Project No DripProject No DripFinal PresentationFinal Presentation

Jacqueline Greene Jacqueline Greene

Michele DufallaMichele Dufalla

Tania ChanTania Chan

May 17, 2007May 17, 2007

ObjectiveObjective

http://www1.istockphoto.com/file_thumbview_approve/1168596/2/istockphoto_1168596_plastic_can_container.jpg, http://www.baproducts.com/spigot.jpg

+

18 Countries in Africa

12 Countries in Asia

2 Countries in Central America

3 Countries in South America

Project Overview: Low Cost Project Overview: Low Cost Water TapWater Tap

•2 to 3 million children under 5 years old die of diarrhea diseases each year resulting from water contamination

•Safe water system for water sanitation

•Low cost water dispenser for use with a variety of storage canisters

http://www.cdc.gov/safewater/about_pages/about_where.htm

Project Overview: Plastic WeldingProject Overview: Plastic Welding

http://www.cooking.com/images/products/shprodde/743196.jpg,http://www.flagstaff.az.gov/images/pages/SC581/plastic%20bag.JPGhttp://www.midi-classics.com/i/p19228.gif

Solution:

Simple low cost polyethylene tap and tubing

Focus of our project:

Heat welding as a method to join polyethylene tap and tubing to polyethylene containers

Sample preparationSample preparation temperature1/8” thick HDPE plastic sheets (McMaster) were cut in temperature1/8” thick HDPE plastic sheets (McMaster) were cut in

1x6 in strips, while LDPE plastic film was cut into 1x3in pieces. 1x6 in strips, while LDPE plastic film was cut into 1x3in pieces. Samples were welded together with a clothes iron at a constant Samples were welded together with a clothes iron at a constant

setting, pressed together and allowed to cool at room temperaturesetting, pressed together and allowed to cool at room temperature Shear samples were prepared by heating two HDPE substrates, Shear samples were prepared by heating two HDPE substrates,

and layering up to 4 pieces of LDPE film with the iron, and heating and layering up to 4 pieces of LDPE film with the iron, and heating them together with the iron.them together with the iron.

Peel samples were prepared by heating 1 LDPE film to an HDPE Peel samples were prepared by heating 1 LDPE film to an HDPE substrate substrate

For select samples, disposable thermocouples were inserted into For select samples, disposable thermocouples were inserted into the joint during the heating process and the change in temperature the joint during the heating process and the change in temperature was measured every 20 seconds. This experimental data was was measured every 20 seconds. This experimental data was compared to the cooling model.compared to the cooling model.

Shear TestsShear Tests1/8” HDPE

1/8” HDPE

4 layers of clear LDPE film (0.0006”) 3x1 in contact

area

Shear TestsShear TestsDateDate SampleSample Max Load (kN)Max Load (kN) Stress at Peak Stress at Peak

(kPa)(kPa)

4/2/074/2/07 Black LDPE (110-112°C)Black LDPE (110-112°C) 0.2260.226 117117

4/2/074/2/07 Black LDPE (120-123°C)Black LDPE (120-123°C) 1.3571.357 701701

4/2/074/2/07 Black LDPE (130-138°C)Black LDPE (130-138°C) 0.0560.056 2929

4/2/074/2/07 Black LDPE (155-170°C)Black LDPE (155-170°C) 0.3540.354 274274

4/2/074/2/07 Clear LDPE (155-165°C)Clear LDPE (155-165°C) 0.9540.954 739739

4/2/074/2/07 Clear LDPE (130-134°C)Clear LDPE (130-134°C) 0.2500.250 129129

4/2/074/2/07 Clear LDPE (115-122°C)Clear LDPE (115-122°C) 0.3180.318 164164

4/2/074/2/07 Clear LDPE (141-150°C)Clear LDPE (141-150°C) 0.2380.238 123123

4/2/074/2/07 Clear LDPE (165-180°C)Clear LDPE (165-180°C) 0.9380.938 727727

Shear Max stress vs. Temperature of Formation LDPE

0100200300400500600700800

100 110 120 130 140 150 160 170 180 190 200

Temperature (deg C)

Max

Stre

sskP

a kP

a

Shear TestsShear TestsDateDate SampleSample Max Load (N)Max Load (N) Stress at Peak Stress at Peak

(kPa)(kPa)

4/24/074/24/07 Bag LDPE – 1 Bag LDPE – 1 (thermocouple)(thermocouple)

514514 398398

4/24/074/24/07 Bag LDPE – 2 Bag LDPE – 2 (thermocouple)(thermocouple)

710710 550550

4/24/074/24/07 Bag LDPE – 5 Bag LDPE – 5 (thermocouple)(thermocouple)

958958 742742

4/24/074/24/07 African BagAfrican Bag 15131513 11731173

4/26/074/26/07 Preprocessed Black LDPE – Preprocessed Black LDPE – 1 layer1 layer

13411341 10391039

4/26/074/26/07 Preprocessed Black LDPE – Preprocessed Black LDPE – 2 layers2 layers

559559 433433

4/26/074/26/07 Preprocessed Black LDPE – Preprocessed Black LDPE – 2 layers + thermocouple2 layers + thermocouple

757757 587587

5/1/075/1/07 Bag LDPEBag LDPE 8585 6666

5/1/075/1/07 Bag LDPEBag LDPE 410410 318318

Mechanisms of failureMechanisms of failure

NECKING

Fibrillar failure

Courtesy of Dr. Joseph Parse

Peel TestsPeel Tests

Thermal Processing: Thermal Processing: Molded LDPEMolded LDPE

Heated to 190Heated to 190ººC at 10C at 10ººC/minute. Left C/minute. Left to dwell for 20 minutes, then left to to dwell for 20 minutes, then left to cool to room temperature.cool to room temperature.

Additional heating cycles at low Additional heating cycles at low temperature does not disturb LDPE’s temperature does not disturb LDPE’s welding propertieswelding properties

Potential application for discarded Potential application for discarded plastic bagsplastic bags

Water pressure testingWater pressure testing

•Test the water sealing properties of the LDPE “glue”

•Test the strength of the LDPE “glue”

Water pressure testing:Water pressure testing:ResultsResults

Base PlasticBase Plastic Layer of LDPE Layer of LDPE Film “Glue”Film “Glue”

ResultsResults

HDPEHDPE 44 Up to 50psi for Up to 50psi for 5 mins5 mins

LDPELDPE 44 Up to 50psi for Up to 50psi for 5 mins5 mins

HDPEHDPE 22 Leakage Leakage without without pressurepressure

LDPELDPE 00 Leakage Leakage without without pressurepressure

DSCDSC

Preprocessed McMaster-Carr LDPE Preprocessed McMaster-Carr LDPE Melting point ≈ 111Melting point ≈ 111ººCC

Preprocessed commercial LDPE Preprocessed commercial LDPE No clear melting peakNo clear melting peak

Modeling Heat Modeling Heat Conduction in HDPEConduction in HDPE

sx

Tk

t

Tc

2

2

Governing equation:

= density, k = thermal conductivity,

c = specific heat, s = heat generation

Semi Infinite Solid

Polyethylene

x = 0

x

Constant Heat Flux (q)

Boundary Conditions:

At t = 0: T = T0 = 25oC

At x = 0: q

At x = ∞: T|x = ∞ = T0 = 25oC

S = 0, no heat generation

k

c

Thermal Diffusivity:(Materials Parameter)

Finite Differences: 1-D Finite Differences: 1-D Heat Conduction Heat Conduction

ModelingModeling

Tt

2Tx 2

Modified Governing Equation:

Finite Differences Approximations:

Ti,n1 Ti,nt

Ti 1,n 2Ti,n Ti1,nx 2

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0 20 40 60 80 100 120 140 160 180 200

Temperature (C)

Po

lye

thyle

ne

Th

ickn

ess (

m) 0 sec

5 sec10 sec15 sec20 sec25 sec30 sec35 sec40 sec45 sec50 sec55 sec60 sec

Modeling Cooling at Weld Modeling Cooling at Weld junctionjunction

HDPE

HDPELDPE

0.125in=0.003175m

0.00735m

Boundary Conditions:•At x=0, x=L (L=0.00735m) the Temperature is set at 25ºC•At x=0.003-0.004m (LDPE region) the Temperature is 120ºC at t=0

•HDPE and LDPE have slightly different thermal properties

1-D explicit finite 1-D explicit finite differences modeldifferences model

)()21( ,1,1,1,

2

nininini

p

TTFomTFomTx

tFom

c

k

7 intervals HDPE data

Fom k(W/mK)delta t (sec)

density (kg/m^3) cp (J/kgK) delta x (m)

0.479893 0.641.8253311

3 960 2300 0.00105

center 2 intervals LDPE data

Fom k(W/mK)delta t (sec)

density (kg/m^3) cp (J/kgK) delta x (m)

0.302691 0.33 950 1900

POSITION

TIME 0 0.00105 0.0021 0.00315 0.0042 0.00525 0.0063 0.00735

0 25 25 25 130 130 25 25 25

1.825331 25 25 75.3887129398.2174240

1 98.2174240175.3887

1 25 25

3.650662 2549.181165

6 62.1628746391.3073740

6 91.3073740662.1628

749.1811

7 25

5.475993 2543.806630

3 69.919276682.4855905

5 82.4855905569.9192

843.8066

3 25

7.301325 2547.312732

6 63.41849327 78.6818779 78.681877963.4184

947.3127

3 25

9.126656 2544.334053

3 63.0142433374.0617856

9 74.0617856963.0142

444.3340

5 25

10.95199 2544.020269

2 59.3513929370.7177918

4 70.7177918459.3513

944.0202

7 25

12.77732 2542.249875

9 57.4487512267.2772829

1 67.2772829157.4487

542.2498

8 25

Temperature Profile with 7 intervals

0

20

40

60

80

100

120

140

-0.00065 0.00035 0.00135 0.00235 0.00335 0.00435 0.00535 0.00635 0.00735

Depth of plate (m)

Tem

per

ature

(deg

C) 0sec

1.82sec

5.47sec

10.9sec

16.42sec

20sec

40sec

Cooling Curves

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140 160 180 200

Time (sec)

Tem

p (C

) Predicted

exp1

exp2

exp3

Solvent = solute in system, system has only 1 value of chemical potential for any mole fraction BSolvent = solute in system, system has only 1 value of chemical potential for any mole fraction B

Two phases are always in equilibrium are always miscibleTwo phases are always in equilibrium are always miscible

Polymer Mixing Polymer Mixing ThermodynamicsThermodynamics

Gmix Hmix TSmixGmix 0

http://www.msm.cam.ac.uk/doitpoms/tlplib/solid-solutions/free-energy.php

Polymer-polymer interdiffusion at an interface Polymer-polymer interdiffusion at an interface proceeds in two stagesproceeds in two stages

1.1. At time shorter than reptation time, the diffusion At time shorter than reptation time, the diffusion process is explained by the reptation modelprocess is explained by the reptation model

Diffusion scales: wDiffusion scales: wtt1/41/4

2.2. At time great than reptation time, the diffusion At time great than reptation time, the diffusion process can be explained by continuum theories, process can be explained by continuum theories, Fick’s LawFick’s Law

Diffusion scales: wDiffusion scales: wtt1/21/2

Polymer Diffusion in Polymer Diffusion in MeltsMelts

Material 1

Material 2

Interface

1. http://wwwcp.tphys.uni-heidelberg.de/Polymer/day3/p3-1.htm

1

Courtesy of Dr. Joseph Parse

Conclusions about welding Conclusions about welding of polyethleneof polyethlene

water-tight seal between plastic water-tight seal between plastic jerrycans and tapsjerrycans and taps

Requires low temperatures (120-180Requires low temperatures (120-180ºC) ºC) and a short time frame (~1 min to cool)and a short time frame (~1 min to cool)

Feasible option for installing water taps Feasible option for installing water taps due to availability and low-cost of due to availability and low-cost of polyethylene through recycled plastic polyethylene through recycled plastic bags to facilitate easier access to water bags to facilitate easier access to water as well as prevent water contamination. as well as prevent water contamination.

AcknowledgementsAcknowledgements

The authors would like to thank MIT DMSE’s Prof. Yet-Ming Chiang, Prof. David Roylance, Dr. Joseph Parse, Dr. Yin-Lin Xie, Michael Tarkanian and the rest of the 3.042 teaching staff as well as the CMSE.