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Solvent restoration of trunk floor mats

Started by raueda1, 01 April 2023, 03:15 PM

raueda1

I'm hoping some fellow chemist here might help.  One of my trunk wheel well mats was soaked in oil - motor oil, hydraulic fluid, tranny fluid, you name it.  Now it's all distorted from oil swell and doubtless weakened too.  I thought that maybe it could be restored by a long soak in lighter fluid or kerosine, naphtha spirits or whatever.  The idea is that the kerosine would eventually soak into the mat and help solublize the oils.  Eventually an equilibrium would be reached whereby the mat would be swollen by a kerosine/oil solution, effectively leaching the oil out of the mat.  Then let it dry.  A tiny amount of the oil would remain but probably not enough to matter.  I'm pretty confident that this could work, at least in theory.  The problem is, how long to reach the equilibrium?  Days?  Weeks or years?  Maybe centuries!  Any thoughts would be welcome before I just go for it and report back.  Hopefully that won't be in 2114.  Cheers,
-Dave
Now:  1976 6.9 Euro, 2015 GL550
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

ptashek

Tried this approach with my car when I first bought it. It was a complete waste of time unfortunately. What I did in the end last year, was just recover the original carpet with van liner fabric. It looks factory fresh now.

https://forum.w116.org/mechanicals/what-have-you-done-for-your-w116-today/msg153007/#msg153007
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE

BCK1963


The equilibrium approach is a good and valid theory but in the real world of limited willingness to invest time and solvents it will not work.

As an example, engine oils are composed of the basic hydrocarbon oil and additives. Different oils, e.g. some hydraulic fluids, are often so-called PAGs / polyalkylene glycols. Additives are a broad variety of different chemicals. Gasoline, kerosene or brake cleaner fluid are hydrocarbons and miscible with hydrocarbon oils.

Mat fibers are mostly polyamides or similar plastics (I guess that not even Mercedes use notable amounts of cotton for their mats). The oils and additives can permeate into the fibers or adsorb / bind on the fiber surface.
Kerosene and the like is theoretically capable of dissolving the hydrocarbon oil but if the oil is stuck to or in the fibers it takes 1. a long time of drowning the mats and 2. repeatedly fresh solvent to catch major amounts of the oil.

The additives are not necessarily soluble in kerosene, even if they appear soluble in oil. Oil formulations are very complex and some additives are emulsified in the oil (like oil drops in water with the help of detergents). Once this emulsion is destroyed, the additives may not be soluble in kerosene anymore and remain in or on the fibers.

Some hydraulic PAG fluids are not miscible with hydrocarbons at all and require different solvents, e.g. ethanol. Since fibers may be impregnated by the oil, its effectivity is poor.

Last but not least: The oils and additives, when exposed to oxygen for a long time, age: They are attacked by oxygen and may become some king of gunk which is not soluble at all.

There are a bunch of mechanisms and effects applying which eventually lead to the result which Lucas has put in exactly the right words  8)
Bernd

1976 Merc 6.9   Magnetit blue

ptashek

1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE

rumb

Dave, are your wheel well mats they gray non woven fabric or the ribbed plastic ones? The plastic ones were only used a few years.

I found a near exact match to the fabric in an auto parts store,  - looks like the stuff you found. they sold it as floor or drip mats I think.

The side panels were all curled and rotted, made new ones with wax board and glued fabric to them.

I think later cars the carpeting panels changed and is a different base material.
'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS
'21 E450 Cabrio

raueda1

Thanks to all for the comments.  A few points of clarification.  I'm talking here about the rubber wheel well mats, not textile covers or whatever.  I had no idea that these were superseded by carpet mats. All the cars I've messed with had the old rubber mats.  Somehow I always end up with the old stuff.  ???

Anyway, to me they look like mineral filled SBR rubber (e.g. silica, CaCO3, clay, etc).  As others commented, the theory behind the extraction method is solid.  Motor oil, hydraulic fluid and ATF, which are the problem, are infinitely soluble in kerosine/naphtha/etc.  Not concerned with brake fluid or coolant.  Some chemist at Goodyear would certainly have the data to do calculations. All I have is a workshop so I guess I'll just go ahead and try it - cover mats in a thin bath of kerosine for a few weeks and see what happens.  The question is just how long it might take.   If that's not enough time for everything to equilibrate then I'll try to reconstruct a la Rumb.

As for cleaning up the carpet mats, I'm no surprised that similar methods failed.  Unstaining stained nylon is all but impossible.  And most such pads (probably all of them) have a foam backing of filled SBR or XSBR.  This stuff is notoriously oxidatively unstable and starts disintegrating almost immediately.  Cheers,
-Dave
Now:  1976 6.9 Euro, 2015 GL550
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

raueda1

Well guess what?  It more or less worked! To repeat, the mat is the old, gray rubber style, not carpet/textile.

Method: The mat was soaked overnight in charcoal lighter fluid (light naphtha, mineral spirits or whatever you want to call it) in a flat SS tray.  The sides and ends were quite curled, and so therefore held flat in the tray by a lot of large socket wrenches.  It was left to soak for about 36 hours and flipped over halfway through. The mat became quite swollen from the solvent, actually growing about 3 cm wider.  The solvent turned dark brown from whatever it was extracting.  The mat was then dried, mostly in the sun for about 12 hours.

Result: Pretty good, actually better than I expected!  The swelling is greatly reduced.  I expect it to be gone after another day in the sun.  Though it's not perfectly flat, the curling is dramatically reduced.  The bottom line is that it's usable again, a helluva lot better than it was in the first place, before the oil soaking.  After the oil soaking it was so bad as to be useless.  I'll post a pic after it's completely dried (assuming that it doesn't crumble to dust or otherwise revert).  Cheers,
-Dave
Now:  1976 6.9 Euro, 2015 GL550
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0