i want to do physical properties tests for porous material which going to be used as a sound absorption material.please suggest technique and equipments.
Liquid displacement porosimetry methods can be useful if you have slides (like membranes) of material and pores cross it. You can use the 'bubble point' method. For further details see https://www.researchgate.net/publication/244144654_Characterization_of_UF_membranes_by_liquidliquid_displacement_porosimetry and related bibliography.
Article Characterization of UF membranes by liquid–liquid displaceme...
If you want to go for a rough estimation of the porosity from a measure of the bulk density of your material, just put a sample of it on a balance scale and divide the mass with the total volume of the sample.
For a usual acoustical porous material with two phases: a fluid one (the air) and a solid one (the skeleton), the bulk density obtained is rho_1 = (1-phi) rho_s
where phi is open porosity of the material and rho_s is the mass density of the material from which the skeleton is made of.
This will only give you a rough estimation as it is usually difficult to know the exact value for rho_s. For example, in the case of a glass-wool, what is the mass density of the "glass" used to obtain the wool ? It can range from e.g. 2000 kg.m-3 to 5000 kg.m-3. In fact, there is usually more than 1 chemical component in the material from which the skeleton is made of. This is also true for foams, manufacturers need to add at least ~10% in mass of binder and other ingredients such as foaming agent(s)...
There are other techniques to assess the [open] porosity of acoustical materials. Some of them are briefly presented on this webpage:
http://apmr.matelys.com/Parameters/Characterization/Acoustics/OpenPorosity.html
hey
you can use very attractive ways such as describe above and with a liquid displacement.
also you can use picnometer or density bubble
you can use this way too:
cut your sample in a cubic pieces and calculate: length, width and height (volume)
weight your sample
with known your density of base material you can have a ratio of porosity
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