Plastic Portlight Clouding?
 

I have long been curious as to why the polymer lights on my boat
become cloudy relatively fast, whether near the sea or not & whether
under cover or not. It polishes off fine with a bit of work, but I
never see this occur in other acrylic or lexan windows I have around
my place, and it is a minor annoyance. Is there one particular type
of clear polymer which clouds up like this? If left for months, they
will become only translucent until repolished.

On 3 Oct 2004 16:17:24 -0700, wrote:

I have long been curious as to why the polymer lights on my boat
become cloudy relatively fast, whether near the sea or not & whether
under cover or not. It polishes off fine with a bit of work, but I
never see this occur in other acrylic or lexan windows I have around
my place, and it is a minor annoyance. Is there one particular type
of clear polymer which clouds up like this? If left for months, they
will become only translucent until repolished.

Here's my guess: most plastics are degraded by the uv component of
sunlight. Acrylic and lexan hold up pretty well. If I recall,
polycarbonate holds up pretty well too.

Still looking over your query one more time: you say the cloudiness
appears when under cover too? Maybe you're downwind from some
pollution source?

Brian W

On Mon, 04 Oct 2004 02:43:08 +0000, Brian Whatcott wrote:

On 3 Oct 2004 16:17:24 -0700, wrote:

I have long been curious as to why the polymer lights on my boat
become cloudy relatively fast, whether near the sea or not & whether
under cover or not. It polishes off fine with a bit of work, but I
never see this occur in other acrylic or lexan windows I have around
my place, and it is a minor annoyance. Is there one particular type
of clear polymer which clouds up like this? If left for months, they
will become only translucent until repolished.

Here's my guess: most plastics are degraded by the uv component of
sunlight. Acrylic and lexan hold up pretty well. If I recall,
polycarbonate holds up pretty well too.


Lexan is a trademarked name for polycarbonate.

I used some special polycarbonate that had a UV coating on one side and it
seemed to hold up well for the 5 or 6 years I had it on the boat. It
wasn't a lamp cover, though.

Still looking over your query one more time: you say the cloudiness
appears when under cover too? Maybe you're downwind from some
pollution source?

Brian W

Ozone (as found in smoggy areas) might attack plastics. It definitely
attacks some types of rubber.

--Mac

On Mon, 04 Oct 2004 04:43:54 GMT, Mac wrote:

On Mon, 04 Oct 2004 02:43:08 +0000, Brian Whatcott wrote:

On 3 Oct 2004 16:17:24 -0700, wrote:

I have long been curious as to why the polymer lights on my boat
become cloudy relatively fast, whether near the sea or not & whether
under cover or not. It polishes off fine with a bit of work, but I
never see this occur in other acrylic or lexan windows I have around
my place, and it is a minor annoyance. Is there one particular type
of clear polymer which clouds up like this? If left for months, they
will become only translucent until repolished.

Here's my guess: most plastics are degraded by the uv component of
sunlight. Acrylic and lexan hold up pretty well. If I recall,
polycarbonate holds up pretty well too.


Lexan is a trademarked name for polycarbonate.

I used some special polycarbonate that had a UV coating on one side and it
seemed to hold up well for the 5 or 6 years I had it on the boat. It
wasn't a lamp cover, though.
//
Ozone (as found in smoggy areas) might attack plastics. It definitely
attacks some types of rubber.

--Mac

Quite right: the two popular transparent plastics are polycarbonate
and polyacrylate

Brian W

Brian Whatcott wrote in message . ..

Still looking over your query one more time: you say the cloudiness
appears when under cover too? Maybe you're downwind from some
pollution source?

Interesting thought. FWIW:

- Maine is famous for acid rain (though it doesn't cloud/oxidize my
other plastic lights); ozone is also generally higher here than most
places (much of it naturally-produced by conifers);

- occurs equally on both the sun-exposed side & the total shade side
(during long haulout), so doesn't appear to be UV-related;

- occurs at the same rate when afloat;

- all portlights are below & surrounded by typically-oxidized/chalked
older white gelcoat (pigment dust *bonding* somehow to the lights? A
SWAG).

It's a rather minor issue but one I thought might or might not be
pertinent to those here who exhaustively evaluate various materials.

I guess your boat is trailerable? What kind of lights are you talking about,
navigation, courtesy, etc.? If this appears no matter what, you might be
seeing "blooming" where additives in vinyl plastics come to the surface. I
kinda doubt the lenses are made of PVC though, although that's all I can
imagine. UV degradation wouldn't polish off, so you've got some sort of
contamination on the surface. Try spraying with a little Pam or silicone
spray after you clean them next time.

--


Keith
__
When the chips are down, the buffalo is empty.
wrote in message
om...
I have long been curious as to why the polymer lights on my boat
become cloudy relatively fast, whether near the sea or not & whether
under cover or not. It polishes off fine with a bit of work, but I
never see this occur in other acrylic or lexan windows I have around
my place, and it is a minor annoyance. Is there one particular type
of clear polymer which clouds up like this? If left for months, they
will become only translucent until repolished.

"Keith" wrote in message ...
I guess your boat is trailerable?

Nope.

What kind of lights are you talking about,
navigation, courtesy, etc.?

See subject title.

If this appears no matter what, you might be
seeing "blooming" where additives in vinyl plastics come to the surface. I
kinda doubt the lenses are made of PVC though, although that's all I can
imagine. UV degradation wouldn't polish off, so you've got some sort of
contamination on the surface.

Whatever it is bonds to the surface as if it were part of it & must be
abrasively polished off.

Try spraying with a little Pam or silicone
spray after you clean them next time.

I have done this in the past (other more suitable product - silicone
sprays are awful to get on anything one cares about, especially where
long-term visual clarity is an issue, are impossible to remove from
plastics, and often cause degradation themselves; I would like to see
people who put them on things they sell mildly tortured; Pam is
vegoilarrgghh).

Poly carbonate comes in many grades. The untreated grade is the least
expensive. The treatment applied can be on one side or both. Treatments can
vary as well. You can have just a UV treatment or a hardness treatment that
is alsoUV resistant. The last variant is the most expensive. I am going to
venture a guess. Either the manufacturer used cheap poly or you trashed the
coating by using an abrasive polish. You are definitely suffering UV
degradation. Your choices are to continue polishing forever, replace the
poly panels with the appropriate grade. Or buy new portlights. Please note
that I did not specify using armor glass and that is the best, but it is
only applicable to wooden and metal boats, not FG, as they will shatter with
hull flex.
Steve
wrote in message
om...
I have long been curious as to why the polymer lights on my boat
become cloudy relatively fast, whether near the sea or not & whether
under cover or not. It polishes off fine with a bit of work, but I
never see this occur in other acrylic or lexan windows I have around
my place, and it is a minor annoyance. Is there one particular type
of clear polymer which clouds up like this? If left for months, they
will become only translucent until repolished.

On 5 Oct 2004 07:03:40 -0700, wrote:

"Keith" wrote in message ...
I guess your boat is trailerable?

I have done this in the past (other more suitable product - silicone
sprays are awful to get on anything one cares about, especially where
long-term visual clarity is an issue, are impossible to remove from
plastics, and often cause degradation themselves; I would like to see
people who put them on things they sell mildly tortured; Pam is
vegoilarrgghh).

Hi,

Try taping over part of one of them with foil tape, and part of
another with foil taped loosely at the edges. This will give some idea
of whether it's related to light or some reaction with the air.

If it's UV degradation then you might be able to get a clear coating
that blocks UV.

cheers,
Pete.

wrote in message
om...
"Keith" wrote in message
...
- silicone
sprays are awful to get on anything one cares about, especially where
long-term visual clarity is an issue, are impossible to remove from
plastics, and often cause degradation themselves; I would like to see
people who put them on things they sell mildly tortured; Pam is
vegoilarrgghh).

Quite right!
Silicon is virtually impossable to remove.

Put a drop of the stuff of a GRP mould.... Leave for 10 mins....
Clean it off and repolish the mould.
You will see a blemish where the silicon was on every component from that
mould... for years!