The answer is really simple. Have you inspected the plastic on the MPC? Compare it to the Yammie 1/60 and you will notice that it is of significantly lower quality, much softer than the Yammie. Not only that, it is more translucent than the yammie, which is basically opaque. Hence, the glowing head syndrome... The Rick 1J MPC is white. Without the presence of dyes and combined with the translucence and cheap plastic, the yellowing will show up much easier and earlier.
Anyways, in the end ALL plastics will oxidize by virtue of the air we breathe. Yellowing is inevitable. It can be slowed but not stopped. Ok, that's not true. You could keep it in a sealed chamber flooded with inert gas and it will probably not yellow, but if you have that kind of money and devotion to a toy, I think you need to get a life.
Air oxidation is usually not a big problem for quality plastics. UV is much more effective at breaking apart organic bonds. That's why we wear sunblock: so our DNA doesn't get damaged. Not only that, UV is capable of initiating free radical oxidations, a chain reaction, in compounds that have halogens. Since many plastics contain halogens, I would guess this could be a problem.
Just to clarify, I do organic chemistry as well as molecular biology for a living and while I do not work with plastics, the principles involved in any organic chemical reaction is pretty much universal.
you call that simple?
its still strange that i went to such great lengths to take care of it and keep it away for sunlight and otehr outside forces yet it still yellowed? i always thought it was sunlight that did this but now i have to find all new method(other than inert gases..do farts count? ) for storing my toys.
and yes, the plastic is WAY CHEAP!
I finde it strange how you took such great lengths to take care of it and keep it in the best condition possible...But its crap right? I think you had to justafy the fact of having a MCP by still being cool and saying its crap.