Plastic Tank problems: Discussion thread, see info thread sticky for updates

[Scissors]

Where are you/they located? It might be the gasoline there is worse.

Ethanol content in gasoline can vary -- the label on the pump will always say "contains up to 10% ethanol" but that means it could contain 5% or 1% or even 0%, depending on the supplier. 

the best way to know is to test the gas, kits available online. 

Everywhere around here is pretty much the same.  Testing gas can't help you because one shipment can be completely different from the next.  But it's not the ethanol, though, it's the water.  Ethanol is miscible with water, which just allows water that makes it into the fuel tank to be exposed to a greater surface area of the tank.  PA6 doesn't absorb alchol, but it absorbs 8-11% of its mass in water, which is why it expands.

In my case, the tank never held onto its fuel long enough for ethanol to absorb enough water to be a concern.  I do, however, keep it outside and ride through rain, so those could easily be the source of the water absorption.  This area is also humid during the summer, allowing condensation to form in the morning if the fuel in the tank is cool enough.

[ducatiz]

Everywhere around here is pretty much the same.  Testing gas can't help you because one shipment can be completely different from the next.  But it's not the ethanol, though, it's the water.  Ethanol is miscible with water, which just allows water that makes it into the fuel tank to be exposed to a greater surface area of the tank.  PA6 doesn't absorb alchol, but it absorbs 8-11% of its mass in water, which is why it expands.

In my case, the tank never held onto its fuel long enough for ethanol to absorb enough water to be a concern.  I do, however, keep it outside and ride through rain, so those could easily be the source of the water absorption.  This area is also humid during the summer, allowing condensation to form in the morning if the fuel in the tank is cool enough.

You need to go back an re-read our previous interaction on this matter:

http://www.ducatimonsterforum.org/index.php?topic=25074.msg829421#msg829421

I've been following this issue for over 2 years now.  Nylons do indeed absorb alcohols.  The various kinds of nylon absorb at different rates depending on the conditions, but there is no doubt that Nylon6/PA6 is absorbing ethanol along with water.

[Scissors]

You need to go back an re-read our previous interaction on this matter:

http://www.ducatimonsterforum.org/index.php?topic=25074.msg829421#msg829421

I've been following this issue for over 2 years now.  Nylons do indeed absorb alcohols.  The various kinds of nylon absorb at different rates depending on the conditions, but there is no doubt that Nylon6/PA6 is absorbing ethanol along with water.

You are incorrect.  You have yet to post a single shred of evidence that PA6 absorbs ethanol.  The only study previously cited added water to the sample prior to measuring absorption.

Post up a link where a gasoline/ethanol mixture which is devoid of water is shown to cause absorption of the ethanol by the PA6.  Go ahead, I'll wait.  I won't hold my breath.

[ducatiz]

I actually do have something, but it is at home.  Published by a petroleum producer's consortium in Europe.  It recommends against the use of nylon containers for any ethanol enriched fuel.

It does not show a direct result -- no one to my knowledge has looked the specific issue.  However, there are analogous studies with other alcohols (namely benzyl and methyl) and both show absorption. 

Also, the lab that I had test PA6 samples from a Ducati tank did in fact show absorption in the presence of PURE ethanol (100%), which was decided as an appropriate methodology to test whether absorption occurred at all.

[ducatiz]

Here are the sources I have:

CONCAWE, the "conservation of clean air and water in europe" group prepared this document to help manufacturers prepare for the coming ethanol-enriched fuels.

CONCAWE "Guidelines for blending and handling motor gasoline containing up to 10% v/v ethanol"

It does not come out and say right off that "nylon absorbs ethanol" but it does list nylon 66 as an unacceptable material for use with ethanol. Even though our tanks are Nylon 6, they are close enough in composition.  Nylon 6 was developed specifically as an alternative to Nylon 6,6 and they are very similar.

Elsewhere, Nylon 6 has been shown to absorb benzyl and phenol alcohols.  Both are more aggressive solvents than ethanol, but ethanol does have the hydroxyl group as do all phenols.

http://onlinelibrary.wiley.com/doi/10.1002/pen.760080410/abstract

The absorption of ethanol will mostly occur after the tank has undergone hydrolytic degradation -- that is, it has absorbed water and is heated, which occurs whenever the tank is deformed due to water and the engine is on.  Whenever the bike is stationary, heat rises off the engine and warms the tank.  The hydrolytic process breaks the bonds with some of the methyl groups and permits invasion by more moisture and/or other liquids.

Lastly, of the multiple forms of Nylon 6 (6, 6-6, 6-12, etc) several are soluble in ethanol.  This doesn't prove that nylon 6 is easily absorbed by ethanol.  However, when I sent a tank to be tested, one of the tests was contact with 100% ethanol.  The test piece did in fact show increased weight and volume, but it was nowhere near the increase seen when tested in water.

[Scissors]

Here are the sources I have:

CONCAWE, the "conservation of clean air and water in europe" group prepared this document to help manufacturers prepare for the coming ethanol-enriched fuels.

CONCAWE "Guidelines for blending and handling motor gasoline containing up to 10% v/v ethanol"

It does not come out and say right off that "nylon absorbs ethanol" but it does list nylon 66 as an unacceptable material for use with ethanol. Even though our tanks are Nylon 6, they are close enough in composition.  Nylon 6 was developed specifically as an alternative to Nylon 6,6 and they are very similar.

As you can see here:
http://www.ides.com/articles/polyamide_moisture_absorption.asp

...Polyamide 6 is significantly better at resisting dimensional changes due to water absorption than Polyamide 6,6.  Both are still quite a bit worse than most other plastics.  (See figures 3 and 4)

Both materials are unacceptable when used with ethanol in significantly higher concentrations, such as with E85.  This is why E85 vehicles come with fuel tanks made from other materials.  But we're not dealing with E85 in our bikes.

Elsewhere, Nylon 6 has been shown to absorb benzyl and phenol alcohols.  Both are more aggressive solvents than ethanol, but ethanol does have the hydroxyl group as do all phenols.

The hydroxyl group is why it mixes so well with water.  You know what else has a lot of hydroxyl groups?  Carbohydrates, such as glucose and fructose.  But that doesn't cause problems for the PA6.

Benzyl and phenol alocohols are not ethanol and have their own sets of properties.  See page 275 here:
http://books.google.com/books?id=7Qq_vknrP4kC&pg=PA277&lpg=PA277&dq=PA6+benzyl+alcohol&source=bl&ots=0n4Dq1BcQu&sig=Vim_R_4mrVlueGvYlztiL_IYtaI&hl=en&ei=eUIxTuLfKonGgAfs7ZygDQ&sa=X&oi=book_result&ct=result&resnum=1&ved=0CBUQ6AEwAA#v=onepage&q&f=false

Note that it says that PA6 has "better solvent, grease and detergent resistance than PA66."

Also note the following:

"PA 6 is resistant to alcohols, aromatic hydrocarbons, esters and ketones:  the resistance to chlorinated hydrocarbons is only fair.  Has good resistance to oils, greases, fuels, fats, greases and, to alkalis (in say concentrations, of up to 20%).  PA6 is not resistant to acids (dilute and concentrated) and to solutions of oxidizing agents.  Formic acid, concentrated sulphuric acid, dimethyl formamide, phenol and m-cresol are solvents (as for all PA materials).  The density is 1.12 gcm^3/0.65 oz in^3.  As the natural colour of the material ranges from a translucent white to translucent beige, then a wide colour range is possible; both translucent and opaque colours can be obtained.

Both PA 6 and PA 66 will absorb large amounts of water, for example, they will absorb approximately 10% of water at saturation.  However, PA 6 absorbs more water than PA 66 under the same conditions.  The material is supplied dry; as supplied the material is suitable for processing however, if containers are left open rapid water absorption will occur.  If moisture content is >>0-2%, flow and component properties are affected and the material must be dried.  Dry in a well ventilated, hot air oven for 16 hours at 80 degrees C."

Bold added for emphasis.

http://onlinelibrary.wiley.com/doi/10.1002/pen.760080410/abstract

The absorption of ethanol will mostly occur after the tank has undergone hydrolytic degradation -- that is, it has absorbed water and is heated, which occurs whenever the tank is deformed due to water and the engine is on.  Whenever the bike is stationary, heat rises off the engine and warms the tank.  The hydrolytic process breaks the bonds with some of the methyl groups and permits invasion by more moisture and/or other liquids.

I'm still waiting for you to supply a source on this.  You claim that it's also absorbing the ethanol, but still have nothing backing it up.  It may very well also be the case, but I'd like to see actual research, or even just a source.  On top of that, the water absorption alone is enough to explain what people are seeing.

Lastly, of the multiple forms of Nylon 6 (6, 6-6, 6-12, etc) several are soluble in ethanol.  This doesn't prove that nylon 6 is easily absorbed by ethanol.  However, when I sent a tank to be tested, one of the tests was contact with 100% ethanol.  The test piece did in fact show increased weight and volume, but it was nowhere near the increase seen when tested in water.

Luckily E5, E10, and E15 are nowhere near this concentration.  As we all know, concentration matters greatly.

Edit:  Even if it absorbs minute amounts of ethanol, the effect is nowhere near the expansion seen with water absorption.  It's like worrying about the tack in your foot while there's a sword piercing your gut.

[ducatiz]

As I indicated, I don't have that.  I posted what I do have.  We observed a dimensional change in the samples when in contact with ethanol.  Yes, the concentration is different, but my original point was simply that "pa6 absorbs ethanol."  "How much" and "under what conditions" are very relevant questions, but for purposes of demonstrating that the tank material is inappropriate for use as an ethanol-enriched gasoline cel, our test was sufficient.

Industry review of PA6 as a fuel container have focused on the water absorption issue because of the dimensional changes and the likelihood of hydrolytic degradation.  However, the interaction of specific fuel ingredients has ~never~ been reviewed by anyone until now.  My guess is that the material is so new (in this use) that the issue hasn't arisen until now.  I would be surprised if there weren't a few people looking at it and will be publishing in the coming year(s).

However, right now, we know that PA6 does absorb ethanol.  It's possible that in a 10% v/v solution that it does not do so due to other interactions with the gasoline component, or maybe it is faster due to the water component. 

At this point there is only my work on the matter.

I don't have any more to contribute here, this isn't really helpful to the thread.  If you need to reply, please do so in PM and we can post the results later. 

[corey]

Progress report. Had my bike up the shop on June 18th for photos, measurements and analysis. Service manager stated that in his experience, my tank was a good candidate for replacement. They started the good will claim, and mentioned epoxy coating as a "customer pay" service for the new tank.

Heard back yesterday, June 29th, that my tank will indeed be replaced. When the dealer is made aware of shipment, they will schedule a service appt. to install the tank. There was no suggestion or guess of the arrival date of the replacement tank.

I'll post up in the future with more updates as a frame of reference of ONE person's experience.

More progress. My dealer received my tank last week. Had my tank checked on June 18th, replacement was confirmed on June 29th, and I am now scheduled for installation on August 19th. About 2 months in process so far.

My dealer also SUGGESTED "ethanol-resistant" epoxy coating at about $175. They are going to do this ahead of time so the tank is ready to install on the 19th.

They stressed that epoxy coating isn't a Ducati-approved solution. They also stressed that they are unsure how willing Ducati will be to replace tanks in the years to come.

I'll post up pics after the install, but so far, so good.

[ducatiz]

More progress. My dealer received my tank last week. Had my tank checked on June 18th, replacement was confirmed on June 29th, and I am now scheduled for installation on August 19th. About 2 months in process so far.

My dealer also SUGGESTED "ethanol-resistant" epoxy coating at about $175. They are going to do this ahead of time so the tank is ready to install on the 19th.

i would like to know what he plans to use.  ask please?

[corey]

i would like to know what he plans to use.  ask please?

just called them up. it's caswell.

[Uncle Mofo]

 New tank in transit. I'm going to have Indianapolis Ducati coat it.  (Caswell)

[BoDiddley]

I have a plastic gas container that I have had gas in for at least ten years.  It has ridges molded into it for strengh and I can tell that it is not stretched wrinkled or expanded.  I bought two of them, used the one and put the other one away for future use but never needed it.  They are still identical.  I am thinking about doing a Caswell on the unused one. Seems curious that not all plastics expand with E10?  Not a very technical observation but then sometimes the simple ones get you. 

[ducatiz]

I have a plastic gas container that I have had gas in for at least ten years.  It has ridges molded into it for strengh and I can tell that it is not stretched wrinkled or expanded.  I bought two of them, used the one and put the other one away for future use but never needed it.  They are still identical.  I am thinking about doing a Caswell on the unused one. Seems curious that not all plastics expand with E10?  Not a very technical observation but then sometimes the simple ones get you. 

It's probably layered HDPE.  Not the same material.  HDPE has been in use for car gas tanks for a while probably around 10-15 years.

[BoDiddley]

It's probably layered HDPE.  Not the same material.  HDPE has been in use for car gas tanks for a while probably around 10-15 years.

Yep : That is my point.   How could R/D engineers be that blind to not use materials that are available and proven to work for their project.  Instead use a material that is already a proven nightmare in the boating and other industries.  Odds are it was a production decision.  And Ducati is still using the same company. WOW!   Sounds like politicians are running the show.  

[Howie]

Yep : That is my point.   How could R/D engineers be that blind to not use materials that are available and proven to work for their project.  Instead use a material that is already a proven nightmare in the boating and other industries.  Odds are it was a production decision.  And Ducati is still using the same company. WOW!   Sounds like politicians are running the show.

One reason is paint adhesion problems..