On 2/8/21 8:45 AM, Dave Cole wrote:
Are you referring to PVC here?
yes, it's kind of like nylon in that way, and unlike, say polyethylene, PTFE, or polypropylene, which "as delivered" tend to be fairly hydrophobic.
From what I understand, depending on what kind of PVC you get, it might have contaminants in it (from remelting other batches), fillers, and the porosity can vary.
For example you can take 4 or 5 pieces of PVC pipe and put them in a microwave oven and they will not necessarily heat the same (a rough and ready RF absorption test, granted at a higher frequency than HF, but easier to do)
I've had the interesting experience of putting a piece of white PVC pipe on a lathe to cut grooves in it, and found that only the surface was white, and that there were black streaks in other parts.
I guess the story here is that if you go look up plastic dielectric properties, that's typically for a lab sample, not necessarily what's extruded on your hookup wire or plastic tubing.
That might also explain the varying results people get with stuff not designed for RF (or at least with properties controlled), like zipcord.? For hookup wire insulation, all they care about is that it passes the breakdown voltage test, not that it has low dissipation.
