ISO 7231-2010 pdf free download.Polymeric materials, cellular, flexible – Determi nation of air flow value at constant pressure-drop.
ISO 7231 specifies two methods for determining the air flow value of flexible cellular polymeric materials:
— method A. for conventional types of flexible cellular polymeric material;
method B. for all types of flexible cellular polymeric material, but especially for materials with a low permeability to air.
NOTE 1 Air flow values can be used to give an indication of the effects of fo’rnuIation and production variables on the cellular structure.
NOTE 2 In this International Standard, the expression ‘conventional type of flexible cellular polymeric materiar means types which are unsuitable for sealing purposes.
2 Normative references
The following referenced documents are indispensable for the application of this document, For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISOITR 9272, Rubber and rubber products — Determination of precision for test method standards
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
air flow value
volume flow rate required to maintain a constant pressure differential across a flexible foam test piece
4 Principle
A specified constant air pressure differential is created across a standard flexible foan specimen. The rate of flow of air required to maintain this pressure differential is the air flow value.
5 Method A
5.1 Apparatus
5.1.1 General
Diagrams of suitable apparatus are shown in Figure 1 (using an air pressure below atmospheric) and Figure 2 (using an air pressure above atmospheric). The essential parts are described in 5.1.2 to 5.1.5.
5.1.2 Flow-meters
Low-pressure-drop flow-meters with an accuracy of up to ±2 % are required for air flow measurements. The actual air flow shall be adjusted by a combination of valve restriction, as shown in Figures 1 and 2, and blower or vacuum pump speed, so that the required pressure difference across the specimen [see 5.4 c)J is maintained constant.
Air flow-meters with at least 250 mm scales are recommended. Flow-meters measuring in the range 0 dm3/s to 10 dm3ls will cover a wide variety of cellular polymeric materials.
5.1.3 Manometer
A manometer graduated in the 0 Pa to 250 Pa range and with an accuracy of ±2 % is required. Traps to prevent manometer fluid being drawn into the test chamber by accidental pressure changes shall be provided.
A plunger in the fluid reservoir is used to set the zero point after levelling the manometer.
The use of an inclined manometer with 2 Pa graduations is recommended. A level mounted on the manometer should be used to ensure that the proper degree of inclination from the horizontal is maintained
5.1.4 Air supply or suction equipment
The air supply or suction may be such that positive or negative pressure differences from atmospheric pressure are obtained across the test piece, using compressed air, an exhaust blower or a vacuum pump, etc. NOTE A particular apparatus can be constructed to use only positive or negative pressure
5.1.5 Test piece mounting
A chamber of nominal dimensions 140mm diameterx 150mm depth (see Figure 1) or 75mm diameter x 1 000 mm length (see Figure 2), incorporating a test piece mounting and fittings for the manometer and exhaust, shall be provided. The test piece cavity shall be (50 ± 0,05) mm x (50 ± 0,05) mm x (25 ± 0.05) mm.
The test piece shall be supported by suitable means, for example by the use of vanes, wires or a perforated support. The support shall provide a minimum open proportion of 70 % of the overall area, evenly distnbuted over its area (see Figures 1 and 2 for the positioning of the supports). Manometer and exhaust fittings shall be as shown in Figures 1 and 2.ISO 7231 pdf download.