We wanted to make polymer that acts as the back side of the phone case, so it should be comfortable to hold and convenient to use. That’s why we want our polymer to have the following physical properties:
Low stretch – A phone case shouldn’t soft and stretchy. We can test it just by stretching it.
Firm – In order for the polymer to protect the phone. Also, no one wants to use a case that’s soft and slimy. we can test by feel if it’s firm.
Sticky (only to flat surfaces) – Our whole purpose was to make a phone case that can stick. We can test it by sticking it onto a wall, see if it’s easily attached or removed.
Not moldable – We don’t want the polymer to easily take shape, because it would be really annoying for the user to adjust it every minute if it’s blocking the charger port, camera, etc. We can test this by trying to roll it into a ball.
Not sticky to hand – We only want it to be sticky to walls and tables, because sticking on to hand would be very inconvenient for the user. We will test this by holding on to the polymer for 15 seconds, and then removing it. See if it’s easily removed, and if there are any left overs on hand.
Rubbery – This is just a optional physical property we hope our polymer would have, so it improves the grip and feel of the case.
OUR FIRST PLAN
From what I said before in Journal #2, we decided to use gloop as our base polymer, and modify it to fit our goal.
Prorotype #1: We planned to add 3g of guar gum to thicken the gloop and additionally add some rubbery properties, and 5g of PVA glue to make the gloop more sticky. (We also added 5g of borax, I think we were just being dumb. There wasn’t a reason since it decreases the stickiness) The polymer didn’t stick to anything; it was probably because of the borax we added randomly.
Prototype #2: We did the same thing except that we took out the borax. The gloop has gotten much more sticky and the grip was much more comfortable, but also, without borax to decrease the stretch, our polymer was more moldable and stretchy (we want to change that).
*We took the prototype out of the bag after a week, that’s when we were done with prototype 4. It worked really well, since some of the liquid was probably dried up through out the week, so it was sticky and thick. We stuck our phone on it and placed it on the wall, and it did stick. This was probably our best prototype yet, however, it looked bad and the grip wasn’t that good.
Prototype #3: We wanted to make the next one thicker, so we took out guar gum and put in 2g of solid corn starch which thickens the polymer. Our goal was achieved, the new polymer had very low moldability and stretch. But again, it wasn’t sticky enough.
Prototype #4: We thought the stick was decreased because it was way too thick and solid, so we 4g of water. (we added 4g of borax again, so stupid) The water made the polymer more stretchy but did nothing to the stickiness.
After Ms. Lemly came in and told us about the environmental issues of some of the materials we used, we decided to try using only the environmentally safe materials — water, guar gum, and solid corn starch.
Prototype #6: For this prototype, used 40ml of white glue, 7g of corn starch, and 3g of guar gum. With too much glue and less material to thicken the polymer, it turned out to be too sticky and watery.