Particular hygiene applications, such as Moist Toilet Tissue (MTT), toddler wipes, bathroom cleaning wipes 'and feminine hygiene wipes lend themselves to convenient disposal via the sewer network. The high volume of wipes now disposed of through the sewer network is increasing pressure on pipework systems and wastewater treatment plants. The main objectives of this study were to review the prior art and published literature on flushable nonwoven technology, identifying the fundamental mechanisms of function, benchmark the performance of currently available commercial flushable wipes and through experimentation and empirical modeling, begin to form an understanding of flushable wet wipe structure-property relationships. Commercially available wet wipes were found to exhibit varying dispersibilities when assessed using the industry-standard shake-flask test methodology, a test designed to assess the disintegration of a wipe following disposal in the sewer network. All were composed from cellulose, usually blends of wood pulp and lyocell. It was observed that fibrillation of lyocell increased as a result of mechanical agitation during dispersibility testing. These fibrils apparently hindered the dispersion of the wipe into individual fibres. In experimental wipes, fibre fibrillation was found to have a negative influence on the dispersibility behaviour of both wetlaid and airlaid hydroentangled wipes. Hydroentangled fabrics containing non-fibrillating regenerated cellulose fibres exhibited the greatest resistance to fibrillation and also the highest dispersibility. Experiments were performed to assess the wet strength and dispersibility of both wetlaid and airlaid hydroentangled wipes composed of wood pulp and regenerated cellulose. The influence of fabric structure including fibre length, aspect ratio (fineness), blend composition and process (specific energy and hydroentanglement forming belt open area) were studied. Based on the findings from the present work, using an airlaid-hydroentangled platform it is possible to produce a wet wipe with a wet strength as high as 22 N/50mm with dispersibility of 100% (<12.5 mm screen), which exceeds the aspirational target of 15 N/50 mm and ?.95% dispersibility (12.5 mm screen). Empirical models based on linear multiple regression methods suggested specific energy and the total regenerated fibre length positively influence the wet tensile strength of the fabrics. However, the total fibre length negatively influences dispersibility. Fibres that are resistant to fibrillation were found to benefit dispersibility. The model for wet tensile strength was found to have a relatively good correlation with the experimental data, but less so for dispersibility. Furthermore, it was established that the most likely dispersion mechanism in the shake flask is the result of fibre slippage, meaning that wet fibre-to-fibre cohesion and frictional resistance to sliding is critical in governing the break-up of the substrate. To understand the magnitude of the wet cohesive forces involved, a wet pull out test was devised. Airlaidhydroentangled wipes with a carboxymethylcellulose (CMC)' binder exhibited improved dispersibility performance but with decreased wet tensile strength. This could be explained in terms of the modification of the coefficient of friction by the CMC allowing the fibres to separate more easily when subjected to mechanical forces during agitation. Optimum pH conditions and electrolyte addition levels were established for the stabilisation of CMC binder in wetwipes.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:713699 |
| Date | January 2016 |
| Creators | Tipper, Matthew James |
| Publisher | University of Leeds |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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