CC BY
16
УДК 678.74/677.14/677.862.2
M. V. Bazunova, A. I. Islamgulova, V. P. Zaharov, G. M. Rafikova, S. V. Kolesov
REGULARITY OF OXIDATION OF WASTE FIBROUS MATERIALS ON POLYPROPYLENE
The keywords: surface oxidation, waste of polypropylene, chemical modification.
It seems reasonable to study the simple and technologically advanced methods of surface oxidation of the waste fibrous and film materials of polypropylene (PP) as a method of creating of the secondary polymeric materials. Comparing the results of oxidative modification (oxidation by atmospheric oxygen in an aqueous medium or in the gas phase, ozonation) of waste fibrous materials of PP shows that the most effective method of pre-oxidation are ozonation. These modified samples has better adhesion to hydrophilic surfaces and sorption properties than unmodified ones. So we can suggest that there is possibility of their usage as multifunctional additives in various composite materials, polymerbitumen compositions, etc.
Ключевые слова: поверхностное окисление, отходы полипропилена, химическая модификация.
Представляется целесообразным изучение простых и технологически доступных методов поверхностного окисления отходов волокнистых и пленочных материалов из полипропилена (ПП) в качестве способов создания вторичных полимерных материалов. Из сравнения результатов окислительной модификации (окисление кислородом воздуха в водной среде или в газовой фазе, озонирование) поверхности отходов волокнистых материалов ПП видно, что наиболее эффективным методом предварительного окисления оказалось озонирование. Полученные модифицированные образцы имеет лучшую адгезию к гидрофильным поверхностям и сорбционные свойства, чем немодифицированными. Таким образом, мы можем предположить, что существует возможность их использования в качестве многофункциональных присадок в различных композиционных материалов, полимерно-битумных композиций и т.д.
Introduction
The purpose of chemical modification of polymers is to change chemical structure by introducing the functional groups with different chemical nature into the macromolecules. In some cases, it is necessary to improve the characteristics of a polymer surface by chemical modification while retaining the properties of materials in the volume and shape of the polymer material (fiber, film, bulk product). It is necessary, for example, when changing the wettability, sorption, adhesion and electrical characteristics of materials in the desired direction [1].
An effective method of modifying of the surface of polymeric material is oxidation. It is known that at temperatures below 90 °C the reaction takes place mainly on the surface and is not accompanied by oxidative degradation of the polymer in the bulk. Obvious, that it is impractical to create complex chemical surface modification technology simultaneously saving money on technical costs of creating the necessary forms of materials. Oxidation is also a convenient method of pre-activation of the polymer surface, which leads to the appearance of oxygen-containing functional groups capable of being active centers during the further chemical modification. For example, it is known that the polyole-fins oxidation is accompanied by the formation of hydroperoxide (HP) groups (fig. 1). Further thermal decomposition of the HP - groups leads to the appearance of free radicals on the surface and initiate growth of the grafted chains.
■/vwwCH2—CH—CH2w
O„
OOH
I
(O/Oj)
■™<-CH9—C—CH,™
Therefore, it seems reasonable to study the simple and technologically advanced methods of surface oxidation of the waste fibrous and film materials of polypropylene (PP) and polyethylene (PE) as a method of creating of the secondary polymeric materials.
Experimental part
Previously cleaned and dried waste PP-fibers (original PP-fiber GOST 26574-85) have been used as an object of research in this paper.
Concentration of HP-groups on the surface of oxidized samples is defined by modified iodometric method [2] with the photo-electric calorimeter K®K-2Mn.
The limited wetting angle is defined by the standard procedure [3].
The adsorption capacity (A) of the samples under static conditions for condensed water vapor, determined by method of complete saturation of the sorbent by adsorbate vapor in standard conditions at20°C [4] and calculated by the formula: A=m/(M^d), wherein m -mass of the adsorbed water, g; M - mass of the dried sample, g; d - density of the adsorbate, g/cm3.
PP - fibersand their wastes oxidation procedure (in an aqueous medium)
1.5 g of the particulate polymer material charged into a round bottom flask equipped with reflux condenser, thermometer, mechanical stirrer and a bubbler for air-supplying.120 ml of H2O2 solution and the necessary amount of FeSO4 • 7 H2O was added, then heated under stirring to 70-900C and supplied by air from the compressor during 3-20 hrs. After the process gone, hydrogen peroxide solution was drained, samplethoroughly washed by water (first tap, then distilled) and dried in air at room temperature.
Fig. 1 - Oxidation of carbon-chain polymers (R = -CH3, -H)
R
R
PP - fibers and their wastes solid-phase oxidation procedure
A weighed sample of the particulated polymer material placed into the thermostated reactor (a glass tube with diameter of 15 mm and a length of 150 mm).The reactor was fed by heated air from the compressor, at a rate of 7.2 l/h. Oxidation was conducted at 85 °C for 410 hrs.
PP - fiber and their wastes ozonation procedure
A) 1.5 g of the particulated polymer material charged into the thermostated reactor (a glass tube with diameter of 15 mm and a length of 150 mm). For 60 min ozone-oxygen mixture, produced by an ozonizer (design is described in [5]),with flow rate of 30 l/h at ambient temperature was passed through the sample. Ozonator's performance by ozone is 12.5 mmol/h. After the ozonation sample is purged with an inert gas to remove the residual ozone and analyzed for HP-groups content.
B) 1.5 g of the particulate polymer material charged into a round bottom flask equipped with thermometer, mechanical stirrer and a bubbler for air supplying. 120 ml of distilled CCl4 is added, the ozone-oxygen mixture is passed through the reaction mixturefor 60 minat a flow rate of 30 l/h at room temperature. After the ozonation sample is purged with an inert gas to remove the residual ozone, solvent is merged. The sample was washed with chloroform and distilled water, dried in air at room temperature and analyzed for HP-groups content.
[HP]
0 1 ? 3 4 5 fi 7 8 9 10 11 1? 13
Fig. 2 - The dependence of the HP-groups concentration (mol/sm2) on the surface of the waste PP- fiber from the oxidation time (temperature 85 0C)
Results and Discussion
The literature describes the oxidation of the PP-fibers in the medium of toluene by air at a temperature of 70-120 °C in the presence of radical initiators and without them. In practice, these processes lead to the pollution of atmosphere by organic solvents vapor and require the inclusion of the solvent regeneration step in the production scheme. Previously, [6], we describe the method of oxidation of the waste PP-fibers by air oxygen in an aqueous medium in the presence of H2O2 / Fe2+ initiating system, and found that when carrying out the oxidation process at 85 0C for 4 hours in the presence of 2.7 mol /l H2O2the content of HP-groups in the oxidized material is 1,5 • 10-5 mol/sm2 (Table 1).
Uninitiated solid-phase surface oxidation of PP-fiber with atmospheric oxygen at a temperature of 85 0Cwas studied for the first time. Found that the content of HP-groups on the surface of oxidized samples, achieved during the process for 4 hours, is 3,42 • 10-5mol/sm2 (Table 1).
The most effective method of the oxidation is ozona-tion that even at room temperature during the process for 1 hour, gives the same results as in the previous cases: accumulation of HP-groups on the surface of the studied samples (Table 1).
The oxidation conditions and properties of the obtained samples are shown in Table 1.
Kinetic curves of HP-groups accumulation during solid-surface oxidation of waste PP-fiber are shown in Figures 2-3.
[HP]
0 1934 5 6 7 8 9 10 1119 13
Fig. 3 - Dependence of the HP-groups concentration (mol/sm2) on the surface of PP-fibers (GOST 26574 -85) from the oxidation time (temperature 85 0C)
Table 1 - Terms of oxidation of the waste polypropylene and their properties
Object Oxidationterms HP-groups concentration in the material, 10-5 mol/sm2 Limited wetting angle А, cm3/g
Medium Oxidant Initiator Time, hour Т, 0С
PP-fiber (GOST6574- 85) 0,45 840 1,10
Waste PP-fiber - - - 1,5 810 1,30
Waste PP-fiber - air - 4 85 3,4 690 1,38
Waste PP-fiber Н2О air 2,7 МН202, 0,37 mg/m lFeS04*7H20 4 85 3,2 710 1,39
As follows from the data presented in Figure 2, the storage character of HP groups on the surface of the original PP-fiber having no exploitation, and accordingly, the period of aging in vivo and on the surface of the waste PP-fibers, subjected to aging in vivo, generally, identical. Only the initial part of the kinetic curve of recently produced PP-fibers have the minimum. It can be caused by an intensive breakage of HP-groups emerged in the material during its processing, which dominates over the accumulation of HP-groups during thermal oxidation. It must be concluded that the background of polyolefin material has virtually no effect on the course of its oxidative modification.
Dyeability by azo-dyes and wettability of the modified samples are studied to confirm the changing of their surface properties. Dyeability of all oxidized samples obtained from waste PP-fiber by azo-dyes is significantly better than dyeability of unmodified materials. Data on reducing of the limited wetting angle of the modified samples indicates increasing of hydrophilic surface.
Also, sorption activity of the modified and unmodified samples measured to evaluate the properties of the polymeric materials obtained by the oxidative modification (Table 1). As can be seen from Table 1, the materials subjected to the oxidative modification (aging or oxidation by atmospheric oxygen in an aqueous medium) have greater sorption capacity for water vapor than an unmodified ones. This is probably due, first, to the accumulation of oxygen-containing groups and, respectively, with increasing of hydrophilic properties of the surface, and secondly, with the change in the form of supermolecular features on the surface of the polymer
macromolecules, leading to the softening of the structure.
Conclusions
Thus, it seems reasonable to study the simple and technologically advanced methods of surface oxidation of the waste fibrous and film materials of polypropylene (PP) as a method of creating of the secondary polymeric materials.Comparing the results of oxidative modification (oxidation by atmospheric oxygen in an aqueous medium or in the gas phase, ozonation) of waste fibrous materials of PP shows that the most effective method of pre-oxidation are ozonation. These modified samples has better adhesion to hydrophilic surfaces and sorption properties than unmodified ones.So we can suggest that there is possibility of their usage as multifunctional additives in various composite materials, polymer-bitumen compositions, etc.
Literature
1. V.I. Povstugar, V.I. Kondolopov, S.S. Mikhailov. The structure and surface properties of polymeric materials. Moscow: Khimiya, 1988, 190 p.
2. V.L. Antonovskii, M.M. Buzlanova. Analytical chemistry organic peroxide compounds. Moscow: Khimiya, 1978
3. I.N. Putilova. Guide to practical work on colloidal chemistry. Moscow: VisshayaShkola, 1981, 292 p.
4. N.V. Keltsev. Fundamentals of adsorption technology. Moscow: Khimiya, 1984, 595 p.
5. V.G. Vendillo, Y.M. Emelyanov, Y. Filippov. The laboratory setup for ozone, ZavodskayaLaboratoriya, 11, p. 1401, (1950)
6. M.V. Bazunova, S.V. Kolesov, A.V. Korsakov. Journal of Applied Chemistry.79(5), Pp. 865-867 (2006)
© M. V. Bazunova, Bashkir State University, Ph.D., Associate Professor, Department of Macromolecular Compounds and General Chemical Technology, mbazunova@mail.ru; A. I. Islamgulova, Branch of PAO ANK "Bashneft", "Bashneft UNPZ" assistant of chemical analysis OTC GAP, nesteshen@mail.ru; G. M. Rafikova, Bashkir State University, student of 3 year, the Department of High-Molecular Compounds and General Chemical Technology, rafikovagaliya@mail.ru; V. P. Zaharov, Bashkir State University, Professor, Department of Macromolecular Compounds and General Chemical Technology, zaharovvp@bashedu.ru; S. V. Kolesov, Bashkir State University, Professor, Department of Macromolecular Compounds and General Chemical Technology, kole-sovservic@rambler.ru.
© М. В. Базунова, Башкирский государственный университет, к.х.н., доцент кафедры высокомолекулярных соединений и общей химической технологии, mbazunova@mail.ru; А. И. Исламгулова, ФилиалПАОАНК «Башнефть» «БашнефтьУНПЗ», лаборантхимическогоанализаОТКГАП, nesteshen@mail.ru; Г. М. Рафикова, Башкирский государственный университет, студент 3 курса, rafikovagaliya@mail.ru; В. П. Захаров, Башкирский государственный университет, д.х.н., профессор кафедры высокомолекулярных соединений и общей химической технологии, zaharovvp@bashedu.ru; С. В. Колесов, Башкирский государственный университет, д.х.н., профессор кафедры высокомолекулярных соединений и общей химической технологии, kolesovservic@rambler.ru.
