Proseal / Aerolite damage to acrylic plexiglass.

I discussed a failure of plastic fuel level sensors with the principle of a polysulfide sealant supplier. My problem involves polysulFONE molded level sensors and the jury is still out if polySULFIDE sealants caused the failure.HOWEVER, I was informed that polysulfide sealants attach acrylic plastics The specific example given was boat windows that initially craze and eventually become opaque brown. Canopies cost at least $800 but the work to replace is priceless. So, beware of your choice of sealants on plastic.

AC-251

From ACS:

"AC-251 Black Class B are two-part, quick curing, polysulfide based canopy and windshield sealants. These products are formulated for sealing acrylic, glass, and polycarbonate aircraft canopies and windshields. AC-251 Black Class B Sealants contain no solvent and do not craze. The sealants quickly cure and exhibit excellent adhesion and resistance to UV and weather exposure."

This is recommended over pro-seal for sealing acrylic...

Larry DeCamp said:

I discussed a failure of plastic fuel level sensors with the principle of a polysulfide sealant supplier. My problem involves polysulFONE molded level sensors and the jury is still out if polySULFIDE sealants caused the failure.HOWEVER, I was informed that polysulfide sealants attach acrylic plastics The specific example given was boat windows that initially craze and eventually become opaque brown. Canopies cost at least $800 but the work to replace is priceless. So, beware of your choice of sealants on plastic.

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WHO is the source of your info about PolySulfide causing crazing in acrylic plastics?

I attached the windshield of my RV-6 with PolySulfide over 22-years ago and have over 3,300 flying hour without any of the issues.

MSDS

If you look at the MSDS for pro seal, the curing process yields acetic acid and alcohol. Checking charts on acrylic, it is not resistant to the acetic acid, which may cause undesirable effects in the acrylic...

rocketman1988 said:

If you look at the MSDS for pro seal, the curing process yields acetic acid and alcohol. Checking charts on acrylic, it is not resistant to the acetic acid, which may cause undesirable effects in the acrylic...

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Post a link to the MSDS.

I have no dog in this fight

Just wanted to help folks be aware of one source?s opinion. Do your own research and satisfy yourself.

rocketman1988 said:

If you look at the MSDS for pro seal, the curing process yields acetic acid and alcohol. Checking charts on acrylic, it is not resistant to the acetic acid, which may cause undesirable effects in the acrylic...

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Here is the chart I have on acetic acid and acrylic.

Says: "Slight attack by absorption. Some swelling and a small reduction in mechanical likely."

Some 22+ years later, I still have not experienced any issues.

post

You may want to READ what I wrote.

According to the MSDS, which is readily available online, the curing process yields acetic acid and alcohol. That is fact.

I also said the acetic acid MAY cause undesirable effects with acrylic; the key word being MAY.

Is your acrylic chart for the specific composition of the material used for the canopy? Maybe, maybe not...there are numerous formulations.

...and to generalize that because your particular experience using pro seal and acrylic yielded no undue effects to every other case, well that is just silly.

The point is, the acetic acid is real; it may or may not negatively affect acrylic canopies...do the research, make your own decisions on whether to use pro seal, knowing that there is another polysulfide sealer that cures WITHOUT the acid, and is readily available from ACS and other suppliers...

Larry DeCamp said:

I discussed a failure of plastic fuel level sensors with the principle of a polysulfide sealant supplier. My problem involves polysulFONE molded level sensors and the jury is still out if polySULFIDE sealants caused the failure.HOWEVER, I was informed that polysulfide sealants attach acrylic plastics The specific example given was boat windows that initially craze and eventually become opaque brown. Canopies cost at least $800 but the work to replace is priceless. So, beware of your choice of sealants on plastic.

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I just downloaded and searched the SDS and TDS for PPG PS-890 (Proseal), PRC 1440 and PRC 1422, no mention of the production of acetic acid or alcohol.
You sure you are not thinking of the common RTV types which do give off these chemicals during cure and are known to have some issues with acrylics?

Many aircraft manufacturers have used Proseal fuel tank sealants for window bonding and sealing for more than 50 years, and I never heard of this issue.

I looked this up about a year ago and some manufacturers had cautions about their products in proximity to acrylics. There were some similar products with different formulations specifically for use in sealing structures against acrylics, mostly intended for certified, pressurized aircraft.

As Bob said, do your own research.

I'll see if I can locate the documents I found back then.

Here is one I found which contains no solvents, recommended for this application: https://multimedia.3m.com/mws/media...ce-sealant-ac-251-black-class-b-datasheet.pdf