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Project No Drip Final Presentation

Project No Drip Final Presentation. Jacqueline Greene Michele Dufalla Tania Chan May 17, 2007. Objective. +. http://www1.istockphoto.com/file_thumbview_approve/1168596/2/istockphoto_1168596_plastic_can_container.jpg , http://www.baproducts.com/spigot.jpg.

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Project No Drip Final Presentation

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

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

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

  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. • 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. • 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.

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

  7. Shear Tests

  8. Shear Tests

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

  10. Peel Tests

  11. Thermal Processing: Molded LDPE • 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 • Potential application for discarded plastic bags

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

  13. Water pressure testing:Results

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

  15. Constant Heat Flux (q) x = 0 Semi Infinite Solid Polyethylene x Governing equation: Modeling Heat Conduction in HDPE • = density, k = thermal conductivity, c = specific heat, s = heat generation Thermal Diffusivity: (Materials Parameter) Boundary Conditions: At t = 0: T = T0 = 25oC At x = 0: q At x = ∞: T|x = ∞ = T0 = 25oC S = 0, no heat generation

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

  17. Modeling Cooling at Weld junction 0.125in=0.003175m HDPE 0.00735m LDPE HDPE • 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

  18. 1-D explicit finite differences model

  19. Polymer Mixing Thermodynamics • 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 http://www.msm.cam.ac.uk/doitpoms/tlplib/solid-solutions/free-energy.php

  20. Polymer Diffusion in Melts Material 1 Interface Material 2 Polymer-polymer interdiffusion at an interface proceeds in two stages • At time shorter than reptation time, the diffusion process is explained by the reptation model Diffusion scales: wt1/4 • At time great than reptation time, the diffusion process can be explained by continuum theories, Fick’s Law Diffusion scales: wt1/2 1 Courtesy of Dr. Joseph Parse 1. http://wwwcp.tphys.uni-heidelberg.de/Polymer/day3/p3-1.htm

  21. Conclusions about welding of polyethlene • water-tight seal between plastic jerrycans and taps • 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.

  22. 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.

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