Shelf Life of Polyurethane in Boots

I have a beard trimmer with a rubber coating that has gotten sticky, although I don't know if this is the same as your problem.

This might be of interest:

"

Biodegradation[edit]

Two species of the Ecuadorian fungus Pestalotiopsis are capable of biodegrading polyurethane in aerobic and anaerobic conditions such as found at the bottom of landfills.^[55] Degradation of polyurethane items at museums has been reported.^[56] Polyester-type polyurethanes are more easily biodegraded by fungus than polyether-type.^{[57] "}

^{https://en.wikipedia.org/wiki/Polyurethane}

The stickiness of plastics is usually due to migration of plasticizers (like Pthalates) in products of lower quality. These plasticizers are used to improve or give certain desired properties to plastics (like flexibility).

Myth Under Test

Mythbusters MUT(Myth Under Test): Worn shoes last longer than stored ones.
What can shoe manufacturers do ? Include a warning not to store shoes ? Unsatisfying!

An excerpt from an offshoot of Rixter's references says:

https://aem.asm.org/content/77/17/6076.full
"In the current study, endophytes were isolated from plant stems collected in the Ecuadorian rainforest. A subset of these organisms was screened for their ability to degrade polyurethane. Several active organisms were identified, including two distinct isolates of Pestalotiopsis microspora with the ability to efficiently degrade and utilize PUR as the sole carbon source when grown anaerobically, a unique observation among reported PUR biodegradation activities."

So, anecdotally, worn PU shoes may have a longer lifetime why ?
Perhaps, shoes with soles which have never, or very few times, been worn remain
anerobic since manufacturing. Worn shoes are having air pumped in and out of them
during the diurnal cycle of having human weight on them or not. Worn shoes are
also having moisture and thermal cycles which superficially would seem to lead to
earlier deterioration so the observed data seems to be reversed for these(thermal
and hydro) cycles.

Perhaps, during the final stages of manufacture, the shoe manufacturer could use
a large hyperbaric chamber to drive oxygen into the soles of their shoes.
Just put a pallet load into the chamber, pump it up with oxygen, then let it
return to one atmosphere slowly to prevent marshmallowing of the soles. Do the
shoes now last longer on the shelf than the normal anaerobic ones ? Maybe the
sellers could treat only right shoes and automatically send fully treated
replacements to all customers who return pairs of shoes with only the left one
deteriorated. Once the results statistically prove the validity of the data, the
manufacturer might treat all right and left hand shoes for a more reliable product.
Lots of other testing should be performed on treated and untreated shoes to see
if there are any unintended consequences of hyperbaric oxygen treatment.
_______________
thewildotter

That's not the only factor at play. Besides the amount of oxygen, is the oportunity for organisms to attach themselves. A ship/boat in port gets more barnacles than one at sea.

Realy interesting test,lol

Had a pair of military jump boots, the soles deteriorated as you described. I attributed it to placing moth balls in the same bin

I had a pair of $100 sketchers I bought, one white pair, one black pair, I wore the white pair for 5 years, and had the black pair still in the box in a closet....when I took the black pair out I wore them for about two days, kept seeing little black things everywhere, finally noticed they were coming from the sneakers after the soles came loose and just deteriorated into chunks.....unrepairable...

I had a pair of Wolverines that the sole separated, but I took them to a cobbler who was able to reglue them back....

I'm of the opinion that the black pair were Chinese copies, I've noticed that the rubber products from China are of inferior quality, I have at least 4 or 5 instances in which rubber products have failed prematurely...It might be possible that this relates to your experience....

https://www.npr.org/templates/story/story.php?storyId=11656278

https://www.cpsc.gov/business--manufacturing/international/chinese/monthly-recall-summaries

I bought a pair of Dr. Martens when I was 20, I’m now 64 and I still wear them on odd occasions. I now have a new pair, they’re only 4 years old. I’ll be dead before they wear out.

Forget Sketcher’s, buy some descent boots.

I wear them occasionally because they are comfortable, I have extremely high arches and wide feet, but don't worry I have many pairs of shoes, including several pairs of hiking boots...

Prolonged exposure to heat or moisture will cause PU to melt (revert back to its constituent chemicals.

The military had a big problem with connector potting boots melting in Viet Nam.

Buy known quality, with a warranty.

..."Molded polyurethane foam soles can be amazingly comfortable but, unlike leather soles, they have a limited shelf life. According to footwear industry consultant Phillip Nutt, the shelf life of a direct-injected polyurethane sole should be in the range of four to five years. He says the material tends to "crumble into a sticky mess" when stored for "periods longer than four years or so."

Disuse apparently increases the risk that polyurethane soles will degrade — and that probably increases the indignation of consumers whose barely worn shoes disintegrate. If you wear your shoes every day and walk miles in them, you expect the soles to show wear. You don't expect shoes to be destroyed by months or years of sitting unworn in their box in your closet."...

https://www.stltoday.com/lifestyles/fashion-and-style/shoes-aren-t-made-the-way-they-used-to-be/article_3f00f4fa-2f43-5d6b-83fd-b6b0a4de43db.html

I haven't met a shoe / boot that I couldn't destroy in less than 3-4 months/weeks.

My only way to make them last is to have others to wear.

..that and wear the ones with my toes hangin' out in the garden.

I had a pair of Timberland's in the 90's that wore like iron.. all replacement pairs failed in comparison. I've had similar issues with other quality brands like Doc's, Born and so on. The main issue is that my size 12 wide feet along with my nearly 200lb frame don't give shoes much of a chance.

If my shoe crumbled I'd just grumble.. I had soles crack open on nice boots and the soles peel off.. I've also had $29.99 footwear that outlasted "premium" products.

It's a crap shooooo t.

Hey Maw... I found some shoes I can wear! I can go to school! I can be somebody!

Give up hope boy.

Dreams are for suckers.

This sounds like a product warranty return, as the boots were not fit for their intended purpose.

YES!

Our company store handles safety boots for all staff. Boots older than 18 months often fail as you described while issued boots survived.

Colleague (office worker) had her issued boots in air conditioned office and same happened to them, so doesn't relate to the storage.

Did your boots have electrostatic dissipative additive in the soles? Maybe that additive is affecting the outcome.

Don't know a solution other than to not store for prolonged time.

We now send staff to local supplier and buy off the shelf.

Hi fellow down underan.

These boots were well known brand of heat, oil, acid resistant, soled steel toe capped boots laced up to above the ankle, mine spec boots.

Had a pair of Redwings once the sole just flew off of them so got Doc Martens but was thinking of suing for malpractice when they failed just out of warranty. Maybe the manufacturer has installed time dependent biodegradable plasticizer.

I take 11.5 or 12 depending on the wideness of the fit but the mine spec boots seem to all suffer from the same failures.

Now my gum boots are twenty years old and not a sign of failure though they were made in Oz back when we did make things instead of off shore manufacturing.

Hello,

The boots we issued were steel caps but in high side and low side, lace up and elastic sided. All styles were observed to fail. Blundy's and the other brand both as bad as each other.

Also saw same failure mode on women's raised fashion shoes last week. 40mm soles and heels. The heels on both almost simultaneously failed as she entered Church. She is a regular attender, so wasn't the wrath from above, just co-incidence.

Gum-boots not seen to have the same outcome.

Welcome on board.

Yes I've had the same problem many times. Like JE I am death to footwear anyway but I really get ticked when the seams fail before I've ground the soles down to unusable wreckage.

I had one pair of boots which belonged to someone else, were bought about 20 years ago, and I only used them for snow shoveling, miraculously lasted about 18 years before they started to fail in the same place, the seam between the upper and rubber. So it may well be that new additives are causing the poly to fail more quickly.

Umm.. I had a pair of coveted Sorel boots that were pawned behind my back some 20 years ago. You don't think?... you didn't pick those up in Chicago by any chance?

One other experience... The head piece and ear pads on Bose Quiet headphones failed. Bose offered a "great deal" on a new pair. I found Bose replacement pads and installed them. They too, failed within 18 months. Somehow I think that $300 headphones are of poor quality

A recurring problem for me: Sure, adhesive between soles and uppers disintegrates/melts when accidentally left in sun or walking on very hot surfaces.

However, with newer shoes the polyurethane soles themselves crumble after a year now (Rockport), whereas 5year-old Rockports with similar construction are still going strong. Ecco had this problem much earlier: they may have fixed it by now - I don't know: I just stopped buying them.

I think the issue is that in trying to reduce weight, they use a foamed polyurethane rather than solid, and then to get the right stiffness they have to use a much stiffer material, whereas if it were solid PU, it could be much more elastic. The problem is not just the stress on a stiffer material. Even in storage, the stiffer material degrades more quickly, so my guess is the issue is that the stiffness is achieved by increasing the cross-polymerisation, and to do this they must increase the concentration of catalyst or whatever, so that the chemical reaction keeps on going for months, ending up with it falling apart.

Whatever, I now attack them viciously with a sander at the first sign of failure, until the soles are really thin and take 5-10mm of the heels too. Then I spread Sikaflex 11FC polyurethane rubber thinly over the fresh surface and thickly on a piece of woven Kevlar, working it through the latter, apply, let set for a week and then stick on new rubber soles and heels using the same stuff, then leave 2 weeks before finishing off with a belt sander and maybe a smear of a harder grade of polyurethane just to give it a bit more gloss and cover up any edges of Kevlar.

Then they're OK for another few years (I have a bad habit of running in black lace-up leather business shoes, and this still works for me)

One.. I'm glad to see we're not the only one's dealing with newer shoes failing.

Two.. I won't buy a shoe if the layers look iffy or weak, but then the sole could pop off easier. Yes.. I've got some very fresh Levi boots with this problem.

Three.. the rest of you post is insane!

You do what? Kevlar and.. I gotta read this aloud to a group of people.

I bought a brand-new pair of Milwaukee (the tool company) boots that failed on me. I was up in a tree with a chainsaw, with the heels hooked on branches for stability. It was too much for the boots, and a heel came all the way off with no warning. I was lucky I recovered from it before I got hurt. That was the first time that ever happened to me; I never had such a bad experience with boots before. I still have my Navy issue boondockers, They've given no trouble at all.

Glue (any kind) should NEVER be the only method of attachment. Nails prevent sheer motion, and glue prevents tension movement. Both together gives a secure attachment. But, glue by itself can start at the edges and slowly detach itself without extreme force. It slowly weakens to the point of catastrophic failure. Glue might even survive degradation, while the substrate weakens. Nails or bolts or something else to prevent the sheer forces from weakening the glue joint will help the glue maintain its grip.

I really think that no boot should be called a work boot, without some minimum standard/reliability to live up to. We got UL standards for 'trons, we even got the Good Housekeeping Seal of approval for curtains. What about OSHA's seal of approval for work boots? You never know what you'll encounter on-the-job. Bad boots beg bad bedrest before betting beleaguered boys backs don't break.

Apparently, once polyurethane soled shoes are removed from the climate controlled environment of your local shoe store, the degradation process begins.