Aging of Polymers and Polymeric Materials Caused by EnvironmentalImpact. Part 1 = Старение полимеров и полимерных материалов под действием окружающей среды. Часть 1


The Ministry of Science and Higher Education of the Russian Federation Kazan National Research Technological University










            AGING OF POLYMERS AND POLYMERIC MATERIALS CAUSED BY ENVIRONMENTAL IMPACT


            Part 1



        Tutorial











Kazan
KNRTU Press
2018

         UDK 541.64:66 (076.5)



Published by the decision of the Editorial Review Board of the Kazan National Research Technological University

Reviewers:
Professor, PhD in Chemistry A. Burilov
Associate Professor, PhD in Chemistry S. Egorova






        Authors: E. Cherezova, G. Nugumanova, G. Timirbaeva, Yu. Karaseva
        Aging of Polymers and Polymeric Materials Caused by Environmental Impact : tutorial : In 2 parts. Part 1 / E. Cherezova [et al.]; The Ministry of Science and Higher Education of the Russian Federation, Kazan National Research Technological University. - Kazan : KNRTU Press, 2018. - 104 p.


         ISBN 978-5-7882-2588-3
         ISBN 978-5-7882-2589-0 (p. 1)

       The main data on issues of polymer aging caused by various factors are summarized. The characteristics of macromolecular reactions in addition to thermal, thermal-oxidative degradation, degradation caused by the aggressive environment, high-energy radiation, etc. are considered.
       The Study Guide is intended for students studying Master Degree Program 18.04.01 «Chemical Engineering» related to such study fields as Chemical Engineering of Polymers and Polymeric Materials as well as Chemical and Physical Modification of High Molecular Compounds, Chemical Engineering of Synthetic Rubber, Chemistry and Physics of High Molecular Compounds, Catalytic Engineering in Petroleum Chemistry and Polymer Chemistry.
       The Study Guide is prepared by Technology of Synthetic Rubber Department.

UDK 541.64:66 (076.5)


ISBN 978-5-7882-2589-0 (p. 1)
ISBN 978-5-7882-2588-3

© Cherezova E., Nugumanova G., Timirbaeva G., Karaseva Yu., 2018

© Kazan National Research Technological University, 2018

    INTRODUCTION


                                     Polymers are a vitally important creation of the mankind. Scientists are capable of prolonging their youth and their working life.

       Polymer products change their properties during their processing or exploitation. These changes are called aging. In the language of science, aging of polymers is a set of chemical and physical transformations occurring during treatment, storage, and application of polymers and leading to the loss of essential properties (physical, mechanical, thermophysical, electrical and other properties). The process of polymer aging is accompanied by the damage of structure and architecture of macromolecules, that is, the change of the number and arrangement of monomer units in their chain. In a more comprehensive sense, aging can be called any change of molecular, supramolecular and phase structure of polymers and polymeric materials.
       Actual polymeric material is a complex system including various specific additives (plasticizers, inhibitors, fillers and others) and admixtures (traces of catalysts and initiators, metal deactivators and others), alongside with the main component, a macromolecular compound. That is why the study of aging requires the research of a wide range of issues and chemical transformations (radical, ionic and molecular ones) in multi-component systems. The competing processes of destruction and cross-linking (structuring) of macromolecules play a key role in these transformations.
       Destruction is a process in which the polymer breaks down with the cleaving of bonds in macromolecules and the formation of macromolecules’ fragments. In the case of structuring, after the cleaving of bonds in macromolecules, the formation of new macromolecules from the formed macromolecules’ fragments occurs.
       The traditional problem in the field of stabilizing the properties of polymers is to preserve the operational properties as long as possible, and, therefore, to extend the service life of polymer products. Strictly speaking, stabilization of polymers means a complex of methods for suppressing or slowing down the processes responsible for aging.
       The range of technical requirements for stability and, consequently, stabilization of polymers is wide. For example, polymer threads used in surgery serve only a certain period, after which they must spontaneously break down. On the contrary, polymeric anticorrosive coatings of main oil

3

and gas pipelines should fulfill their functions as long as possible. All this determines numerous tasks to be performed when stabilizing polymer products.
       In the first part of the study guide, the main processes that occur in polymers under the influence of various physical and chemical factors are considered. In the second part, methods that allow to slow down the aging process of polymers are covered.
       We hope that the range of issues discussed in the book will be of interest not only to students but also to post-graduate students.
       The authors express their gratitude to S. Sh. Saigitbatalova, K. A. Medvedeva, the staff members of Technology of Synthetic Rubber Department, for the technical aid.

4

    PREFACE


    AGING AND STABILIZATION OF POLYMERS. BACKGROUND

                                  There are no good or bad things, it all depends on circumstances
Niccold Machiavelli

       The issue of polymer aging makes up a large section of polymer material science, the science of creating polymeric materials, preserving and controlling their properties.
       Professor Alexander Samojlovich Kuzminsky, who worked at the Research Institute of Rubber-Processing Industry (now The Research Institute of Elastomeric Materials and Products, Moscow), was the first in the world who realized the importance of this field of science for prolonging the lifetime of polymeric products and predicting the period of their reliable exploitation. He published the first studies in this field in the forties. Unfortunately, the world scientific community could not become familiar with the works of A. S. Kuzminsky, which were published mainly as research reports of the Institute.
       For this reason, Professor Norman Grassie, University of Glasgow, Scotland, UK, is considered to be the originator of this field of polymer science, he started to publish his works on aging and stabilization of polymers ten years later after the publication of the first articles of A. S. Kuzminsky. Later Professor Gerald Scott from University of Birmingham started to study the processes of polymer aging. N. Grassie founded an international journal called Polymer Degradation and Stability (Pergamon Press, Oxford, UK), emphasizing by this the importance of the polymer aging issue.
       At the end of the fifties of the 20th century, the study of aging and stabilization of polymers in our country was led by Professor Moisey Borisovich Neyman (The Institute of Chemical Physics of Academy of Science of the USSR, Moscow). He was asked to deal with these issues by Nikolay Nilolaevich Semyonov, Director of the Institute of Chemical Physics, Noble prize winner, a member of the Academy of Sciences, N.N. Semyonov deserves credit for the creation of the chain chemical reaction theory. M.B. Neyman applied quantitative parameters to the research on aging of polymers using chemical kinetics.


5

       The intensive research on the issues of thermal destruction (pyrolysis), oxidation, ozonizing, hydrolysis, radiation damage, photo-, biomechanical destruction of polymers and on the synthesis of stabilizers for polymers was conducted under the guidance of Nikolay Markovich Emmanuel¹, а member of the Academy of Sciences of the USSR, during seventies-eighties of the 20th century. The work of studying the flammability decrease of polymeric materials was started at the end of the seventies of the 20th century.
       The general theory (kinetics and mechanism) of polymer aging and stabilization was developed owing to this research. The possibility of using destruction processes as a method of modification of polymeric products’ properties was shown.
       The Russian scientists Anatoly Leonidovich Buchachenko, Gennady Efremovich Zaikov, Evgeny Timofeevich Denisov, Viktor Yakovlevich Shlyapintokh, Yuriy Aleksandrovich Shlyapnikov, Oleg Nikiforovich Karpukhin and a number of others (the Institute of Chemical Physics of the Russian Academy of Sciences) played a key role in the development of the theory of radical reactions in solutions and solid polymers during oxidation, photodegradation. Their research has contributed greatly to the creation of the scientific basis of polymer aging and stabilization, prediction of the period of reliable exploitation and storage of polymeric products in different climatic zones of the country.
       The extensive fundamental and applied studies in the field of aging and stabilization of halogen-containing polymers were conducted under the guidance of Karl Samoylovich Minsker (Bashkir State University, Ufa). The studies on aging and stabilization of heterochain polymers and elastomers conducted by Berta Mikhailovna Kovarskaya (The Research Institute of Polymeric Materials, Moscow), Konstantin Borisovich Piotrovskiy (The All-Soviet Union Research Institute of Synthetic Rubber, Leningrad, now The Research Institute of Synthetic Rubber, St. Petersburg), Petr Anatolyevich Kirpichnikov (Kazan Chemical Technological Institute, now Kazan National Research Technological University, Kazan) and many others are of considerable practical importance.
       The activity related to creating domestic stabilizers for polymers started in the seventies of the 20th century. A number of stabilizers were implemented into practice in Moscow Oil Refinery in Kapotnya (V. V. Ershov), in the Research Institute of Polymers in Tambov

¹ Bibliographical notes on scientists mentioned in the text are given in Appendix.

6

(E. G. Rozantsev), at the plants of fine organic synthesis in Sterlitamak (G. A. Nikiforov, A. G. Liakumovich) and in Ivanovo-Frankovsk (Ukraine, A. A. Volodkin) and others.
      In our country, approximately 700 scientists worked in 100 research centers solving problems of aging and stabilization of polymers during the 1970s and 1980s.
      To date, the number of researchers in our country continuing studies in this area has significantly decreased. However, we cannot ignore the groups of actively working scientists under the guidance of Academician Yury Borisovich Monakov (Bashkir State University, the Institute of Organic Chemistry of the Bashkir Branch of the Russian Academy of Sciences, Ufa), Academician Aleksandr Aleksandrovich Berlin (the Institute of Chemical Physics, Moscow), Corresponding Member of the Russian Academy of Sciences Peter Anatolyevich Kirpichnikov (Kazan National Research Technological University, Kazan), Academician of the Russian Academy of Sciences Ivan Aleksandrovich Novakov (Volgograd State Technical University, Volgograd), Corresponding Member of the Russian Academy of Sciences Alexander Vasilyevich Kuchin (the Institute of Chemistry of the Komi Scientific Center of the Ural Branch of the Russian Academy of Sciences). About 20-30 famous scientists in the country periodically refer to this problem while solving other problems.
      In general, the world science strengthens its positions in this field, and Polymer Degradation and Stability journal has increased its capacity three-fold. Every two years, the MoDeSt Conference (Modification, Degradation, Stabilization) is held, the international conference The Time of Polymers and Composites organized by the University of Naples Federico II has became a traditional one, and there are some other examples.
      Now the main attention is shifted to the aging of polymers in conditions of the polluted atmosphere (oxides of nitrogen, sulfur, etc.), biodegradation of polymers, prediction of the operation time of polymeric products in a body (prostheses, retention suture, adhesives, endovascular therapy with hydrogels, etc.). Studies on reducing the flammability of polymer materials are successfully developed.
      What have we already received and what can we expect from the solution of the problem of aging and stabilization of polymers?
      G. E. Zaikov, Professor of N. M. Emanuel Institute of Biochemical Physics, an enthusiast and popularizer of the achievements of the Russian science, answers these questions in the form of the following postulates:
      1. Extension of reliable operating time of polymers.

7

       The increase of service life, for example, twice, is equivalent to the twofold increase in the manufacture of these polymer products. This is an important practical task at large-scale production.
       2. Forecasting the lifetime of polymer products.
       Underestimation of the service life will lead to the withdrawal of good products, and the overestimation of the operating life will lead to accidents and, possibly, to lethal outcomes.
       3.       The use of destruction processes as methods of polymer modification (creation of new polymeric materials with improved performance properties).
       4.       Secondary use of end-of-life polymer products. Numerous natural resources can be saved due to the recycling of products from polymers.
       5.       Creation of polymers with a strictly defined lifetime. Polymers should be used as long as they are needed, but disappear (decompose) immediately after they become unnecessary.

    References

1. Zaikov, G. E. Starenie i stabilizatsiya polimerov. Komu i zachem eto nado? [Aging and Stabilization of Polymers. Who needs it and Why?]. Istoricheskiy aspekt himicheskaya fizika i mezoskopiya [Historical Issues of Chemical Physics and mesoscopy]. 2005. vol. 10, no.1, pp 118-122. (in Russian).
2. Fedtke, M. Himicheskie reaktsii polimerov. perevod s nem [Chemical Reactions of Polymers]. Moscow, Khimiya Publ., 1990. 152p (in Russian).
3. Volkov, V. A. Vyidayuschiesya himiki mira [Outstanding Chemists of the World]. Moscow, Vyisshaya shkola Publ., 1991. 656 p. (in Russian).
4. Zaikov, G. E. Starenie, stabilizatsiya i gorenie polimerov i kompozitov. O prioritetah v issledovaniyah [Aging, Stabilization and Combustion of Polymers]. Izvestiya vyisshih uchebnyih zavedeniy. Seriya: Himiya i himicheskaya tehnologiya [Proceedings of Higher Educational Institutions. Chemistry and Chemical Technology]. 2010, vol. 53. no.12. pp 143-145. (in Russian).
5. Zaikov, G. E. Nikolay Markovich Emanuel. K 95-letiyu so dnya rozhdeniya [Nikolay Markovich Emanuel, to his 95 Years’ Birthday]. Izvesti vyisshih uchebnyih zavedeniy. Seriya: Himiya i himicheskaya tehnologiya [Proceedings of Higher Educational Institutions. Chemistry and Chemical Technology]. 2010, vol.53. no.11, pp126-130. (in Russian).

8

6. Zaikov, G. E. Gorenie, starenie i stabilizatsiya polimerov, polimernyih smesey i kompozitov [Aging, Stabilization and Combustion of Polymers, Polymer Mixtures and Composites]. Izvesti vyisshih uchebnyih zavedeniy. Seriya: Himiya i himicheskaya tehnologiya [Proceedings of Higher Educational Institutions. Chemistry and Chemical Technology]. 2011, vol. 54, no.1, pp 110-112. (in Russian).
7. Zaikov, G. E. Gorenie, starenie i stabilizatsiya polimerov, polimernyih smesey i kompozitov. Obschie soobrazheniya [Aging, Stabilization and Combustion of Polymers, Polymer Mixtures and Composites]. General Considerations]. Plasticheskie massyi [Plastics]. 2010, no. 8, pp 62-64. (in Russian).
8. Zaikov, G. E. Gorenie, starenie i stabilizatsiya polimerov, polimernyih smesey i kompozitov. Chast 1. Obschie soobrazheniya [Combustion, Aging and Stabilization of Polymers, Polymer Mixtures and Composites. Part 1. General Considerations]. Kauchuk i rezina [Rubber and Vulcanized Rubber]. 2011, no. 2, pp 36-38. (in Russian).
9. Zaikov, G. E. Gorenie, starenie i stabilizatsiya polimerov, polimernyih smesey i kompozitov. Chast 2. O prioritetah v issledovaniyah [Combustion, Aging and Stabilization of Polymers, Polymer Mixtures and Composites. Part 2. About Research Priorities]. Kauchuk i rezina [Rubber and Vulcanized Rubber]. 2011, no. 2, pp 38-40. (in Russian).
10.  Zaikov, G. E. Starenie i stabilizatsiya polimerov (komu i zachem eto nado? Istoricheskiy aspekt) [Aging and Stabilization of Polymers. Who needs it and Why? Historical Issues]. Kauchuk i rezina [Rubber and Vulcanized Rubber]. 2008, no. 4, pp 10-13. (in Russian).
11.  Stoyanov, O. V. Professor Gennadiy Efremovich Zaikov. Shestdesyat let v nauke [Professor Gennadiy Efremovich Zaikov. Sixty Years in Science] Vestnik Kazanskogo tehnologicheskogo universiteta [Herald of Kazan Technological University]. 2014, vol. 17, no. 24, pp 9-12. (in Russian).

9

1. MACROMOLECULAR REACTIONS



    1.1. Particular Characteristics of Chemical Transformations in Polymer Chains


      Chemical processes change the structure and physical properties of polymers. Whereas, their structural and physical properties strongly affect the course and speed of chemical transformations of the polymer.
      There are two historical stages in the development of ideas about the reactivity of functional groups of macromolecules. At the first stage, which began in the 30s of the twentieth century, the study of the chemical reactions of polymers developed as part of organic chemistry. At the same time, the approach to macromolecules as typical organic reagents was carried out. For the primary evaluation of the chemical reactions of polymers, the «principle of equal reactivity» (Flory-principle) was formulated. According to this principle, the reactivity of a functional group does not depend on the fact whether it is attached to a polymer chain or it is in a small molecule.
      There are many experimental examples, from which it follows that the kinetic parameters of various chemical reactions for polymers and low molecular weight analogs are practically the same (Table 1.1).
      However, the wider circle of polymeric objects became, the more information was accumulated that the reactivity of functional groups of macromolecules differs from that of low-molecular analogs.
      For example, it was observed that the ensemble of even one-type units of the macromolecule can behave not as the sum of small molecules of a similar structure with respect to another low-molecular, and certainly not to a macromolecular reagent. For example, if we compare the bonddissociation energy of a hydrogen atom in a series of saturated hydrocarbons in comparative units, it will be 11 for heptane, 3 for polyethylene, 2 for polyisobutylene.
      Accumulated facts led to the conclusion that the development of the theory of the reactivity of macromolecular objects requires a special approach.



10