Polyurethane moulded soles are quite common in a variety of shoes but increasingly in the flexible style walking or work boot.
they are distinct from other types of sole in that they are often spongey, moulded direct onto the leather upper often without a traditional stitched on welt
I have several pairs of these including a matched pair of Kodiak boots I bought in Canada approximately 5-6 years ago.
one pair I brought back here which have seen viscous abuse as combined work boot, general walkabout boot and sometime shooting/stalking boot.
the other pair I left in Canada with my inlaws for use when visiting them. I have used them probably 6-7 times in that time.
in the last 3.5 years I have not been back or seen them and they have been stored in a warm dry cupboard.
i planned to bring them back with me this trip.
when I got there this time when I went to put them on I noticed the bead between sole and upper had a few cracks, nothing major.
but on closer inspection it was soft and could be picked away.
closer still revealed a section of sole cracked away from the upper.
i bought some glue and did a quick repair ready for a fishing escapade the following day.
duly fixed I set off, thankfully not too far, a short drive, an even shorter walk and a spot under a bridge.
after about 45 mins of standing and occasional moving around the rocks I noticed on one boot the toe was gaping crocodile style
as I moved off the heel gave way on the other!
Calling it a night for fear of going barefoot I started back along the 200 yds of Tarmac back to the car.
within 20 yds one sole fell off
within 100 yds the other fell off!!
when I got back and examined the sole the foam polyurethane was completely perished and crumbled at the slightest touch.
the entire surface that was not exposed to the air was mush.
kodiak had this to say:
According to the labels inside the boots, they were manufactured in February 2001. These boots are 14 years old.
These boots have polyurethane soles and the present state of these soles is due to aging. They have basically dried out in time. This usually happens after 5 years.
What is occurring is a common phenomenon in the footwear manufacturing industry known as "hydrolysis".
This refers to the natural breakdown and decomposition of the polyurethane compound of the mid and outsole.
It is not a manufacturing defect, but a natural process that occurs in time and which cannot be prevented, regardless if the footwear is worn or not and regardless of the brand of the footwear. Please note that hydrolysis does not affect rubber, therefore footwear with rubber outsoles would last longer(although it is a bit heavier than polyurethane).
The manufacturer's warranty is 6 months from the date of purchase and unfortunately your boots are no longer under warranty.
Bilingual Customer Service & Inside Sales Representative
KODIAK GROUP HOLDINGS INC
Phone: 519-620-4000 x 4022
Apparently despite being only 7 years old to me they had been made some years earlier, more concerning was the firm's expectation of a 5 year life span!!
Some time on Google shows me that this is a much bigger problem with a huge number of brands.
polyurethane hydrolysis soles - Google Search
they are now off to be repaired and have a nice pair of rubber soles fitted to the essentially untouched uppers!!