Vacuum degassing chamber lid explosion.


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Finnluxury
Finnluxury
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Hi.

Last night happened something really weird. I use EC 26L professional vacuum degassing chamber as a resin catch pot (resin trap). So I have 25mm clear acrylic lid, where i have a hole for resin to go inside the chamber. So the weird thing goes like this:

I resin infused a carbon fiber front fender just like I normally do. This time only different were that I used IP2 infusion polyester resin instead of Epoxy that i didn't have at the moment. Infusion went very well like usually. I closed the hoses, closed the pump and leaved the part cure over night. When I came back to the warehouse, I saw that the Acrylic lid were missing from the chamber. When I looked more closely there were Acrylic pcs all over the ware house, and 4 bigger parts of the lid. Clearly somekind of explosion have happened during the night. I am usually very carefull to not leave too much resin in the resin trap, that it will not start to gain heat. I even leaved the vacuum to the chamber, so there is no oxygen that the resin could start a fire, and only around 6mm of resin were in the bottom of the chamber. So I am wondering what have happened? I dont believe that the 6mm of polyester have gained heat so much that it would made  over pressure and this would happend. Also I dont believe that the vacuum can make the acrylic lid to get broken. I am wondering that maybe the hole middle of the lid for the vacuum hose have something to do with this. Just wanted to share what happened, and maybe someone could have idea what have happened. Smile
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Dravis
Dravis
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Actually 1 Ato "overpressure" will create a significant force on the acrylic lid ..  You could visualize it like this -- on top of the lid place a 76 cm high column of mercury, with a diameter like the lid itself ...

It should be obvious that very significant stress is placed on the acrylic .. which is a brittle material .. not tough like Polycarbonate/Lexan 

When you drill holes in it, or use a router to shape it, you will get tiny radiating cracks If you are not using VERY sharp cutters or drills and going VERY slowly in the machining.  These cracks will act as fracture initiators.

The end result will most likely be a build up of stress on the lid, resulting in an abrupt and catastrophic release of all the forces acting on the lid .. Styrene vapours may well be accelerating the building of the cracks.

@finnluxury:  Where in the lid did you drill the hole -- in the middle? (Where forces would be the greatest .. Cool )

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Finnluxury - 8 Years Ago
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