Abstract
The thermal insulating abilities were evaluated using the guarded hot plate technique (ASTM D 1518-77) for the following selected nonwoven insulating materials: air-laid structures of low linear density polyolefin and low linear density polyolefin mixed with conventional linear density polyester, and carded structures of hollow polyester fiber, crimped polyester filament, and conventional polyester fiberfill. The thermal resistance of the materials varied directly with thickness, but on a per thickness basis the air-laid structures provided more thermal resistance than the carded structures. The thicker, low linear density, air-laid structure was an exception in that it did not exhibit as large an advantage over the carded structures as did the other air-laid struc tures. Under the conditions of the guarded hot plate apparatus, correlations of intrinsic thermal conductivity with the structural characteristics of the insulators indicated that the proportion of heat loss by convection was lower for the air-laid structures than for the carded structures. This reduction of heat loss by convection was due to high tor tuosity of the air flow path and larger fiber surface area.
Each nonwoven insulator was subjected to 10 launderings to evaluate the effect of this action on thermal properties, thickness, air permeability, and weight. The mixed linear density, air-laid structures, hollow fiber insulator, and conventional fibafill decreased markedly in thermal resistance, while the low linear density insulators and the crimped polyester insulator exhibited only small changes as a result of the laundering process.
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