane-, dihydropyrane, etc. groups in structure of PVC macromolecules and "curing" of labile oxovinilenchloride groups results in increase of PVC's optical density in the field of a UV-spectrum. As a result, these groups act as internal light stabilizers that results in the phenomenon of self-photostabilization of PVC [47] (Fig. 4).
Fig. 4 - Dependence of whiteness coefficient retention Kw in PVC films on exposure time: 1 - unstabilized PVC and polymer treated with: 2 - 2-tris-(2-ethylhexyl)phosphite; 3 - 2-ethylhexyl-9,10-expxy stearate with ZnCl2; 4 - piperylene; 5 -cyclopentadiene (295 K, X - 254 nm, 1 - 1; 5*1015 quantum/s*cm2)
Thus, the determining factors causing high rate of PVC's disintegration and necessity of its stabilization are the presence of abnormal groups in structure of polymeric molecules, mainly oxovinylene ones, i.e. mac-romolecule's chemical structure.
6. PVC degradation in solutions. Effect of placticizers
As to plasticized (semi-rigid and flexible) PVC materials as well as PVC in solutions, the rate of their thermal destruction and effective stabilization are caused by essentially different fundamental phenomena in comparison to aging of PVC in absence of the sol-
O
O
C
CHCl
vent.
Epoxy compounds
Inhibition of PVC's photodectruction and macromolecules' cross-linking, color change
Conjugated dienes
is observed at destruction in certain ester-type solvents (plasticizers) (Fig. 5, points 25 - 28), that apparently caused by structural changes of macromolecules. This was never before taken into account at work with PVC in solutions.
Scheme 2
Both structure and macromolecules' dynamics render the significant influence on its stability, i.e. chemical nature of the solvent, it's basicity, specific and non-specific solvatation, contents of PVC in a solution, segmental mobility of macromolecules, thermodynamic properties of the solvent, formation of associates, aggregates, etc. from macromolecules, etc. The chemical stabilization of PVC plays a less significant role.
At PVC's destruction in solution, one of the basic reasons of change of the process kinetic parameters is the nucleophilic activation of a PVC's dehydrochlorination reaction. The process is described by E2 mechanism. Thus, there is a linear dependence between PVC's thermal dehydrochlorination rate and parameter of solvent's relative basicity B cm-1 (Fig. 5) [48 - 50]. (The value B cm-1 is evaluated by shift of a characteristic band OH of phenol at X = 3600 cm-1 in an IR-spectrum at interaction with the solvent [51]). It is essentially important that the rate of PVC's dehydrochlorination in the solvents with relative basicity B > 50 cm-1 was always above, than the rate of PVC's dehydrochlorination without the solvent, while when B < 50 cm-1, PVC's desintegration rate was always less, than at it's destruction without the solvent. The revealed dependence VHCl = f (B) is described by the equation:
V*cl = VhC, + k(B - 50) (2)
An inhibition of PVC's disintegration in the solvents with basicity B < 50 cm-1 is very interesting and practically important phenomenon. It has received the name "solvatational" stabilization of PVC. Let's notice, however, that ignoring of the fact that PVC solutions even at low concentration (2 wt. %) do not represent solutions with isolated macromolecules but rather with structured systems, results that in a number of cases a deviation from linear dependence of PVC dehydrochlorination rate of the solvent basicity B cm-1 is observed. In particular, an abnormal behavior of PVC
Fig. 5 - Influence of the solvent's basicity on the rate of thermal dehydrichlorination in solution: 1 - n-dichlorobenzene, 2 - o-dichlorobenzene, 3 - naphthalene, 4 - nitrobenzene, 5 - acetophenone, 6 -benzonitrile, 7 - di-n-(chlorophenyl-chloropropyl) phosphate, 8 - triphenylphosphite, 9 - phenyl-bis-(P-chloroethyl) phosphate, 10 - tri-(n-chlorophenyl phosphate), 11 - 2-ehtylhexylphenyl phosphate, 12 -tricresyl phosphate, 13 - cyclohexanone, 14 - phenyl-bis-(P-chloropropyl) phosphate, 15 - tri-P-chloroethyl phosphate, 16 - tri-p-chloropropyl phosphate, 17 - di-2-(ethylhexyl) phosphate, 18 - 2-ethylhexylnonyl phosphate, 19 - tri-(2-ethylhexyl) phosphate, 20 - tributyl phosphate, 21, 25 - dibutyl phthalate, 22, 26 - di-2-ethylhexyl adipinate, 23, 27 -dioctyl phthalate, 24, 28 - dibutyl sebacinate. Concentration of PVC in solution: 1-24 - 0.2 wt. %, 25 -28 - 2 wt. %; 423 K, under nitrogen
It was revealed quite unexpectedly that not only interaction "polymer - solvent", but also interaction "polymer - polymer" in solutions provide significant influence on rate of PVC disintegration. It's known that structure and properties of the appropriate structural levels depend from conformational and configurational nature of macromolecules, including a supermolecular structure of the polymer, which in turn determines all basic (both physical and chemical) characteristic of polymer.
"Polymer - polymer" interaction results to formation of structures on a supermolecular level. In particular, as getting more concentrated the PVC-solvent system consistently passes a number of stages from isolated PVC macromolecules in a solution (infinitely diluted solution) to associates and aggregates from macromolecules in a solution. At the further increase of PVC concentration in a solution formation of spatial fluctuational net with structure similar to a structure of polymer in the block occurs.
When polymer's concentration in a solution increases, the rate of PVC's dehydrochlorination reaction changes as well, and various character of influence of the solvent on a PVC disintegration rate in solution is
observed depending on a numerical value of basicity parameter B cm-1 [52 - 57]. If the relative basicity of employed solvents was B > 50 cm-1, the polymer's degradation rate decreases when its concentration increases. If a basicity of the employed solvents was B < 50 cm-1, the polymer's degradation rate increases with increased concentration of a polymer. In all cases the rate of HCl elimination from a polymer has a trend in a limit to reach values of PVC dehydrochlorination rate in absence of the solvent VHV = 5*108 (mol HCL/mol PVC)/s. (Fig. 6).
VHCi*10* (mol HCl/mol PVC)*s
VHC.*108 (mol HCl/mol PVQ*s
VHCi*108 (mol HCl/mol PVC)*s
Concentration of PVC in solution, wt %
Fig. 6 - A change of PVC's dehydrochlorination rate of its concentration in a solution: 1 - cyclohexanol, 2
- cyclohexanone, 3 - benzyl alcohol, 4 - 1, 2, 3 -trichloropropane, 5 - o-dichlorobenzene, 6 - no solvent; 423 K, under nitrogen
Equation (2) turns into an equation (3) if to take into account that the PVC's degradation rate is determined not only by parameter of relative basicity of the solvent B, but also by its concentration in a solution (C, mol PVC/L), as well as by degree of "polymer -polymer" interaction (degree of macromolecules structurizarion in a solution AC = /C-C0 /, where C0 -concentration of a beginning of PVC macromolecules association in a solution):
VHCl = V0cl + A /(C + / AC / + d1)(B - 50) (3)
Here factor Ai = (0.8+0.2)*10-9 (mol HCL/mol PVC)/s; d1 - dimensionless factor reflecting interaction "polymer
- solvent" (d1 = 0.5+0.25). The deviation from the moment of a beginning of macromolecules association in a solution is taken on the absolute value, since it can change in both directions to more concentrated and more diluted solutions of a polymer.
Equation (3) well describes a change of PVC's thermal dehydrochlorination rate of its concentration in a solution in view of parameter of relative basicity of the solvent B, irrespective of the chosen solvent (Fig. 7).
The observable fundamental effect has the significant importance at production of plasticized (in particular, by esters) materials and products made from PVC. Despite of very high basicity of ester-type plasti-cizers (B = 150 cm-1) in an interval of PVC concentration in solutions more than 2 %, a noticeable reduction of PVC degradation rate is observed (Fig. 4, curve, points 25 - 28), i.e. on - essence, stabilization of PVC occurs.
OJt 0.6 1.«
Concentration of PVC in solution, wt %
Fig. 7 - A change of PVC's dehydrochlorination rate from its concentration in a solution: 1, 2 - 1, 2, 3 -trichloropropane, 3, 4 - cyclohehanol, 1, 3 - experimental data, 2, 4, - calculated data with equation (4) at Ax=10-9 and di=0.8 and 0.7 correspondingly; 423 K, under nitrogen
This effect is caused by formation of dense globules, associates, etc. in the system PVC - plasticiz-er. Practically this allows to create economic formulations of plasticized materials from PVC with the very little contents of metal-containing stabilizers - HCl acceptors, or without their use at all.
Temperature is very important on formation of the heterophase system. Even at low concentration of PVC in ester-type plasticizer (for example, in dioctyl phthalate at C> 0.1 mol/L) the true solutions are formed only at temperatures above 400 K. Globular structure of suspension PVC and formation of associates retain at temperatures up to 430 - 445 K. In other words, PVC at plasti-cization, is capable to keep its structural individuality on a supermolecular level, which is formed during polymer's synthesis. Specifically in these conditions the ester-type plasticizer behaves not as a highly-basic solvent, but as a stabilizer at PVC's thermo-degradation due to formation of associates etc. This leads to a reduction of stabilizer's amount, extension of exploitation time of materials and products, etc.
It is necessary to note that the change of PVC's degradation rate at association of macromolecules is the general phenomenon and does not depend on how it was achieved. In particular, similar (as well as at concentration of PVC solutions (Fig. 6, 7)), character of change of PVC dehydrochlorination rate in a solution is observed, if the change of PVC's structural - physical condition in a solution is reached upon addition even chemically inert non-solvents, for example, hexane, decane, undecane, polyolefines, polyethylene wax, etc. [53, 56 - 59] (Fig. 8).
It is interesting to note that the degree of relative change of PVC disintegration rate under action of the second inert polymer (non-solvent) is much higher, than at concentration of a PVC solution, especially in case of use of the low-basic solvents (trichloropropane, dichlorobenzene - a result of formation of more dense formations on a supermolecular level, corresponding associates and aggregates, thanks to whom there is a significant change of a PVC destruction rate.
Fig. 8 - A change of PVC thermodegradation rate of the contents of the secong inert polymer in solution of trichloropropane (1, 3), dichlorobenzene (2), and cyclohexanol (4 - 6) for blends of PVC with poly(ethylene) (1, 4), poly(propylene) (2, 5), and poly(isobutylene) (3, 6); 423 K, under nitrogen
The more contents of non-solvent (including an inert polymer) in a blend and lower thermodynamic compatibility of components in a solution, the more structural formation takes place in a solution, including one at the presence of a polymer blends (associates, aggregates). Formation of a fluctuational net with participation of macromolecules is probable. Since the reason of change of PVC thermal dehydrochlorination rate in case of its blends with chemically inert thermody-namically incompatible polymers is the same, as at concentration of a PVC solution (structural - chemical changes of a polymer in a solution), the parameters determining the rate of PVC disintegration, will be, obviously, similar. Therefore, at consideration of PVC thermal destruction a concentration of the second polymer in a blend with PVC, as well as a degree of its thermo-dynamic affinity to PVC have to be taken in account in addition to an influence of polymer's concentration in a solution, basicity of the solvent B cm-1 and forces of interaction "polymer - solvent". In view of these factors the equation (3) turns into an equation (4): VHd = Kci+(A /c+/(c+ d +an))(B-50)+A /B)(d2an /c) (4)
where a - fraction of the second polymer, varying from 0 to 0.99; n - dimensionless parameter describing a degree of thermodynamic affinity of PVC to the second polymer and varying from zero (in a case of a complete thermodynamic compatibility of the components) up to certain value equals ~10 (in a case of a complete ther-modynamic incompatibility of the polymers). Dimen-sionless coefficient d2 reflects interaction of the second polymer with the solvent. At destruction of PVC in a blend with poly(ethylene) in a solution of dichlorobenzene, trichloropropane, and cyclohexanol it equals 2.5+0.1.
Observable changes of PVC thermal disintegration rate under action of second thermodynamically incompatible with PVC polymer (or owing to an increase of PVC concentration in a solution) are caused by a displacement of the solvent from macromolecular globules of PVC with transformation to the structure, which it has in
absence of the solvent. This evokes unexpected effect of "the solvent action" (a delay or an acceleration depending on the solvent's basicity B cm-1) in relation to PVC's thermal disintegration. The solvent's displacement, which accelerates PVC's disintegration (B > 50 cm-1), results to easing of its interaction with PVC and leads to a delay of process of HCl elimination from macromolecules, i.e. to stabilization. This occurs both in a case of concentration of PVC's solutions, and in case of addition of second polymer, which is thermodynamically incompatible with PVC. In the solvents slowing down PVC's disintegration (B < 50 cm-1) by virtue of low nucleophilicity, an effect of the solvent displacement and the easing of its influence on PVC results in an opposite result - an increase of HCl elimination rate from PVC upon of increase of its concentration in a solution or at use of chemically inert non-solvent. It is obvious that irrespective of the fact how to make changes in PVC's structure in a solution -by increase of its concentration in a solution or by addition of second thermodynamically incompatible with PVC chemically inert non-solvent - the varying structural - physical condition of the polymer results in a noticeable change of its thermal dehydrochlorination rate in a solution. These effects are caused by structural - physical changes in system polymer - solvent, and previously unknown phenomena can be classified as structural - physical stabilization (in case of a reduction of gross - rate of PVC disintegration in highly-basic solvents at B > 50 cm-1) and, respectively, structural -physical antistabilization (in case of increase of gross -rate of PVC disintegration in low-basic solvents with B < 50 cm-1).
7. "Echo" - stabilization of PVC
At last, it is necessary to specify to one more appreciable achievement in the field of aging and stabilization of PVC in a solution. In real conditions the basic reason of the sharp accelerated aging of plasti-cized materials and products is the oxidation of the solvent by oxygen of air (Fig. 9, curve 3).
Fig. 9 - "Echo"-stabilization of PVC. Elimination of HCl during thermo- (argon) (1, 2) and thermo-oxidative (air) (3 - 5) destruction of PVC in solution of dioctyl sebacinate: 1 - 4 unstabilized PVC, 5 - PVC, stabilized with diphenylpropane (0.02 wt. %) -"echo" stabilization; 2, 4 - PVC with no solvent; 448K
RO2* + RH —^^ ROOH + R* ROOH ——^ RO* + HO*
RO2* + RO2* * inactive products
Peroxides, formed at oxidation of ester-type plasticizers, initiate disintegration of macromolecules. In these conditions the rate of PVC destruction can increase in two and more orders of magnitude and is determined by oxidizing stability of the solvent to oxygen - parameter Kef = K2*K30-5*K6-0-5. Then higher an oxidizing stability of the solvent (in particular, ester-type plasticizer), at which's presence a thermooxidative disintegration of PVC occurs, then lower its degradation rate and longer an exploitation time of semi-rigid and flexible materials on a basis of PVC [60, 61, 63]. An inhibition of process of the solvent's oxidation (including plasticizers) due to of incorporation of stabilizers - antioxidants or their synergistic compositions slows a thermo-oxidative disintegration of PVC in a solution (Fig. 9, curve 5).
At effective inhibition of the ester-type plasti-cizers' oxidation by oxygen of air the rate of PVC ther-mo-oxidative destruction in their concentrated solutions is getting closer to the rate of polymer's disintegration, what is characteristic for its thermal destruction at plas-ticizer's (solvent's) presence, i.e. slower, than PVC's desintegration without a solvent. This occurs due to a structural - physical stabilization. In these cases an inhibition of reaction of the solvent's oxidation at use of "echo" - type stabilizers - antioxidants causes PVC's stabilization (Fig. 9, curve 5). This fundamental phenomenon of PVC's stabilization in a solution at its thermo-oxidative destruction has received the name of an "echo" - stabilization of PVC [49, 62, 63].
8. Tasks for a future
Thus, a creation of high-quality and economic semi-rigid and flexible materials and products on a basis of PVC, including ones where solvents are employed, require the specific approach, essentially differing from principles of manufacture of rigid materials and products from PVC. In particular, account and use of the fundamental phenomena: solvatational, structural -physical and "echo" - stabilization of a polymer in a solution.
As to paramount tasks of fundamental and applied research in the field of PVC's manufacture and processing in the beginning of XXI century, obviously they are following:
* Manufacture of an industrial PVC, not containing of labile groups in a backbone. It will provide drastic increase of an intrinsic stability of polymeric products, possibility of PVC processing with the minimal contents or in total absence of stabilizers and other chemicals - additives and opportunity of creation of materials and products on a PVC basis with the essentially increased service life-time;
* Wide use of the latest achievements in area of destruction and stabilization of PVC, both at presence and absence the solvents. First of all, phenomena of
chemical, solvatational, structural - physical, self-and "echo" - stabilization of PVC will allow to create rigid, semi-rigid and flexible (plasticized) materials and products with the minimal contents of chemicals - additives and increased life-time of their service at exploitation in natural and special conditions;
* The use of non-toxic, non-flammable products which do not emit toxic and other poison gaseous and liquid products at elevated temperature at manufacture of materials and products from PVC;
* Complete slimination of all toxic and even low-toxic (particularly compounds based on Pb, Cd, Ba, etc.) chemicals - additives from all formulations;
* Search of non-toxic and highly effective inorganic chemicals - additives, first of all, stabilizers of a zeolite - type, modified clays, etc.
At the same time new "surprises" may be expected, which undoubtedly will be presented us by this outstanding polymer - puzzle, a plastic's "working horse" for many decades. Certainly it will give new stimulus in development of scientific bases and practical development with opening of new pathways, conducting to essential delay of PVC's ageing in natural and special conditions at reduction of amounts of the appropriate chemicals - additives, down to their complete elimination.
References
1. Pudov, V. S. Plasticheskie Massy 1976, 2, 18-22.
2. Braun, D.; Quarg, W. Angew. Makromol. chem. 1973, 29/30(1), 163-178.
3. Abbas, K. B.; Sorvik, E. M. J. Appl. Polym. Sci. 1976, 20(9), 2395-2406.
4. Valko, L.; Tvarovska, I.; Kovaric, P. Eur. Polym. J. 1975, 11(5/6), 411-416.
5. Toitsky, B. B.; Troitskaya, L. S. Vysokomol. Soedin. 1978, 20A(7), 1443-1457.
6. Arlman, E. J. J. Polym. Sci. 1954, 12, 547.
7. Geddes, W. C. Eur. Polym. J. 1967, 3(2), 267-281.
8. Bataille, P.; Van, B.T. J. Polym. Sci. 1972, A-1(10), 1097.
9. Abbas, K. B.; Erling, M.; Sorvik, E. M. J. Appl. Polym. Sci. 1973, 17(12), 3577-3594.
10. Onoluzka, M.; Asahina, M. J. Macromol. Sci. 1969, 3(2), 235-280.
11. Carrega, M.; Bonnebat, C.; Zednic, G. Anal. chem. 1970, 42, 1807.
12. Schmidt, L. Angew. Macromol. chem. 1975, 47(1), 79-95.
13. Lisitsky, V. V.; Kolesov, S. V.; Gataullin, R. F.; Minsker, K. S. Zh. Analit. Khimii 1978, 33(11), 2202-2207.
14. Minsker, K. S.; Lisitsky, V. V.; Zaikov, G. E. J. Vinyl Technol. 1980, 2(4), 77-86.
15. Minsker, K. S.; Berlin, Al., Al.; Lisitsky, V. V. Vysokomol. Soedin. 1976, 18B(1), 54.
16. Minsker, K. S.; Fedoseeva, G. T. Destruction and Stabilization of poly(vinyl chloride); Nauka: Moscow, 1979; p 272.
17. Minsker, K. S.; Kolesov, S. V.; Zaikov, G. E. Degradation and Stabilization of Vinyl chloride based polymers; Pergamon Press, 1988.
18. Talamini, G.; Pezzin, G. Makromol. chem. 1960, 42, 2638.
19. Chytry, V.; Obereigner, B.; Lim, D. Eur. Polym. J. 1969, 5(4), 379-388.
20. Mayer, Z. Macromol. Sci. 1974, 10(2), 263-292.
21. Mayer, Z.; Obereigner, B.; Lim, D. J. Polym. Sci. 1971, 33, 289-305.
22. Minsker, K. S.; Berlin, Al. Al.; Lisitsky, V. V.; Kolesov, S. V.; Korneva, R. S. Dokl. Akad. Nauk SSSR 1977, 232(1), 93-96.
23. Minsker, K. S.; Lisitsky, V. V.; Zaikov, G. E. Vysokomol. Soedin. 1981, 23A(3), 498-512.
24. Minsker, K. S.; Kolesov, S. V.; Yanborisov, V. M.; Berlin, Al. Al.; Zaikov, G. E. Vysokomol. Soedin. 1984, 26A(5), 883-899.
25. Shemyakin, M. M.; Shchukina, A. A. Usp. Khim. 1997, 26(5), 528-555.
26. Minsker, K. S.; Berlin, Al. Al.; Lisitsky, V. V.; Kolesov, S. V. Vysokomol. Soedin. 1977, 19A(1), 32-34.
27. Yanborisov, V. M.; Kolesov, S. V.; Berlin, Al. Al.; Minsker, K. S. Dokl. Akad. Nauk SSSR 1986, 291(6), 14251427.
28. Minsker, K. S.; Berlin, Al. Al.; Lisitsky, V. V. Vysokomol. Soedin. 1976, 18B(1), 54-58.
29. Minsker, K. S.; Mukmeneva, N. A.; Berlin, Al. Al.;Kazachenko, D. V.; Yanberdina, M. Ya.; Agadzhanyan, S. N.; Kirpichnikov, P. A. Dokl. Akad. Nauk SSSR 1976, 226(5), 1088-1091.
30. Mukmeneva, N. A.; Agadzhanyan, S. N.; Kirpichnikov, P. A.; Minsker, K. S. Dokl. Akad. Nauk SSSR 1977, 233(3), 375-377.
31. Minsker, K. S.; Mukmeneva, N. A.; Kolesov, S. V.; Agadzhanyan, S. N.; Petrov, V. V.; Kirpichnikov, P. A. Dokl. Akad. Nauk SSSR 1979, 244(5), 1134-1137.
32. Mukmeneva, N. A.; Minsker, K. S.; Kolesov, S. V.; Kirpichnikov, P. A. Dokl. Akad. Nauk SSSR 1984, 274(6), 1393-1396.
33. Mukmeneva, N. A.; Cherezova, E. N.; Yamalieva, L. N.; Kolesov, S. V.; Minsker, K. S.; Kirpichnikov, P. A. Izv. Akad. Nauk SSSR, Ser. Khim. 1985, 5, 1106-1108.
34. Minsker, K. S.; Kolesov, S. V.; Petrov, V. V. Dokl. Akad. Nauk SSSR 1980, 252(3), 627-630.
35. Minsker, K. S.; Kolesov, S. V.; Petrov, V. V.; Berlin, Al. Al. Vysokomol. Soedin. 1982, 24A(4), 793-800.
36. Ivanova, S. R.; Zaripova, A. G.; Minsker, K. S. Vysokomol. Soedin. 1978, 20(4), 936-941.
37. Minsker, K. S.; Kolesov, S. V.; Petrov, V. V. Dokl. Akad. Nauk SSSR 1982, 268(3), 6332-635.
38. Kolesov, S. V.; Petrov, V. V.; Yanborisov, V. M.; Minsker, K. S. Vysokomol. Soedin. 1984, 26A(2), 303-308.
39. Minsker, K. S.; Kolesov, S. V.; Ivanova, S. R. Vysokomol. Soedin. 1982, 24A(11), 2329-2333.
40. Kolesov, S. V.; Minsker, K. S. Vysokomol. Soedin. 1983, 25A(8), 1587-1594.
41. Minsker, K. S. J. Polym. Plast. Technol. and Engineering 1997, 36(4), 513-525.
42. Minsker, K. S.; Kolesov, S. V.; Zaikov, G. E. J. Vinyl Technol. 1980, 2(3), 141-151.
43. Minsker, K. S.; Kolesov, S. V.; Zaikov, G. E. Vysokomol. Soedin. 1987, 23A(3), 498-512.
44. Minsker, K. S.; Kolesov, S. V.; Yanborisov, V. M.; Adler, M. E.; Zaikov, G. E. Dokl. Akad. Nauk SSSR 1983, 268(6), 1415-1419.
45. Kolesov, S. V.; Minsker, K. S.; Yanborisov, V. M.; Zaikov, G. E.; Du-Jong, K.; Akhmetkhanov, R. M. Plast. Massy 1983, 12, 39-41.
46. Kolesov, S. V.; Steklova, A. M.; Zaikov, G. E.; Minsker, K. S. Vysokomol. Soedin. 1986, 28A(9), 1885-1890.
47. Minsker, K. S.; Fedoseeva, G. T.; Strelkova, L. D.; Petrov, V. V.; Kolesov, S. V. Vysokomol. Soedin. 1983, 25B(3), 165-167.
48. Minsker, K. S.; Abdullin, M. I.; Manushin, V. I.; Malyshev, L. N.; Arzhakov, S. A. Dokl. Akad. Nauk SSSR 1978, 242(2), 366-368.
49. Minsker, K. S. Polymer Yearbook; Pethrick, A., Ed.; Acad. Publ.: Harwood, 1994; p 229-241.
50. Minsker, K. S.; Kulish, E. I.; Zaikov, G. E. Vysokomol. Soedin. 1993, 35B(6), 316-317.
51. Palm, V. A. Osnovy kolichestvennoi teorii organicheskikh reaktsii; Khimiya: Leningrad, 1977, p 114.
52. Kolesov, S. V.; Kulish, E. I.; Minsker, K. S. Vysokomol. Soedin. 1994, 36B(8), 1383-1384.
53. Kolesov, S. V.; Kulish, E. I.; Zaikov, G. E.; Minsker, K. S. Russian Polym. News 1997, 2(4), 6-9.
54. Kulish, E. I.; Kolesov, S. V.; Minsker, K. S. Bashkirskii Khimicheskii Zhurnal 1998, 56(2), 35-37.
55. Kulish, E. I.; Kolesov, S. V.; Minsker, K. S.; Zaikov, G. E. Vysokomol. Soedin. 1998, 40A(8), 1309-1313.
56. Kolesov, S. V.; Kulish, E. I.; Zaikov, G. E.; Minsker, K. S. J. Appl. Polym. Sci. 1999, 73(1), 85-89.
57. Kulish, E. I.; Kolesov, S. V.; Minsker, K. S.; Zaikov, G. E. Chem. Phys. Report 1999, 18(4), 705-711.
58. Kulish, E. I.; Kolesov, S. V.; Akhmetkhanov, R. M.; Minsker, K. S. Vysokomol. Soedin. 1993, 35B(4), 205-208.
59. Kulish, E. I.; Kolesov, S. V.; Minsker, K. S.; Zaikov, G. E. Int. J. Polym. Mater. 1994, 24(1-4), 123-129.
60. Martemyanov, V. S.; Abdullin, M. I.; Orlova, T. E.; Minsker, K. S. Neftekhimiya 1981, 21(1), 123-129.
61. Minsker, K. A.; Abdullin, M. I.; Zueva, N. P.; Martemyanov, V. S.; Teplov, B. F. Plast. Massy 1981, 9, 33-34.
62. Minsker, K. S.; Abdullin, M. I. Dokl. Akad. Nauk SSSR 1982, 263(1), 140-143.
63. Minsker, K. S.; Zaikov, G. E. Chemistry of chlorine-containing polymers: synthesis, degradation, stabilization; NOVA Science: Huntington, 1999; p 295.
© |K S. Minsker|- (June 14, 1929, Kiev - May 25, 2003, Ufa), academician of Republic Bashkortostan Academy of Sciences (1991), Doctor of Chemistry (1967), Professor (1969), Bashkirian State University, Ufa, Russia, M.I Artsis - researcher, PhD (chemistry), N. M. Emanuel Institute of Biochemical Physics, Moscow, Russia, G.E. Zaikov - Doctor of Chemistry, Professor of Plastics Technology Department, Kazan National Research Technological University, Kazan, Russia, ov_stoyanov@mail.ru.
© К С. Минскер - (14 июня 1929, Киев — 25 мая 2003, Уфа) — академик АН РБ (1991), доктор химических наук (1967), профессор (1969), Башкирский государственный университет, Уфа, Россия, М. И. Арцис - кандидат химических наук, сотрудник Института биофизической химии им. Н.М. Эмануэля РАН, Москва, Россия, Г. Е. Заиков - доктор химических наук, профессор кафедры технологии пластических масс Казанского национального исследовательского технологического университета, Казань, Россия, ov_stoyanov@mail.ru.
