[bigbob2]

Hi there,

Can I get some advice on a type of Cellulose that would dissolve with isopropyl alcohol (99%), and as it drys out it would set in to a solid (type of plastic), that could again be dissolved in isopropyl alcohol.
If cellulose would not actually work in that way, can you suggest any other type of polymer (or combination of materials) that would dissolve in iso and set again?

I have been experimenting with anything I can find around the workshop but can't find anything solid and plastic that dissolves in iso.

Thanks
Kevin

[Arkcon]

I don't believe anything will work the way you describe.  But for starters, you can look up for yourself, with Google, what sorts of things are soluble in isopropanol.  Perhaps a mixture of these isopropanol solutions, when dried together, would resist the IPA afterward.

[Corribus]

Looks like 40 mol% EVOH has some solubility in isopropanol at elevated temperatures.

http://www.evalevoh.com/media/36999/ea%20-%20technical%20bulletin%20no%20180.pdf

[Enthalpy]

Does it really have to be isopropanol?

In acetone, that would be easy. Acetone dissolves ABS and many more polymers. This is used to make glues, or even to glue parts just by impregnating them and pressing them in place.

Good chances with trichloroethylene too.

One worry with isopropanol is that the polymers it may dissolve (polyvinylic alcohol, intuitively) are often soluble in water and this isn't desired usually.

I doubt very much that isopropanol dissolves cellulose, since paramedics use cotton wool to clean the skin with isopropanol.

[bigbob2]

What I am looking for is the substance to be soluble in isopropanol but insoluble in water.  I have looked at tons of film forming polymers, but I can't find one that dissolves in iso but not in water. 

Thanks
Kevin

[billnotgatez]

One would think based on the history of plastics and cellulose that some method would meet your needs.

http://inventors.about.com/od/pstartinventions/a/plastics.htm

[bigbob2]

One would think based on the history of plastics and cellulose that some method would meet your needs.

http://inventors.about.com/od/pstartinventions/a/plastics.htm

That's a really cool article, thanks.  I know there is a solution (no pun intended) out there, and I am on a mission to find it!

Cheers
Kevin

[Intanjir]

Cellulose is very commonly chemically modified to improve solubility. The most common modifications are to build on the exposed  -OH groups to make an ether or an ester. This is a rather versatile, inexpensive and non-toxic group of materials.

So perhaps a modified cellulose is what you meant when you asked for a cellulose that would dissolve in isopropanol and people just interpreted you as meaning literal cellulose.

-OH groups are hydrophilic and cellulose has plenty of them and yet is so water insoluble. My understanding is that cellulose is so water insoluble because it hydrogen bonds too strongly with itself. This may in part be because it can more easily form stronger crystals when compared against the very similar, but helical, amylose.

Randomly substituting -OHs with a hydrophilic ether or an ester can interrupt this excessive hydrogen bonding whilst still supporting water solubility. So methylcellulose with its hydrophilic methoxy groups is water soluble, but the longer ethoxys of ethylcellulose aren't.

However, ethylcellulose is soluble in isopropanol and will at least form films. Whether it can be made to have the physical properties you are after via plasticizing additives I do not know.

[bigbob2]

Cellulose is very commonly chemically modified to improve solubility. The most common modifications are to build on the exposed  -OH groups to make an ether or an ester. This is a rather versatile, inexpensive and non-toxic group of materials.

So perhaps a modified cellulose is what you meant when you asked for a cellulose that would dissolve in isopropanol and people just interpreted you as meaning literal cellulose.

-OH groups are hydrophilic and cellulose has plenty of them and yet is so water insoluble. My understanding is that cellulose is so water insoluble because it hydrogen bonds too strongly with itself. This may in part be because it can more easily form stronger crystals when compared against the very similar, but helical, amylose.

Randomly substituting -OHs with a hydrophilic ether or an ester can interrupt this excessive hydrogen bonding whilst still supporting water solubility. So methylcellulose with its hydrophilic methoxy groups is water soluble, but the longer ethoxys of ethylcellulose aren't.

However, ethylcellulose is soluble in isopropanol and will at least form films. Whether it can be made to have the physical properties you are after via plasticizing additives I do not know.

Thanks Intanjir, I will get hold of some ethylcellulose and run some tests.  I probably didn't word my question very well if it has been misunderstood.  I am new to hobby chemistry and I have a lot to learn 

Thanks again for all the advice everyone.