I'm bored with gelcoat and so are you - this forum was supposed be generalised about all PLASTICS. Any comments- war stories, horror stories? I'm still working on the non-skid repair mini-essay (but want the practical experience first). I think that inflatable care and repair might be interesting. Jim W
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How About Plexiglass?
There have been many queries about crazing, causes, repair, reduction, protection, etc. However, there has not been much expertise in evidence. Since most of the production power and sail boats employ large areas of plexy, this is an issue of interest to many owners. A related issue is the annoying yellowing of some components. Rick D.
There have been many queries about crazing, causes, repair, reduction, protection, etc. However, there has not been much expertise in evidence. Since most of the production power and sail boats employ large areas of plexy, this is an issue of interest to many owners. A related issue is the annoying yellowing of some components. Rick D.
Clear Plastics Part I: Acrylic
Nobody really uses celluloid (celluoose-based plastic) or mica (fiberproof- used to be used on electrical devices) anymore. Clear (i.e. transparent) plastics are now mainly of three types. 1. Acrylic sheet or plate (lucite, plexiglass, perspex etc) 2. Polycargonate (lexan etc) 3. Vinyl (Isinglass etc). This posting is about acrylic. Acrylic: Clear acrylic is actually more transparent than glass. If you see a block of polished acrylic (can also be dissolved in solvent and moulded into shapes etc) if is extremely clear and transparent without that "greenish" look on the edge that glass has. However, like glass it is brittle and can shatter when hit. Also like glass it can be bent and moulded into shapes when heated. After such heat treatments it should be annealed (warmed and slowly cooled to remove internal stresses). It is lighter than glass and can be glued together, either by special solvent cements or just by glacial acetic acid. You can even make a cement by dissolving scrap acrylic in glacial acetic acid! Heat-rolled acrylic, like heat bent acrylic usually has internal stresses too!. As clear acrylic ages, it does not yellow (like lexan or vinyl) but starts so show surface "starring" or "crazing". due to the action of UV and (more important repeated cycles of expansion/contraction. That is why stress-rise crazing is seen around metal fittings and on the sunniest side of the boat. SOLVENTS etc: NEW plate plexiglass: This is often used to make windows and sealants (u.e. silicone- but be aware of the acetic acid content that could dull the surface) or Sikaflex, DAP etc can be used in sealing around the window. Some "non-selective" solvents such as acetone, MEK, lacquer thinner etc should never be used on plexiglass. This also foes for ammonia (which is actually used to strip acrylic coatings from kitchen floors or fiberglass) and (for obvious reasons) acetic acid. Toluene or Xylol (sort of "oily" solvents) can be used to clean up smears of sealant as can IG cleaners. Pink is preferable becuase it is very gentle and can be neutralized with water and cleans up any sealant, grease or marker pen. (6 years of boat shows!), Rolled acrylic will start to show some "starring" if repeated rubbing with solvents is done. OLD plaste plexglass: While surface starring can be polished out with an abrasive wheel (progessively finer grit) it is at a brittle stage and NO solvents should be used to clean the surface. You can use just soapy water followed by a mild silicone-based polish like Maguires. IG's Clear Horizons can also be used. Do NOT use any type of solvent to clean older "stressed" acrylic, even toluene or undiluted IG cleaners that was safe to use on new "unstressed" acrylic. Such products can initiate a "zipper" reaction that joins all the stress riser areas together causing actual cracks. Next time- Lexan and my 8 year experience with it! Thanks ALW .
Nobody really uses celluloid (celluoose-based plastic) or mica (fiberproof- used to be used on electrical devices) anymore. Clear (i.e. transparent) plastics are now mainly of three types. 1. Acrylic sheet or plate (lucite, plexiglass, perspex etc) 2. Polycargonate (lexan etc) 3. Vinyl (Isinglass etc). This posting is about acrylic. Acrylic: Clear acrylic is actually more transparent than glass. If you see a block of polished acrylic (can also be dissolved in solvent and moulded into shapes etc) if is extremely clear and transparent without that "greenish" look on the edge that glass has. However, like glass it is brittle and can shatter when hit. Also like glass it can be bent and moulded into shapes when heated. After such heat treatments it should be annealed (warmed and slowly cooled to remove internal stresses). It is lighter than glass and can be glued together, either by special solvent cements or just by glacial acetic acid. You can even make a cement by dissolving scrap acrylic in glacial acetic acid! Heat-rolled acrylic, like heat bent acrylic usually has internal stresses too!. As clear acrylic ages, it does not yellow (like lexan or vinyl) but starts so show surface "starring" or "crazing". due to the action of UV and (more important repeated cycles of expansion/contraction. That is why stress-rise crazing is seen around metal fittings and on the sunniest side of the boat. SOLVENTS etc: NEW plate plexiglass: This is often used to make windows and sealants (u.e. silicone- but be aware of the acetic acid content that could dull the surface) or Sikaflex, DAP etc can be used in sealing around the window. Some "non-selective" solvents such as acetone, MEK, lacquer thinner etc should never be used on plexiglass. This also foes for ammonia (which is actually used to strip acrylic coatings from kitchen floors or fiberglass) and (for obvious reasons) acetic acid. Toluene or Xylol (sort of "oily" solvents) can be used to clean up smears of sealant as can IG cleaners. Pink is preferable becuase it is very gentle and can be neutralized with water and cleans up any sealant, grease or marker pen. (6 years of boat shows!), Rolled acrylic will start to show some "starring" if repeated rubbing with solvents is done. OLD plaste plexglass: While surface starring can be polished out with an abrasive wheel (progessively finer grit) it is at a brittle stage and NO solvents should be used to clean the surface. You can use just soapy water followed by a mild silicone-based polish like Maguires. IG's Clear Horizons can also be used. Do NOT use any type of solvent to clean older "stressed" acrylic, even toluene or undiluted IG cleaners that was safe to use on new "unstressed" acrylic. Such products can initiate a "zipper" reaction that joins all the stress riser areas together causing actual cracks. Next time- Lexan and my 8 year experience with it! Thanks ALW .
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