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Author: Subject: Keeping polypropylene sheets soft and flexible after autoclaving.
kclo4
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[*] posted on 21-11-2016 at 04:57
Keeping polypropylene sheets soft and flexible after autoclaving.


I am autoclaving thin bags/sheets of polypropylene, and after the process it loses some of its flexibility and becomes more ridgid. This is undesirable, and I'd like to treat the polypropylene with an agent to make it more flexible. I'm not sure that this is possible, but it seems like some type of wax or oil could possibly alter or inhibit the polypropylene from becoming ridgid and could be added to the plastic or the autoclave.

Any ideas or pointers?

I have tried researching it but I just do not have the language to find such a "softening agent"

Thanks.




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Metacelsus
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[*] posted on 21-11-2016 at 06:19


It would be called a plasticizer. It would probably have to be added to the bags during manufacturing.



As below, so above.
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CuReUS
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[*] posted on 21-11-2016 at 08:26


diethylhexyl phthalate is used for softening vinyl gloves,so you could try that.
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kclo4
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[*] posted on 22-11-2016 at 01:19


Great. I'll look into some of these. What do you think causes polypropylene to become more brittle after the heat? I assume it's that it is crystalizing or having it's polymer units become less stretched out and kind of fall into themselves?



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DJF90
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[*] posted on 22-11-2016 at 01:55


Is it possible that you might be losing/degrading whatever plasticiser may be present during the autoclaving process?
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UC235
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[*] posted on 22-11-2016 at 10:09


Sounds like autoclaving them is allowing the plastic to release strain built into it during manufacturing or permitting it to recrystallize. Do you experience shrinkage or just a change in flexibility? I'm not aware of any plasticizers that are compatible with polypropylene (and they would need to be incorporated during manufacturing). It's properties are usually managed by modifying chain lengths and tacticity instead.

[Edited on 22-11-2016 by UC235]
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kclo4
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[*] posted on 22-11-2016 at 18:40


Suppose I should elaborate:
They are spawn bags for mushrooms production, from unicornbags.com.

They are very flexible pre-autoclave, but after the fact, folding them sometimes results in pin holes where they are folded. This lets in spores and ruins the bag. I have to fold them since I sell them online and shipping would be impossible, along with fitting them into the autoclave.


I am not sure that they shrink, if anything they expand.




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Cezium
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[*] posted on 26-11-2016 at 00:41


then don't autoclave. try to iradiate it, few tens kGy should be enough.
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kingroobythefith
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[*] posted on 26-2-2019 at 13:17
autoclaving polypropyline


while I don't know much about chemistry its possible the heat or pressure caused it to stick together on a small scale or possibly melt its also possible the structure of the threads in the cloth changes under those condition
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Ubya
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[*] posted on 26-2-2019 at 14:34


Quote: Originally posted by kingroobythefith  
while I don't know much about chemistry its possible the heat or pressure caused it to stick together on a small scale or possibly melt its also possible the structure of the threads in the cloth changes under those condition


kclo4 never mentioned problems with sticking or melting, and definitely he was not talking about cloth fibers...
you don't know much about chemistry, ok not a problem, but you should be able to read





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