hot water submerged bags with esters inside
hot water submerged bags with esters inside
(OP)
I am trying out all different sorts of bags to encapsulate a wax (ester) "pentaerythritol adipate stearate" which melts at around 135F. The bags are to store heat in the phase change region and over a temperature range of between 100F and perhaps as high as 190F. I have been having problems with different material compatabilties. A slight elasticity is preferred as there may be a volumetric expansion of 10%. Even when the bags are evacuated of gas, oxygen is entrained within the molecular matrices and will eventually escape, so there is potentially a volumetric expansion associated with that (boyle's law). The bags are underfilled so that even with the expansion there should not be enough pressure to cause a break;
however, the temperature may be a problem.
The requirements of the bag are that it must be relatively impermiable to water and air on the outside, and submersible in hot water which may fluctuate from 100 to 190F daily. Perhaps 20,000 cycles of expansion/contraction. The elasticity required is not known but the volumetric expansion of the entire bag must allow for a 10% change. The inside of the bag must be compatible with the same temperature fluctuations and it must be compatible with esters. Also the bag may contain copper wool. There is puncture resistance to consider.
Fluoropolymer film seems like an obvious homogenous choice. It seems too easy, but anything that is layered with aluminum (Mylar, etc.) either delaminates upon cycling volume or else the seal breaks at the temperatures in consideration.
Any help is appreciated!
Is there any advice?
however, the temperature may be a problem.
The requirements of the bag are that it must be relatively impermiable to water and air on the outside, and submersible in hot water which may fluctuate from 100 to 190F daily. Perhaps 20,000 cycles of expansion/contraction. The elasticity required is not known but the volumetric expansion of the entire bag must allow for a 10% change. The inside of the bag must be compatible with the same temperature fluctuations and it must be compatible with esters. Also the bag may contain copper wool. There is puncture resistance to consider.
Fluoropolymer film seems like an obvious homogenous choice. It seems too easy, but anything that is layered with aluminum (Mylar, etc.) either delaminates upon cycling volume or else the seal breaks at the temperatures in consideration.
Any help is appreciated!
Is there any advice?





RE: hot water submerged bags with esters inside
Your choice of fluoropolymer is a good one, that is so low polarity (solubility parameter) that it will not be affected by water or the ester. Silicones may well work as well.
The other option is multilayer films as you suggested. In drug packaging multilayer films are used for their special properties, up to 7 layers in some cases. Aluminium is one option as a barrier layer but very thing silica (SiOx) layers are common as well. It won't delaminate if it's made properly with the right layers and tie layers.
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: hot water submerged bags with esters inside
In multilayer films, I have a dozen spec sheets but none which contain facts that I am interested in. I think that the temperature considerations are the most important, as I've tested the multilayer films with polyethylene on the inside and they tend to creep open at 190F. I can't seem to find any HDPE or HDPE/Aluminum/BOPET. I assume this combination is not easy or reasonable to produce, or else there is something better.
Is there any multilayer film available that has something that will work like this?
Thanks for the tip Demon3- I am looking into silicone right now.
RE: hot water submerged bags with esters inside
h
Here is the new Polyester bag that is good to around 400F.
http://
RE: hot water submerged bags with esters inside
Nylon 6 or 6/6.6 copolymer are common in multilayer films for food packaging. While they do soften due to moisture absorption, they still retain useful properties. Nylons that have moisture conditioned are used in a huge number of load bearing applications.
Nylons will also hydrolyse, but at a much slower rate than polyester. It will also be more ductile.
The real problem is the inside layer. Any PE, even HDPE will be pretty useless re load bearing at 190 deg F. Polypropylene will do better.
We are currently doing work on nylon that is good water barrier, but it is not fully developed yet.
Someone might do a film grade nylon 12 with nanoclay filler. That will ruin mechanical properties, but substantially improve barrier, so a multi layer nylon 12 might work, say standard grade outside surface 15 microns, nano filled say 60 microns and weldable layer say 20 microns. The weldable layer might be plasticised nylon 12, or nylon 12 with tie layer or compatibiliser type additives.
To develop a custom multilayer structure, you would need considerable volume of usage as equipment to do this is difficult to start and has high production rates.
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RE: hot water submerged bags with esters inside
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RE: hot water submerged bags with esters inside
RE: hot water submerged bags with esters inside
http
They are beads with a microencapsulated wax that does what you want. Because the wax is already encapsulated in a polymer shell you can probably get away with a bag that doesn't need to be elastic or have great barrier properties. No idea on cost but may be not too much as itÄs used in building materials like plaster.
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: hot water submerged bags with esters inside
http://www.nahpco.com/small_colorful.htm
http://w
ht
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RE: hot water submerged bags with esters inside
polymers cost around $1.00 per pound. they tend to hold their phase change enthalpy properties over 10000 cycles, whereas the performance of salts deteriorate a great deal over 3 or 4 cycles.
Until i can find an alternate material, I'll have to go with teflon.
RE: hot water submerged bags with esters inside
Would this do what you want?
You have to request a data sheet, but as it's a PA/PP alloy it is supposed to have the benefits of each...
http://www.arkema-inc.com/index.cfm?pag=104
I note there are film/flexible grades.
Cheers
Harry
RE: hot water submerged bags with esters inside
a very severe environmental application. It is made into all types of bags, mainly for sample bags.
In our application we saved a ton of money.
h
RE: hot water submerged bags with esters inside
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell