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Need a lesson in boot plastic... how to estimate stiffening effect of cold?

post #1 of 14
Thread Starter 
I was wondering if someone could give me some guidelines on how to guess which boots will stiffen more with temperature change. Which plastics are most succeptible to variation, and does it vary with brands?
post #2 of 14
thicker the plastic the stiffer it will be..

this is also the case with higher end boots = stiffer in the cold
post #3 of 14
Quote:
Originally Posted by mntlion View Post
thicker the plastic the stiffer it will be..

Not necessarilly true. In boots it also depends on what type of plasitics are being used. Race boots are different plastics than beginer boots, and many intermediate boots will be a blend of a couple types of plastics in different parts of the boots. Now to further the complexity, the different plastics respond differently to the cold.
post #4 of 14
Thread Starter 
Quote:
Originally Posted by Manus View Post
Not necessarilly true. In boots it also depends on what type of plasitics are being used. Race boots are different plastics than beginer boots, and many intermediate boots will be a blend of a couple types of plastics in different parts of the boots. Now to further the complexity, the different plastics respond differently to the cold.
Could you elaborate more on the specifics of this? I'm interested in the properties of the different types of plastics.
post #5 of 14
Two main types of plastics used in boots:

Polyurethane: Found in cheaper boots. Usually has a very plastic-y look to it- think Salomon Performas. Has a linear increase in stiffness in the cold, and doesnt stiffen up as much as polyether. You can tell a polyurethane boot by the soles- they almost always have replaceable sole pieces or a different plastic molded into the soles.

Polyether: Used in higher performance boots because of its higher rebound. Stiffens exponentially in the cold- get much stiffer below a certain temperature. Some polyether boots have replaceable sole pieces, although they are more for canting purposes (Lange) due to polyether's durability.
post #6 of 14
Look up the Tg of the plastic in question here:http://www.ptonline.com/

Basically the lower the Tg and th thinner the plastic, the softer it will be at colder temps.

Tg stands for the Temperature of teh glass transition state. Bascially at what temperature the plastic goes from being hard and ridged like to being more leathery.

Also most boots have a two or three letter abreviation on the inside of the shell that will tell you what kind of plastic that they are made off. This will be found on multiple parts of the shell. It can tell you if the boots has a differnt upper and loer material as well.
post #7 of 14
Thread Starter 
Cool... I was just looking at the shells of my Dobermann 150s and the tg is actually listed on the shell itself. The cuff has a tg of 5/6 and the lower has a tg of 6.

Edit... oops, in this case, tg refers to size. But I did find a stamp that said TPU on it...
post #8 of 14

In case of emergency, eat your boots.

I remember back in the 70's Nordica came out with a boot made from a vegetable based plastic that was not suppose to change stiffness with temperature changes. Apparently the concept never caught on.
post #9 of 14
Thread Starter 
Quote:
Originally Posted by mudfoot View Post
I remember back in the 70's Nordica came out with a boot made from a vegetable based plastic that was not suppose to change stiffness with temperature changes. Apparently the concept never caught on.
My dad had a pair of really old Nordicas that lived in the bathroom cabinet for a couple of years. They pretty much melted and decomposed, leaving a sticky, red residue. Could they have been the edible ones?
post #10 of 14
Does anyone remember Dynafit alpine boots from the 80s? They had interchangeable rubber "wedges" that were installed on the spine to change the forward flex. Temperature fluctuations pretty much had no effect on their boots since the flex was completely controlled by the wedges which, being fairly small, were not greatly affected by the temp.

I have long wished that a manufacturer would "pick up the torch" and create a new boot that flexes consistently no matter what the temp is.
post #11 of 14
Got a freezer?
post #12 of 14
Quote:
Originally Posted by D(C) View Post
My dad had a pair of really old Nordicas that lived in the bathroom cabinet for a couple of years. They pretty much melted and decomposed, leaving a sticky, red residue. Could they have been the edible ones?
I never had a pair but I believe the vegetable ones were black and grey, but there may have been other models in other colors. To be on the safe side, I would not recommend trying to eat them.
post #13 of 14
Thread Starter 
Quote:
Originally Posted by mudfoot View Post
I never had a pair but I believe the vegetable ones were black and grey, but there may have been other models in other colors. To be on the safe side, I would not recommend trying to eat them.
Too late
post #14 of 14
Quote:
Originally Posted by Noodler View Post
Does anyone remember Dynafit alpine boots from the 80s? They had interchangeable rubber "wedges" that were installed on the spine to change the forward flex. Temperature fluctuations pretty much had no effect on their boots since the flex was completely controlled by the wedges which, being fairly small, were not greatly affected by the temp.

I have long wished that a manufacturer would "pick up the torch" and create a new boot that flexes consistently no matter what the temp is.
A boot with mechanical flex is not affected by cold. There were quite a lot of boots with a mechanical flex "back in the day", Dachstein, with it's springed upper comes to mind. I don't know of any today.
But what's wrong with temp variations. Stiff when it's cold, and you're going fast. Soft in the spring, when you're doing bumps...
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