CHM 110 - CHEMISTRY AND ISSUES IN THE ENVIRONMENT
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Home Laboratory # 6
C. Ophardt, Elmhurst College, c. 2002

PROPERTIES, CLASSIFICATION, AND RECYCLING OF PLASTICS
PRE-LAB: SOLID AND HAZARDOUS WASTE ASSESSMENT (5 pts)

QUES. 1: a. Calculate the total tons of waste per person per year. Assume a population of 250 million.
(Approx. ans. = 10-50 tons)

b. Convert the tons of waste per person per year to pounds. 1 ton = 2000 pounds.
(Approx. ans. = 25,000-100,000 pounds)


Composition of Municipal Waste: 159 Million tons municipal waste (excluding commercial) per year

Graphic # 2:

QUES. 2: Calculate how many total tons and then pounds of municipal or household garbage is produced per person per year.
(Approx. ans. = 500-2000 pounds)

QUES. 3: Calculate how many pounds of paper per person are thrown away per year.
(Approx. ans. = 100-1000 pounds)


INVENTORY # 1: Weekly Garbage Survey

Devise a method to calculate the pounds of garbage thrown away for one/two weeks. Since most of you probably have a bathroom scale, use this to weigh the garbage. First find your weight, then hold a bag of garbage and reweigh yourself. The difference is the weight of the garbage. Note: If you do not have a bathroom scale, an alternative is to do some type of volume measurement for the inventories.

QUES. 4: Weight of garbage week # 1: _______ Weight of garbage week # 2: ________

Weight of garbage per household / year: _______


INVENTORY # 2: Recycling 

Another way to dispose of waste products is through recycling. An increased public and municipal awareness has resulted in a variety of recycling efforts.

Measure the pounds of recycled materials collected in a one/two week period. Then pro rate them to a yearly number. Choose any TWO of the following four categories.

QUES. 5:
 Material
 Pounds/ week
  Pounds/year
 Paper
 
 
 Aluminum
 
 
 Glass
 
 
 Plastic
 
 
 Total lbs. recycling
 
 

QUES. 6: How much do you currently recycle and what specific methods could you use to increase the amount that you recycle?


 
QUES. 7: Develop a plan of action to safely use, store, and dispose of the hazardous wastes in your house. Should you put them in the normal garbage for pick-up?
 


INTRODUCTION TO LABORATORY:

Within the last 15-30 years, a large variety of plastics have found many uses in the consumer market including bottles and containers, wrappings, and packaging. What happens to the millions of plastics items that are discarded each day? There are a variety of methods to deal with this solid waste including: source reduction, reuse, recycling, landfill, and incineration.

The purpose of this laboratory is to use both physical and chemical properties, to identify and classify various plastic items, and finally to devise a method to separate and recycle the plastic.

Pre-Laboratory Collection of Representative Samples: (Ques 8-11 - 4 points)

Most plastic items have a recycle code stamped or printed on them in the form of a triangle and number. Try to find at least one sample of each of the six types of plastics that have recycle codes. Cut the samples into smaller pieces about 1 inch square.
In addition, you will need a plastic garbage bag or grocery plastic bag and a newspaper page.
QUES. 8: Use the textbook to look up the abbreviation, such as PVC, and the chemical name of the plastic that corresponds to each recycle number.

 Recycle Code
Abbreviation and Chemical Name of Plastic
 Types of Uses and  Examples

 1
 
 Clear, 2 liter beverage bottles

 2
 
 Milk jugs, detergent bottles, some water bottles

 3
 
 Saran wrap, plastic drain pipe, shower curtains, some water bottles

 4
 
 Plastic bags, garment bags, coffee can lids

 5
 
 Aerosol can tops, rigid bottle caps, candy wrappers, 
bottoms of bottles

 6
 
 Hard clear plastic cups, foam cups, eating utensils, 
deli food containers, some packing popcorn

 -
 
 Biodegradable, Some packing popcorn




EXPERIMENTAL PROCEDURES: At home collection of lab data

1. Cold Drawing of Plastic Films:

When polymer films are stretched (cold-drawn), the chains orient themselves. This is similar to the molecular changes that occur in a rubber band when it is stretched. However, polymer films such as plastic wrap, generally are not cross linked and thus do not have a restoring force that is observed in rubber bands. Orientation (alignment ) of macromolecule chains also occurs during the processing that occurs prior to use by consumers. As a result, plastic films tend to have more of the chains lined up in one direction than the other. If polymer chains are all aligned in the same direction, then they should stretch longer, and more easily. In this part of the experiment, we will try to determine the orientation of the chains in a plastic film.

a. Cut several strips about 1 in wide and about 10 in long from one edge of a large plastic trash bag. (Carefully keep track of the direction of the cut.) Grasp the strip firmly between the thumb and fore finger of each hand so that your hands are about three inches apart.

b. Pull the film by moving the hands apart slowly. Notice how the sample narrows (necks) as the molecules align within the sample. Notice any changes in the amount of pressure required to pull the strip - initially and as the strip necks. Continue to stretch the film until it breaks. Place the two broken ends next to each other and use a ruler to estimate the total length that the film stretched before breaking. Repeat the procedure one or two times to see if the observed lengths are reproducible. length ___________

c. Cut several similar strips from the plastic bag, but along an edge that is perpendicular to the first strips that were cut. (Carefully keep track of the direction of the cut.) Repeat the procedure in (#b) on these strips. length ______

QUES. 9: Which strip direction in the bag were the polymer molecule chains more closely aligned i.e. are the polymers running lengthwise or cross wise?


2. Ripping a Newspaper: A newspaper is made of cellulose polymer chains of glucose units. 

QUES. 10: Are the cellulose polymer chains in a newspaper randomly distributed or are they aligned in a particular direction? Which direction does a newspaper rip more easily with less jagged edges? If so which direction? Rip the newspaper in various ways until you can answer the question. Definitions: The vertical direction is the up/down direction as you read the newspaper. The horizontal direction is when you rip it crossways left to right as you hold it to read the paper.
Give the name of the newspaper you are using such as Tribune, Sun Times, etc.


3. Density of Plastics: 


Set up one cup and put about 1/2 to 3/4 cup of water in it. Test the density of each of the samples in the water as described below.
****At home collection of lab data ****
a. Density in Water: Drop the plastic sample into water. Try various ways of putting the piece into the water, including pushing it below the surface if it appears to float; so that surface effects and air bubbles are minimized. If the sample floats, it has a density of less than 1.0 g/ml. If the sample sinks, it has a density of greater than 1.0 g/ml. List/describe.
 
****All Data for Part 3 b and c are given online****
****You do not actually have to complete these procedures. Dr. Ophardt did them for you and took pictures of the results. You should read the procedures to see what was done, record the data, and answer the questions.*****
b. Density in Saturated Salt Solution: Test the density of the plastic in saturated salt solution that has a density of 1.20 g/ml. List/describe.
c. Density in Rubbing Alcohol: Test the density of the plastic in rubbing alcohol (70% isopropanol/water), with a density of 0.94 g/ml.
List/describe.
QUES. 11: RECORD the density behavior in the DATA TABLE. Such as floats on water, sinks in alcohol, etc.
****Click on the number to get the online computer data on the behavior of the plastics in alcohol and salt water.****
 Recyle Number
 Abbreviation
 Alcohol
 Water
Salt Water
 Density Range
 1
 
 
 
 
 
 2
 
 
 
 
 
 3
 
 
 
 
 
 4
 
 
 
 
 
 5
 
 
 
 
 
 6
 
 
 
 
 


DENSITY RANGES: From the density behavior tests, develop a range of densities for each example of plastic. Record on the Data Table - below and above. If the sample floats, the density is less than the solvent. If the sample sinks, the density is greater than the solvent. To determine the density ranges for the plastics the following concepts may be useful. Think of the behavior and densities of water, a rock, and a piece of wood. The density of water is 1.0 g/ml, the rock sinks so its density is greater than 1 g/ml, the wood floats so its density is less than 1 g/ml.
If the above three solutions are very carefully layered, the salt solution is on the bottom, the water is in the middle, and the alcohol floats on top. To help determine, the density ranges, list the plastics in the proper places on the diagram. The plastics that float on alcohol are less than 0.94 g/ml.

 Solvent Density
 Plastic abbrev. and recycle number
 Floats on rubbing alcohol
 
 ---0.94 g/ml rubbing alcohol---
 
 sinks in alcohol, but floats on water
 example from Help: 
# 2 - HDPE = dens. range 1.0-0.94
 ---1.0 g/ml water---
 
sinks in water, but floats on salt water

 
 ---1.2 g/ml sat. salt water---
 
sinks in salt water
 
PHYSICAL AND CHEMICAL PROPERTIES OF PLASTICS
Ques. 12-14 (4points)
****At home collection of lab data ****

 Summary of samples for full credit: Five of six plastics with recycle numbers(1-6).

4. Transmission of Light:
 

5. Flexibility: 

6. Solubility in Solvents: 


Most plastics are insoluble in water and insoluble in acetone.

Two types of packing "popcorn" are found in the lab equipments baggie. Conduct the following solubility tests ONLY on those.
Set up two porcelain or glass cups. Put about 1/2 cup of water in one and 1/8 to 1/4 cup of acetone or finger nail polish remover in the second. Test the solubility of each of the packing "popcorn" samples in acetone and water. Stir around and wait about 2-3 minutes to see if anything is going to happen, as these may prove to be the most interesting. These samples were provided in the "baggie". For some fun try a styrofoam coffee cup with acetone. One of the packing "popcorns" is starch based and eventually will dissolve at least partially in the water but not the acetone.

DATA TABLE: RESULTS OF PROPERTY TESTS AND IDENTIFICATION

.
Summary of samples for full credit: Five of six plastics with recycle numbers(1-6).

QUES. 12: IDENTIFICATION OF THE SAMPLES: 

Based upon the results of your property tests, compare the properties/characteristics given from other sources. In many cases, they do not necessarily follow the theory as our methods are a little crude. Use the textbook to look up the name of the plastic that corresponds to each recycle number.
 Recycle Nos/
Description
 Name of the plastic
 Trans-
mission 
Light 
Behavior
 Flexibility
 Solubility
Properties/
Characteristics
from other
sources
 #1 /soft drink bottle
 PET -polyethylene-
terephthalate
 
 
insoluble in acetone, insoluble in water
transparent, flexible but crazes, glossy

density: 1.38-1.39 g/ml
 #2
 
 
 
soluble in acetone, 
insoluble in water
stiff but will bend, opaque, rough surface 

density: 0.95-0.97 g/ml
#3
 
 
 
insoluble in acetone, insoluble in water
 rigid or flexible, very glossy

density: 1.30-1.34 g/ml
 #4
 
 
 
soluble in acetone, 
insoluble in water
 opaque, very flexible, 

density: 0.92-0.94 g/ml
#5
 
 
 
insoluble in acetone, insoluble in water
translucent to opaque

density: 0.90 g/ml 
#6 Packing popcorn
 Polystyrene
 
 
 
transparent or opaque, brittle soluble in acetone, insoluble in water
density: 1.04-1.07 g/ml
Starch
based packing 
popcorn
 
 
 
 
opaque, slightly flexible but brittle no number
(Biodegradable) insoluble in acetone, soluble in water
density: ??




QUES. 13: Use the textbook to find the monomer or partial polymer chemical structures for at least three of the polymers listed above. At least give a word description of the monomers present in the polymers and some of the more important atoms.


SUMMARY ACTIVITY:

QUES. 14: Why can plastics not be recycled or reused as one large group of all plastics such as glass or paper or aluminum cans? Or stated another way, why must plastics be separated by recycle numbers before they can be recycled? Be specific.


QUES. 15: (2 points)
Recycling Scenario: Form a plan to separate and recycle as many of the plastics as possible. Start with a mixed batch of household plastic items that might be present in the recycling bin for garbage pickup. The recyclables are transported to a large recycling center. How are you going to separate all of the different types of plastics after they arrive at the recycle center and are all mixed up?

Remember that you have paper labels, possible metal rings on some bottles, plastic caps, and aspirator assemblies.

Other items to keep in mind are that you will need to wash or clean the plastic, probably crush or break it into pieces, some hand inspection or sorting is also currently used. Although not previously considered, blowing air might be a way to separate some items. Can you separate some of the plastics by the solubility or density properties as found in this lab exercise? 

A written explanatory narrative is expected for an email submission. For a paper or a fax submission, a diagram/flow chart to show the steps in the separation procedure may be useful. For full credit, your plan must include an application of some of the concepts and principles of this lab - mostly density. Be specific about the recycle numbers and/or types of plastic that float, sink, or dissolve at various stages of the operation.