Timothy English
Gen. Chem. 1 Lab
Section: 009
Introduction:
Poly-Vinyl Alcohol (PVA) is a water-soluble synthetic polymer that will be used as one element to form the well know bouncing ball, along with Sodium Borate (borax), which has a variety of uses because of its weak base. PVA is ideal for this experiment because it is odorless, nontoxic, has high tensile strength and flexibility. The binder characteristics of PVA offer excellent adhesion to porous, water-absorbent surfaces.
A local manufacturer wants to find a material to create a simple toy: a bouncing ball. Research institutions collaborate with local manufacturers and provide …show more content…
In efforts to do so, our TA supplied PVA, along with sodium borate, to the students. Each group could only acquire so much at a time. My group acquired 100 mL of both PVA and sodium borate. To start, we did a 1:2 ratio just as a test to see if it would solidify into a ball. As a result, it came out slimy so we tried to up the amount of sodium borate (1:10 ratio), which lead us to a more watery product. Since increasing the amount of borax lead us in the wrong direction, we increased PVA and lowered sodium borate to a 10:1 ratio. This ratio gave us a play-dough outcome, which was closer to what we needed. Decreasing the amount of solution to a 5:1 ratio, we moved even closer. The 5:1 was starting to feel rubbery. After seeing how close we were with the 5:1, we tried the 4:1. Our 4:1 and 7:1 were fairly similar and the closet to our projected outcome but it was not quite there yet. So, by heating and cooling each result gave us a somewhat reasonable result. The result of cooling our 7:1 product for 30 minutes was a harder but still lacked shape as well as the 4:1 product that was cooled for 30 minutes. The 7:1 result was able to bounce 9-11 cm in height while the 4:1 product was able to bounce to a similar height of 8-10 cm. Both products heated would not bounce or keep form, so we immediately put both on ice. As most people should know, with the rapid temperature (from hot to cold), it causes an object to harden from the inside out. So, with this theory in mind, after the heated products failed we placed them on ice and let it sit there and harden. The products hardened over a 15-minute time frame and we could clearly see the difference between these and the rest of our trials. The heated then cooled product for the 7:1 ratio could bounce to a height interval of 19-20 cm, while the product from the 4:1 ratio could bounce to a height interval of 30-32 cm.