| Hydroentangling is a nonwoven mechanical bonding technique which uses a curtain of fine, high-speed water-jets to entangle fibers in a web structure. The interactions among fibers, impinging water-jets and forming surface create a strong textile-like fabric as fibers twist, turn, intermingle and penetrate through the web as a result of water-jet(s) impact. Such integrated web structures are found in diverse applications Nevertheless, the entangling characteristics like fiber movement, fiber entangling and its possible path in the integrated structures are not well understood. Thereby, the purpose of this research is to study the effect of hydroentangling parameters like jet pressure, nozzle diameter, nozzle-to-nozzle distance and number of manifolds on fiber entangling and changes occurring within the web structure.;To meet the above objectives, a comprehensive hydroentangled web structure needs to be analyzed. Hydroentangled structure is three-dimensional (3D) in nature because water jet impact cause movement of fibers in all directions as well as twisting and turning of fibers. Thus, digital volumetric imaging (DVI) technique, originally used for medical imaging has been successfully employed as a means to visualize and characterize the web structures. This technique is a block-face imaging technique (based on principle of micro-tomography) and successfully employed to acquire 3D images of the hydroentangled web structure.;In the first part of the study, 3D structures of hydroentangled nonwoven were comprehensively analyzed using DVI. This study focused on developing and modifying the available characterizing techniques respectively. For the very first time, key terminologies like, surface fiber transfer and its profile, 3D fiber orientation, and density/porosity variations were introduced that defined a typical hydroentangled structure. Furthermore, these techniques were also employed in other parts of the study to characterize the produced structures.;In the second part of the study, to understand the fiber entangling mechanisms the study begun by analyzing the effects of impact of single water-jet on the web structure and followed by two and three jets respectively. The findings from this study disclosed the internal structure of hydroentangled nonwovens for the very first time. Besides, the study also defined a unique assessing parameter called -- depth of fiber penetration which played an important role in fiber entangling. This also includes the study on the effect of nozzle diameters on the web structures.;In the third part of the study, effects of hydroentangling process variables were studied by scaling-up the process. This mainly dealt the effects of multiple jets and increasing number of manifolds which changed the hydroentangled web structure during every individual impact. This study disclosed the 3D structures for multiple impacts and concluded that fiber mobility plays an important role in fiber entangling and mechanical properties. Impinging multiple jets showed formation of loops by surface penetrating fibers which were interlocked within the web structure. This is unlike one, two and three jets due to fiber interaction under the influence of adjacent water-jets.;In the concluding part of this study, the effects of orifice-to-orifice distance on web structure were studied. Analyzing the produced structures disclosed increase in fiber penetration and amount of surface fiber transfer into the web structure. The key finding was increase in fiber interlocking with increase in jet spacings due to improved fiber mobility. In addition, when web structures were hydroentangled in a novel fashion the mechanical properties were retained. And most importantly, this was achieved by expending only half the amount of required hydroentangling energy. |
