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Title: Study of the interaction among abrasive particles, applicator and cleaning surfaces in household and tooth cleaning
Author: Zorcolo, Alberto
ISNI:       0000 0004 2740 1373
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2011
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Tooth cleaning and household cleaning are common tasks people undertake on a daily basis and they share significant analogies. Both rely on the combined action of a detergent - usually a fluid which may contain abrasive particles - and an applicator on a cleaning surface. While scientific information covers some of the aspects related to abrasive tooth cleaning, such as the main tooth wear mechanisms and the influence of dental care products on tooth cleaning and wear, household cleaning has not been covered in such detail. The aim of this work was to investigate abrasive tooth cleaning and abrasive household cleaning from a tribological perspective in terms of the interactions between human/applicator, applicator/abrasive particles and abrasive particles/substrate, in order to expand the knowledge on both subjects and gather information useful to improve the design of current cleaning products. A study has been carried out by means of a hand operated friction rig to measure the loads applied by human subjects while performing simulated abrasive cleaning operations in order to better understand the interaction between human test subject and applicator. The analysis investigated the loads applied during tooth cleaning processes and household cleaning processes, and the results (from 180g to 4230g for tooth cleaning tests and from 290g to 4.3Skg for household cleaning tests) helped Unilever in developing their friction analysis techniques. Particle entrainment into the contact area between the applicator and the surface has been analysed using two types of test rig- one with a unidirectional motion and the other a reciprocating motion - and an optical apparatus featuring a microscope and a camera for image and video capturing. The scratches produced by abrasive particles were studied with an optical microscope and a Scanning Electron Microscope in order to understand how they scratch the surface during abrasive cleaning processes. The investigation helped to gather information on how abrasive particles were trapped at the tip of the toothbrush filaments and between the cloth fibres and the observation of the scratched surfaces led to identify grooving abrasion as the main wear mechanism taking place in both abrasive tooth cleaning and household cleaning. A friction analysis of both tooth cleaning and household cleaning processes was carried out using the hand operated rig and a friction rig on which the applicators were mounted, to study the connection between the friction coefficient )l and the ability of the particles to remove material from the test surface. It was found that under the adopted experimental conditions, the lubricating action exerted by the carrying fluids in both tooth cleaning and household cleaning is mainly based on boundary lubrication. The values of the friction coefficient determined from the experiments ranged from around 0.20 (in wet condition, without abrasive particles) to 0.37 (in dry condition, without abrasive particles) for brushing tests, and from around 0.20 (in lubricated condition, with 5 urn Calcium Carbonate particles) to 0.66 (in dry condition, without abrasive particles) for cloth tests. The influence of the applied load, the particle size and concentration on friction coefficient was also investigated. Finally, a semi-empirical model was developed to estimate the rate of material removal during a simulated household cleaning process, in order to gather information useful to improve the ability of cleaning fluids to remove stain while reducing the damage to the cleaning surfaces. Results from the modelling were compared with data from reciprocating cleaning tests. Although the model often overestimated the amount of material removed from the test surface due to the assumptions made in order to simplify its implementation, it produced results of the same magnitude order of those obtained from material removal experiments within the ranges of applied loads, particle sizes and concentrations. lJ
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available