Interesting question, and it is expected that such materials have low dielectric constant, probably in the range from 1.2 to 1.8 depending on the density of cross wirings of the substrate. This work may be of interest:

https://www.ijert.org/research/wearable-textile-patch-antenna-using-jeans-as-substrate-at-2.45-ghz-IJERTV3IS050548.pdf

There is a single frequency method, basically the resonant frequency which enables investigation of dialectic constant of a substrate upon the design of wearable materials. The effective rectangular patch length (Leff)or the radiation patch width (w) is dependent on the resonant frequency and the dialectic constant of the material. This method enables interpolation of possible range of values for the dialectic constant of substrates, which can be expressed as

Leff = L + 2∆L = C0/2fr.(sqrt( 𝜀𝑟eff ))

Where,

L = physical patch length

∆L = extended patch length due to fringing field effect

C0 = speed of light in vacuum

fr = resonance frequency of the patch

𝜀𝑟eff = effective real part of the dielectric constant

But assuming a radiation patch width (w) to be approximately equal to 2Leff, hence we have the dialectic constant expressed as

𝜀𝑟eff = (C0/w.fr)2

Dear Meenakshi,

I found values between 1,2 and 1,3. But for cotton fibre flour I found 3,2 (see table in attachement).

Yours

R. Mitdank

Thank you fo the table . It is really good and helpful but I could not find where is denim in this table. Please help if I am missing

In the first row you find "Baumwoll-Fasermehl". The second row then gives the english expression but not in alphabetic order.

R. Mitdank