Softening old hardened vinyl trim is possible it seems

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Over some months I've been looking into softening the old vinyl trim in my 1600M and have found a way this can be done, though it's still a work in progress. The process involves re-plasticising the vinyl with Epoxidised Soybean Oil (also called ESBO or ESO) which, among it's many uses is as a plasticiser for PVC and rubber. It's used in food products like the gaskets of screw top jars, cling film, surgical tubing etc. as it has a very low toxicity.
The only problem with this stuff is getting hold of it on small quantities. I was lucky and picked up a US gallon tin on fleabay. Price was $65 but with postage and import duty it cost me £100. This particular stuff is labelled "Nordson Type K fluid" but is 100% ESBO. I've used maybe a quarter of it, most of which has been lost to seepage, evapouration and washing it off my hands.

Unfortunately I have no "before" pics but these "during" pics show where I'm up to.



This is the outer door trim resting loosely on the panel with padding removed.




This is a detail of the leading edge.




This gives some indication of how flexible it has become.

As you can see in the pictures, the issue is that in order to get the really hardened areas to become flexible and regain some elasticity, the ESBO coated vinyl needs to be kept at around 55C for anything from 2 to 5 days. Durng this time, adjacent softer areas are still absorbing ESBO at the same or greater rate than the hardened areas. The end result is that quite a lot of the vinyl ends up over plasticised. Where the backing material is still there, this results in a thickening of the surface, a very exagerated look to the grain and a tendency to curl. Where the backing has been eaten by mildew, the vinyl thickens less but expands a lot, causing the big wrinkles along the bottom of the panel.

I've only tried small samples as yet, but Isopropyl Alcohol (which is PVC safe) will successfully extract the excess plasticiser. From my experiments with samples ranging from "about right" to "seriously over plasticised", they all end up quite consistent in therms of flexibility and elasticity after about 3-5 days immersed in IPA.

I have 5L of IPA on the way and a large-ish shallow plastic container with a lid so I'll try extracting the excess on one of the inner door trims. I'll monitor progress with a 1g resolution balance that I've belatedly bought.

Costs so far:

ESBO - £100
45w reptile terrarium heat mat - £20
1g resolution balance - £39
Isopropyl 99.9% - £30 and counting (may end up using quite a lot of this)

I'll post a progress update after the IPA arrives.

Dom

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Progress!

The LH inner trim has been in slightly diluted IPA for nearly 3 days now and weighs 30g less, which is around 12.5%. The vinyl is still very thickened in places but large areas of this panel are now very close to the original finish. Not all of the 30g will be due to excess plasticiser removed from the vinyl as virtually all of the remaining old contact glue has now been dissolved, and the backing fabric still retained a little plasticiser too.

This panel will be in some nice clean IPA tomorrow, but first I need to improve the sealing of the cheapo containers I'm using to keep evapouration under control.

Shown in the pic is a piece of original vinyl cut from under the dash near the a post for comparison. It still has a faint vinyl type odour and has probably never been washed nor seen a lick of sunlight or wear since leaving the factory. A such I'm not expecting an absolutely exact match to this but it should be very very close, and it is in places.