Experimental and Theoretical Investigation of Jet Roping in Melt and Solution Blowing Set Up

The main objective of this thesis is to investigate the probability of roping for smaller inter-needle distances during nonwoven formation processes. Nonwovens are materials comprised of fibers that are entangled physically and are bonded together mechanically, thermally or chemically. Nonwovens have become essential in our daily lives, in such applications as filtration media, life sciences, biomedical industry and its products (wipes, single-usage garb, etc.). In order to produce suitable polymer micro/nanofibers for various applications, several manufacturing techniques have been developed, including electrospinning, meltblowing, solution blowing, phase separation, self-assembly, and template synthesis. Specifically, solution blowing and meltblowing are widely used in industry not only because they are more cost-effective, but because they also possess high integrity of fabrication processes. Solution blowing process utilizes flow of a slowly moving polymer solution jet into a high-speed air co-flow. This process is used to form micro/nanofibers. In contrast to the other forms of fiber production, solution blowing can be easier applied to both petroleum-derived polymers and biopolymers (especially, bio-waste), thereby increasing the range of materials that can be utilized. Accordingly, multiple problems arise in relation to product innovation. Most-used fabrication technique in nonwoven manufacturing is meltblowing, which is employed in forming multiple products, including protective fabrics, filter media, wipes and medical gowns. In meltblowing, relatively slowly moving molten polymer jets are issued from a nosepiece into a high-speed co-flowing hot air stream. As a result, the polymer jets are stretched, bent and thus, additionally, stretched by the surrounding air stream. The thinning polymer jets are cooled, solidified and partially crystallized, as they are entrained by the surrounding gas further from the nosepiece. Eventually, the solidified polymer jets are deposited either on a moving belt or a stationary screen forming a nonwoven laydown. There are many potential defects which diminish the overall quality of meltblown products, like, in particular, die drool, flies, roping and shots. This thesis focusses on roping defect during non-woven production processes. How to quantify roping? What happens when multiple jets rope in flight? How much porosity of the laydown is affected by roping phenomenon? Also, how is the probability of roping affected by the processing parameters? In particular, figuring out inter-needle distances upto which probability of roping stays within statistically tolerable limit? Thus, the current study aims to establish novel theoretical, numerical, and experimental approaches, which are expected to elucidate the roping phenomenon in nonwoven formation processes. Such an insight would be helpful to foster improvements in the quality of nonwoven products and enhance throughput, particularly facilitating the use of nonwoven dies with reduced spacing between the needles.