PURPOSE
The purpose of this
experiment was to find a way to separate different types of plastics by their
densities.
I became interested in this idea because I might want to be involved in the plastics industry later in life. Lots of people I know (including my dad) work with plastics. I also think there could be much better methods regarding separation recycling of plastics. Recycling is very important because it’s an important way to minimize pollution.
The information gained from this experiment could affect the world by not putting recyclable plastics to waste, by finding a more efficient way to separate different plastics.
HYPOTHESIS
My hypothesis was that varying the density of the liquid bath could effectively separate at least 90% of the six major polymers.
I based my hypothesis on information received from a website on densities of solids and liquids. The site showed simple ways to realize that anything with a greater density than H20 will sink in a water bath, and anything with a smaller density will float. I also based it on an article in Plastics Technology about the invention of plastics separation.
EXPERIMENT DESIGN
The constants in this study
were:
• Sizes of pieces of plastics (1x1cm.)
• Types of plastics: PET (polyethylene terephthalate), HDPE (high density polyethylene), PVC (polyvinyl/vinyl chloride), LDPE (low density polyethylene), PP (polypropylene) and, PS (polystyrene).
• Room temperature
• Water temperature
• Oil temperature
• Water Bath Sizes
• The densities of the specific types of plastic
• Salt in saline solution
The manipulated variable was the density of liquid bath.
The responding variable was the percentage of the plastics successfully separated using the “float/sink” density method.
To measure the responding variable, I simply counted the pieces of plastic recovered and identified successfully, and the ones not effectively separated, then found the percentage.
QUANTITY |
ITEM
DESCRIPTION
|
1
|
Glass Water Bath
|
1x1cm Piece
|
Polyethylene Terephtalate
|
1x1cm Piece
|
High Density Polyethylene
|
1x1cm Piece
|
Polyvinyl Chloride
|
1x1cm Piece
|
Low Density Polyethylene
|
1x1cm Piece
|
Polypropylene
|
1x1cm Piece
|
Polystyrene
|
500 Milliliters
|
Water for water baths and
solutions
|
1.8 Kg
|
Sodium Chloride
eventually added to water bath
|
375 Milliliters
|
Sunflower Oil
|
1. Set Up
The Experiment
a) Get polymers 1-6.
b) Cut plastic into squares that each are about 1cm x 1cm.
c) Get 3 containers for each solution.
d) Fill up the first container with 250 ml of pure water.
e) Fill up one of the other two with 250 ml Sunflower oil and the other with 250 ml of more pure water. Add 10 grams of salt to the water and stir thoroughly.
f) Make sure each different type of plastic is identifiable from others.
2. Conduct the Experiment
a) (During the experiment, write down the slightest things that happen and record all of the measurements.)
b) Put 2 pieces of each type of plastic into the saline solution, without getting anything into the solution besides the plastic.
c) After putting the plastic into the saline solution, wait 1 minute and make sure none that are floating will sink and none that are sinking will float.
• (While removing the floating plastics throughout the experiment, make sure that all of the water is removed from the plastic so it does not affect the density of the other liquid baths.)
d) Take the floating plastic out of the solution, leaving the sinking plastic, and put the pieces into the water bath. Stir thoroughly and wait 1 minute.
e) Remove the floating plastic from the water and put it into the sunflower oil.
f) Then, take the floating plastic out of the sunflower oil.
g) Repeat Step #2, three times
3. Recording Data
a) Calculate how much of the percentage of plastic was separated successfully. (Meaning that it was a definite identification.) Write down anything unusual or unexpected that happens throughout the experiment.
The original purpose of
this experiment was to find a way to separate different types of plastics by
their densities.
The results of the experiment were, that 33% of the plastic was successfully separated. So therefore, the hypothesis was rejected. But, the experiment was still a success because now recyclers and plastic corporations will not falsely use the “liquid density separation” method by getting plastics mixed together.
My hypothesis was that varying the density of the liquid bath could effectively separate at least 90% of the six major polymers, at the same time.
The
results indicate that this hypothesis should be rejected, because the method
only separated 33% of the six major polymers. Also, I believe that if a plastic
or recycling plant specifically needed to separate 2 or even 3 different types
of plastic, (unless they were extremely close densities like Polyethylene
Terephtalate and PVC or, HDPE and LDPE) this method would work well. Even
better if one plastic was less dense than water and the other more dense than
water, then all you would have to do is dump the plastic into water then stir
it up and skim out the ones that float, and the remove the ones that sink. That
would work successfully.
After
thinking about the results of this experiment, I wonder if there is another
liquid that I could have used instead of a salinity solution that is denser
than water.
If
this project was to be conducted again, there would be many important changes
that would need to occur. There would need to be much more researching prior to
the experiment. Also, there would need to be more trials with more plastics and
more liquids. These would make the project much more successful.
Researched
by ----- Conner O
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