Tensile Strength of different plastics

Chloe Arnold, Chris Lan, Daniel Amador

ENGR45, F2013, SRJC

Engr 45 project (plastics)

Chloe Arnold Daniel Amador Chris Lan

Original Plan

• Carbon Fiber: Tensile strength • Problem: Fixture needed for tensile machine

and different from previous semesters.

Last semesters problem:

Fixtures

• We designed a fixture to test carbon fiber. • Problem: No source to obtain carbon fiber. • Solution: Test plastics instead

Replacement for Carbon Fiber

Plastics collected around the world: • Polyethylene (two forms found)

– High density - Notebook – Low Density - Tarp

• Polyvinyl Chloride (PVC) – Pen case • Polyvinyl Chloride (PVC) – Shrink Wrap

PROBLEM!!

• Tested the plastics in the Tensile Machine • Plastics were not strong enough.

– Ripped before any measurement.

Different Way to Test

• The string machine. – Slightly altered the fixture for fitness and stability

• More precise – Added on small amounts of mass (200-1000 grams) – Measured stretch in cm – Could track change so it yielded better data

Low Density Polyethylene

• Used in: – Carrier bags – Bin liners – Packaging films – Tarp

Theoretical Young’s Modulus: 0.11-0.45 GPa

Graph of Data for Low Density Polyethylene (Tarp)

Our Young’s Modulus: .290GPa

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0 0.1 0.2 0.3 0.4

Stre

ss (G

Pa)

Strain

y = 0.2902x + 0.003 R² = 0.9667

00.005

0.010.015

0.020.025

0.030.035

0.040.045

0 0.1 0.2St

ress

(GPa

)

Strain

Low Density Polyethylene

Theoretical Value: 0.11 to 0.45 GPA

Our Value: 0.29

It was in the range.

High Density Polyethylene

• Used in – Milk bottles – Bleach – Cleaners – Shampoo bottles – Notebook cover

Theoretical Young’s Modulus: 0.8 GPa

Graph of Data for High density Polyethylene (Notebook)

Our Young’s Modulus: .937GPa

y = 0.9374x + 0.0346 R² = 0.8799

00.020.040.060.08

0.10.120.140.16

0 0.05 0.1 0.15St

ress

(GPa

) Strain

00.020.040.060.08

0.10.120.140.16

0 0.05 0.1 0.15

Stre

ss (G

Pa)

Strain

High Density Polyethylene

Theoretical Young’s Modulus: 0.8 GPa

Our Young’s Modulus: .937GPa

Percent Difference: 14.6% Discrepancy because: -It barely stretched -Not enough mass to continue -Not enough space to add mass

Polyvinyl Chloride

• Used in – Pipes – Fittings – Window and door frames

Theoretical Young’s Modulus: 0.05 GPa

Graph of Data for Polyvinyl Chloride (Pen Case)

Our Young’s Modulus: 0.158GPa

y = 0.1583x + 0.0044 R² = 0.96839

0

0.01

0.02

0.03

0.04

0.05

0.06

0 0.2 0.4St

ress

(GPa

)

Strain

00.010.020.030.040.050.060.070.080.09

0 0.5 1

Stre

ss (G

Pa)

Strain

Polyvinyl Chloride

Our Value: 0.158

Theoretical Young’s Modulus: 0.05

Percent Difference: 216% Discrepancy because of: -Could have been a combination of different plastics. Therefore there would be a different value for Young’s modulus.

Polyvinyl Chloride (shrink film) • Industrial shrink wrap containment of large plant equipment/components, • Scaffold wrap containment of buildings/bridges, • Building temporary shrink wrap structures for storage or other business

operational uses, Marine shrink wrapping of boats and other vehicles.

Graph of Data for PVC (shrink film)

0

0.05

0.1

0.15

0.2

0.25

0.3

0 0.2 0.4 0.6 0.8

Stre

ss (G

Pa)

Strain

y = 2.4814x - 0.0194 R² = 0.93998

00.020.040.060.08

0.10.120.140.160.18

0 0.05 0.1

Stre

ss (G

Pa)

Strain

Our Young’s Modulus: 2.5Gpa

Polyvinyl Chloride (shrink film)

Theoretical Young’s Modulus: 2.8GPa

Our value: 2.5GPa

Percent Difference: 11.1% Discrepancy because of: -Parallax -Thickness measurement

Comparing

• Highest to Lowest Young’s Modulus: • 2.5 GPa Film Wrap • .937 GPa Notebook • .290 GPa Tarp • .158 GPa Pen Case

LINK

• TYPES OF PLASTICS http://www.wrap.org.uk/content/types-plastic

• TYPE OF PACKAGE PLASTICS http://www.wrap.org.uk/content/types-plastic-packaging