Tefzel

Jay Baldwin, the inventior of Pillow Domes, recommends the use of DuPont's Tefzel material. Here is some information on Tefzel and Tefzel T2 that I have obtainned from DuPont.

To order DuPont's Technical Data sheets on Tefzel and Tefzel T2 you can call DuPont's Product Information at (800) 237-4357.

Tefzel Fluoropolymer Films
Property	1 mil	2 mil	5 mil
Tensile Strength, psi	6000	6000	6000
Elongation at Break,%	200	250	250
Shrinkage, %, Max. at 200 C, MD/TD	+0/-7	+0/-5	+0/-4
Tear Strength, g/,mil, Min	300	400	400
Melt Temp, Melting Endotherm Peak, C	250-270	250-270	250-270
Density, g/cm^3, 23 C	1.73-1.77

Tefzel Fluoropolymer Films Approx. Cost
Gauge	Dollars Per Sq Ft
200LZ	0.66
300LZ	0.99
500LZ	1.66

Tefzel T^2

DuPont has another clear film called Tefzel T^2 which has enhanced mechanical properties in the machined direction (MD). We have considered using the T^2 film for the pillow dome project, but we feel that more research would be needed for the T^2 film than for the "normal" Tefzel material (which we know works from Jay Baldwin's experience.) At least two properties of T^2 need further investigation

Comparison of T^2 puncture resistance to "normal" Tefzel. DuPont has done some "Impact Resistance" on T^2 and have reported their results in their "T^2 Films of TEFZEL ETFE Technical Data" bulletin, but there doesn't seem to be a direct comparison between Tefzel and Tefzel T^2. We will be conducting our own puncture test comparison at SUNY Oswego sometime in Oct. or Nov. of 1996. The results will be listed below.
Heat sealing of T^2 is more of a problem than for "normal" Tefzel. Heat sealing melts the material and so you loose the enhanced properties of the film at the seam. And because the T^2 film would be a thinner film (1.5 or 2.5 mil) the seams will be weaker. One solution might be to add more Tefzel along the seam as part of the heat sealing process. So you end up heat sealing 2 layers of T^2 plus another layer or two (on the "top" and "bottom") of "normal" Tefzel just to make the seam thicker.

Tefzel T^2 comes in roles up to 50 inches wide.
MD = Machine Direction
TD = Transverse Direction

Tefzel T^2 Properties
Property	Value MD/TD
Tensile Strength at Break	34,000/7,000 psi
Elongation at Break	45/650%
Impact Resistance	14.8 in-lb/mil
Light Transmission	95%

Tefzel T^2 Fluoropolymer Films Approx. Cost
Gauge	Dollars Per Sq Ft
90ZM	0.42
150ZM	0.70
250ZM	1.17

Note that in the machined direction, T^2 has a tensile strength of approx. 5 times the normal tensile strength. This makes me wonder if it would be possible to laminate two layers of T^2, 0.9mil thick, with one layer rotated 90 degrees to the other layer to give a resulting material approx. 1.8mil thick and a tensile strength in either direction well over 34,000 psi.