Structural and chemical transformations on the surface of films of polyethylene and polyvinyl chloride by reaction with halides of phosphorus, vanadium, titanium and silicon

A. K. Bulkina
Language of the thesis
Thesis name in original language
Структурно-химические превращения на поверхности пленок полиэтилена и поливинилхлорида при взаимодействии с галогенидами фосфора, ванадия, титана и кремния
Abstract & Cover

Research relevance . The problem of regulating the functional properties of polymeric materials (thermal, electrophysical, adhesive, barrier, etc.) is one of the most important in obtaining products for various purposes. One of the promising directions for solving this problem is the modification of the surface of solid polymeric materials, which does not require changes in the existing technology for the production and processing of organic polymers. These methods include the method of molecular layering (ML) [1], based on the implementation of chemical reactions between reagents supplied from outside and functional groups on the surface of a solid substrate under conditions of maximum distance from equilibrium.

It has been established that the introduction of element-containing structures into the surface layer of phenol-formaldehyde, polyamide, epoxy and other polymeric materials by the MN method makes it possible to influence their thermal-oxidative properties and flammability, change the electrical characteristics of polyethylene and polytetrafluoroethylene [2]. It is shown that as a result of the interaction of the surface reactive centers of polymers (-OH, =NH, -CH2-, etc.) with volatile reagents (PCb and VOCb), chemical grafting of modifying structures occurs. However, given the complexity of the "polymer-modifier" system, to understand the nature of the observed changes in functional properties, a deeper study of the structure of the surface layer of the initial modified materials, their morphology, and the distribution of chemically active centers in them is required.

Polyethylene, polyvinyl chloride and products made from them are widely used both in engineering and in everyday life. Depending on the intended purpose, it is necessary to enhance their various performance characteristics. At the same time, in a number of cases, certain physical effects (UV, laser radiation, corona discharge) are used to increase the efficiency of chemical modification of the surface of solids.

In this regard, it is relevant to study the structural-chemical transformations on the surface of polyethylene and polyvinyl chloride films under the influence of halide vapors of elements of various nature, their influence on the surface-energy, thermal-oxidative, and other properties of modified polymers, as well as the study of the effect of corona pretreatment of the surface of solid-phase matrices on the effectiveness of chemical modification and functional properties of the obtained products.

Research on the topic of the dissertation was carried out within the framework of the state budget topics of St. Petersburg State Technical University (TU) (order-orders No. 1.7.04, I.1.03), grants from the Russian Foundation for Basic Research (grants No. 05-03-08172, 07-03-00330) and the government of St. Petersburg (grant series PSP Xo080191).

Purpose of the work: to study the relationship of structural-chemical transformations and functional properties of the products of the interaction of films of high-pressure polyethylene (LDPE) and polyvinyl chloride (PVC) with halogenide vapors of nioc^ora, titanium, vanadium and silicon, incl. combined with exposure to a corona discharge.

The main objectives of the study:

- development of modes of synthesis of element-containing structures on
the surface of HDPE and PVC films by gas-phase treatment with chlorides
PC1 3 , VOCl 3 , T1CI4 and Si(CH3)2Cb, including
pre-treatment in a corona discharge;

study of the relationship between chemical and structural transformations of solid-phase polymers upon interaction with vapors of the indicated halides;

study of the influence of the chemical composition, structure and morphology of the surface of modified polymeric materials on their thermal-oxidative, surface-energy and electrophysical properties.

Scientific novelty:

it has been shown that in the presence of oxygen, the grafting of element-containing structures to the surface of LDPE and PVC is carried out due to the formation of the E-O-C bond (E = P, V, Ti, Si). At the same time, according to AFM data, as a result of treatment with phosphorus chloride and vanadium oxochloride vapors, hydrated structures appear on the polymer surface in the case of phosphorus-containing films and cavities in the case of vanadium-containing films, with lateral dimensions of 200–300 nm, the adhesive characteristics of which differ significantly from the rest of the surface. The synthesis of titanium- and silicon-containing structures contributes to the formation of a uniform surface layer;

It was established that the structures formed on the surface of LDPE are the main Brønsted centers with pK A -10.5. Treatment of PVC films with halide vapor leads to the appearance of acid Brønsted centers with pK A of 1.3 and 2.5. The presence on the polymer surface of groupings containing -E=0 bonds contributes to an increase in the concentration of Lewis basic centers with pK A -4.4 and -0.29.

- the relationship of the chemical composition and topography
of the surface of polymeric materials with its energy characteristics was
revealed. It has been established that in the case of phosphorus- and vanadium-containing LDPE
and PVC, the components of surface
energy are redistributed with a significant increase in the polar component and total
energy by 1.4-1.8 times. When the surface is treated with pairs of titanium
and silicon halides, a decrease in surface energy by 30-40% is observed due to a
decrease in its dispersion component;

- it is shown that the introduction of surface element-containing structures
has an effect on the initial stage of the thermal-oxidative destruction
of LDPE, as evidenced by an increase in the temperatures of the beginning of decomposition and
10 0 /o-th weight loss by 15-75C;

- the effect of pre-treatment of the initial matrix by a corona discharge on the efficiency of the chemical modification of LDPE and PVC with phosphorus and vanadium halides and the functional properties of the resulting products was studied. It has been established that the impact of a positive corona discharge contributes to a further decrease in the surface energy by 10-20% compared to chemically modified samples, and a negative one - its increase by 10%. In the case of a preliminary physical impact on the PVC surface, complete wetting of the films with test liquids is observed, regardless of the sign of the charge.

The practical significance of the work. The results obtained can be used in the development of the technology for modifying the surface of polymeric materials according to the (MN) method to control their thermal-oxidative stability and wetting, which is important for applying various coatings, paints, and controlling the barrier properties of materials.

Approbation of work.The main results of the work are presented at scientific conferences and seminars: International Scientific Conference "Thin Films and Nanostructures" (Moscow, 2005); II, III and IV St. Petersburg Conference of Young Scientists "Modern Problems of Polymer Science" (St. Petersburg, 2006, 2007 and 2008); III All-Russian Conference (with international participation) "Surface Chemistry and Nanotechnology", (St. Petersburg-Khilovo, 2006); International scientific and technical conference "Fundamental problems of radio-electronic instrumentation" (Moscow, 2006); All-Ukrainian Conference of Young Scientists with International Participation "Nanomaterials in Chemistry, Biology and Medicine", (Kyiv, 2007); XVIII Mendeleev Congress on General and Applied Chemistry, (Moscow, 2007); III International Scientific and Technical Conference "Polymer Composite Materials and Coatings", (Yaroslavl, 2008); International scientific and technical school-conference "Young scientists - science, technology and professional education" (Young scientists - 2008), (Moscow, 2008).

Publications. The materials of the dissertation work are reflected in 12 scientific publications, including 5 articles, one of which was published in a journal included in the list of the Higher Attestation Commission, and abstracts of 7 reports.

The volume and structure of the dissertation. The dissertation is presented in 149 steps of matpinppig.nlgg. tekt.tya splgpchgit CHA ppgapyu ”23 of Table II consists of an introduction, a literature review, including two chapters, four chapters describing the experimental part, conclusions, a list of references, including 174 titles of works by domestic and foreign authors

Source of Information
Malygin et al., Chem. Vap. Deposition 21 (2015) 216-240
Saint-Petersburg State Technological Institute (SPbSTI)
(Saint Petersburg, Russia)
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