SU113009A1 - Method for determining moisture permeability of films - Google Patents

Description

Methods are known for determining moisture permeability of films based on measuring the diffusion flow of water vapor through the film. The disadvantages of the known methods are the absence of stationary diffusion conditions, the presence of hardly eliminable effects of gas or vapor sorption in the sample, and the lack of accuracy of the results obtained.

The proposed method, in comparison with the known, eliminates these drawbacks. reduces test duration and improves accuracy of determination.

For this, water vapor is tritiated and their penetration through the film sample is recorded radiometrically, for example using gas-filled counters, subject to the conditions of a stationary diffusion flow. In order to eliminate the loss of active water vapor, the latter are directly introduced into the meter by freezing, for example, liquid nitrogen.

FIG. 1 is a schematic diagram of a known vacuum unit; in fig. 2 is a diagram of a part of a vacuum setup in which a diffusion process directly takes place; in fig. 3 is a diagram using a flow counter.

The radioactive water is in the reservoir /, connected. Through a valve with one part of the diffusion cell 2, which is separated from the other part by the test film sample. One part of the diffusion cell 2 is connected through the valve either to the lumen 5 or to the rest of the vacuum system. The vacuum control in the system is carried out using a thermomanometric lamp 4 or a MacLeod type pressure gauge. Ethyl alcohol, used as a quenching component, is contained in vessel 5 or 6. The flow meter is shown at 7. And the counter for the internal gaseous radioactive source, equipped with a blind process to freeze vapors of active gas in it.

Noah's position by cooling with liquid nitrogen - position 8. (/ -shaped pressure gauge 9 serves to measure high pressures (up to atmospheric pressure), and monometer 10 of the Huygens type is used for small (up to 40 mm Hg) traps // and 12 do not prevent the ingress of radioactive water vapor into the surrounding atmosphere. A vacuum in the installation is created by a forevacuum pump operating on a forba.llop 13 and a line connected to a two-type Arthut diffusion pumps 14 of the Leggmür type. crane 17 and calibrated about Plug 18 have an auxiliary assignment.

Vessel 19 (Fig. 2), belonging to the part of the vacuum installation, in which the diffusion process under investigation directly takes place, contains labeled water and communicates with one part of the diffusion cell 2; The other part of the cell through the valve 20 is attached either to the blind process, or to () () bn1, comes with a vacuum ciicrema, to which various devices, including a 22, with absolute alcohol and a counter 8 for an internal gas source of a radioactive source.

The method is as follows.

Sun system. Shown on fng. 2, evacuation, with the exception of the volume of the carrier containing radioactive 5oda and absolute alcohol. Water and alcohol nrsdvar11te; 1b; cho Tn.iaTe.4bi; o; odvss-rga; {) ts evacuate the world with multiple times: with periodic freezing g: subsequent thawing. Counter 8 is recorded as a burr norm (argon-blended gas mixture (20 mmHg. Alcohol and up to 100 mm pi, art. Argopa) to check the level of natural background. Diffuse1; cell 2 and other alema b: schemes, necessary for the establishment of oHbrja, can be disconnected by crane 2 from counter 8 and auxiliary components; as a result, all operations with the counter (vacuum, flushing steam for alcohol “Memories, with an argon – synthetic mixture for the npoBeiJKi level patur.chyyugo fs. On, etc.). Can be iroiz. Or not.

In this way, checking the background of the filter and the negative pressure to prepare it for taking the sample and the aperture of the 11B1 Spray of water vapor can be performed parallel to the ground, with the advantage of the similarity.

The beginning of the 1st moment ispapazhch (I 0 | s, 13zh:. | G vapor inlet active through the park with vessel 19.

Water pressure over the jjaiiiit sample. ;; It is under pressure (orMeHepaType of the process of determining the permeability; permeability) and is constantly maintained due to phase 1.

In order to ensure that the utavium etacyopair process during the experiment (the constancy gradient of the sample but not the sample, it is necessary to maintain zero pressure in the other part D1 (| k |) of the ionization cell 2) water) c. This is achieved by joining cell 2 of the blind appendage -. cooled with nitrogen. The water vapor diffused through the sample film condenses and their pressure is almost equal to;

The task of measuring the moisture permeability coefficient is to determine the mass of water ions diffusing through the film sample under the conditions of an established stationary process for a certain period of time, i.e., to determine the diffusion flux.

It is known that, owing to copets} and; n, the diffusion rate of the stationary process is established. It doesn’t feel immediately, but after a certain period of time determined by the sorption capacity of the sample material. Accordingly, the diffusion flow of water vapor through the liver sample increases over time and then becomes constant. Therefore, the measurement of the coefficient of moisture permeability is reduced to periodically checking the diffusion of water vapor through a sample of a sample of water, 1е1П1 constant of its value corresponding to a given differential pressure.

In practice, the measurement of the diffusion flow of water vapor through the sample is made as follows.

The process of the evacuation counter is discharged into liquid nitrogen. The counter 8 (with the tap 21 open) is pushed to the cell 2 using the tap 20. The turning moment of the tap 20 is recorded by starting the stopwatch. From this point in time, water vapor passing through the film sample is frozen out directly into the process of counter 6. At the same time, the conditions of the steady-state diffusion process are preserved, because the vapors condense and their pressure remains almost equal to zero, and on the other hand, all the bunks that are diffused through the sample, have been collected into the counter 8. After some vapor is taken into the counter, it is possible for some time with the crane 20 to switch part of the cell back to the blind process 3, fixing this moment of time new stopwatch.

To measure the activeness of a vapor-rich set, an argon-gas mixture must be introduced into the effector. Since some, although very small, part of the active water vapor can be sorbed by the glass walls of the plant, the entire vacuum system is washed with alcohol vapors, which are then frozen out into the meter and serve as an extinguishing component. Argon is added to the meter to a total pressure of 100 mm Hg. Art., the thread of the meter connects to the input of the radiometer and after 30-40 minutes. After filling, a measurement is made of the activity entered into the vapor meter, after which the meter is diluted for 40-60 MtiH.

After checking the level of natural background and rarefaction, the counter is again ready for the selection of the next norm of diffusing vapor.

To save time, you can work in parallel on two or more meters (installation design provides for this). While in one of them the activity is being measured, others were being prepared for work.

The measured vapor activity, referred to the time of their collection into the counter, is (with a constant experimental geometry and a given concentration gradient) the diffusion flow.

The second option, which is the use of a flow counter, serves as a further development of the on-line technique.

In the first variant of the technique, the change in diffusion flux over time is recorded and the sequential selection of individual portions of diffused vapor into the meter to measure their activity. If all the planks diffusing through the sample are made to flow directly through the counter, this makes it possible to observe not individual points characterizing the increase in the diffusion flow, but to continuously record the integral value of the flow in time.

As a recording device, it is advantageous to apply a counting rate meter (integrator) with access to a recorder.

- 3 -To 113009

No. 113009

The individual flow meter is convenient when working on single-component filling with organic vapors or gases (instead of the usual mixture of organic vapors, like quenching components, with an inert gas).

Such an opportunity makes it extremely easy to carry out a flow through the meter not only of water vapor diffusing through the sample, but also of the filling itself. Constantly changing the metering, on the one hand, provides for a more complete and quick movement of active water vapor through the sensitive volume of the meter and, on the other hand, reduces the effect of continuous washing of the entire system with organic beds.

Opti.ma; P) Nymi nano.tneti.ln, satisfied the requirements of all requirements in equal walling, these pairs of fresh alcohol are at a pressure of 26-30 LTM. Art. and also gas flow. Their flow through the meter is determined by evaporation from the liquid phase on one side of the meter and freezing with liquid nitrogen (or continuous vacuum) but on the other side.

The required pressure drop at the outlet of the meter is selected by means of a crane in front of the oh,: each impressed trap (or exit to the vacuum pump).

Water labeled with tritium is in the vessel / (Fig. 3). The sample is sandwiched between a two-meter and a half diffusion cell 2. Ethyl alcohol (or butane) vapors from reservoir 23 fall into one part of diffusion cell 2, nrom it and carry water with it diffusing through the sample on the other part of the cell through the meter 24, vymora k1 va with liquid nitrogen in the wrench 25 (nl pumped out without directing it with a vacuum pump).

In order for the counter to work optimally, the vapor pressure of the alcohol (or butane) is selected by pressing the valve 26 and measuring it with a pressure gauge 27.

The use of a flow counter doesn’t mean a significant unrost method and, in part, auto measurement of measurement.

Indication of water vapor by tritium T1ri studying their diffusion in synthetic materials using both differential and integral methods izvozt. Not only functionally to improve the accuracy of measurements, at the same time juice) their d,: .

Predmemt and z obreteni

1. The method of determining the chronoprecipability of ira films based on the measurement of the flow of water vapor diffusion through H; i.e. y, o t, i and h is the fact that, in order to increase the limits and reduce the duration of the test, water vapors mark tritium and their penetration through a sample through a radiometric method, using gas-filled counters, and with () b, 11de1pp1 ye; 101 ИИ stationary diffusion flow.

2. Software method P. 1, that is, so that, in order to exclude the loss of active water levels, the hereditary} 1 is directly introduced into the meter by freezing, for example, with liquid nitrogen.

/eight

13

four

Clfiull at 1 / h | p I

FIG. 2