From: "Barry L. Ornitz" <ornitz+U@dpnet.net>
Subject: Re: CERAMIC OPEN WIRE INSULATORS
Date: 18 Feb 1999
Newsgroups: rec.radio.amateur.antenna

Patricia Gibbons wrote in message <36CA6428.5B04@ix.netcom.com>...
>Doesn't Styrene degrade in U/V ??
>Delrin may last longer than Styrene ..


Delrin is a polyacetal and does not have the best ultraviolet resistance.
Acrylics have about the best UV resistance (PMMA, polymethylmethacrylate,
Lucite, Plexiglas).  Polyethylene and polypropylene have poor UV
resistance.

A generous spray of Krylon acrylic lacquer over any plastic insulator will
give considerable UV protection.

        73,  Barry L. Ornitz     WA4VZQ     ornitz@dpnet.net

From: "Barry L. Ornitz" <ornitz@tricon.net>
Subject: Re: Will Teflon hold up to UV and weather?
Date: 14 Nov 1998
Newsgroups: rec.radio.amateur.homebrew

Roy Lewallen wrote in message <364E1802.405873D6@teleport.com>...
>Frank Dinger wrote:
>>
>> That polypropylene rope was probably coloured , perhaps blue or orange.
>> The pigment is the problem.
>> Black polypropylene (with carbon black ) would definitely survive.
>>
>> This problem  has been recognised by industry for a long time.
>> . . .
>
>I've used white, green, and black. The black lasts the longest, but
>all deteriorated after a while. And as I said, my location is nowhere
>near a worst case for sunlight exposure.
>
>By "the pigment is the problem" do you mean that a pigment-free
>polypropylene rope won't deteriorate due to UV exposure?
>
>I'd always thought that it was the plastic itself which was
>deteriorated by UV, and that making it black simply prevented the
>penetration of the UV to the interior of the rope. Consequently, black
>rope degrades more slowly, as the outside layer has to deteriorate and
>fall off before the inner layer can deteriorate. That is, the pigment
>is the solution (as much as the problem can be solved) rather than the
>problem.
>
>Roy Lewallen, W7EL

Roy,

You are absolutely correct.  Filling the plastic with carbon black prevents
the light from going past slightly below the surface.  Thus the surface
degrades.  If the degraded surface can fall off, more plastic will be
exposed and the process will continue.  Another additive is titanium
dioxide, which is a highly reflective white.  Instead of absorbing the
ultraviolet, it reflects most (but not all) of it back out.
For longevity, you should not use polyolefin ropes at all (polyethylene and
polypropylene).  Nylon is much better, and polyester ropes are the best of
all for ultraviolet resistance.  Dacron is just DuPont's name for their
polyethylene terephthalate polyester fiber, and it is popular for outdoor
fabrics.  Polyesters by other manufacturers are similar.  For _really_ high
UV resistance, the polyesters can be produced with internal ultraviolet
absorbers in the polyester backbone.

                                                            73,  Barry L.
Ornitz  WA4VZQ  ornitz@dpnet.net