[kirstan]

For a general chemistry lab, we are experimenting with polyvinyl alcohol and sodium borate.  This is the objective we were given:
"Local baby food manufacturer, Yummies, needs to find a material for packaging its new toddler snack line.  A polymer, polyvinly alcohol (PVA), is odorless, nontoxic, and biodegradable.  Your objective is to explore the change in physical properties of this polymer as a result of cross-linking (with sodium borate).  Report your assessment of this polymer as a packaging material, and the reagent amounts, tests, and physical properties you performed."

Any suggestions on what tests to perform in order to create a suitable packaging product? Any information would be greatly appreciated.

[Arkcon]

Well, once you've formed the cross-linked polymer, and you review the properties, you can make a determination as to its fitness.  To answer the question:  What do you look for in a package?  Have you ever seen a bad one?  Look around at all the plastic items around you, do any of them have properties that would make a terrible package?

[kirstan]

Thank you for your response. We did a few cross-links at different ratios but each one created slime, as we anticipated (which would not be great for packaging snacks). We've contemplated letting it sit out to solidify or heating it with a heating plate. Are we on the right track? Or are there aspects that we are over looking?

[Arkcon]

Oh yes, definitely try those and report on it. Also try to look up how plastics are made, to see how a problem like you've encountered may be solved in industry.

I'm so glad to hear that you've done it already.  I was afraid you were doing a pre-lab, and I was sure someone would arrive soon and say "that recipe just makes slime!"  And then you'd miss out on all the fun.  Did you see any difference in consistency with varying amounts of cross-linker?

[kirstan]

We noticed that an increased ratio created a better consistency to mold the polymer, but only to a point. When the ratio became too large, there was an excess reagent (the polyvinyl alcohol), and we were left with part slime, part liquid. I will look into how plastics are made so we can further our course of action.