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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. 
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SkiFreak
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On the larger sections of lid that you found, is there any evidence of crazy cracking on the surface of the acrylic?
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Hanaldo
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Well that's odd... Especially because in the event of failure under vacuum, you would normally experience an 'implosion' of sorts, and likely just find the broken lid inside the vacuum chamber. It's highly unusual that the pieces flew off all over the place! Have you got any photos of the lid? I am also suspicious that the hole caused defects in the plastic that caused it to break.
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Warren (Staff)
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Hi Finnluxury,
Was this the catch pot or the degassing chamber as only the catch pot comes with a hole in the lid. We would be very interested to know what has caused this as obviously we do not want such equipment failing suddenly in this way! Please do keep us updated on what happened so we can take any action if necessary.
Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
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Dravis
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You should really pick up and collect all the pieces of the Acrylic lid, at take a few pictures ..
My theory is that you have drilled the hole for your vacuum hose yourself, and drilling in thick Acrylic can create pre-stressing in the material if not done correctly-
Where did you find the largest pieces of the lid? any shards inside the chamber?
"Sapere Aude"... Dare to KNOW!
The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind...
103% of all people do not understand statistics...
Do not adjust our mind, theres a fault in reality :-)
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oekmont
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It's a common mistake that an implosion does not lead to broken prices flying away from the center. After accelerating inward, the prices have a high momentum, bounce against each other, or the chamber, and then take their way away from the center. Also an explosion doesn't make sense, since the chamber is not designed to take any pressure from the inside. The lid would just pop up.
It could be, that your lid was not styrene compatible. Just my suggestion. Weakened bis the hole the styrene softened the underside a bit, until it could not stand the pressure anymore.
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Finnluxury
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I will take some photos tomorrow if I remember. The lid were shaped with router and then the hole were drilled. I use degassing chamber as catch pot, because it allows more resin to be suck out if need. Also the same chamber works for degassing job. One reason is also that I can use two different vacuum Gauge. Basic one and digital micron meter. I would never work anymore with just Glycerin filled vacuum Gauge. The micron meter is life changing product. My personal guess is that the hole has something to do with the happening. as 25mm thick acryl is quite strong. its either the polyester resin, or the drilling of the hole. or maybe both helps each other. Largest pieces of the lid were 1 meter away from the lid. Only smaller pieces were inside the lid. Also the resin were already cured before this happened, as the acrylic pieces were not glued in the resin, they were over the dry resin inside the chamber. I will check the pieces more carefully tomorrow.
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Warren (Staff)
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So it was your own design lid? I guess a stress fracture is possible depending on the holes.
Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
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Hanaldo
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oekmont (20/06/2017)
It's a common mistake that an implosion does not lead to broken prices flying away from the center. After accelerating inward, the prices have a high momentum, bounce against each other, or the chamber, and then take their way away from the center. Also an explosion doesn't make sense, since the chamber is not designed to take any pressure from the inside. The lid would just pop up.
It could be, that your lid was not styrene compatible. Just my suggestion. Weakened bis the hole the styrene softened the underside a bit, until it could not stand the pressure anymore.Yeh you're quite correct, it just isn't what I would have expected in this case. Anything under vacuum shouldn't really 'implode' in the truest sense of the word, it is really just being crushed. I find it hard to imagine that on something the size of a degassing chamber, there is enough atmospheric pressure to accelerate pieces of 25mm thick acrylic so much that they bounce and fly all over the place. Especially considering that as soon as the seal is broken, virtually all the energy would be dissipated. This does still seem the most likely explanation, but I just can't help but be a little amazed. I've seen a lot of things fail under vacuum, but nothing with the sort of energy that this would have required.
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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 ..  )
"Sapere Aude"... Dare to KNOW! The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind... 103% of all people do not understand statistics... Do not adjust our mind, theres a fault in reality :-)
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