Investigating the effects of material and process variables on the mechanical properties of low-density thermally bonded nonwovens produced from Estabragh (milkweed) natural fibers

Uniaxial tensile and bending properties of lightweight thermally bonded nonwoven layers produced from the blends of Estabragh (milkweed)/polypropylene fibers have been focused in this paper. For this, different material variables such as the blend ratio as well as some parameters of thermal bonding process including the calendering speed and temperature were considered in this study. Eighteen fibrous samples from six Estabragh/polypropylene blend ratios of 10/90, 25/75, 40/60, 55/45, 70/30, and 85/15 at three different layer weights (g/m ² ) were produced on a laboratory-scale carding machine. During needle-punching operation, different punch densities at low levels of 20, 30, and 40 punches/cm ² were applied to the samples in order to increase the layer strength by increasing the fiber entanglement while the fiber breakage remains in such minimized level. Thermal bonding process was then carried out on the produced nonwoven samples using an apparatus equipped with a pair of heated calendering in which three different levels of temperatures as well as three levels of calendering speed were considered as the process variables. Taguchi’s analyzing method was employed for statistical investigations of the results. The findings showed that the blend ratio of fibers, layer weight, and the applied temperature during the thermal bonding process significantly increased the nonwoven layer resistance against axial tensile forces. On the contrary, variables punch density and calendering speed had no significant effects on the breaking force values of the samples. Considering the samples' bending rigidity, it was fount that all the variables except the calendering speed, have significant effects.