DMSE G Love Prototype Presentation Kristin Brodie Jeff Colton Colin Galbraith Bushra Makiya Tiffany Santos

DMSE Presentation Topics Materials Selection Processing Testing Future Work

DMSE Materials Selection: Fabrics Key Properties: Heat transfer coefficient, good breathability, lightweight, low cost, good durability. 100% polyester (fleece) 80% polyester, 20% cotton 20% polyester, 80% cotton 100% cotton (flannel)- intended as inner lining Cotton ignites at 250  C Polyester melts at 260  C

DMSE Materials Selection: Heating Element Key Properties: High resistivity, mechanical strength, large elastic region.

DMSE Materials Selection: Wire Coating Key Properties: High electrical resistivity, high thermal conductivity, high T m, low water absorption, good ductility, good weather resistance. Teflon (CF 2 ) is the best candidate. Polyethylene has too low T m and may melt. Braided tubing will allow water through. Glass is not flexible enough. Silicone rubber has low thermal conductivity. Teflon: Resistivity>10 18 ohm*cm Tensile strength21-34 MPa T m 327  C Thermal conductivity0.25 W/m*K H 2 O Absorption<0.01%

DMSE Materials Selection: Battery Key Properties: Flat, flexible, rechargeable, high capacity, weight.

DMSE Materials Selection: Temperature Sensor Key Properties: Fast reaction time, good temperature control, cost.

DMSE Materials Selection: Phase Change Materials Key Properties: T m near that of human body, high heat of crystallization, ease of processing.

DMSE Materials Selection: PCM Base Materials PDMS resin: Used as the base material for octadecane. Easy to process-when mixed with a cross- linker it sets into a flexible rubber overnight. Key Properties: Flexible, hydrophobic, easy to process, contains microspheres, thermal conductivity, high T m. Polypropylene: Can be made into fibers or sheets. PEG can be incorporated directly, rather than fabricating microspheres first. Atactic polymer should be easy to process. High solvent resistance.

DMSE PCM Processing: Microsphere Fabrication Microspheres increase surface area, releasing heat faster. Small particles can be incorporated into the fabric easily. SEM image of octadecane microspheres. They appeared to have melted and recrystallized during fabrication.

DMSE PCM Processing: Incorporation 1) Embed microspheres in a base material. Octadecane microspheres were embedded in PDMS. There was no difference in DSC results compared to a regular piece of PDMS resin. This could be due to the quality or quantity of the microspheres or to properties of the PDMS. 2) Incorporate PCM directly into base material (polypropylene) and form into flat sheets. 3) Coat fibers or fabric with the PCM.

DMSE Testing Heat transfer coefficient of fabric  Place heating element in gloves  Use thermistor to measure inside/outside temp.  Measured to be W/m 2  K  Equilibrium time ~5 min Next Step: Repeat this experiment with gloves containing PCMs

DMSE Thermal Testing h = I*V/[A*(T 1 -T 2 )] = 3.6*0.55/(.04*  T) As h goes up, less heat is lost (small  T) Polyester has the highest value for h Graph for values with 3.6V and 100cm of wire 100P100P*20C 80P80C 20P h

DMSE Power Requirement Serial # W*h @32F

DMSE Future Work Improve octadecane fabrication process, make more microspheres, test a larger piece of silicone rubber with more microspheres. Test PEG as an alternative PCM, either by making microspheres or by directly incorporating it into a polypropylene sheet. Continue heat transfer testing of gloves. Test gloves with PCMs incorporated. Coat or insulate wires (Teflon tubing is in the mail). Test and incorporate thermal switch (in the mail). Connection of wires to battery. Cost analysis. Continue working on quantitative heat transfer analysis