Topband: Insulator problems- Notr og caution

[Shoppa, Tim]

Non-UV-rated clear 0.118" Polycarbonate is visibly yellowed and mildly brittle after 5 years in my outdoors environment in the sunshine and other weather.

I think this is the plasticizers "drying out" but I'm sure a polymers chemist would correct me.

Even though it's "mildly brittle" none of my insulators broke in service. They only broke when I flexed them with physical force. I would say the stuff was still way more flexible than similar new acrylic.

I still have the original non-UV-rated polycarbonate up 80 feet in the sky, and last year I added some UV-rated polycarbonate spacers.

Tim N3QE

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Bill Wichers
Sent: Monday, December 16, 2013 2:36 PM
To: Charlie Cunningham; 'Greg - ZL3IX'; 'Topband Reflector'
Subject: Re: Topband: Insulator problems- Notr og caution

Yep, that's the "black pigment commonly used" that I refer to. It's used in the PE jacks of coax too!

I can't say I've tested black - vs - white materials in the microwave region, but I've never seen a problem with them down in the HF (or 2m/6m) range.

Regarding acetal itself, I have a white bearing block on a boat lift that (was) in the sun pretty much all day, all summer, every year, and it lasted about 15 years. It gets "chalky" after that time and starts to fracture. It would be a problem in tension, and it was a problem in constant used as a rotary bearing. The black material I replaced it with is about 5 years old now and still like new. 

  -Bill

> -----Original Message-----
> From: Charlie Cunningham [mailto:charlie-cunningham at nc.rr.com]
> Sent: Monday, December 16, 2013 2:33 PM
> To: Bill Wichers; 'Greg - ZL3IX'; 'Topband Reflector'
> Subject: RE: Topband: Insulator problems- Notr og caution
> 
> Many black plastics are "blackened" by the addition of "carbon black" 
> that can make them rather lossy at RF!  "Been there, done that" in my 
> work - at
> 900 MHz.
> 
> 73,
> Charlie, K4OTV
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