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ABSTRACT Antimicrobial textiles (65% cotton - 35% polyester) were functionalized using a patented technology that combines an antimicrobial molecule - polyhexamethylene biguanide (PHMB) and a precipitating agent - sodium laurylsulphate. Surface characterization was performed by x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry, and both techniques made clear signatures of PHMB at the top surface of treated textiles. Washing led to a strong decrease of PHMB concentration at the surface. Comparison of textile surface analysis and antimicrobial tests indicated that the amount of PHMB at its extreme surface of textiles after five or 10 industrial washings was sufficient to inhibit Listeria innocua but not Pseudomonas aeruginosa growth. The viability of L. innocua cells after contact with PHMB-treated textile after one industrial washing was estimated using the Live/Dead BacLight kit (Molecular Probes, Eugene, OR): the combination of epifluorescence microscopy observations coupled with classic enumeration allowed detection of the presence of viable but nonculturable cells. PRACTICAL APPLICATIONS Protective clothing is required in the food-processing industry to protect products from being contaminated by microorganisms carried by workers' clothes or filtration systems. Consequently, there is an increasing interest in the use of antimicrobial functionalized textiles in the food industry to avoid that textiles could be vectors for pathogenic or food spoilage microorganisms. In the present study, the correlation between PHMB (the antimicrobial agent) at the surface of textiles (monitored by surface analysis characterization methods) and their antibacterial activity was assessed. After contact with antimicrobial textiles, the enumeration of bacteria was performed either by plate counting or by direct observation by epifluorescence microscopy in the presence of fluorescent viability markers in order to determine whether viable but nonculturable bacterial cells were present. [ABSTRACT FROM AUTHOR]

Tribochemical interactions between zinc dithiophosphate (ZDDP) and micellar calcium borate (CB) under boundary lubrication were investigated by coupling, in the same location of the wear track, both analytical TEM analysis of collected wear fragments from the tribofilm and XPS surface analysis of the tribofilm directly underneath. This is the so called dual analysis approach, which improves the interpretation of tribochemical reactions. The elemental composition inside the wear scars was analysed by micro spot XPS. By depth profiling, the film thickness could also be determined. In particular, the efficiency of the additive combination could be proven by quantification of iron oxide. The nature of wear particles was investigated in the TEM by using EELS and EDX simultaneously, with the result that phosphorus, boron and sulphur contributions have been carefully distinguished. The technique is very powerful for determining the composition of the material through quantification of both EELS and EDX spectra on the same specimen. The main result, when ZDDP and CB additives are used together, is the formation of a calcium and zinc borophosphate glass tribofilm. The overall data confirm the general friction induced glass model as being a unifying concept that explains the mechanisms of antiwear additives under boundary lubrication. Moreover, the analytical results strongly suggest the role of viscous flow of the magma state glass tribofilm above its glass transition temperature to be a main contribution to the antiwear mechanism under mild wear conditions. [ABSTRACT FROM AUTHOR]

The friction reduction mechanisms of Modtp and Zndtp were highlighted by submitting tribofilms to friction in ultra high vacuum (UHV). The use of an UHV tribometer to understand these phenomena is justified by the fact that the friction coefficient recorded in UHV is close to the friction coefficient obtained in traditional tests in oil. After UHV friction, the transfer films on the pin were analyzed by in situ AES, XPS and AES mapping. Low friction is associated with the transfer to the pin of a sulfur rich film. In the case of Modtp, we observe a very thin MoS2 film. The UHV friction coefficient approaches 0.04. In the case of Zndtp, the transfer film contains ZnS together with some phosphates. Because of the poor capacity of ZnS to reduce friction, the UHV friction coefficient recorded is near 0.15. A global model of the action of dithiophosphates in reducing friction is described on the basis of the hard and soft acids and bases (HSAB) principle. [ABSTRACT FROM AUTHOR]

Some aspects of the effect of adsorption on friction have beenexperimentally investigated by using a multi-technique AES/XPSUHV tribotester. Actually, testing in-vacuo gives the opportunityto clean, to create and to characterise the surface. Moreover,AES microanalysis can give insight in tribochemical reactions.Preliminary data are presented in several fields of tribology,including gas-phase lubrication, MoS2 superlubricityand lubricated wear with lubricant additives. New insight intothe understanding of the processes are made possible because in-vacuo tribology permits the environmental factors to be perfectlycontrolled. [ABSTRACT FROM AUTHOR]

By means of a UHV analytical AES/XPS pin-on-flat tribotester, we have investigated tribochemical change as well as transfer mechanisms in static reaction films on steel from ZDDP (anti-wear) and MoDDP (friction modifier) lubricant additives. The results show that solid ZDDP reaction films are able to strongly reduce friction to a value of 0.1-0.3 (in the absence of a film, steel-on-steel gives a friction coefficient value of up to 2). MoDDP reaction films produce ultra-low friction (below 0.05) after an induction period. In situ AES analysis and energy-filtered XPM gave definitive evidence of frictioninduced chemical changes and selective material transfer from the flat to the pin. In the case of MoDDP, the thiophosphate film is decomposed and a 'MoS' residual film is found in the wear scar on the pin. [ABSTRACT FROM AUTHOR]