RU2696354C1 - Method of determining defects on the surface of polymer films - Google Patents

Abstract

FIELD: measurement technology.SUBSTANCE: invention relates to quality control of articles and can be used for checking quality of polymers used for industrial purposes and products based thereon. Method of determining defects on polymer films includes their holding in gaseous tritium at pressure of 2–10 Pa for 10–25 minutes at temperature of 325–332 K in the presence of palladium in form of at least 7 wt% of oxide or hydroxide deposited on carbon substrate, with subsequent determination of radioactivity of the film by autoradiography and analysis of histograms of distribution of film sections by degree of blackening.EFFECT: technical result is the development of a method of determining defects of solid materials using radioactive indicators with high contrast of distributing tritium on the surface of the material.1 cl, 5 dwg

Description

Technical field

The invention relates to techniques for quality control of products and can be used to verify the quality of polymers used for industrial purposes, and products based on them.

State of the art

Polymer films are widely used as packaging material, electrical insulators, substrates in various types of products, anti-corrosion coating of pipelines. As a rule, for the effective use of polymer films, they are presented with a whole set of requirements for mechanical strength and chemical resistance. Upon receipt of polymer films, during their storage and use, micro- and macrodefects (mechanical scratches, microcracks formed along the packaging of polymer molecules, or in layered structures of polymers, or during thermal deformations) can form on their surface, which can eventually lead to irreversible changes that reduce their performance.

To identify defects on the surface of polymer films using ultrasound [RU 2520950 C1, 06.27.2014], capillary (color) [GOST 18442-80; RU 2184366 C1, 06.27.2002], radiation [RU 2304766 C1, 08.20.2007; Rumyantsev S.V. Radiation flaw detection. M., Atomizdat, 1974, 510 S.] and other defectoscopy, as well as microscopy.

To identify defects, you can use a radioactive indicator - tritium, which is a universal labeling agent of any organic molecules. Atomic tritium obtained using the thermal activation method can be used to determine the structure of complex molecular complexes. In this case, after treatment with atomic tritium, an analysis of the distribution of radioactivity between the constituent parts of the complexes is carried out [L.A. Baratova, E.N. Bogacheva, V.I. Goldansky, V.A. Kolb, A.S. Spirin. Tritium planigraphy of biological macromolecules. M .: Science. 1999. 175 s]. However, in this case, the use of lengthy and expensive procedures for the selective decomposition of the drug with the separation of its components and the determination of their radioactivity is required.

A technically simpler version of the use of tritium as a labeling agent for determining traces of foreign bodies [RU 675648, 11/23/1977] and fingerprints on objects and paper [RU 947058, 02.29.1980] is possible. The described approaches do not allow the determination of surface defects of polymer films.

A known method based on the thermal activation of tritium on a tungsten wire, when atomic tritium is formed and non-selectively interacts with all organic materials [RU 2499785 C2, 11/27/2013]. In this case, when treating films of polyethylene (PE), polyethylene terephthalate (PET) and polyamide (PA) with atomic tritium obtained on a tungsten wire at a temperature of 1950 K, a pressure of tritium gas of 1.4 Pa and a film temperature of 298 K under conditions of thermalization of atoms, labeled tritium films with a uniform distribution of radioactivity on the surface [Razzhivina IA, Badun GA, Chernysheva MG, Korobkov VI, Zhirnov A.E. Polymer films as an indicator of hydrogen spillover through the gas phase. // Radiochemistry. 2017.V. 59, No. 3. S. 248-254.]. However, it is not possible to identify the presence of defects on the surface of these materials.

In the same work, it was found that when the polymer films were kept for 25 minutes in gaseous tritium in the presence of palladium deposited on activated carbon in an amount of 5 mass. % (5% Pd / C), at a temperature of 335 K, tritium is included in the composition of polymer films and an increase in the intensity of blackening was observed at the points of their cutting, at bends and visible minor injuries, but with its help it was not possible to detect film defects invisible to the eye. The described approach is a prototype of this invention.

Disclosure of invention

The technical problem solved by the claimed invention is the development of a new method for determining defects in solid materials using radioactive indicators.

The technical result is the development of a method for determining defects in solid materials using radioactive indicators with increasing the contrast of the distribution of tritium on the surface of the material. The inventive method allows to identify not only visible, but also hidden defects caused by the aging of the material during storage and other effects on it. Such violations can be precursors of mechanical damage to films or coatings based on them, especially at additional loads.

The specified technical result is achieved by a method for determining defects in polymer films, including their exposure to gaseous tritium at a pressure of 2-10 Pa for 10-25 minutes at a temperature of 325-332 K in the presence of palladium in the form of at least 7 mass. % oxide or hydroxide deposited on a carbon substrate, followed by determination of the radioactivity of the film by autoradiography and analysis of histograms of the distribution of film sections by degree of blackening. In this case, solid polymers are used as polymer films at a temperature of 325-332 K, including nylon, polyethylene, polyethylene terephthalate.

Brief Description of the Drawings

The invention is illustrated by the following drawings.

In FIG. Figure 1 shows the image of the distribution of blackening over the film obtained using the Cyclone Plus Phosphor Imager (a) and a histogram of the distribution of sections of the film with different degrees of blackening (b) (illustration for example 1).

In FIG. Figure 2 shows the image of the distribution of blackening over the film obtained using the Cyclone Plus Phosphor Imager (a) and a histogram of the distribution of film sections with different degrees of blackening (b) (illustration for example 2).

In FIG. Figure 3 shows the image of the distribution of blackening over PET films obtained using the Cyclone Plus Phosphor Imager (a) and a histogram of the distribution of film sections with different degrees of blackening (b) (Illustration for example 3).

In FIG. Figure 4 shows the image of the distribution of blackening over the nylon films with microcracks (a) and without defects (b), obtained using the Cyclone Plus Phosphor Imager, and histograms of the distribution of areas with different degrees of blackening for films with microcracks (c) and without defects (d) (illustration for example 4).

In FIG. Figure 5 shows the image of the distribution of blackening over the nylon films with microcracks (a) and without defects (b), obtained using the Cyclone Plus Phosphor Imager, and histograms of the distribution of areas with different degrees of blackening for films with microcracks (c) and without defects (d) .

The implementation of the invention

Below is a more detailed description of the claimed invention. The present invention may be subjected to various changes and modifications understood by one skilled in the art upon reading this description. Such changes do not limit the scope of claims.

Defects can be determined by this method for any polymers in the form of films that are solid at a tritium treatment temperature, that is, up to 332 K. Examples of such films are: polyethylene, polyethylene terephthalate, polyamide. A polymer film and a palladium-based catalyst with the obligatory presence of oxidized forms in its composition are placed in the reaction vessel. The amount of catalyst used determines the rate at which the final result is achieved. The mass of the metal and its oxidized forms is from 0.2 to 1 mg, and their content on the carbon substrate is from 5 to 10 mass. % The total weight of the used catalyst suspension on the carbon substrate may be in the range from 1 to 10 mg. The catalyst and the film are placed at a distance from millimeters to several centimeters, direct contact is not necessary.

A vessel with a film and a catalyst is attached to a vacuum unit, after evacuation, it is filled with gaseous tritium to a pressure of 2-10 Pa and placed in a thermostat with a temperature of 325 to 332 K. It is important to maintain the temperature in this range, since its decrease leads to a sharp decrease in the efficiency of introduction tritium in the film, and with increasing temperature, the contrast of defect detection decreases.

The holding time of the films at this temperature can vary from 10 to 25 minutes. Reducing the contact time with tritium reduces the activity of the films, which leads to an increase in exposure time to obtain a high quality image. Increase the exposure time of more than 25 minutes. does not lead to an improvement in image quality, since during this time an isotopic equilibrium occurs in the system. The reaction is stopped when the gas pressure in the system stops changing. Pressure can be determined using a thermocouple vacuum gauge.

After 10-25 minutes. By heating the system, cool and disconnect the reaction vessel from the installation. The films are cleaned of tritium removed from the surface by washing in acetone and water. Then determine the distribution of radioactivity on the film surface by autoradiographic methods. The use of a digital version of autoradiography using a luminescent screen sensitive to tritium is recommended.

The digital image obtained using autoradiographic methods is analyzed using image processing programs and a histogram of the distribution of film sections by brightness (degree of blackening) is obtained, where 0 is taken as white, 100% for black. A film processed under the indicated conditions and free from defects has a monomodal distribution with a maximum blackening in the region of less than 40%. The presence of small mechanical defects, including the cut line, is manifested by the presence of areas with a degree of blackening of more than 60%. If the image contains uniform areas with a degree of blackening of 60% or more, this indicates the presence of microcracks in the material that are invisible to the eye.

The use of the proposed invention is described in Examples 1-5.

Used catalysts, which are oxidized forms of palladium (the proportion of oxidized forms of at least 7 wt.%) With a predominant particle size of from 1.5 to 3.5 nm, deposited on carbon substrates.

In all examples, the films were washed sequentially in toluene, acetone, water, and acetone with sonication for 10 minutes before tritium treatment. The films were treated with tritium at a gas pressure of 2-10 Pa and a temperature of 325-332 K for 10-25 minutes, until the pressure stopped changing. Possible organic contaminants were removed by briefly washing the film in acetone. To remove labile tritium, the films were placed in water, which was periodically replaced. The purification of the films was stopped when the radioactivity of the wash water decreased to the background level. A Cyclone Plus Phosphor Imager (PerkinElmer, USA) with OptiQuant software and a luminescent screen (PerkinElmer, USA) sensitive to tritium were used to detect the distribution of radioactivity on the surface of the treated film. The resulting digital images were analyzed using Python 2.7 with the SKimage library.

Example 1. Used 5 mg of catalyst in the form of 5 mass. % Pd applied to activated carbon. According to x-ray photoelectron spectroscopy 7 mass. % palladium was in the form of oxide and hydroxide (Pd ²⁺ ). The catalyst was placed in a cup at the bottom of the reaction vessel, and a polymer film of 1.5 × 12 cm in size and 0.011 cm thick was placed along the axis of the vessel. Interaction with gaseous tritium was carried out at a temperature of 328-332 K provided by a water thermostat and an initial tritium pressure of 4 , 2 Pa. Over 15 minutes, the pressure decreased to 4.1 Pa and then did not change. The reaction was stopped, purification was carried out according to a standard method: the film was washed in acetone, then it was kept in water with periodic replacement. After 20 hours of exposure of the films on the fluorescent screen, an image was obtained with a uniformly low radioactivity on the surface and an increased degree of darkening at the place of film cut and scratches. The autoradiogram of the film and the histogram of the distribution of blackening are shown in FIG. one.

Example 2. Used 5 mg of catalyst in the form of 5 mass. % Pd applied to activated carbon. According to x-ray photoelectron spectroscopy 84 mass. % palladium was in the form of oxide and hydroxide (Pd ²⁺ ). The catalyst was placed in a cup at the bottom of the reaction vessel, and a polymer film of polyethylene terephthalate 2 × 12 in size, 0.022 cm thick was placed along the axis of the vessel. Interaction with gaseous tritium was carried out at a temperature of 330-332 K and an initial tritium pressure of 5.9 Pa. The pressure decreased to 4.9 Pa in 13 min and then did not change. The reaction was stopped, purification was carried out according to standard methods. After 24 hours of exposure with a luminescent screen, an image was obtained with a uniformly low radioactivity on the surface and an increased degree of darkening at the point of cut of the film and scratches. The autoradiogram of the film and the histogram of the distribution of blackening are shown in FIG. 2.

Example 3. Tritium treated assemblies of three PET films 2 × 6 cm in size, 0.02 cm thick, tightly pressed against each other. A hole with a diameter of 10 mm was preliminarily made in the two upper films, into which the catalyst was placed on the lower film in the form of 5 masses. % Pd applied to activated carbon. According to x-ray photoelectron spectroscopy 84 mass. % palladium was in the form of oxide and hydroxide (Pd ²⁺ ). The experiment was carried out at a temperature of 325-332 K with an initial tritium pressure of 3.3 Pa. The pressure dropped to 2.8 Pa in 25 minutes. The reaction was stopped, purification was carried out according to standard methods. After 20 hours of exposure with a luminescent screen in areas of films that do not have direct contact with the catalyst, an image with uniformly labeled areas with a low degree of blackening (<40%), pronounced surface damage and an increase in the degree of darkening at the cut point is obtained. The autoradiogram of the film and the histogram of the distribution of blackening are shown in FIG. 3.

Example 4. At the bottom of the reaction vessel, 5 mg 10 wt. % Pd applied to activated carbon. According to x-ray photoelectron spectroscopy, the sample contained 94 mass. % palladium in the form of oxide and hydroxide (Pd ²⁺ ). Along the axis of the vessel, polymer films of kapron with a size of 1.5 × 12 and a thickness of 0.0055 cm with varying degrees of defect were placed. Interaction with gaseous tritium was carried out at a temperature of 330-332 K and an initial tritium pressure of 10 Pa. The pressure decreased to 4.2 Pa in 15 minutes and after that did not change. The reaction was stopped, purification was carried out according to standard methods. After 100 minutes of exposure with a luminescent screen, images were obtained for a film with and without microdefects. A higher blackening of the film was observed, containing areas with microdefects invisible to the eye. A similar treatment of kapron without defects led to a significantly lower binding of tritium, and the degree of darkening of the photographic material was minimal. Autoradiograms of films and histograms of the distribution of blackening are shown in FIG. four.

Example 5. At the bottom of the reaction vessel, 5 mg 5 wt. % Pd on activated carbon. According to x-ray photoelectron spectroscopy, the sample contained 32 mass. % palladium in the form of oxide and hydroxide (Pd ²⁺ ). Along the axis of the vessel, polymer films of kapron 1.5 × 12 in size, 0.0055 cm thick with varying degrees of defectiveness were placed. Interaction was carried out with gaseous tritium at a temperature of 330-332 K and an initial tritium pressure of 9.3 Pa. The pressure decreased to 6.5 Pa in 18 min and then did not change. The reaction was stopped, purification was carried out according to standard methods. After 100 minutes of exposure with a luminescent screen, an image of the film was obtained, on which a section with an increased degree of blackening was observed (> 40%). Increased blackening corresponds to a section containing microdefects of the material invisible to the eye. A similar treatment of kapron without defects led to lower tritium binding and a low degree of darkening of the photosensitive material. Autoradiograms of films and histograms of the distribution of blackening are shown in FIG. five.

Claims (2)

1. A method for determining defects in polymer films, including maintaining them in gaseous tritium at a pressure of 2-10 Pa for 10-25 minutes at a temperature of 325-332 K in the presence of palladium in the form of at least 7 wt.% Oxide or hydroxide deposited on carbon substrate, with subsequent determination of the radioactivity of the film by autoradiography and analysis of histograms of the distribution of film sections by degree of blackening. 2. The method according to p. 1, characterized in that solid polymers are used as polymer films at a temperature of 325-332 K.

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