Testing the Hardness of
Various Polymers
Procedure
Question
Does molecular weight, concentration, and
structure affect the hardness of a polymer?
Structure Related to Hardness
Step 1: Put on protective goggles and latex gloves.
Step 2: Label each micro slide according to its solution i.e. Poly (vinyl acetate)
M.W 100,000. Write down observations (shake bottle and record
characteristics).
Step 3: Label the pipettes 7 centimeters using the permanent marker.
Step 4: Collect one solution and cast it onto the opposite side of the micro slide
(away from the writing).
Step 5: Repeat the steps for the remaining 7 solutions. Write observations and
record viscosity.
Step 6: Let the polymers dry for two days
Step 7: Put on protective goggles and latex gloves.
Step 8: Scratch each micro slide by using the following items: fingernail,
toothpick, tab of a soda can, razor blade
Step 9: Record observations
Polyvinyl Alcohol on a micro slide
Hypothesis
If the molecular weight and concentration increases,
then the hardness will also increase. Poly (vinyl alcohol)
has a lower molecular weight than polystyrene,
therefore it will not be as hard as polystyrene.
Figure 2
Table 2
Materials
 8 pipettes,
 8 micro slides,
Polyvinyl Acetate on a micro slide
 Goggles,
 Latex gloves,
 Poly (vinyl acetate) M.W. 100,000
 Poly (vinyl acetate) M.W.170,000,
 Poly (vinyl acetate) M.W. 260,000
 Poly (vinyl acetate) 1 g/40 mL
 Poly (vinyl acetate) 5 g/40 mL
 Polyvinyl acetate) 10 g/40 mL
 Poly (vinyl alcohol)
 Polystyrene
 Ruler
 Marker
 Razor blade
 Toothpick
 Tab of a Soda Can A toothpick, a razor, and a tab of a soda can
Data Analysis/ Discussion
Our hypothesis was not completely supported by the data. After the polymers
were cast and had hardened, we tested for hardness using a fingernail,
toothpick, tab of a soda can, and a razor (Table 1). Like expected, the
polymers with the lowest molecular weight scratched easily with a fingernail
and a toothpick (Table 2 and Figure 3). The highest molecular weight of
260,000 scratched with a tab of a soda can. Next, we did the scratch test in
polymers that varied only in concentration. As predicted, the polymers with a
lower concentration of 1 g/ 40 mL and 5g/ 40 mL scratched with a toothpick,
while 10 g/ 40 mL scratched only with the razor. The hypothesis regarding poly
(vinyl alcohol) and polystyrene was rejected due to the fact that both of those
polymers scratched with the razor. In our hypothesis, we thought that poly
(vinyl alcohol) would not be as hard as polystyrene because of its structural
differences as seen in Figure 1.
Conclusion
Based on our results, molecular weight, concentration, and structure does affect the hardness of a polymer.
As seen in (Figure 3 and 4), the polymers that had both the highest molecular weights and concentrations
not only expressed the highest levels of viscosity, but also scratched with the sharpest objects. Although the
structures of poly (vinyl alcohol) (M.W 2,000) and polystyrene (M.W 190,000) are very different, when
testing its hardness, the results were the same. In our hypothesis, we had stated that if the molecular weight,
and concentration were greater then the polymer would be harder. The data largely supported the
hypothesis as seen in Table 2 and Figures (3). However, the hypothesis for was rejected because Poly (vinyl
alcohol) was as hard as Polystyrene.
Table 1
Figure 1
Melissa Santiago,
Bianca Randolph,
DaVaun Green,
& Jason Rivas
Poly (vinyl alcohol)
Figure 3
Polystyrene
Poly (vinyl acetate)
Figure 4