Effect of Polysulfide and polyurathane on plastic ports

[windship]

Has anyone observed first hand any negative effects caused by polysulfide or polyurathane on plastic ports?

Dennis

[windship]

Nobody has seen the so called ill effects of polysulfide or polyurathane on plastic ports???

Dennis

[GordMay]

Could be that the Sailnet membership are smart enough to have avoided the problem?

[GordMay]

Polysulfides & Polyurethanes will adhere to metal, glass, fiberglass, wood, or any combination of these. Do not use either on PVC, Acrylic (Plexiglas, Lucite), ABS, or Polycarbonate (Lexan) plastics.
Although the modalities are (more or less) opposite, both “Poly” products are incompatible with the above “plastics” (excluding Nylon, Dehlrin, Marelon, or Epoxy):
The solvents in polysulfides can leach the plasticizer from these plastics and cause them to harden and crack.
Solvents, leaching from some plastics, can react with polyurethanes and cause a failure of the adhesive sealant compound.
For an adhesive seal of plastic components, select a silicone/polyurethane or epoxy/polyurethane hybrid.
Never use any caulk that is catalyzed by acetic acid (i.e., smells like vinegar) on acrylic; it will cause crazing.
Silcone has little if any adhesion. It is merely a gasket material, but an excellent gasket. It will not attack plastics, but may cause crazing on acrylics.

[windship]

Gord.
Thanks for your response.
Yeah, we''re pretty smart here I guess and I''m well aquainted with the different types of sealant/adhesives and their applications but that wasn''t the question.
The reason I asked the question is last week I removed a port in a boat that was installed 27 years ago. It hasn''t leaked in 27 years and it was bedded in with 5200 and the port is still in perfect shape.
???
If both polys are supposed to attack plastic ports, why did this beddidg job last so long and why is the port(and the rest of the ports that still aren''t leaking)still in perfect shape?

Dennis

[GordMay]

I can''t explain your excellent experience /w 5200 on plastics - except to wonder if the bedding might have been something other than pure polyurethane (5200).
Perhaps Life-Caulk (or some other) hybrid?
Gord

[windship]

Gord,
Yeah, I can''t figure it out either however I am suspicious of this thing. Maybe I''ll do an experiment on an old port I have laying around.
Were hybrids around back then?
Life-caulk is polysulfide.

Dennis

[GordMay]

Windship (Dennis):
You''re correct of course (Life Caulk = Polysulfide); I should have said "Life-Seal" (Polyurethane + Silicone).
At 27 years old, we''d be talking late 70''s
I encountered Polysulfides, Polyurethanes, and Silicone’s in the automotive & glazing industries in the early to mid 1960''s.
I know that Thiokol (now Morton-Thiokol) developed the Polysufides during WWII.
I’m not certain when the hybrids (Polyurethane-Silicone, Epoxy-Poly'') were first introduced.
Interestying ...
Gord

[windship]

Gord,
Alright, thanks. Guess it will remain a mystery for now.

Dennis

[priwall]

Hi Dennis,

For the last 29 years we have used many gallons of 2-part Thiokol (Paraseal, no longer made) on Plexiglass ports and hatches, on ABS, PVC, CPVC, and other plastics, metals and wood on our boat, from keel to truck, stem to stern. ALL IS STILL PRISTINE, after 27 years of sailing, tropics to sub-zero.

Since Paraseal was discontinued about two years ago I have just completed some research in order to find a new supplier, and settled on AC Tech AC240B2. AC Tech and Rohm & Haas, the inventor of Plexiglass, both agreed with my use of Thiokol. AC240B2 is aircraft grade.

We tried some small projects with Boatlife 2- part and were very disapointed with the poor adhesion and mixing unfriendliness, including the insistence by the manufacturer that you MUST mix the whole can in one go!

You can check the specs of AC240B2 (2 is the cure time denominator) at www.actechaero.com

All the best - Peter