RU2165609C2 - Method determining air permeability of volumetric materials - Google Patents

Abstract

FIELD: study of materials for light industry, investigation of structure and properties of materials. SUBSTANCE: for test of domestic and technical fabrics ( materials ) there are used devices determining air permeability as volume of air passed through specified area of tested material per time unit with definite rarefaction under point sample. Given method of test provides for pressing of material against testing table over perimeter of round hole of specified area with pressure effort being constant. As with growth of diameter area of contact of pressure ring with sample increases then pressure on sample changes which does not provide for generation of comparable stable results and leads to impossibility of comparison of indices of air permeability of various materials. Testing unit makes it feasible to determine air permeability of volumetric materials having thickness up to 200 mm under different pressure, to avoid air ingress through side surface of point sample, to distribute pressure evenly over surface of point sample but not over perimeter, to check thickness of point sample in process of test, to determine air permeability of volumetric materials with due account of thickness of point sample, pressure on this sample and air pressure differential. EFFECT: increased informativity with generation of comparable stable results. 2 dwg

Description

 The invention relates to materials science of light industry products, in particular to methods for studying the structure and properties of materials.

For testing household and technical fabrics (materials), VPTM-2, VPTM-2M, ATL-2 (FF-12) and UPV-2 devices are used, which determine air permeability as the volume of air passing through a given area of the test material per unit time at a certain discharge under a point breakdown. These instruments provide air permeability measurements in the range from 25 to 10,750 dm ³ / (m ² s), a vacuum under a point sample of 49 Pa (5 mm water column), and a pressure force of a point sample of 147 N (15 kgf). The test method implemented on devices involves clamping a sample to a test table around the perimeter of a circular hole of a given area. The diameter of the hole is selected depending on the breathability of the point sample, but the clamping force remains constant. Since the contact area of the pressure ring with the sample increases with increasing diameter, the pressure on the sample changes. Therefore, this method does not provide comparable stable results and the possibility of comparing the air permeability of various materials (GOST 12088-77. Textile materials and products from them. Method for determining air permeability - M .: Publishing house of standards. - 12 p .; Laboratory workshop on materials science sewing production: Textbook for high schools (Buzov B.A., Alymenkova N.D., Petropavlovsky D.G. et al., - 4th ed., revised and enlarged. - M.: Legprombytizdat, 1991 - 432 from).

 Known device brand VPTM-2, which is equipped with six removable tables with holes with a radius of 8, 12.5, 17.8, 25.2. 39.9 and 56.5 microns. The width of the contact zone of the clamping ring is 13 mm. During testing, the pressure on the sample between the first and sixth stage changes 4.34 times, which does not allow to compare the performance of different materials.

 During the tests, bulk materials (non-woven fabrics, synthetic winterizer, bags with feather mass) undergo significant deformations both in the contact zone with the pressure ring and on the surface of the blown area. The test results are also affected by air leakage through the side surfaces of a point sample between the table and the pressure ring.

 The closest in purpose and technical essence to the claimed one is a method for determining the air permeability of bulk materials, including uniform distribution of pressure on the sample along the end surface of the bulk material sample using a loading system with the exception of air inflow through the side surface and air permeability assessment (ed. St. USSR N 679658 Cl. G 01 N 33/36, 1979).

 However, this method is not sufficiently informative due to the invariance of the pressure on the sample and its volume during the test.

 The aim of the present invention is to obtain comparable stable results in determining the breathability of bulk materials.

 The proposed method for determining the air permeability of bulk materials is based on a fundamentally new approach based on changing and measuring the applied pressure on a point sample and the corresponding calculation of the specific air permeability index.

This goal is achieved through the use of a test unit (remote table), which allows you to:
determine the air permeability of bulk materials up to 200 mm thick at various pressures;
exclude air leakage through the lateral surface of a point sample;
evenly distribute the pressure along the end surface of the point sample, and not along the perimeter;
control the thickness of the spot sample during the test;
assess air permeability by calculating the air permeability index of bulk materials, taking into account the thickness of a point sample, the pressure on this sample and the pressure drop of air when creating and measuring the vacuum under the sample.

 In FIG. 1 is a schematic diagram of an additional unit consisting of a loading system 1 with a mesh pad for pressure on the sample, a point sample of bulk materials 2, a hollow cylinder 3, a mesh 4 and a discharge chamber 5.

The study of the breathability of sintepon and goose down using the proposed method showed that an increase in pressure on a point sample leads to a decrease in the thickness of this sample and a decrease in air permeability. To compare the air permeability of various bulk materials that differ in thickness, the specific permeability is determined by:
B _beats = B _{p, Δp} · h,
where B _{p, Δp} is the air permeability of a point sample under loading by pressure P and discharge under a point sample ΔP, dm ³ / (m ² s);
P is the pressure on the point sample, Pa;
ΔP - vacuum under a point sample, mm water. st .;
h is the height of the point sample, mm

 In FIG. 2 shows the dependence of the specific air permeability of the down mass on the density of point samples obtained using the developed method.

 The density of point samples during the breathability test was changed by changing the pressure on these samples when measuring the value of this pressure.

 The results showed that with an increase in the density of point samples at the initial stage, there is a sharp decrease in specific air permeability. A further increase in density is not associated with a sharp change in specific air permeability.

 Using the results obtained, it is possible to calculate the air permeability of bulk materials of any thickness and any density, in addition, the specific air permeability obtained by applying the developed method is a universal value and can significantly reduce experimental studies in the design of heat-protective clothing and in the development of various filters.

Claims (1)

 A method for determining the air permeability of bulk materials, including the uniform distribution of pressure on the sample along the end surface of a point sample of bulk material using a loading system, with the exception of suction of air through the side surface of the sample, air permeability assessment, characterized in that a vacuum is created and measured under the sample, pressure is measured on the sample and change during the test, control the thickness of the sample, calculate the air permeability rate taking into account the thickness of the point samples s, pressure on it and differential pressure of air during rarefaction.

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