Lower Adhesion Values Research Articles

Icephobic Coating Based on Novel SLIPS Made of Infused PTFE Fibers for Aerospace Application.

The development of slippery surfaces has been widely investigated due to their excellent icephobic properties. A distinct kind of an ice-repellent structure known as a slippery liquid-infused porous surface (SLIPS) has recently drawn attention due to its simplicity and efficacy as a passive ice-protection method. These surfaces are well known for exhibiting very low ice adhesion values (τice < 20 kPa). In this study, pure Polytetrafluoroethylene (PTFE) fibers were fabricated using the electrospinning process to produce superhydrophobic (SHS) porous coatings on samples of the aeronautical alloy AA6061-T6. Due to the high fluorine-carbon bond strength, PTFE shows high resistance and chemical inertness to almost all corrosive reagents as well as extreme hydrophobicity and high thermal stability. However, these unique properties make PTFE difficult to process. For this reason, to develop PTFE fibers, the electrospinning technique has been used by an PTFE nanoparticles (nP PTFE) dispersion with addition of a very small amount of polyethylene oxide (PEO) followed with a sintering process (380 °C for 10 min) to melt the nP PTFE together and form uniform fibers. Once the porous matrix of PTFE fibers is attached, lubricating oil is added into the micro/nanoscale structure in the SHS in place of air to create a SLIPS. The experimental results show a high-water contact angle (WCA) ≈ 150° and low roll-off angle (αroll-off) ≈ 22° for SHS porous coating and a decrease in the WCA ≈ 100° and a very low αroll-off ≈ 15° for SLIPS coating. On one hand, ice adhesion centrifuge tests were conducted for two types of icing conditions (glaze and rime) accreted in an ice wind tunnel (IWT), as well as static ice at different ice adhesion centrifuge test facilities in order to compare the results for SHS, SLIPs and reference materials. This is considered a preliminary step in standardization efforts where similar performance are obtained. On the other hand, the ice adhesion results show 65 kPa in the case of SHS and 4.2 kPa of SLIPS for static ice and <10 kPa for rime and glace ice. These results imply a significant improvement in this type of coatings due to the combined effect of fibers PTFE and silicon oil lubricant.

Adhesion of WTi to polyimide measured by complementary methods

Quantification of thin film adhesion to their substrates is crucial to ascertain reliable multi-material components, which are typically encountered in technologically relevant structures such as microelectronic devices. Metal-polymer interfaces have gained increased attention in the past since they open a new research field towards developing flexible electronic devices, yet their quantification is often experimentally challenging since standard routes to assess adhesion such as nanoindentation-based techniques or four-point bending may not be applicable due to lack of rigidity. In the present study interface adhesion of nominally 150 nm thin WTi films sputtered onto polyimide, part of a multi-material stack consisting of brittle and compliant materials, was determined experimentally. Upon contactless removal of the bilayer by etching a sacrificial layer, originally part of the multilayer stack, the WTi film showed cracks and buckles, which could be characterized by atomic force and confocal laser scanning microscopy. Hence, two models to quantify adhesion were compared: the model of tensile induced delamination – typically employed for metal films on compliant substrates – and the model of Hutchinson and Suo, which is usually applied on spontaneously formed, straight buckles. The first model reveals adhesion values for the native WTi-polyimide interface of 2.4 ± 0.8 J/m2 and the latter model 4.7 ± 2.3 J/m2. The slight difference in adhesion results, which are both rooted in the same theory, could be rationalized by the fact that the model for tensile induced delamination gives a measure of the lower bound of the adhesion energy. The overall rather lower adhesion values could be explained by additional transmission electron microscopy investigations conducted on the cross section of the interface, which reveals no interlinking morphology and a flat interface.

The Effect of Various Lasers on the Bond Strength Between Orthodontic Brackets and Dental Ceramics: A Systematic Review and Meta-Analysis.

Background/objective: This systematic review and meta-analysis aimed to assess how laser conditioning affected brackets bonded to dental ceramics' shear bond strength (SBS). Materials and methods: The study was conducted by searching Pubmed/Medline, Scopus, Embase, Web of Science, the Cochrane Library, and Google Scholar up to September 14, 2022. In addition, the reference lists of the relevant articles were checked manually. Articles that compared SBS of laser-treated feldspathic, lithium disilicate, or zirconia surfaces with other standard techniques for bonding metal or ceramic orthodontic brackets were considered. Using a random-effects model, data pooling was carried out as the weighted mean difference (WMD). Results: This study initially contained 1717 reports, and following review, 32 articles were deemed suitable for our meta-analysis. The pooling results showed that the treatments with lasers such as "Er:YAG" [WMD = -1.12 MPa; 95% confidence interval (CI): -1.93 to -0.31], "Er:YAG + Silane" (WMD = -3.08 MPa; 95% CI: -4.77 to -1.40), and "Nd: YAG + Silane" (WMD = -2.58 MPa; 95% CI: -3.76 to -1.40) had statistically significant lower adhesion values compared with controls. Contrarily, "Ti:Sapphire femtosecond" demonstrated significantly higher bonding values (WMD = 0.94 MPa; 95% CI: 0.29-1.60). In contrast, other interventions obtained no statistically significant difference in SBS. Conclusions: Most of the laser groups showed results comparable with those of conventional approaches. Although more research is necessary for definitive conclusions, laser treatment may be an effective option for treating the surfaces of ceramic materials.

Evaluation of the Sealing Ability and Bond Strength of Two Endodontic Root Canal Sealers: An In Vitro Study.

Obturation represents a critical step in endodontic treatment, which relies on a core material and a sealer. This study aims to evaluate the sealing ability and bond strength to the root canal walls of an epoxy resin-based sealer (AH-Plus®, Dentsply Sirona, Johnson City, TN, USA) and a bioceramic sealer (GuttaFlow Bioseal®, Coltène/Whaledent, GmbH + Co. KG, Langenau, Germany). Thirty-eight maxillary anterior teeth with single roots and identical round sections were separated into two experimental groups according to the root canal sealers used, namely, G1 = AH-Plus® and G2 = GuttaFlow Bioseal®, and two control groups, specifically, G3 = the negative control and G4 = the positive control. The sealing capacity was measured by the penetration of the radioactive isotope 99mTc. For the push-out test, the compressive force test was performed in a universal machine and the force was applied by exerting pressure on the surface of the material to be tested in the apical to the coronal direction and using three test points with different diameters. GuttaFlow Bioseal® exhibited superior sealing ability compared to AH-Plus® (p = 0.003). Regarding the bond strength, AH-Plus® provided higher adhesion values than GuttaFlow Bioseal® in the three sections of the tooth root (p = 0.001). GuttaFlow Bioseal® had significantly better sealing ability than AH-Plus® but lower adhesion values in the three zones of the root canal, with statistically significant differences between the groups. However, it is important to note that for the action of endodontic sealers to be maximized, the root-filling technique must be most appropriate.

Effects of different waxy rice varieties and their starch on the taste quality of zongzi

Waxy rice is an important food item comprising numerous varieties, and zongzi is a popular waxy rice product. Here, 15 varieties of waxy rice were selected to make zongzi and determine their taste quality using texture profile analysis and sensory methods. In addition, the composition of waxy rice and the hierarchical structure and properties of starches isolated from waxy rice were also evaluated to understand the causal relations between waxy rice varieties and zongzi quality. It can be observed that the composition of waxy rice showed a significant difference among varieties, and the adhesiveness and chewiness of zongzi were affected by trace components such as ash and lipid in waxy rice. Furthermore, the gelatinization temperature and viscosity of the starch extracted from waxy rice varieties with low amylose content were lower than other samples, and zongzi made from those varieties had low hardness and high adhesiveness value. We considered that starch properties had a major influence on the zongzi. These results can serve as a reference for screening raw materials in the zongzi industry.

Effects of texture properties of semi-solid food on the sensory test for pharyngeal swallowing effort in the older adults

BackgroundIncreasing viscosity can reduce the risk of aspiration into the airway, but excessively thickened food may require more force and effort. We assumed that semi-solid foods with similar viscosities will behave differently in the oropharynx and there might exist the possibility that properties other than viscosity may have clinical relevance. This study aimed to find out the texture of semi-solid foods that affects the effort of pharyngeal swallow in the older adults.MethodsNine kinds of semi-solid foods not requiring mastication were selected for texture profile analysis (TPA), and included whipped cream, mayonnaise, soft tofu, mango pudding, boiled mashed pumpkin, boiled mashed potatoes, boiled mashed sweet potatoes, red bean paste, and peanut butter. Hardness, adhesiveness and cohesiveness of each food were measured three times by using the rheometer. A blinded sensory test using a 9-point hedonic scale was also conducted in eighteen older adults people to investigate how much effort was required to swallow food, and how much of the food remained in the pharynx after swallowing. The correlation between texture and sensory outcome was statistically analyzed.ResultsFoods that belonged to the same viscosity category showed different texture values, and the participants also rated different scores respectively. Only adhesiveness among three properties was significantly correlated with the sensory test. (r = 0.882, p = 0.002 for difficult to swallow, r = 0.879, p = 0.002 for sense of residue).ConclusionsAdhesiveness was the most important property of the semi-solid foods, requiring most efforts in pharyngeal swallow in the older adults. If we select and provide food having low adhesiveness value in the same viscosity category, there might be the possibility to make it easier to swallow in older adults.

Shear Bond Strength of Three Composite Resins to Fluorosed and Sound Dentine: In Vitro Study.

Introduction This in vitro study compared the shear strength of three composite resin systems to fluorosed and normal dentin. Methods Silorane FiltekTM P90, FiltekTMZ250 XT in combination with the adhesive system AdperTM Single bond 2, and Amelogen® Plus in association with Peak Universal Bond® were tested. Fifteen normal and 15 fluorosed dentine disks were prepared per material. The shear bond strength test was performed using a universal machine. Results One-way ANOVA revealed significant differences in bond strength between the tested composite resins. All tested materials had significantly different adhesion at the fluorosed and the nonfluorosed interface. FiltekTM Z250 XT and Silorane had lower adhesion values to fluorosed than to normal dentin. In contrast, Amelogen® Plus presented a better average resistance at the fluorosed interface. Conclusion Amelogen® Plus presented a better average shear bond strength on the fluorosed dentine. FiltekTMZ250 XT showed the best adhesion forces and shear bond strength with sound dentine. Further studies are needed to better understand the sealing of these systems.

Glass-particle adhesion-force-distribution on clean (laboratory) and contaminated (outdoor) surfaces

This paper explores whether laboratory-clean samples are representative of real outdoor surfaces – often covered in dust and other contaminants – with respect to adhesion properties, which ultimately affect particle resuspension. In this study, Atomic Force Microscopy (AFM) was used to measure the adhesion force between a clean, smooth glass particle (5 µm in diameter) and two glass slides, one prepared according to common laboratory practices (hereafter, clean glass) and a second one left outdoors for six weeks (hereafter, contaminated glass). It was found that the adhesion force distribution was bimodal for the clean glass while it showed three peaks for the contaminated glass. For both surfaces, the adhesion force showed a peak at very low adhesion values (< 100 nN) representing 1.2% of the measurements for the clean glass and 58% for the contaminated glass. This low-adhesion peak is important because it represents the particles that would be resuspended first even in light winds. The low adhesion-force measurements were associated with the presence of contaminants on the surface. Another notable difference between the adhesion force distributions was a long tail at high adhesion forces for clean glass (up to ~1900 nN) and the absence of the tail for the contaminated glass, which had a maximum adhesion force of 950 nN. The mean adhesion force on the contaminated glass was also lower than on the clean glass (206 ± 240 nN vs. 516 ± 354 nN). These observations indicate that the adhesion force distribution between a 5-µm smooth and clean glass sphere and the outdoor contaminated glass surface is quite different from that of the clean glass surface. Hence, one should be cautious when using adhesion force measurements from clean surfaces to estimate particle resuspension from outdoor surfaces.

Hydrophilic Self-Replenishing Coatings with Long-Term Water Stability for Anti-Fouling Applications

Hydrophilic coatings have recently emerged as a new approach to avoiding the adhesion of (bio)organisms on surfaces immersed in water. In these coatings the hydrophilic character is crucial for the anti-fouling (AF) performance. However, this property can be rapidly lost due to the inevitable damages which occur at the surface, reducing the long-term effectiveness of the AF functionality. We report hydrophilic polycarbonate-poly(ethylene glycol) methyl ether (mPEG) polyurethane coatings with tunable hydrophilic properties as well as an excellent and long-term stability in water. The coatings exhibit low protein adhesion values and are able to self-replenish their hydrophilicity after damage, due to the existence of a reservoir of hydrophilic dangling chains incorporated in the bulk. The combination of low Tg and sufficient mobility of the mPEG dangling chains (enabled by chains with higher molecular weight) proved to be crucial to ensure autonomous surface hydrophilicity recovery when the coatings were immersed in water. This coatings and design approach offers new possibilities towards high-performance AF coatings with an extended service life-time which can be used in several major applications areas, such as marine and biomedical coatings, with major economic and environmental benefits.

Icephobic Surfaces Induced by Interfacial Nonfrozen Water.

It is known that smooth, hydrophobic solid surfaces exhibit low ice adhesion values, which have been shown to approach a lower ice adhesion strength limit (∼150 kPa) defined by the water receding contact angle. To overcome this limit, we have designed self-lubricating icephobic coatings by blending polydimethylsiloxane (PDMS)-poly(ethylene glycol) (PEG) amphiphilic copolymers into a polymer matrix. Such coatings provide low ice adhesion strength values (∼50 kPa) that can substantially reduce the lower bound of the ice adhesion strength achieved previously on smooth, hydrophobic solid surfaces. Different molecular mechanisms are responsible for the low ice adhesion strength attained by these two approaches. For the smooth hydrophobic surfaces, an increased water depletion layer thickness at the interface weakens the van der Waals' interactions between the ice and the polymeric substrate. For the self-lubricating icephobic coatings, the PEG component of the amphiphilic copolymer is capable of strongly hydrogen bonding with water molecules. The surface hydrogen-bonded water molecules do not freeze, even at substantial levels of subcooling, and therefore serve as a self-lubricating interfacial liquid-like layer that helps to reduce the adhesion strength of ice to the surface. The existence of nonfrozen water molecules at the ice-solid interface is confirmed by solid-state nuclear magnetic resonance (NMR) spectroscopy.

Improved adhesion of Ni/Cu/Ag plated contacts with thermally formed nickel silicon interface for C-SI solar cells

In this work the copper (Cu) conducting electrode was appraised as an alternative to standard screen printed silver (Ag) front contacts. Laser ablation and photolithography based wet chemical etching were adapted to pattern and analyze adhesion for reliable crystalline silicon (C-Si) solar cell technology. Nickel (Ni) surface treatment after the sintering process contributed to an improved Cu plating with an adhesive Ni–Cu interface. The soldering process for the pull tab adhesion test has an impact on adhesion strength and could reduce the overall value. Smoother surfaces resulted in lower adhesion values in comparison to rough surfaces. Excellent adhesion greater than wafer breakage force with an average value of 1.72N/mm and maximum adhesion strength of 4.6N/mm on laser-ablated surfaces were achieved.

Multiscaling Approach for Non-Destructive Adhesion Studies of Metal/Polymer Composites.

The adhesion of polyamide 6 (PA6) and polyethylene (PE) toward an aluminum alloy (Al-A) and a dual phase steel (DPS) is studied by contact angle (CA) measurements and atomic force microscopy (AFM). With the combination of the two methods the adhesion properties on a macro- and (sub)microscopic scale can be determined in a nondestructive way. The work of adhesion per area (Wad) of the studied metal/polymer hybrids qualitatively scales the same on both length scales, that is, Al-A/PA6 > DPS/PA6 > Al-A/PE, DPS/PE. The polymer dominates the adhesion. The lower adhesion for PE toward the metal surfaces is explained by dominating van der Waals attraction forces, whereas adhesion for PA6 can also be attributed to attractive polar forces such as hydrogen bonding. For metal/PA6, Wad on a macro- and microscopic length scale is similar. For metal/PE, a discrepancy is measured with lower adhesion values on the microscopic scale than on the macroscopic scale.

Influence of PEEK surface modification on surface properties and bond strength to veneering resin composites.

To test the impact of mechanical and chemical treatments of PEEK on surface roughness (SR), surface free energy (SFE), and tensile bond strength (TBS) to veneering resin composites. PEEK specimens (N = 680) were fabricated and divided into treatment groups (n = 170/group): 1. air abrasion (AIA); 2. etching with piranha solution (PIS); 3. air abrasion + piranha acid etching (AIP); and 4. no treatment (NO). Ten specimens of each treatment group were assessed with a contact angle measuring device and profilometer to determine SFE and SR, respectively. The remaining 160 specimens of each group were divided into subgroups according to coupling method (n = 32/subgroup): 1. Monobond Plus/ Heliobond (MH); 2. Visio.link (VL); 3. Clearfil Ceramic Primer (CCP); 4. Signum PEEK Bond (SPB); and 5. control, no coupling (CG). Specimens were veneered using Signum Composite/SiCo or Signum Ceramis/SiCe (both: n = 16), incubated in water (60 days at 37°C) and thermocycled (5000 cycles of 5°C/55°C). TBS was measured and data analyzed by three- and one-way ANOVA, Kruskal-Wallis and Mann-Whitney tests (p < 0.05). A significant effect of surface treatment (p < 0.001) and coupling agent application (p < 0.001) on TBS was observed. AIA specimens with/without PIS showed the highest SFE, SR, and TBS. No differences were measured between PIS and NO, and between AIA and AIP. When no coupling agent was used, no adhesion was obtained. CCP resulted in low adhesion values, whereas MH, SPB, and VL exhibited increased TBS. No significant impact of the veneering resin composite on TBS was found (p = 0.424). AIA and AIP combined with VL, SPB, and MH can be recommended for clinical use.

Comparative study of enamel adhesion between RelyX™ Unicem® (3M), a self-adhesive bonding agent, and the combination of MIP® (3M), a hydrophilic adhesive, and Transbond Supreme Low Viscosity® (3M), a traditional hydrophobic adhesive

Although the bond strength of self-adhesive bonding agents is inferior to that of other families of adhesives, it is still adequate for orthodontic purposes provided prior enamel etching is performed. To determine the efficacy of RelyX™ Unicem(®)(3M) self-adhesive cement both in vitro and in vivo and to compare it with the combination of MIP(®) (3M), a moisture-insensitive primer, with a traditional hydrophobic adhesive, Transbond Supreme Low Viscosity(®) (3M). Comparison of bonding results on 23 trial dentures using RelyX™ Unicem(®)(3M) with bonding results on 29 trial dentures using a combination of MIP(®) and Transbond Supreme Low Viscosity(®) (3M), by means of a multipurpose Instron(®) 4444 testing machine. the breaking force of MIP(®)/Transbond Supreme Low Viscosity(®) (3M)(mean: 144±37.5 Newtons) was significantly higher than that of RelyX™ Unicem(®) (3M) (mean=110±26 Newtons) (P=0.001). A 12-month prospective, randomized, monocentric, single-blind clinical study in order to investigate the failure rate of orthodontic attachments according to the type of adhesive used, and the precise site of the debonding. Bracket bonding was performed on 16 patients with randomized allocation of the two adhesives to each of the semi-arches. The failure rates were: 15.3% for the MIP(®)/Transbond Supreme Low Viscosity(®) (3M)combination and 8.2% for the RelyX™ Unicem(®)(3M), with a significant difference (P=0.039). The more posterior the bonded teeth, the greater the superiority of RelyX™ Unicem(®)(3M). The in vivo results did not concord with those obtained in vitro. RelyX™ Unicem(®) (3M) exhibited lower adhesion values in vitro and yet it presented a debonding rate almost half that of the MIP(®)/Transbond Supreme Low Viscosity(®) (3M). The viscosity of RelyX™ Unicem(®)(3M) and its moisture tolerance would appear to account for these results. With prior etching, RelyX™ Unicem(®)(3M), a self-adhesive, self-etching bonding agent is compatible with use in the orthodontic indirect bonding technique. The MIP(®)/Transbond Supreme Low Viscosity(®) (3M) combination, though very effective, still remains sensitive and requires special care during usage.

Evaluation of icephobic coatings—Screening of different coatings and influence of roughness

Icing of wind turbines affects energy production, causes mechanical failures and increases safety hazards in general; hence there is an enormous demand for powerful anti-icing methods. To investigate the icephobic properties of different coatings, ice adhesion measurements were performed with a 0° cone test to determine ice adhesion strengths between coating and ice. Various coatings with different icephobic properties were investigated, e.g., hydrophilic and hydrophobic coatings, sol–gel based coatings containing fluorinated compounds and viscoelastic rubbers, as well as commercially available icephobic products. The coatings currently used on wind turbines showed an adhesion to ice that is comparable to that of bare aluminium; meaning a quite high adhesion to ice. Very low adhesion values were obtained in the case of coatings consisting of viscoelastic elastomers. Additionally, the influence of surface roughness on ice adhesion has been examined. Aluminium pins were chemically and mechanically roughened and their ice adhesion was determined. These pins were further coated with a fluorine-containing coating in order to study the influence of minimized surface energies. Shear stress of those coated pins was considerably reduced, however, rough surfaces showed higher ice adhesion than smooth ones.

The effects of virulence factors on invasion in various species of Candida

In the present study, we determined the in vitro and in vivo virulence characteristics ofCandida isolates from 75 non-neutropenic patients with candidemia and analyzed the isolates by receiver-operating characteristics (ROC) analysis to define threshold values of adhesion and hydrophobicity occurring in invasive Candida isolates. Specific virulence traits that were measured included hydrophobicity, epithelial cell adhesion, phospholipase and proteinase activity. In our in vivo investigations, all isolates were diluted in phosphate-buffered saline (PBS) and were administered to mice (Swiss albino) through tail-vein injection. Liver and spleen tissues were evaluated for evidence of invasion. Though onlyCandida albicans isolates produced detectable phospholipase activity, all isolates secreted proteinase enzyme. However, while this observation was significant among C. albicans and Candida parapsilosis isolates, the reverse was seen for Candida tropicalisand Candida krusei isolates. Interestingly, in contrast with C. parapsilosis and C. tropicalis, lower median adhesion values were determined for C. albicans and C. krusei, particularly in isolates that showed invasion in mouse experiments. It has not been possible to identify meaningful threshold values for adhesion and hydrophobicity in the repeated ROC analysis on the sub-groups in differentiating the isolates that cause and do not cause invasion in mice among the various Candida isolates. Key words: Candidemia, virulence factors, ROC analysis

Effect of grafting on microstructure, composition and surface and transport properties of ceramic membranes for osmotic evaporation

The effect of grafting with fluoroalkylsilanes on microstructure, composition and surface and transport properties of alumina membranes having different pore sizes (0.2, 0.5 and 0.8 μm) was studied. Surface and transport properties were evaluated in terms of contact angle, adhesion work and hydrodynamic membrane pore response. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS) were employed to evidence the induced microstructure and composition changes after grafting. Contact angle higher than 90°, in addition to low work adhesion and surface tension values confirmed the hydrophobic character of all three membranes after chemical treatment. SEM analysis showed facetted alumina grains in unmodified membranes while grains with rounded edges appeared after grafting. This effect induced compaction on internal and intermediate layers mainly on the 0.2 μm membrane. The insertion of hydrophobic chains on the outer surface and the porous structure of membranes after grafting, were evidenced by detection of fluor in the active and internal structure of treated membranes as well as by increments on the Si/Al ratios followed by EDXS. In addition, water permeability drastically decreased and intrusion pressure rose, mainly on the membrane of lower pore size tested. Hydrodynamic membrane response indicated pore size reductions of 53%, 65% and up to 82% in 0.2, 0.5 and 0.8 μm grafted membranes, respectively. However, silane chains inserted inside of 0.5 and 0.8 μm membrane pores were apparently more susceptible to flow induced deformation, limiting the potential application of these membranes on the osmotic evaporation process. Results from grafted 0.2 μm alumina membrane during OE of clarified cane juice and model sucrose solution indicate that feed and brine layer resistances contribute in less than 10% while membrane resistance contribution to the total process resistance was around 90%. Results from this work indicate that applicability of grafted alumina membranes in the OE process might further improve by using 0.2 μm < d P < 0.5 μm average pore size membranes and/or by decreasing membrane thickness.

Corrosion stability of polyester coatings on steel pretreated with different iron–phosphate coatings

The influence of steel surface pretreatment with different types of iron–phosphate coatings on the corrosion stability and adhesion characteristics of polyester coatings on steel was investigated. The phosphate coating was chemically deposited either from the simple novel plating bath, or with the addition of NaNO 2, as an accelerator in the plating bath. The morphology of phosphate coatings was investigated using atomic force microscopy (AFM). The corrosion stability of polyester coatings on steel pretreated by iron–phosphate coatings was investigated by electrochemical impedance spectroscopy (EIS) in 3% NaCl solution, while “dry” and “wet” adhesion were measured by a direct pull-off standardized procedure. It was shown that greater values of pore resistance, R p, and smaller values of coating capacitance of polyester coating, C c, on steel pretreated with iron–phosphate coating were obtained, as compared to polyester coating on steel phosphated with accelerator, and on the bare steel. The surface roughness of phosphate coating deposited on steel from the bath without accelerator is favorable in forming stronger bonds with polyester coating. Namely, the dry and wet adhesion measurements are in accordance with EIS measurements in 3% NaCl solution, i.e. lower adhesion values were obtained for polyester coating on steel phosphated with accelerator and on the bare steel, while the iron–phosphate pretreatment from the novel bath enhanced the adhesion of polyester coating on steel.

Micro and nanostructures found on insect wings &amp;ndash; designs for minimising adhesion and friction

Adhesion and friction have been measured on insect wings where contamination (water and/or contaminating particles) can potentially have a detrimental effect on their flight capabilities or daily functioning. Adhesional forces as low as 2 nN were recorded in air for particles with radii of 10-15 nm, and 20 nN for particles of 31 mm radius. The effective coefficients of friction were in the range of 0.01 to 0.10. The low adhesion and frictional values demonstrate that only very low out-of-plane and in-plane forces are required to remove contaminants of nanometre and micron dimensions from the cuticle membranes. Many of the surfaces demonstrate superhydrophobic properties and will not only reduce the effects of contact with surfaces but also promote a self-cleaning function for removing foreign bodies. It has also been demonstrated that surface structures and properties can be duplicated on polymer surfaces by using the wing membrane as a 'natural template'.

Delamination of multilayer packaging caused by exfoliating cream ingredients

AbstractExfoliating creams were packed in sachets of composite packaging consisting of polyethylene, aluminium and polyester layers stuck together by polyurethane adhesive, and they were kept in an oven at 40°C in order to accelerate the delamination process. The sachets were then delaminated and the resulting layers were analysed. A headspace solid‐phase microextraction mass spectrometry method (HS–SPME–GC–MS) using a 75µm carboxen polydimethylsiloxane fibre was used to identify the compounds migrating from the exfoliating creams through the polyethylene layer to the aluminium interface and suspected to be responsible for packaging delamination. Several volatile compounds used in the cosmetic industry as perfumes, fixing agents and preservatives, such as menthol, dihydromyrcenol and 2‐phenoxyethanol, were detected in the aluminium/polyester delaminated layer. The exfoliating creams were also analysed by HS–SPME–GC–MS. The study of loss of adhesion of the laminated material exposed to the exfoliating products revealed that the product with a higher concentration of 2‐phenoxyethanol caused a faster decrease in adhesion strength, but the lower adhesion values were found in products with higher concentrations of menthol and dihydromyrcenol. The results obtained showed that the analytical method used was suitable for identifying volatile compounds that migrate through polyethylene to the inner layers of the packaging of exfoliating products, as well as for providing prior information on which products may be difficult to package in sachets. Copyright © 2006 John Wiley &amp; Sons, Ltd.