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

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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

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

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.

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

Shear Tests DateSample Max Load (kN) Stress at Peak (kPa) 4/2/07 Black LDPE ( °C) /2/07 Black LDPE ( °C) /2/07 Black LDPE ( °C) /2/07 Black LDPE ( °C) /2/07 Clear LDPE ( °C) /2/07 Clear LDPE ( °C) /2/07 Clear LDPE ( °C) /2/07 Clear LDPE ( °C) /2/07 Clear LDPE ( °C)

Shear Tests DateSample Max Load (N) Stress at Peak (kPa) 4/24/07 Bag LDPE – 1 (thermocouple) /24/07 Bag LDPE – 2 (thermocouple) /24/07 Bag LDPE – 5 (thermocouple) /24/07 African Bag /26/07 Preprocessed Black LDPE – 1 layer /26/07 Preprocessed Black LDPE – 2 layers /26/07 Preprocessed Black LDPE – 2 layers + thermocouple /1/07 Bag LDPE /1/

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

Peel Tests

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

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

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

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

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)

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

Modeling Cooling at Weld junction HDPE LDPE 0.125in= m m Boundary Conditions: At x=0, x=L (L= m) the Temperature is set at 25ºC At x= m (LDPE region) the Temperature is 120ºC at t=0 HDPE and LDPE have slightly different thermal properties

1-D explicit finite differences model

7 intervalsHDPE data Fomk(W/mK) delta t (sec) density (kg/m^3)cp (J/kgK)delta x (m) center 2 intervalsLDPE data Fomk(W/mK) delta t (sec) density (kg/m^3)cp (J/kgK)delta x (m) POSITION TIME

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

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 Courtesy of Dr. Joseph Parse

Conclusions about welding of polyethlene water-tight seal between plastic jerrycans and taps water-tight seal between plastic jerrycans and taps Requires low temperatures ( ºC) and a short time frame (~1 min to cool) Requires low temperatures ( ºC) 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.

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 teaching staff as well as the CMSE.