Engr 45: Materials Semester Project Fall 2005 by 8KY1ZJPu

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									Polymer
Tensile Strength
Michelle Fong and Daniel Matthews
Engineering 45: Properties of Materials
Santa Rosa Junior College
December 5, 2005
Polymers:
        A polymer is a generic term used to describe a substantially long molecule with
 structural and repeating units called monomers.
        In chemistry, a monomer is a small molecule that may become chemically
 bonded to other monomers to form a polymer.
        The process of converting these units to a polymer is called polymerization.
        Polymerization is a process of reacting monomer molecules together in a
 chemical reaction to form linear chains or a three-dimensional network of polymer
 chains. There are many forms of polymerization and different systems exist to
 categorize them.
        The first ‘synthetic’ polymers of the 19th century were actually formed by
 modifying natural polymers. The first man-made polymer, the phenol-formaldehyde
 resin bakelite, was made in 1872. However, research into polymers and
 polymerization only really started to grow in the 1930s after the discovery of
 polyethylene by the chemical company ICI (Imperial Chemical Industries).
        The mechanical properties of polymers can be described with much of the
 vocabulary introduced with metals. Tensile strength and modulus of elasticity are
 important design parameters for polymers as well as inorganic structural materials.
        There are few natural polymers generally considered to be “plastics”.
History of the Plastic Bag
1957 The first baggies and sandwich bags on a roll are introduced.

1958 Poly dry cleaning bags compete with traditional brown paper.

1966 Plastic bag use in bread packaging takes over 25 to 30 percent of the market.
     Plastic produce bags on a roll are introduced in grocery stores.

1969 The New York City Sanitation Department's "New York City Experiment" demonstrates that plastic refuse bag
     curbside pickup is cleaner, safer and quieter than metal trash can pick-up, beginning a shift to plastic can liners
     among consumers.

1974/75 Retailing giants such as Sears, J.C. Penney, Montgomery Ward, Jordan Marsh, Allied, Federated and Hills
       make the switch to plastic merchandise bags.

1973 The first commercial system for manufacturing plastic grocery bags becomes operational.

1977 The plastic grocery bag is introduced to the supermarket industry as an alternative to paper sacks.

1982 Kroger and Safeway start to replace traditional craft sacks with polyethylene "t-shirt" bags.

1990 The first blue bag recycling program begins with curbside collection.
     Consumer plastic bag recycling begins through a supermarket collection-site network.

1992 Nearly half of U.S. supermarkets have recycling available for plastic bags.

1996 Four of five grocery bags used are plastic.
Has this ever happened to you?
Project Overview
Performed Tensile Tests on
  Kitchen/Trash/Grocery plastic
  bags to find:
 Stress, σ
 Strain, ε
 Modulus of Elasticity, E
 Yield Strength, σY.S.
 Tensile Strength, σT.S.
 Toughness
 Ductility
 Price Comparisions
Procedure:
   Cut a 2.54 cm x 30.48 cm strip vertically starting from the bottom crease and
    cutting through both sides of the plastic bag.

   Record the initial thickness with a micrometer.

   Record the initial width with a metric ruler.

   Clamp one end of the plastic strip to the top of the apparatus.

   Record the mass of the clamp device that the hanger will be attached onto.

   Record the mass of the hanger that masses will be added onto.

   Clamp the other end of the plastic strip with the clamp device and
    record the initial length of the plastic strip before letting it hang.

   Add a 20 gram mass and immediately record the new length.;
    Repeat until plastic strip breaks.

   Calculate it’s stress (s = P/Ao) and strain (e = DL/Lo) for each point recorded and
    graph Stress vs. Strain.
Experiment Samples:
13 Gallon Kitchen Bags:
   Safeway
   Costco Kirkland
   Glad Force Flex
   Hefty Ultra Flex

30 Gallon Trash Bags:
   Glad Force Flex
   Hefty Ultra Flex

Shopping Bags:
   Safeway Grocery Bag
   Longs Drugs Bag
                                 Tensile Test for Safeway 13-Gal Kitchen Bag

                  12




                  10




                   8
Stress, σ (MPa)




                                                 Modulus of Elasticity: 128.35 MPa
                                                 Yield Strength: 7.93 MPa
                   6

                                                 Tensile Strength: 10.47 MPa
                                                 Toughness: 8.69 MPa
                   4
                                                 Ductility: 89%

                   2




                   0

                       0   0.1    0.2    0.3    0.4     0.5       0.6   0.7    0.8   0.9   1

                                                 Strain, ε (m/m)
                                 Tensile Test for Costco Kirkland 13-Gal Kitchen Bag

                  10



                   9



                   8



                   7
Stress, σ (MPa)




                   6
                                                   Modulus of Elasticity: 132.83 MPa
                                                   Yield Strength: 6.64 MPa
                   5
                                                   Tensile Strength: 9.01 MPa
                   4
                                                   Toughness: 11.25 MPa
                   3                               Ductility: 150%

                   2



                   1



                   0
                       0   0.2         0.4       0.6         0.8         1      1.2    1.4

                                                       Strain, ε (m/m)
                           Tensile Test for Glad Force Flex 13-Gal Kitchen Bag

                  10



                   9



                   8



                   7
Stress, σ (MPa)




                   6
                                                    Modulus of Elasticity: 10.75 MPa
                   5
                                                    Yield Strength: 7.11 MPa

                   4
                                                    Tensile Strength: 8.97 MPa
                                                    Toughness: 40.53 MPa
                   3

                                                    Ductility: 108%
                   2



                   1



                   0
                       0      0.2         0.4          0.6            0.8         1    1.2


                                                Strain, ε (m/m)
Glad 13-Gal Kitchen Bag
                           Tensile Test for Hefty Ultra Flex 13-Gal Kitchen Bag

                  10



                   9



                   8



                   7
Stress, σ (MPa)




                   6                 Modulus of Elasticity: 149.22 MPa

                   5
                                     Yield Strength: 8.3 MPa
                                     Tensile Strength: ~8.99 MPa
                   4
                                     Toughness: 40.53 MPa
                   3
                                     Ductility: ~490%
                   2



                   1



                   0
                       0       1           2            3            4            5   6


                                                Strain, ε (m/m)
Hefty 13-Gallon Kitchen Bag
                               Tensile Tests for 13-Gallon Kitchen Bags
                  12




                  10




                  8
Stress, σ (MPa)




                                                                              Safeway

                  6
                                                                              Glad Force Flex
                                                                              Hefty Ultra Flex
                                                                              Costco Kirkland
                  4




                  2




                  0
                       0   1         2          3          4    5         6
                                         Strain, ε (m/m)
13-Gallon Kitchen Bags
                  Yield Strength, Y.S.                                                  Tensile Strength, T.S.

        9                                                                  11

        8
                                                                          10.5
        7

        6                                                                  10
                                         Safeway 13-Gal Kitchen                                                  Safeway 13-Gal Kitchen
        5




                                                                  (MPa)
(MPa)




                                         Glad 13-Gal Kitchen                                                     Glad 13-Gal Kitchen
                                                                           9.5
                                         Hefty 13-Gal Kitchen                                                    Hefty 13-Gal Kitchen
        4
                                         Costco 13-Gal Kitchen                                                   Costco 13-Gal Kitchen
        3                                                                   9

        2
                                                                           8.5
        1

        0                                                                   8
             Yield Strength                                                          Tensile Strength



                       Toughness                                                         Modulus of Elasticity

        45                                                                160

        40                                                                140

        35
                                                                          120
        30
                                                                          100                                    Safeway 13-Gal Kitchen
                                         Safeway 13-Gal Kitchen
        25
                                                                  (MPa)
(MPa)




                                         Glad 13-Gal Kitchen                                                     Glad 13-Gal Kitchen
                                                                           80
                                         Hefty 13-Gal Kitchen                                                    Hefty 13-Gal Kitchen
        20
                                         Costco 13-Gal Kitchen             60                                    Costco 13-Gal Kitchen
        15
                                                                           40
        10

        5                                                                  20


        0                                                                   0
               Toughness                                                         Modulus of Elasticity, E
                           Tensile Test for Glad Force Flex 30-Gal Trash Bag

                  12




                  10




                  8
Stress, σ (MPa)




                                                Modulus of Elasticity: 14.57 MPa

                  6
                                                Yield Strength: 8.56 MPa
                                                Tensile Strength: 10.59 MPa
                                                Toughness: 13.21 MPa
                  4

                                                Ductility: 168%

                  2




                  0
                       0     0.2   0.4    0.6      0.8       1       1.2      1.4   1.6   1.8


                                                Strain, ε (m/m)
                           Tensile Test for Hefty Ultra Flex 30-Gal Trash Bag

                  14




                  12




                  10
Stress, σ (MPa)




                  8



                                      Modulus of Elasticity: 169.46 MPa
                  6
                                      Yield Strength: 8.91 MPa
                                      Tensile Strength: ~11.96 MPa
                  4
                                      Toughness: 53.95 MPa
                                      Ductility: ~543%
                  2




                  0
                       0    1            2               3           4          5   6


                                               Strain, ε (m/m)
Hefty 30-Gal Trash Bag
                                           Tensile Tests for 30-Gallon Trash Bags

                  13

                  12

                  11

                  10

                  9
Stress, σ (MPa)




                  8

                  7
                                                                                             Glad 30-Gal Trash
                  6                                                                          Hefty 30-Gal Trash
                  5

                  4

                  3

                  2

                   1

                  0
                       0   0.5   1   1.5      2   2.5    3     3.5   4   4.5   5   5.5   6

                                                  Strain, ε (m/m)
30-Gallon Trash Bags

        14                                                                                  180

                                                                                            160
        12

                                                                                            140
        10
                                                                                            120

        8                                                                                   100
(MPa)




                                                                                    (MPa)
                                                               Glad 30-Gal Trash                                                         Glad 30-Gal Trash
                                                               Hefty 30-Gal Trash                                                        Hefty 30-Gal Trash
        6                                                                                   80

                                                                                            60
        4
                                                                                            40

        2
                                                                                            20

        0                                                                                    0
             Yield Strength, sY.S.   Tensile Strength, sT.S.                                      Modulus of Elasticity, E   Toughness
                                       Tensile Tests for Safeway Grocery Bags
                  40




                  35




                  30
Stress, σ (MPa)




                  25

                                                                                           Safeway Trial 1
                                                                                           (Inconclusive
                  20                       For Trial 2:                                    Results)

                                           Modulus of Elasticity: 476.28 MPa
                  15
                                                                                           Safeway Trial 2
                                           Yield Strength: 21.5 MPa

                  10
                                           Tensile Strength: 25.99 MPa
                                           Toughness: 18.87 MPa
                  5
                                           Ductility: 78%

                  0
                       0   0.1   0.2       0.3      0.4     0.5    0.6   0.7   0.8   0.9


                                                 Strain, ε (m/m)
Why Safeway Trial 1 was Inconclusive:
                                 Tensile Test for Longs Drugs Grocery Bag

                  35




                  30




                  25
Stress, σ (MPa)




                  20




                                           Modulus of Elasticity: 304.95 MPa
                  15
                                           Yield Strength: 24.4 MPa
                                           Tensile Strength: 28.95 MPa
                  10
                                           Toughness: 39.16 MPa
                                           Ductility: 150%
                  5




                  0
                       0   0.2       0.4        0.6          0.8        1      1.2   1.4   1.6


                                                      Strain, ε (m/m)
Longs Drugs Bag
                                       Tensile Tests for Grocery Bags
                  35


                  30


                  25
Stress, σ (MPa)




                  20
                                                                                        Safeway
                                                                                        Longs Drugs
                  15


                  10


                  5


                  0
                       0   0.2   0.4      0.6       0.8           1   1.2   1.4   1.6
                                                Strain, ε (m/m)
Grocery Bags

        45                                                                               600

        40
                                                                                         500
        35

        30                                                                               400

        25
(MPa)




                                                               Safeway Grocery




                                                                                 (MPa)
                                                                                                                          Safeway Grocery
                                                               Longs Drugs               300
        20                                                                                                                Longs Drugs

        15
                                                                                         200
        10

        5                                                                                100


        0
             Yield Strength,   Tensile Strength,   Toughness                              0
                  sY.S.              sT.S.                                                     Modulus of Elasticity, E
                                       Tensile Tests for Kitchen, Trash, & Grocery Bags

                30


                25


                20
Stress, (MPa)




                15


                10


                5


                0
                     0                1                   2                   3                4                   5             6
                                                                      Strain, (m/m)
                         Safeway 13-Gal Kitchen               Glad Force Flex 13-Gal Kitchen   Hefty Ultra Flex 13-Gal Kitchen
                         Costco Kirkland 13-Gal Kitchen       Glad Force Flex 30-Gal Trash     Hefty Ultra Flex 30-Gal Trash
                         Safeway Grocery                      Longs Drugs Grocery
             All Bags
                                                                                                                                                              Modulus of Elasticity
                 Tensile Strength, T.S.

                                                                                                                                               600
        35


        30                                                                                                                                     500
                                                                                                                                                                                      Safeway 13-Gal Kitchen
                                          Safeway 13-Gal Kitchen
        25                                                                                                                                     400                                    Glad 13-Gal Kitchen
                                          Glad 13-Gal Kitchen
                                                                                                                                                                                      Hefty 13-Gal Kitchen
                                          Hefty 13-Gal Kitchen




                                                                                                                                       (MPa)
        20                                                                                                                                                                            Costco 13-Gal Kitchen
(MPa)




                                          Costco 13-Gal Kitchen                                                                                300
                                                                                                                                                                                      Glad 30-Gal Trash
                                          Glad 30-Gal Trash
        15                                                                                                                                                                            Hefty 30-Gal Trash
                                          Hefty 30-Gal Trash                           Yield Strength, Y.S.
                                                                                                                                               200                                    Safeway Grocery
                                          Safeway Grocery
        10                                                                                                                                                                            Longs Drugs
                                          Longs Drugs                      30
                                                                                                                                               100
        5
                                                                           25
        0                                                                                                                                       0
                                                                                                              Safeway 13-Gal Kitchen
              Tensil Strength                                                                                                                         Modulus of Elasticity, E
                                                                           20                                 Glad 13-Gal Kitchen
                                                                                                              Hefty 13-Gal Kitchen
                                                                   (Mpa)




                                                                                                              Costco 13-Gal Kitchen
                                                                           15
                                                                                                              Glad 30-Gal Trash
                        Toughness                                                                             Hefty 30-Gal Trash                                      Ductility
                                                                           10                                 Safeway Grocery
        60                                                                                                    Longs Drugs                      600%

                                                                           5

        50                                                                                                                                     500%

                                          Safeway 13-Gal Kitchen           0
                                                                                                                                                                                      Safeway 13-Gal Kitchen
                                                                                Yield Strength, Y.S.
        40                                Glad 13-Gal Kitchen                                                                                  400%                                   Glad 13-Gal Kitchen
                                          Hefty 13-Gal Kitchen                                                                                                                        Hefty 13-Gal Kitchen
(MPa)




                                          Costco 13-Gal Kitchen                                                                                                                       Costco 13-Gal Kitchen




                                                                                                                                       (%)
        30                                                                                                                                     300%
                                          Glad 30-Gal Trash                                                                                                                           Glad 30-Gal Trash
                                          Hefty 30-Gal Trash                                                                                                                          Hefty 30-Gal Trash
        20                                Safeway Grocery                                                                                      200%                                   Safeway Grocery

                                          Longs Drugs                                                                                                                                 Longs Drugs

        10                                                                                                                                     100%



        0                                                                                                                                        0%
                Toughness                                                                                                                                      Ductility
Recycled Plastic
What you get for your money!
                                 Prices for Each Material Property

                $0.06


                $0.05
                                                                     Safeway 13-Gal Kitchen

                $0.04                                                Glad 13-Gal Kitchen
 U.S. Dollars




                                                                     Hefty 13-Gal Kitchen
                                                                     Costco 13-Gal Kitchen
                $0.03
                                                                     Glad 30-Gal Trash
                                                                     Hefty 30-Gal Trash
                $0.02
                                                                     Safeway Grocery
                                                                     Longs Drugs
                $0.01


                $0.00
                        Price per Bag Price per Bag Price per Bag
                          per Yield    per Tensile per Toughness
                           Strength      Strength
References:
   http://en.wikipedia.org


   http://www.plasticbag.com/environmental/history.html


   http://www.budgetpackaging.com/inofgaba.html


   http://www.santarosa.edu/~yataiiya/E45/LAB/TENSILE%20TEST.pdf


   http://www.americanplasticscouncil.org/s_apc/sec.asp?CID=313&DID=931

								
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