Ok, Heat cycling helps. What about Cryogenically freezing them?
Otto Crosser
>From: Alan Pozner <AlanP@identicard.com>
>Reply-To: Alan Pozner <AlanP@identicard.com>
>To: "'autox@autox.team.net'" <autox@autox.team.net>
>CC: "'kevin_stevens@hotmail.com'" <kevin_stevens@hotmail.com>
>Subject: Re: Heat cycle for the DOT Race tires, needed or not?
>Date: Thu, 27 Jul 2000 15:02:16 -0400
>
>Kevin wrote in part:
> >Allow 24-48 hours mininum time before using or don't bother
> >heatcycling at all.
>
> >>One aspect of heat-cycling I've never understood is the above. If the
>tires
>aren't good to go as soon as they cool, then there must be some bonding
>transitions still going on - that's clear. What's not clear is how. Once
>they have cooled any chemical reactions are going to be happening at a
>glacial rate compared to what goes on when they're heated up.<<
>
>First off plenty of chemical reactions occur at room temp. The difference
>between 130 deg Fahrenheit and 70 degrees Fahrenheit is really small when
>referenced to absolute zero ( -273.15 deg Celsius ).
>
>Second what is it that really takes place? My understanding is that the
>long
>chains of molecules in the rubber compound are unaligned and of various
>sizes before the first heat cycle. After heating the molecular chains are
>shorter and unattached. By letting them cool gradually they can align and
>form similar length long chains making the compound stronger. Did you ever
>do the "grow a purple or blue crystal experiment" in school? Where you heat
>some salt in water with a string dangling from a popsicle stick. The
>crystal
>starts growing as the mixture cools but continues to grow for several
>hours/days after the liquid is back to room temp. I suspect that the rubber
>is going through an analogous process. The chains continue to grow for a
>period after cooling. Experience has shown that most of the growth has
>stopped in 24 - 48 hours hence the waiting period. If you heat the tire up
>before the 24 hours is up you break the chains. After the 24 hours the
>chains are stronger and longer and better resist heat cycle breakdown.
>
>Regards,
>Alan "yes, I do have a Chemistry degree, among others" Pozner
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