Oily Surfaces Research Articles

An Analysis of Slip Incidence for Ankle Angle and Muscle Fatigue During Walking Activities

Human walking speed exposes the higher potential to slip accident especially walking on the oily surface. Prolong walking during working will develop fatigue to the leg and certain body part. In a certain industry, there was a need that worker had to walk and standing in prolong before reaching their break. The aim of this study was to analyze the ankle angle and the muscle fatigue during walking and influence in slip incident. The study involves twelve health participants aged from 23 to 57 years old with a mean of BMI was 27.82 ± 4.01 kg/m2. The procedure will be explained the detail when the participant agreed. Vicon motion capture was used to record movements and the Electromyography (EMG) was used to record muscle fatigue activity. The finding shows that the slip occurred frequently for overweight and obese participants. The female participant experience slips more than a male participant. The range of ankle angle during slip was from 97.2 ± 6.7° for male participants and 112.5 ± 12.7° for female participants. The muscle Soleus and Tibialis were producing high muscles fatigue during slip occurrence. The results of the study show that muscle fatigue was significant with the occurrence of slipping during walking speed. Other findings presented that overweight and obese participants' significant slip occurred when walking on oily surfaces. Both aged groups represent the slip occurrence, there was no significant factor of aged during slip occurrence.

Dynamic Nonlinear Gradient Observer Based Extremum Seeking Control for Optimum Braking

The application of extremum seeking control (ESC) algorithm to antilock braking systems (ABSs) is attractive for maximizing the longitudinal braking force. Most currently reported results suffer from the drawback of steady-state oscillations around the extremum or the need to have the gradient information. In this article, a new ESC algorithm is proposed for application to ABSs to overcome these two drawbacks. The proposed algorithm is based on a novel dynamic nonlinear gradient observer (DNGO) and a longitudinal braking force estimator. The performance and the ultimate boundedness of the proposed ESC, DNGO, and the force estimator are analyzed. The proposed method is validated by simulation for dry and wet road surfaces and compared with two established results. The method is further validated on an experimental setup in the laboratory for dry and oily surfaces.

Development of contact displacement sensor based on frequency-modulated continuous-wave

Frequency-modulated continuous-wave(FMCW) interference measurement has the advantages of length traceability, large range, high precision, simple structure and optical fibre transmission. Based on the characteristics of the axial inductance sensor, a novel laser interference displacement sensor is developed. The formula of FMCW laser ranging is derived in detail and the mechanical structure and optical system of the contact displacement sensor are designed. Integrating the interferometric optical path into the sensor rod, converting non-contact measurement with cooperative targets into contact measurement can realize direct measurement of workpieces with complex surface conditions on the production line, such as free-form surfaces and oily surfaces. This technology expands the application of optical non-contact measurement. Experimental results show that the designed displacement sensor can reach a measuring range of 15 mm with a standard deviation of less than 0.01μm. It can meet the requirements of large-scale and high-precision inspection applications in the field of precision manufacturing.

Efficiency of sorbents used to restore the grip of the surface of the oily road

The use of sorbents is one of the methods most commonly used by the fire departments to remove spilled hydrocarbon liquids. Sorbents approved for use by fire brigades must meet the requirements of the Ministry of Internal Affairs. However, this requirement does not include the assessment of the degree of roughness of the road surface after removal of oily spills. The high degree of restoration of road surface grip is extremely important for the safety of road users. The article presents the results of research on the effectiveness of restoring the coefficient of friction by different sorbents. The tests were carried out for three different asphalt pavements, determining the coefficients of friction for dry, wet and oily surfaces and after applying sorbents. Static friction coefficients were determined by measuring the angle of the inclination of the tested surface specimen, at which the probe imitating the car tire slid. It turned out that none of the used sorbents fully restored the initial coefficient of friction on the asphalt surface. The use of professional sorbents allowed for the restoration of about 80% of the initial coefficient of friction of the dry surface. Significantly poorer results were obtained for the most commonly used sorptive replacement materials, i.e. sand or sawdust.

Tractor safety and related injuries in Iranian farms

BackgroundSeveral thousand worker injuries and fatalities worldwide per year is the consequence of agricultural activities especially working with farm tractors. The aim of this study was to determine current levels of farm tractors drivers' safety attitudes in Iranian agriculture besides type and severity of tractor-related injuries. MethodSocio-demographic properties of a sample of 281 tractor drivers and their injuries were investigated using face to face interview. The severity of injuries were also determined. The drivers' attitudes toward safety issues were analyzed by exploratory factor analysis. ResultsThe results revealed that drivers aged 30–45 years had higher rates of injuries. Most of injuries were moderate (41%) occurring due mainly to oily surfaces on the tractor or implements, carelessness or fatigue during the work. The low-income group had also higher injuries since the drivers in this group work with no regular work-rest schedule and they usually work with old tractors equipped with unsafe facilities. Those that do comply with safety measures are likely to have fewer exposures to unsafe work practices and consequence injuries. Further education of tractors drivers in various aspects of farm safety besides enforced regulations to adjust safety issues are the possible approaches to prevent tractor-related injuries.

Comparison of sliding time of low-rank coal particles on air and oily bubble surfaces

ABSTRACTIn the present communication, the sliding time of low-rank coal particles on air and oily bubble surfaces was investigated. From the analysis of a high-speed camera, it was found that the sliding time of hydrophilic low-rank coal particles attached to air bubble was limited by the maximum angle of contact at about 61º whereas the maximum touching angle for particles attached to oily bubble was about 85º. Meanwhile, the sliding time of particles attached to the oily bubbles was always lower than that of particles attached to air bubbles during the slip process. Moreover, due to the Marangoni effect on the rising oily bubble surface, half of the sliding time of low-rank coal particles passing from about 3º to the bottom of the oily bubble was more than that of particles sliding from about 85º to the bottom of the oily bubble. Furthermore, based on the same hydrodynamic environment, the difference in the sliding time of low-rank coal particles attached to air and oily bubble surfaces was not the same as the difference in induction time between air or oily bubble and particle beds.

Contributions of adhesion and hysteresis to coefficient of friction between shoe and floor surfaces: effects of floor roughness and sliding speed

Improving shoe–floor friction in order to reduce slip and fall accidents requires thorough understanding of the factors that contribute to friction. The friction between a sliding viscoelastic material (shoe) and a hard surface (floor) has two major components: adhesion and hysteresis. This study aimed to quantify the effects of floor roughness and sliding speed on adhesion and hysteresis to determine how each component contributes to the coefficient of friction. Experiments were conducted on a pin on disc tribometer using ceramic tiles with three levels of roughness, six sliding speeds, two common shoe materials and four liquid lubricants. Hysteresis was measured using a lubricant that minimised adhesion. Dry and lubricated adhesion was measured by subtracting hysteresis from the coefficient of friction. Analysis of variance regression models were used to determine the contributions of hysteresis, dry adhesion, sliding speed and fluid to lubricated coefficient of friction. Increased floor roughness led to increased hysteresis, while increased sliding speed reduced both adhesion and hysteresis. These findings are consistent with theory that states that larger asperities increase hysteretic deformation and that sliding speed affects deformation and real area of contact between a viscoelastic material and a hard surface. The model correctly predicted 83% of variation in coefficient of friction based on dry adhesion, hysteresis and fluid dependent constants. The sensitivity of hysteresis friction to shoe material and floor roughness indicates that optimising these parameters may be effective at reducing slip accidents on oily floor surfaces.

The impact of environmental factors on traffic accidents in Iran

:Background:Road traffic crashes are the third highest cause of mortality in Iran. The aim of this study was to determine the impact of roadway environmental factors on traffic crash. Methods:This cross-sectional study was conducted in Iran between March 21, 2010 and December 30, 2010. The data on road traffic crashes were obtained from the Traffic Police Department records. These records were classified to control for the main confounders related to the type of crash and roadway environmental factors. Roadway environmental factors included crash scene light, weather, place of accident, the defects and geometrics of roadway and road surface.Results:The study included 542,863 traffic crashes. The proportions of road traffic crash which led to injury were 24.44% at sunrise and 27.16% at sunset compared with 5.43% and 1.43% deaths at sunrise and sunset respectively. In regard to day time accidents, the proportions were 20.50% injuries and 0.55% deaths. The statistical analysis of the results showed that the ratio of injuries and deaths were significantly higher at sunrise and sunset than those occurring during daytime (P less than 0.001). The highest rate of death (5.07%) was due to dusty weather compared to 5.07% for other weather conditions (P less than 0.001). The highest mortality rate (3.45%) occurred on oily surfaces (P less than 0.001). The defective traffic signs were responsible for 30,046 injuries and 5.58% deaths, and road narrowing accounted for 22,775 injuries and, 4.23% deaths which indicated that the roadway defects inflict most frequent injuries and deaths. The lowest (0.74 %) and highest (3.09%) proportion of traffic crash- related deaths were due to flat straight and winding uphill/downhill roads respectively (P less than 0.001).Conclusions:Sunrise, sunset, dusty weather, oily road surfaces and winding uphill/downhill road were hazardous environmental factors. This study provides an insight into the potential impacts of environmental factors on road traffic accidents and underlines the implementation of appropriate preventive measures.

Screening of Pseudomonas species for biosurfactant production using low-cost substrates

Abstract In the present study, four species of Pseudomonas ( P. cepacia, P. acidovorans, P. picketti and P. fluorescens ) were cultivated in different low-cost substrates and compared with regard to biosurfactant production. Surface tension was used as a preliminary screening standard for potential biosurfactant bacteria. The best result was obtained with P. cepacia grown in mineral medium supplemented with 2.0% corn steep liquor and 2.0% soybean waste frying oil for 144 h at 30 °C and 200 rpm. Kinematic studies on microorganism growth and biosurfactant production were performed. Surface tension of the medium was reduced to 27.57 mN/m at the end of the cultivation, yielding 5.2 g/L of isolated biosurfactant. Tests under extreme conditions of pH, temperature and NaCl indicated the stability of the biosurfactant for use in the treatment of oil-contaminated environments. The critical micelle dilution of the biosurfactant was determined and its use in the removal of motor oil from clay soil demonstrated rates greater than 80%. Washing experiments involving rocks and oily surfaces contaminated with motor oil demonstrated greater than 80% recovery rates. The crude biosurfactant was capable of dispersing approximately 80% of oil droplets in seawater and proved to be non-toxic to indigenous marine microbiota. The crude biosurfactant demonstrated no toxicity against seeds of Brassica oleracea or the microcrustacean Artemia salina employed as a bioindicator. The present findings indicate the application potential of the biosurfactant produced by P. cepacia in the oil industry as a complement to remediation processes involving contaminated soil and water.

Slip Resistance of Floors in a Supermarket

Floor slipperiness assessment was conducted in a supermarket in central Taiwan. The floor slip resistances in the meat cutting, cooking, and baking areas were measured. The friction measurements were conducted using the Brungraber Mark II slipmeter. The results showed that the slip resistance in the meat cutting areas was significantly higher (p<0.05) than those of the other two areas. The slip resistances between the cooking (0.49) and baking (0.51) areas were not significant. The slip resistance of the dry surface (0.64) was significantly higher than those of the wet (0.28) and oily (0.34) surfaces. The slip resistances between the wet and oily surfaces were not significant. All the wet and oily floors in the shop had COF values lower than 0.5, a safety standard commonly adopted in the USA. Ergonomic interventions were recommended.

Trehalose 6,6′-Dimycolate and Lipid in the Pathogenesis of Caseating Granulomas of Tuberculosis in Mice

Trehalose 6,6'-dimycolate (TDM) is the most abundant, most granulomagenic, and most toxic lipid extractable from the surface of virulent Mycobacterium tuberculosis (MTB). We further examined its toxicity, which requires activation by oily surfaces. Injections of MTB and/or TDM into sensitized mice induced caseating granulomas that centered on oil droplets. If large doses of MTB were injected in saline, caseating granulomas developed in adipose tissue, but MTB with surface TDM removed induced only acute inflammation that did not persist. Variations in protocols produced several variants of caseating granulomas, each with characteristics of human tuberculosis. In each instance, MTB were localized in fat cells or oil drops during initiation of caseating granulomas suggesting that necrosis was caused by activation of the toxicity of TDM toxicity. Evidence extending these findings to the lung was derived from the observation that in sensitized mice, as in humans, tuberculosis development stimulates accumulation of lipid selectively in alveoli. MTB preferentially associated with lipid droplets in developing necrotic foci in late-stage murine tuberculosis. This supports the hypothesis that pulmonary tuberculosis sequesters MTB in a protected environment that accumulates lipid until it is able to activate the toxicity of TDM and initiate necrosis that results in caseating granulomas.

Trehalose 6,6′ dimycolate (TDM) and Lipid in the Pathogenesis of Caseating Granulomas of Tuberculosis in Mice

Trehalose 6,6′ dimycolate (TDM) is the most abundant, most granulomagenic and most toxic lipid extractable from the surface of virulent M. tuberculosis (MTB). Its toxicity requires activation by oily surfaces. Injections of MTB and/or TDM into sensitized mice induced caseating granulomas that centered on oil droplets. If large doses of MTB were injected in saline, caseating granulomas developed in adipose tissue. MTB with surface TDM removed induced only acute inflammation and did not persist. Variations in protocols produced several variants of caseating granulomas each with characteristics of human tuberculosis. In each instance, MTB were localized in fat cells or oil drops during initiation of caseating granulomas suggesting that necrosis was caused by activation of the toxicity of TDM. Evidence extending these findings to the lung was derived from the observation that in sensitized mice, as in humans, developing tuberculosis stimulates accumulation of lipid selectively in alveoli. MTB preferentially associated with lipid droplets in developing necrotic foci in late stage murine tuberculosis. This supports the hypothesis that pulmonary tuberculosis sequesters MTB in a protected environment that accumulates lipid until it is able to activate the toxicity of TDM and initiate necrosis that results in caseating granulomas.

Available friction of ladder shoes and slip potential for climbing on a straight ladder

Straight ladder accidents are a major safety problem. As a leading cause of injuries involving straight ladders, slips at the ladder base occur when the required friction exceeds the available friction at the ladder shoe and floor interface. The objectives of this experiment were to measure the available friction at the base of a portable straight ladder in contact with a floor and to estimate the slip potential of the ladder. The results of friction measurements indicated that the measured friction coefficient on the oily surfaces differed among the six commercially available ladder shoes evaluated. A statistical model was used to compare the available friction results from the current study with the friction requirements under different climbing conditions from a previous study based on their stochastic distributions to estimate the slip potential at the base of the ladder. The results showed that different climbing conditions used in the previous study could be supported by available friction on dry surfaces. However, when the ladder was put onto oily surfaces, resulting in a significant reduction in the available friction due to contamination, slip potential was significantly increased.

Effects of environmental and job-task factors on workers' gait characteristics on slippery surfaces

The objective of this study was to investigate the kinetic and kinematic aspects of slips associated with gait on a slippery surface under various environmental and job-task risk factors. Forty healthy industrial workers (age: 40.3 ± 14.9 years) participated in the study. Using a strain gauge type force platform and a video-based motion analysis system, kinetic and kinematic measurements of the subjects' foot movements were obtained. Of all gait trials, there were 1558 slips (60.9%). Slips were likely to occur when subjects were negotiating a turning path and an oily surface. Greater anterior-posterior center of pressure (CP) excursion and maximum required coefficient of friction (RCOF) were found for oily surfaces compared to dry surfaces. Subjects changed their gait patterns by shortening their stride length, slowing walking speed, and decreasing heel contact angle in the poorly lit and slippery environment. Significant correlations were found between slip occurrence and anterior-posterior CP excursion, mean RCOF, sliding distance and sliding velocity, but not the coefficient of friction (COF) of shoes. In addition to good housekeeping and proper selection of floor materials and safety shoes, slip and fall prevention should include proper workers' training in dealing with risk factors of slips and falls in the workplace.

The effect of roughness, floor polish, water, oil and ice on underfoot friction:: current safety footwear solings are less slip resistant than microcellular polyurethane

Research over a period of about 18 years has shown that a microcellular polyurethane known as AP66033 is the most slip-resistant safety footwear soling material on oily and wet surfaces. In recent years it has been replaced in commercially available footwear by a dual density polyurethane (DDP) which has a dense outer layer and a soft microcellular backing. This research programme has compared the slip resistance of AP66033 with DDP and some rubber solings. In addition, data were obtained on the effects of soling and floor roughness, and floor polish on slip resistance. Some data were also obtained for walking on ice. The coefficient of friction (CoF) of the solings was measured on 19 water wet surfaces in three conditions: (I) when the solings were new, (II) following abrasion to create maximum roughness and (III) after polishing. The CoF was measured on four oily surfaces after each of 11 abrasion or polishing treatments. The profound effects of the roughening of all soles and of floor roughness on the CoF were demonstrated for both wet and oily surfaces. The superior slip resistance of AP66033 was confirmed for oily and wet conditions; however, some rubbers not suitable for safety footwear achieved higher CoF values on wet floors. All of the floor polishes reduced the CoF of all floors when contaminated with water. The mean CoF of DDP solings was lower than the mean for AP66033 on wet and oily surfaces. No safety footwear soling provided adequate grip on dry ice and the CoF was reduced by water on the ice. A rubber used for rock climbing footwear was one of the most slip-resistant solings on wet surfaces in the laboratory but recorded the lowest CoF on ice. It is concluded that the incidence of occupational injuries caused by slipping could be reduced by the following: (A) returning to safety footwear soled with the microcellular polyurethane AP66033; (B) abrading all new and smooth footwear solings with a belt sanding machine coated with P100 grit; (C) avoiding the use of floor polish; (D) informing the general public about the poor slip resistance of ordinary footwear on ice and the lowering of slip resistance in cold weather.

Imaging an Oil Droplet under a Latex Film

An age-old dream in the coatings industry has been to develop a paint capable of coating over oily surfaces without first carefully cleaning the surface and still provide protection and coverage. The wettability of the solid surface plays an important role here, as it does in many other areas of technology such as lubrication, detergency, and oil recovery. As a small first step in this direction, we consider the example of a latex clearcoat applied over a surface containing a thin film of oil. From a paint perspective, one asks the questions: Where does the oil end up in the coating? Does it remain at the substrate? Is it displaced to the film surface or does it become dispersed in the coating? From a surface science perspective, one asks different questions. Can one measure the contact angle between micrometer-size droplets of the oil on the substrate, and can one detect the influence of the latex dispersion and the dry film it forms on the properties of the oil droplets remaining at the substrate surface? In this communication, we show that many of these questions can be answered by laser scanning confocal fluorescence microscopy1-6 (LSCFM) if the oil in question is treated with a trace amount of an oil-soluble fluorescent dye. Experiments on the behavior of oil-like films cast onto nonwetting substrates have been reported previously. Wilkinson et al.7 studied the wetting and spreading of two liquids in contact with a solid substrate, including the case of oil on glass in the presence of water. They examined immiscible liquids (oil and water) and macroscopic oil drops and found that as the water films became thinner, rupture often occurred, leading to the formation of stable oil drops surrounded by bare substrate. Bass and Sharma8 used atomic force microscopy (AFM) to measure the forces between oil drops immersed in a NaCl solution and a solid surface of either glass or mica. They found that an oil droplet adhering to the substrate more easily ruptured thin aqueous films on glass than on mica. They speculated that the higher surface roughness of the glass (2 orders of magnitude higher than that of the mica) led to the more facile rupture of the aqueous film. Redon et al.9 studied the evolution of a thin (20 μm) film of a nonvolatile liquid forced to spread onto a nonwetting substrate. Since all films are metastable below a certain thickness controlled by gravity effects (about 1 mm),10 thin films dewet by nucleation and growth of dry patches. The rate of this process depends primarily on the oil/ substrate contact angle. In another set of experiments by this group, the dewetting of a liquid A deposited by solvent evaporation on an immiscible nonwettable liquid B was followed. The dewetting evolved by amplification of capillary waves to form a cellular pattern of A droplets on the surface of liquid B.11 The problem we address is significantly more complex. We are interested not only in the nature of the oil droplets formed on the surface of a substrate but how those droplets are affected when a dispersion of film-forming latex is spread over the substrate and allowed to dry. We employ triolein, a liquid triglyceride, as the oil, quartz as the substrate, and poly(butyl methacrylate) (PBMA) as the film-forming latex. Triolein serves as a model for oils and greases that might appear on a wall to be painted. It is also a model for lubricant traces on the surface of an aluminum sheet that is to be coated. PBMA is an excellent model for a variety of acrylic dispersions that form films at or near room temperature.12,13 Typical latex films are 30 to 60 μm thick. The latex films we prepare are coated over quartz with oil droplets on the surface that are significantly thinner. We wish to understand how the coating affects the contact angle between the oil droplets and the quartz substrate. Contact angles define the tendency of a nonwetting fluid to either adhere to the surface or separate from it, and can be measured by a variety of techniques.14-16 Traditional methods for determining contact angles cannot be used to study a system consisting of micrometer-size oil droplets on a substrate coated with a solid but transparent polymer film. To characterize these oil droplets, we need a technique with 3D imaging capability and submicrometer resolution. Laser scanning confocal microscopy1-4 fulfills these requirements and allows us to image the oil droplets inside the polymer film. This technique is widely used in the biological sciences5,6 and has been used to image domain shapes and sizes in a variety of solid polymer blend systems.17-25

Surface Roughness of Footwear Soling Materials: Relevance to Slip Resistance

Abstract The slip resistance of commercial safety boot and experimental footwear solings has been studied over a period of 15 years. Shoes, with experimental solings, were worn in a factory, and the coefficient of friction (CoF) measured at intervals, using a walking traction test. These measurements have shown that a microcellular polyurethane, AP66033 (formerly T66/103) gives the greatest slip resistance of any soling material on wet or oily factory floors and laboratory test surfaces. This performance is attributed to the statistically significant relationship between CoF and mean peak to trough roughness (Rtm). The surface structure of soling materials was examined using Scanning Electron Microscopy, and images compared with Rtm measurements. There is now sufficient experimental evidence to confirm that surface roughness is one of the determinants of CoF on lubricated floors. The wear characteristics of the floor/sole combination must be considered: some soling materials may become polished on certain floors. However, AP66033 cannot be polished.

Detecting and eliminating slippery footwear.

A recently developed walking traction test has proved to be a reliable and rapid method of measuring coefficient of friction (c.o.f.) of floor surfaces and footwear, and is a suitable method for ranking the grip of footwear solings on slippery floors. This paper describes four new experiments in which footwear samples were ranked. The first experiment compared mean rank orders on water wet (wet) and oily surfaces of seven flat solings. Spearman's rank correlation coefficient rs was 0·893, P < 0·005. In the second experiment, five pairs of women's shoes were ranked on wet and oily surfaces. On the wet surfaces, three samples recorded maximum attainable c.o.f. but rank orders on two oily surfaces were identical, rs = 1·0, P < 0·01. In the third experiment, thirteen pairs of discarded footwear were ranked using three different test methods. The test surfaces were oily stainless steel plates cut from the same sheet. Rank orders of the three test methods were significantly similar. Kendall's coefficient of concordance w = 8·68, P < 0·001. In another experiment samples of commercially available footwear were issued to factory workers and recalled for c.o.f. measurements at intervals. Their rank orders on wet and oily surfaces were not statistically similar but when wet surface results obtained at 4 months, were compared with those at 10 months, rank orders were significant; rs = 0·994, P < 0·01. Also on oily surfaces, rank orders of two measurements were significant, rs = 0·982, P <0·01. Although most experiments have revealed significant correlations between footwear samples on wet and oily surfaces there are examples where a soling performs well on wet surfaces but is at the lower end of rank order on oily surfaces. It is concluded that rank orders on wet, oily and icy surfaces should be calculated but also it is necessary to examine rank orders on each surface-lubricant combination, by comparing results obtained at intervals during the useful lives of the solings. In future, samples at the lower end of the rank orders of c.o.f. will be eliminated from the varieties available to workers.

The superior slip-resistance of footwear soling compound T66/103

Research over a period of fifteen years consistently revealed that a microcellular polyurethane soling known as T66/103 (T66) is the most slip-resistant soling for use on oily floor surfaces. Many experiments have indicated that T66 is also the most slip-resistant soling available for water contaminated (wet) floors. The walking traction test and a new mobile version of the rig were used in eight new experiments designed to obtain further evidence for the superior slip-resistance of T66 especially on wet floors. The surface roughness of T66 after abrasion is believed to be an important contributor to slip-resistance and this hypothesis led to the examination of some microcellular rubbers (MR) which also become rough when abraded. The T66 soling was compared with five MR samples, a dense Polyurethane (PU) and two dense rubbers and in all the experiments the mean coefficient of friction (cof) of the T66 soling was ranked higher than all other solings on surfaces lubricated with water, or by water and a wetting agent ( p< 0.005). On stainless steel lubricated with two grades of mineral oil T66 was in first place in all four ranks although the ranking was not significant. The slip-resistance of four out of five MR samples was better than that of a dense, commercial rubber previously investigated. There was some evidence that a 6 mm thick sole of T66 showed higher cof values than a 12 mm soling and also that higher concentrations of wetting agent can selectively reduce cof of the MR solings. The MR solings were all 12 mm thick and therefore further work is required to compare the MR materials with T66. The MR solings had poor slip-resistance on oily surfaces. The slip-resistance of the dense PU compound (6 mm thick) was consistently ranked lower than a 6 mm soling of T66 but higher than the dense, commercial rubber ( p< 0.001) and the authors believe that the trend in footwear design towards an outer layer of dense PU is retrograde. It is concluded that T66 is the safest commercial soling found for both oily and wet floors and that the more general use of this soling would reduce the enormous number of injuries caused by slipping accidents. Compound T66 should be used as a standard for the assessment of other solings.

Proof of shoe slip-resistance by a walking traction test

Manning, D.P., Jones, C. and Bruce, M., 1990. Proof of shoe slip-resistance by a walking traction test. Journal of Occupational Accidents, 12: 255–270. There is no universally acceptable or reliable method of measuring shoe and floor friction, and few of the many published methods are capable of measuring coefficient of friction (c.o.f.) of shoes worn on the feet. A new walking traction test is described, in which a test subject walks on slippery floor surfaces, pulling against a set of springs and the maximum c.o.f. attained before the feet slip, is measured. Three soling materials were selected from a large number previously tested by a different method of measuring c.o.f. One had registered higher than average c.o.f. and the other two lower than average c.o.f. The three materials were moulded onto bowling shoes with flat soles and no separate heel or tread pattern. One set of three pairs was reserved for water lubricated surfaces and the other set for oily surfaces. Coefficient of friction of the shoes was measured by the new walking test on three separate floor surfaces lubricated in turn with water and oil. The shoe soles were then abraded or polished in ten stages with an orbital sander. Surface roughness and c.o.f. were measured after each abrasion treatment. With successive abrasion treatments, the soling selected for above average c.o.f. gradually became rougher than the other two materials and it nearly always recorded higher c.o.f. readings when tested by the walking traction method. Its superior grip was demonstrated at roughness readings above 15 microns on water lubricated floors; c.o.f. of 0.43 was achieved on all three floors. The other two solings could not be roughened more than 15 microns. On oily surfaces, soling roughness of 21.5 microns only produced a c.o.f. of 0.2. Permanent roughness of solings is one of the properties needed for safer walking in slippery conditions. This new walking traction test convincingly measures shoe and floor friction up to a maximum of 0.43 and will assist the search for slip-resistant footwear.