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Densities of Various Solutions |
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Researched by Conner O.
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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. (http://www.simetric.co.uk/si_liquids.htm). 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.
MATERIALS
QUANTITY |
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| 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.
RESULTS
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.
CONCLUSION
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.
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Introduction It is important to find better ways to separate mixed waste so the plastic contents can then be recycled and molded again. Plastic is very useful, but it is also a growing environmental problem. Better recycling could help. Human Need In modern life, humans use an enormous amount of plastic. Plastics cannot be mixed together during recycling because some polymers are used for different things than others. If all used plastic were put to waste, the environmental impact would be tragic. Without plastic, everything would need to be made out of metals and wood. PLASTIC
Introduction to Polymers
(Types of Plastic)Polymers are high-molecular-weight organic compound, natural or synthetic, with a structure that can be represented by a repeated small unit, or mer. They are long chain molecules such as PVC or nylon, produced by the polymerization of monomers. Plastic is a material made from petroleum capable of being molded, extruded, or cast into various shapes. There are many different kinds of plastic made from different combinations of compounds. There are many different types of plastic. The major polymers include Polyethylene Terephtalate (PET), High Density Polyethylene (HDPE), Polyvinyl/Vinyl Chloride (PVC), Low Density Polyethylene (LDPE), Polypropylene (PP), and Polystyrene (PS). The major polymers (above) have recycling codes so people know which plastic is which, and they do not get mixed together. PET (#1) is mostly molded into soda and water containers. PET is recycled similar to polyethylene. Unlike polyethylene, PET sinks in water but the lids and labels float. The bottles made with PET are sometimes color sorted. HDPE (#2) is molded into gas jugs, milk cartons, oil containers, toys, and plastic bags. HDPE is sometimes called “natural” because it is usually natural color. PVC (#3) is molded into pipes, food wrap, blister packages, vegetable oil bottles, and many other wraps and containers. LDPE (#4) is molded into plastic bags, garment bags, and shrink-wrap. Very similar to HDPE except it is less dense and more flexible. PP (#5) is molded into some bags, most bottle caps, food wrap, and some carpets. PS (#6) is molded into disposable utensils, meat packaging, and protective packaging. #7 is all other layered or mixed plastic. It must be put into the landfill because it cannot be recycled. The symbols (#1-#7) indicate the type of plastic, not the plastic’s recyclability. Types #1 and #2 are generally recycled. Type #4 is less commonly recycled. All the others are generally not recycled. Chemical Engineers sometimes say that there are more types and uses for polymers. But recycling is mostly focused on these seven categories. Molding Plastics Molding is the forming of a resin or fiber material into a solid mass of prescribed shape and size. There are many different ways to mold polymers into various things of different categories. One of the most common is the injection or extrusion molder. This injects the melted plastic into a mold, and then it is cooled and dropped out of the mold and out of the machine. Another common molder is the blow molder. They blow plastic and stretch the plastic into plastic bags. Thermoforming and Calendering are other molds. Uses of Plastics There are many different uses of plastic. Plastics play an important role in the average American’s life. Think of everything you see when you go to a grocery store. How much of it is plastic or is stored in plastic containers or refrigerators? A lot! Plastic helps the food industry, the packaging industry, and in home construction. RECYCLING
Importance of Recycling PlasticPlastic is not biodegradable. Because of this, the only two options for used plastic are to get recycled and turned into new products and other things, or to get put into landfill, which is bad for the environment. But, the downside is that the plastic must be separated before it can be recycled. That is where separation of mixed waste comes in. Separation of Mixed Waste Recovery (Separation) is obtaining certain materials, in this case polymers, from solid waste. Separation (Sorting) is important because the six main recyclable polymers (PET, HDPE, PVC, LDPE, PP, and PS) cannot be recycled together. DENSITY
What is Density?Density is a measure of how heavy a solid, liquid, or gas is for its volume. Density is expressed in terms of mass per unit volume, that is, grams per cubic centimeter or pounds per cubic foot. The density of water is 1.0 gram per cubic centimeter or about 62.4 pounds per cubic foot. What is Specific Gravity? Specific Gravity is the ratio of mass of any material divided by the mass of the same volume of pure water at about 4°C. Specific Gravity of the Six Major Polymers 1.37-1.39 kg/cu.m #3 PVC 1.34-1.39 kg/cu.m #1 Polyethylene Terephtalate 1.05 kg/cu.m #6 Polystyrene 0.96-0.97 kg/cu.m #2 HDPE 0.91-0.93 kg/cu.m #4 LDPE 0.90-0.92 kg/cu.m #5 Polypropylene After looking at this chart, you can see that there are four groups of nearly the same density level. (These would include; Group #1 is PVC/PET, Group #2 is PS, Group #3 is HDPE, and Group #4 is LDPE and PP.) These groups are distinguishable from each other, but the plastics that are in Groups #1 and #4 and indistinguishable from the other plastics they share a group with. Summary As you can see, plastic plays a very important role in our modern lives. This is why recycling and separation is important to our lives. Recycling will also keep our planet a much cleaner and healthy place to live. |
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“Bulk Density and Specific Gravity Chart,” Powder and Bulk.
http://www.powderandbulk.com/resources/bulk_density/material_bulk_density_chart_s.htm "Density," Encarta Deluxe Encyclopedia, 2005 “Density” 1/25/2006 www.nsc.org/ehc/glossary.htm “Densities of Various Materials,” Plastics.11/23/2005 http://www.mcelwee.net/html/densities_of_various_materials.html "Density Separation of Mixed Waste," Plastics Technology, 2005 Jody, Bassam. “World’s First Plastics Separation Plant.” Argonne National Laboratories. November 9, 2005 http://www.transportation.anl.gov/publications/transforum/v4n3/plastics_separation_plant.html “Plastic” 1/25/2006 www.Washingtondc.earth911.org/usa/master.asp "Plastics,” Encarta Deluxe Encyclopedia, 2005 “Plastics”’ 1/11/2006 http://www.epa.gov/epaoswer/non-hw/muncpl/plastic.htm “Plastics by the Numbers,” Plastic Densities. 11/23/2005 http://chem.lapeer.org/chem1docs/3D5PlasticsLab.html “Polymers” 1/25/2006 www .etfinancial.com/coatingsgloss.htm "Recycling,” Encarta Deluxe Encyclopedia, 2005 “Separation Before Plastic Recycling” 11/23/2005 http://www.rohmhaas.com/company/plabs.dir/htmldocs/PlasticRecyc.html “Specific Gravity.” SIMetric. 11/16/05 http://www.simetric.co.uk/si_liquids.htm “The Many Uses of Plastic” 1/11/06http://www.americanplasticscouncil.org/s_apc/sec.asp?CID=312&DID=930 |
ACKNOWLEDGEMENTS
I would like to thank the following people for helping make my project possible:
• My dad for helping me along the way.
• My mom for helping me on my experiment.
• My friends Mary and Scotty for making my year enjoyable.
• Mr. Newkirk for helping me on my project.
• Mrs. Viernes for helping me stay on task.
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