1	Comparison of Insulation Properties for Various Nonwoven Batting Materials
2	Unchin Cho Roy M. Broughton, Jr. Textile Engineering – Auburn University Paul Brady American Nonwovens, Columbus MS.
3	We have been working on insulation materials for a long time.
4	Most recent work International Nonwovens Technical Conference, “ Model Development for Cost and Efficiency Comparisons of Nonwoven Insulation Matereials”, Paul Brady (presentor), and Roy M. Broughton,Jr., September 2000, Dallas, TX. (proceedings)
5	“Chicken Feather as a Fiber Source For Nonwoven Insulation” Weiqin Ye, Roy M. Broughton, Jr. and Joseph B Hess, International Nonwovens Journal, 8(1)Spring 1999, (p53-65). "Thermal Properties of Novel Carbonaceous Battings" Shanley, L. A., B. L. Slaten, P. Shanley, R. M. Broughton, D. M. Hall and M. Baginski, Journal of Fire Sciences 12 (3) 238-245 (1994). The Use of a New Carbonaceous Fiber in Thermal Insulative Battings" R. Broughton, D. Hall, P. Brady, L. Shanley, B.L.Slaten, INDA Journal of Nonwovens Research 5 (4) 38-42 (1993).
6	Tappi Nonwovens Conference: "The Development of A New Carbonaceous Fiber and its Use in Nonwoven Battings" Roy M. Broughton, Jr., D. M. Hall, P. Brady, and Francis. P. McCullough, Atlanta, GA., 1993, (proceedings) INDA Nonwovens Fundamental Research Conference: "The Use of a New Carbonaceous Fiber in Thermal Insulative Battings", Roy M. Broughton, Jr., D.M. Hall, P. Brady, L. Slaten and L. Shanley, June 1993, Clemson, SC, (proceedings). Technical Textiles Conference: "Manufacture of Carbonaceous Fibers and their Use in Thermal Insulative Battings“, Roy M. Broughton, Jr. June 1993, Greenville, SC
7	Major insulation materials Nonwovens Foams
8	These materials are selected because they trap large quantities of undisturbed (“dead”) air
9	“Dead” air is the insulator
10	Fundamentals of heat transfer
11	Heat is transferred by Convection Conduction Radiation
12	Convection – movement of fluid in response to temperature induced differences in density and the effect of gravity.
13	Calculations of convection are complicated because of the difficulties of fluid dynamics.
14	Conduction – transfer of heat caused by vibration induced collisions between molecules. Q = k A T/t Where: Q is heat transfer rate, k is thremal conductivity, A is area, T is temperature, and t is the thickness.
15	Calculation is relatively easy if the geometry is not too complicated – heat transfer through the thickness of a material having a much larger length and width.
16	Radiation – All matter above absolute zero radiates electromagnetic energy (similar to light but generally at a lower frequency). The radiated energy may be converted to heat when it strikes other matter.
17	You can feel radiation when standing in front of a fireplace. The air in the room may be cold, but your clothing intercepts the radiation from the fire and converts it to heat.
18	Q = K (T⁴ – T₀⁴) Where Q is the heat transfer rate, T is the absolute temperature of the body, T₀ is the temperature of the surroundings and K is a constant
19	A simple equation that is complicated by the optical properties and geometry of both the emitter and receiver. Optical properties – emmissivity, reflection, absorption, transmission.
20	Most heat transfer measurements are made using a guarded (well insulated) hot plate. Actually there is a hot plate, a cold plate, and a heat flow transducer.
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23	This tester cannot distinguish between the methods of heat transfer. It uses the conductivity equation Q = k A T/t Where: Q is heat transfer rate, k is thremal conductivity, A is area, T is temperature, and t is the thickness.
24	The equation works to calculate heat transferred, but it is not a good theoretical mathematical representation of either convection or of radiation heat transfer. Sometimes the k is called apparent thermal conductivity in recognition of this problem.
25	We tried the following experiments to try to understand the interaction between the various heat transfer mechanisms. A frame was constructed and various layers were tested to see how they influenced heat transfer.
26	Thin plywood frames for supporting film and foil layers
27	Placed film in the frames Transparent film Spunbonded PES Black film Aluminum foil No film
28	No film – convection, conduction through air, radiation k = 1.196 Btu-in/hr ft^{2 o}F
29	Aluminum foil 5 layers – k = 0.199 Btu-in/hr ft^{2 o}F Minimum radiation (low emissivity). Conduction still present, Low convection.
30	Clear film – conduction unchanged radiation may be reduced, minimum convection Conduction through film is faster than through air. 5 layers clear PE – k = 0.920 Btu-in/hr ft^{2 o}F
31	Black film – radiation must be absorbed by each layer and then reemitted. Conduction unchanged - still minimum convection. 5 layers - k = 0.467 Btu-in/hr ft^{2 o}F
32	Spunbonded PES – minimum convection, conduction unchanged, reduced radiation 5 layers - k = 0.715 Btu-in/hr ft^{2 o}F
33	Aluminum foil. Minimum radiation (low emissivity). Conduction still present, Low convection. 5 layers – k = 0.199 Btu-in/hr ft^{2 o}F
34	When we look at how batting insulates, we find that as we increase the density of batting, the k value goes down – and levels out about 0.2 BTU-in/square foot degree F
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37	Dealing with the exponential equations is difficult. Plotting the data as apparent K vs specific volume gives a graph that can be interpreted.
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39	The intercept is approximately the conductivity of still air and the slope gives some idea of the weight efficiency of the material as insulation.
40	The graphs likely curve upward on each end. On the low end of specific volume, conductivity of the solid material becomes important – we have seen this effect. We believe that on the high end of specific volume, radiation and convection become dominant and the line will curve upward.
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42	Conclusions: As expected, low density cotton batting makes a good insulating material On a weight basis, it is somewhat better than feather and glass fiber, and perhaps a little better than down.
43	But all fibers are really pretty good insulators particularly in the range of 0.5 cubic feet/pound (2 pounds/cubic foot)
44	One inch thick insulation might require a pound of fiber/square yd. Four-inch thick insulation might require four pounds/square yd. Inexpensive for any reasonably priced fiber.
45	So -- Insulation is purchased on the basis of properties like durability, resilience, flammability, environmental resistance, cost. instead of insulation efficiency.
46	What is the problem with cotton (cellulosic) insulation?
47	Remember that k has been normalized for thickness – k is expressed as heat transferred through a 1 inch thick material.
48	Poor resilience of the batting. The batting collapses in thickness under pressure, or when wet and dried, and does not recover.
49	The authors would like to acknowledge the assistance of Swagat Irsale in collecting the data for cotton insulation.
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