next heavier weight was selected the sample was weighed in a dsc apparatus from mettler toledo and heated from 0 u00b0 c to 300 u00b0 c using a temperature program of 10 u00b0 c min the area beneath the endothermic melting peak obtained in conjunction with the original fiber weight and the associated masses of the sheath or core component represents the heat of fusion of the respective component in j g nonwoven fabric a represents a dry laid carded and thermally bonded nonwoven fabric having a weight per unit area of 190 g m 2 this nonwoven fabric was composed of 75 low shrinkage pet pbt dual component fiber having a sheath melting point of 225 u00b0 c and a core to sheath ratio of 50 50 and up to 25 conventional pet fibers the thickness was 0 9 mm and the air permeability was 850 l m 2 s at 200 pa 140 g m 2 of the fibers were carded by combing using a cross layer and the remaining 50 g m 2 were carded in a longitudinal layout the nonwoven fabric was bonded in a thermal fusion oven at approximately 240 u00b0 c and was calibrated to the target thickness using an outlet press tool nonwoven fabric b was produced analogously as for nonwoven fabric a the differences consisted in use of conventional pet copet dual component.