PVC Properties (was Re: Good source of 2.4GHz directional antenna?)

[John Dalton]

As far as my Dad knew, PVC pipes contain mainly
PVC and titaniun dioxide (also called tinania).
There are also other things in there, which he isn't
sure about. He reckons most manufactures would be prepared
to tell you what is in their pipes, if telephoned.


I've looked up a materials safety data sheet at
Hardie Iplex:
http://www.iplex.com.au/technicaldata/MSDSPVCPIPEFITT.pdf

It says the composition of their PVC pipes is:
PVC: 80%
titanium dioxide (pigment) 1.5%
Calcium carbonate: <20%
Colour Pignent <1%
UV stabilisers, heat stabilisers, lubricants such as calcium, zinc soaps 2-4%
Large pipes may contain traces of lead stabilisers

They also give some electrical properties
http://www.iplex.com.au/products/pre-properties.shtm
Volume resistivity: 10^14 ohm.m (60% relative humidity)
Surface resistivity: 10^13-10^14 ohm
Power factor: 0.015-0.020 at 20C
Dielectric Constant: 3.4-3.6 at 25C (60Hz)

Here is another materials datasheet which gives properties up to 100kHz:
http://www.thegundcompany.com/DataPages/Electrical%20Insulation%20Materials/Thermoplastic%20Materials/Vinyls.pdf
Not much different to above.

I guess the dielectric constant may be redically different at 2.5GHz,
but the numbers above cover quite a few octave and so should be a guide.

At least for Iplex pipes, the loss don't seem to be too high.
Possibly surrounding the antenna with a dielectric whose constant
is >>1 is changing the wavelength, causing the antenna to be detuned??
Only guessing.

John