1. Project No Drip Final Presentation Jacqueline Greene Michele Dufalla Tania Chan May 17, 2007

2. Objective http://www1.istockphoto.com/file_thumbview_approve/1168596/2/istockphoto_116859 6_plastic_can_container.jpghttp://www1.istockphoto.com/file_thumbview_approve/1168596/2/istockphoto_116859 6_plastic_can_container.jpg, http://www.baproducts.com/spigot.jpg +

3. 18 Countries in Africa 12 Countries in Asia 2 Countries in Central America 3 Countries in South America Project Overview: Low Cost Water 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

4. Project Overview: Plastic Welding http://www.cooking.com/images/products/shprodde/743196.jpg, http://www.flagstaff.az.gov/images/pages/SC581/plastic%20bag.JPG http://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

5. Sample preparation temperature1/8” thick HDPE plastic sheets (McMaster) were cut in 1x6 in strips, while LDPE plastic film was cut into 1x3in pieces. temperature1/8” thick HDPE plastic sheets (McMaster) were cut in 1x6 in strips, while LDPE plastic film was cut into 1x3in pieces. Samples were welded together with a clothes iron at a constant setting, pressed together and allowed to cool at room temperature Samples were welded together with a clothes iron at a constant setting, pressed together and allowed to cool at room temperature Shear samples were prepared by heating two HDPE substrates, and layering up to 4 pieces of LDPE film with the iron, and heating them together with the iron. Shear samples were prepared by heating two HDPE substrates, and layering up to 4 pieces of LDPE film with the iron, and heating them together with the iron. Peel samples were prepared by heating 1 LDPE film to an HDPE substrate Peel samples were prepared by heating 1 LDPE film to an HDPE substrate For select samples, disposable thermocouples were inserted into the joint during the heating process and the change in temperature was measured every 20 seconds. This experimental data was compared to the cooling model. For select samples, disposable thermocouples were inserted into the joint during the heating process and the change in temperature was measured every 20 seconds. This experimental data was compared to the cooling model.

6. Shear Tests 1/8” HDPE 4 layers of clear LDPE film (0.0006”) 3x1 in contact area

7. Shear Tests DateSample Max Load (kN) Stress at Peak (kPa) 4/2/07 Black LDPE (110-112°C) 0.226117 4/2/07 Black LDPE (120-123°C) 1.357701 4/2/07 Black LDPE (130-138°C) 0.05629 4/2/07 Black LDPE (155-170°C) 0.354274 4/2/07 Clear LDPE (155-165°C) 0.954739 4/2/07 Clear LDPE (130-134°C) 0.250129 4/2/07 Clear LDPE (115-122°C) 0.318164 4/2/07 Clear LDPE (141-150°C) 0.238123 4/2/07 Clear LDPE (165-180°C) 0.938727

9. Shear Tests DateSample Max Load (N) Stress at Peak (kPa) 4/24/07 Bag LDPE – 1 (thermocouple) 514398 4/24/07 Bag LDPE – 2 (thermocouple) 710550 4/24/07 Bag LDPE – 5 (thermocouple) 958742 4/24/07 African Bag 15131173 4/26/07 Preprocessed Black LDPE – 1 layer 13411039 4/26/07 Preprocessed Black LDPE – 2 layers 559433 4/26/07 Preprocessed Black LDPE – 2 layers + thermocouple 757587 5/1/07 Bag LDPE 8566 5/1/07 410318

10. Mechanisms of failure NECKING Fibrillar failure Courtesy of Dr. Joseph Parse

11. Peel Tests

12. Thermal Processing: Molded LDPE Heated to 190ºC at 10ºC/minute. Left to dwell for 20 minutes, then left to cool to room temperature. Heated to 190ºC at 10ºC/minute. Left to dwell for 20 minutes, then left to cool to room temperature. Additional heating cycles at low temperature does not disturb LDPE’s welding properties Additional heating cycles at low temperature does not disturb LDPE’s welding properties Potential application for discarded plastic bags Potential application for discarded plastic bags

13. Water pressure testing Test the water sealing properties of the LDPE “glue” Test the strength of the LDPE “glue”

14. Water pressure testing: Results Base Plastic Layer of LDPE Film “Glue” Results HDPE4 Up to 50psi for 5 mins LDPE4 HDPE2 Leakage without pressure LDPE0

15. DSC Preprocessed McMaster-Carr LDPE  Preprocessed McMaster-Carr LDPE  Melting point ≈ 111ºC Preprocessed commercial LDPE  Preprocessed commercial LDPE  No clear melting peak

16. Modeling Heat Conduction in HDPE 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 = T 0 = 25 o C At x = 0: q At x = ∞: T| x = ∞ = T 0 = 25 o C S = 0, no heat generation Thermal Diffusivity: (Materials Parameter)

17. Finite Differences: 1-D Heat Conduction Modeling Modified Governing Equation : Finite Differences Approximations:

18. Modeling Cooling at Weld junction HDPE LDPE 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

19. 1-D explicit finite differences model

20. 7 intervalsHDPE data Fomk(W/mK) delta t (sec) density (kg/m^3)cp (J/kgK)delta x (m) 0.4798930.64 1.8253311 396023000.00105 center 2 intervalsLDPE data Fomk(W/mK) delta t (sec) density (kg/m^3)cp (J/kgK)delta x (m) 0.3026910.339501900 POSITION TIME00.001050.00210.003150.00420.005250.00630.00735 025 130 25 1.82533125 75.38871293 98.2174240 1 75.3887 125 3.65066225 49.181165 662.16287463 91.3073740 6 62.1628 7 49.1811 725 5.47599325 43.806630 369.9192766 82.4855905 5 69.9192 8 43.8066 325 7.30132525 47.312732 663.4184932778.6818779 63.4184 9 47.3127 325 9.12665625 44.334053 363.01424333 74.0617856 9 63.0142 4 44.3340 525 10.9519925 44.020269 259.35139293 70.7177918 4 59.3513 9 44.0202 725 12.7773225 42.249875 957.44875122 67.2772829 1 57.4487 5 42.2498 825

23. Solvent = solute in system, system has only 1 value of chemical potential for any mole fraction B Solvent = solute in system, system has only 1 value of chemical potential for any mole fraction B Two phases are always in equilibrium are always miscible Two phases are always in equilibrium are always miscible Polymer Mixing Thermodynamics http://www.msm.cam.ac.uk/doitpoms/tlplib/solid-solutions/free-energy.php

24. Polymer-polymer interdiffusion at an interface proceeds in two stages 1. At time shorter than reptation time, the diffusion process is explained by the reptation model Diffusion scales: w  t 1/4 2. At time great than reptation time, the diffusion process can be explained by continuum theories, Fick’s Law Diffusion scales: w  t 1/2 Polymer Diffusion in Melts Material 1 Material 2 Interface 1. http://wwwcp.tphys.uni-heidelberg.de/Polymer/day3/p3-1.htm 1 Courtesy of Dr. Joseph Parse

25. Conclusions about welding of polyethlene water-tight seal between plastic jerrycans and taps water-tight seal between plastic jerrycans and taps Requires low temperatures (120-180ºC) and a short time frame (~1 min to cool) Requires low temperatures (120-180ºC) and a short time frame (~1 min to cool) Feasible option for installing water taps due to availability and low-cost of polyethylene through recycled plastic bags to facilitate easier access to water as well as prevent water contamination. Feasible option for installing water taps due to availability and low-cost of polyethylene through recycled plastic bags to facilitate easier access to water as well as prevent water contamination.

26. Acknowledgements 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.