Teaching Green Chemistry ... with balloons
Green chemistry is a serious subject. But there's no reason why you can't have fun teaching it. A team at Gonzaga University working with green chemistry experts ChemForward had the great idea of providing a module that showed not just that HSP can be used for green formulation, but also provided a detailed procedure for the students to measure the HSP of polyisoprene using party balloons.
The description of the tests and all the required Green Chem background is contained in HSP Balloons.pdf and is deliberately formal as it's addressing real issues and includes important H&S advice.
But as you see from this short video the tests are a lot of fun (at least with a "good" solvent which pops the balloon).
Good and bad solvents
As we know from the classic HSP Sphere measurement, you need to know, for a given polymer, which are "good" solvents and which are "bad". It's up to you how to define good/bad. The classic ways are via solubility or swellability. But you can use your imagination. A good solvent will easily burst a balloon if it is compatible with polyisoprene and a bad solvent won't touch it. Some are borderline and take some time before the balloon bursts.
With a list of good/bad solvents it's then easy to do the classic sphere calculation and calculate HSP Distances (Ra values) from polymer to solvent. The team have provided HSP Calculation Template.xlsx to do the calculations.
Over to you
The team have kindly made their project open source, so you are free to download the resources and use them for your own teaching. Happy balloon popping!