Slip resistance tests for flooring: Two methods compared

In the UK the two most commonly used tests for measuring the slip resistance of flooring are the BCRA Tortus test and the RRL skid test. The corresponding safety criteria usually associated with these tests are assumed to be equivalent. Experimental results obtained on a range of flooring materials tested dry, wet and treated with two different polishes indicate that different slip resistance values are obtained from the two testers, even when the same test slider material is used in each. The relationship of these tests to service conditions remains uncertain and it follows therefore that figures quoted for coefficient of friction in BS 5395 are largely meaningless since neither the test method nor the slider material is specified.     

A new characterisation method for rubber

This paper deals with the mechanical characterisation of elastomeric materials. An original method is proposed to identity the material parameters. It consists of performing only one heterogeneous mechanical test, measuring the displacement/strain field using suitable Digital Image Correlation software and applying an inverse method, namely the Virtual Fields Method, to process the resulting displacement/strain maps. For this purpose, a new apparatus was designed to be adapted to a conventional tensile machine. This apparatus enables us to obtain simultaneously uniaxial tension, pure shear and equibiaxial tension, using only one sample. The heterogeneity of the kinematic fields induced by the test is first discussed in relation to two criteria. The main features of the identification method are then presented, and results provided by a test performed on an elastomeric material are discussed in the context of hyperelasticity.     

Novel approach for thermal diffusivity measurements in inert atmosphere using the flash method

Determining the thermal conductivity is crucial whenever heat transfer issues are considered which play a major role in many technological applications. However, various materials are sensitive to oxygen or moisture and, therefore, cannot be examined with commonly used equipment under ambient conditions. Here, we present a novel approach which combines the inert requirements of ambient-sensitive specimens with the flash method in which the apparatus, a Netzsch LFA 447 NanoFlash^®, is placed under ambient conditions. A new measuring cell with flash-transparent windows was constructed which resembles a gas-tight specimen chamber. This device can be easily adapted to other apparatuses based on the flash method. The thermal conductivities of reference materials in inert and ambient conditions were examined in a temperature range from 25 to 275 °C. In general an excellent agreement was found. Further, the usability of this special sample cell is demonstrated for the investigation of the thermal conductivities of two complex hydride systems which are important for solid-state hydrogen storage applications.     

Atmospheric-pressure ionization mass spectrometric and photoionization techniques for evaluation of barrier film permeation properties

Barrier films are mainly used as food packaging materials to protect food from oxygen and also to retain food flavor and aroma constituents. Since the packaging materials must exhibit very low permeation rates to these constituents, the measuring apparatus must have high sensitivity to the parts-per-billion concentration range. It is also desirable that the permeation rate measurements be conducted at packaging conditions, i.e., both sides of the films at ambient pressure. Two techniques, which are based on atmospheric-pressure ionization mass spectrometry and photoionization, are developed for the permeation rates measurements of flavor and aroma constituents. The film holders are also temperature controlled, which allows one to study the temperature effect on the permeation rates. In this paper, both the techniques and their applications to the study of the permeation rates and the permeabilities of a commercial film will be presented.     

The Use of Miniature Disc Bend Tests with Plastic Materials

The use of miniaturised disc bend tests, a method that is commonly used with metallic materials, is assessed for use with polymeric materials. The test method uses the indention force/displacement characteristics for a hemispherical-ended punch forced onto a small disc of the test material. Characterisation tests were performed using acetal, PMMA and polypropylene, under a range of different test rates and temperatures. These were compared with conventional tensile tests under the same conditions. Although no quantitative comparison between the two methods has been formulated, good qualitative agreement was found for all materials, including a wider comparison with nine materials. The advantages of the disc bend test are that smaller amounts of material are needed, the sample preparation is easier, the test is often easier to perform, it shows ductile–brittle transitions more sharply and is a very convenient method of performing environmental stress cracking tests.     

Drying of organic solvents: quantitative evaluation of the efficiency of several desiccants

Various commonly used organic solvents were dried with several different drying agents. A glovebox-bound coulometric Karl Fischer apparatus with a two-compartment measuring cell was used to determine the efficiency of the drying process. Recommendations are made relating to optimum drying agents/conditions that can be used to rapidly and reliably generate solvents with low residual water content by means of commonly available materials found in most synthesis laboratories. The practical method provides for safer handling and drying of solvents than methods calling for the use of reactive metals, metal hydrides, or solvent distillation.     

Compression stress relaxation

The requirements of apparatus to measure stress relaxation of rubbers in compression are outlined. Apparatus available commercially are described, in particular a universal semi-automatic force measuring head and jigs which accept button test pieces and have no sliding bearings to introduce friction.     

On scale dependence in friction: transition from intimate to monolayer-lubricated contact

Scale dependence in friction is studied in the present paper using the newly developed mesoscale friction tester (MFT). A transition in frictional shear strength from several hundreds of MPa to several tens of MPa was observed over a very limited range of contact radii (20-30 nm) in both ambient and dry environments. Thus, a single apparatus has been able to establish these two limits which are consistent with the values previously obtained from friction experiments using atomic force microscopy (AFM) and the surface force apparatus (SFA), respectively. Consequently, it is hypothesized here that a shear strength in the hundreds of MPa results from intimate contact (solid-solid) and a shear strength in the tens of MPa results from a monolayer-lubricated contact. Furthermore, both the probe size and the normal pressure govern the interfacial conditions in the contact zone and it is these conditions, rather than the nominal environment, which in turn determine the resulting shear strengths. A continuum analysis based on the Lifshitz theory for van der Waals interactions is used to explain the quantized shear strengths which were obtained from our experiments and previous AFM and SFA friction experiments. This quantized friction behavior [J.N. Israelachvili, P.M. McGuiggan, A.M. Homola, Science 240 (1988) 189] results from the discrete separation due to the different interfacial conditions that can arise between two sliding surfaces. The consistency between the analysis and the experimental results shows that this analysis is applicable for nonwear friction with single asperity contact.     

Shear and yarn pull-out grip for testing flexible sheets by universal load machines

The purpose of this research was to develop a novel, multifunctional apparatus that makes possible to carry out two common tests of woven fabrics and flexible sheet-like materials, namely the shear and the yarn-pull out test. We designed an apparatus that can be mounted on a universal load machine and makes possible to test the materials rapidly and precisely.In this paper we introduce the apparatus and the related simple shear and yarn pull-out test methods, as well as the accuracy and reproducibility of the test results obtained. We carried out cyclic shear and yarn pull-out tests on plain and panama weave materials. We found that the relative deviations of the common shear (G, 2HG, 2HG5) and yarn pull-out parameters were around 5–9% in most cases that confirms the repeatability of the test method. With our method, one can carry out these tests without an expensive, dedicated test device.     

测量多孔粉体扩散系数和孔分布的实验装置

多孔粉体在介孔和微孔范围内的表征需要专业的实验仪器,这限定了对该类材料全面的表征只能在大型实验室中进行.本文提出了一种改进的BET测量装置,其核心部件是高精度的压差传感器,这种设备让小型实验室也可以测量多孔粉体的内扩散系数和孔分布.使用数值解析方法和蒙特卡罗模拟方法分析了测量扩散系数实验的数据.     

Vapor-liquid equilibrium for phenanthrene-toluene mixtures at elevated temperatures and pressures

Vapor and liquid equilibrium compositions are reported for the phenanthrene-toluene system at 593, 633, and 675 K and at pressures ranging from 7.3 bar to the binary mixture critical pressure at each temperature. Mixture critical pressures were obtained by visual observation of critical opalescence within a view cell. A flow apparatus for measuring VLE and LLE that is capable of operation at pressures up to 350 bar and temperatures to 675 K is also described. The apparatus can be used with materials such as phenanthrene and petroleum pitches which are solids at room temperature.     

Super-Strong Hydrogel Composites Reinforced with PBO Nanofibers for Cartilage Replacement

Cartilage replacement materials exhibiting a set of demanding properties such as high water content, high mechanical stiffness, low friction, and excellent biocompatibility are quite difficult to achieve. Here, poly(p-phenylene-2,6-benzobisoxazole) (PBO) nanofibers are combined with polyvinyl alcohol (PVA) to form a super-strong structure with a performance that surpasses the vast majority of previously existing hydrogels. PVA–PBO composites with water contents in the 59–76% range exhibit tensile and compressive moduli reaching 20.3 and 4.5 MPa, respectively, and a coefficient of friction below 0.08. Further, they are biocompatible and support the viability of chondrocytes for 1 week, with significant improvements in cell adhesion, proliferation, and differentiation compared to PVA. The new composites can be safely sterilized by steam heat or gamma radiation without compromising their integrity and overall performance. In addition, they show potential to be used as local delivery platforms for anti-inflammatory drugs. These attractive features make PVA–PBO composites highly competitive engineered materials with remarkable potential for use in the design of load-bearing tissues. Complementary work has also revealed that these composites will be interesting alternatives in other industrial fields where high thermal and mechanical resistance are essential requirements, or which can take advantage of the pH responsiveness functionality.     

Measuring the thermophysical properties of porous fibrous materials with a new unsteady-state method

In this article, the authors first introduced a theoretical model dealing with unsteady-state heat conduction in porous fabric to assess the effects due to local convection during the testing. A few important issues are analyzed including the criterion for local thermal equilibrium in the fibrous materials and the confidence time region (t _min–t _max) during measuring process. The influence due to different heat source capacities can be ignored if the measuring time is greater than the minimum time duration t _min , yet the heat loss via outside surface becomes negligible if the testing duration is below the maximum allowable value t _max. Accordingly an apparatus that can simultaneously measure two thermophysical properties (the thermal conductivity k and thermal diffusivity a) of fibrous materials is developed in this study, which then leads to the determination of the volumetric capacity via ρC = k/a. In order to minimize the influence of potential local micro heat convection and the contact resistance during heat transfer, some background, and stacking materials are adopted in the apparatus. The error range of the apparatus is estimated empirically based on the data from measuring some Perspex samples. Finally four kinds of polyester nonwoven fabrics with different porosities are tested using the device and the data analyzed and compared with theoretical predictions.     

An optical surface plasmon resonance biosensor for determination of tetanus toxin

Surface plasmon resonance (SPR) has been successfully applied for the simple, rapid, and label-free assay of various biomolecules. This assay evaluates a novel wavelength modulation SPR biosensor for the detection of tetanus toxin. The wavelength modulation SPR biosensor is designed based on fixing the incident angle of light and measuring the reflected intensities in the resonance wavelength range spanning 400-800 nm simultaneously. Tetanus toxin (TeNT), one of the most potent toxins known, is synthesized as a 150 kDa single polypeptide chain. The SPR biosensor has been shown to be capable of directly detecting concentration of tetanus toxin as low as 0.028 Lf ml⁻¹. Under selected experimental conditions, the SPR biosensor has a good reproducibility, sensitivity and reversibility. The results illustrate how wavelength modulation SPR biosensor can be used to detect biomolecular interactions.     

Determination of tensile strength of UHMWPE fiber-reinforced polymer composites

Quasi-static tensile test of UHMWPE fiber-reinforced composite laminate is challenging to perform due to low interlaminar shear strength and low coefficient of friction. Tensile tests proposed in the literature were conducted and limitations associated with each method led to the evolution of a new method. Tensile test of single-ply was realized as the best representative of tensile strength of a composite than tensile test of UHMWPE laminate. A fixture was developed for single-ply tests which increased friction and provided the mechanical constraint to slipping. The fixture is easy to fabricate and has provided repeatable results for eight grades of UHMWPE fiber-based (0/90) fabrics. Reported tensile strengths are in quite high range of 900–1500 MPa.     

Investigation of sub‐micron size cenosphere fillers and filler loading on the mechanical and tribological peculiarity of polyester composites

This paper investigates the effect of sub‐micron size cenosphere filler and filler loading on mechanical and dry sliding wear property of polyester composites. Composites are fabricated by filling with 10 and 20 wt% of 800 and 200‐nm size of cenosphere filler particles. Neat polyester composite is also prepared for comparison analysis. Dry sliding wear test is conducted for these composites over a range of sliding distance with different sliding velocities and applied loads on a pin‐on‐disc wear test machine. Taguchi methodology and analysis of variance (ANOVA) is used to analyze the friction and wear characteristics of the composites. The artificial neural network (ANN) approach is implemented to the friction and wear data for corroboration. In this work, mechanical properties of composites such as hardness, tensile strength, tensile modulus, flexural strength, and compressive strength revealed that mechanical properties and wear resistance of the composites increase with a decrease in the particle size. The measured Young's moduli are comparable to standard theoretical prediction models. The morphology of worn composite specimens has been examined by scanning electron microscopy to understand the dominant wear mechanisms. Finally, optimal factor settings are determined using a genetic algorithm (GA). Copyright © 2017 John Wiley & Sons, Ltd.     

An improved test method for characterising touch properties of porous polymeric materials

A new test method and instrument was developed to provide overall evaluation and characterisation of touch properties of porous polymeric materials. The test method and instrument can simulate the dynamic contact process between human skin and porous polymeric materials and obtain the mechanical and physical performance during contact. In the improved test method, a new measurement principle was proposed, and the mechanical device was redesigned, including surface friction measurement components. Most indices were redefined and the grading and classification methods were studied to give a direct overall evaluation of the touch properties for industrial applications. The objective test results and analysis, subjective evaluation method and prediction model of touch properties are also presented. The improved test method provides an objective measurement of thermal-mechanical properties using a single measuring instrument for new product development and quality control of porous polymeric materials.     

A simple test method for measuring water vapor resistance of porous polymeric materials

A simple test method is proposed for measuring water vapor resistance of fabrics. A piece of cotton fabric connected to a container filled with distilled water through a plastic tube was used on a hot plate to generate a saturated water vapor condition on one side of the sample. The temperature of the cotton fabric (approximation of human skin covered with sweat) was measured by a thermocouple. The water vapor resistance of the sample was determined based on the water vapor pressure gradient across the sample and the heat flux. Five types of textile fabric laminated to PU/TPU membranes, plus one type of conventional fabric, were tested by using this simple apparatus as well as the sweating guarded hot plate instrument. The results showed that good agreement was observed between these two test methods. In addition, the surface temperature of the cotton ‘skin’ varied with different fabrics. This is in accordance with the actual intended situation, i.e., the skin temperature of the body is related to the ability of clothing materials to transfer water vapor. Therefore, this simple test apparatus better simulates real-life conditions than the sweating guarded hot plate instrument.     

Application of the IFR portable pendulum for the assessment of the mechanical properties of solid foams

The use of the IFR portable pendulum, with further instrumentation, for assessment of the mechanical properties of solid foam structures is described. The instrument has been used to measure the resistance to penetration of various solid foamed foods produced by extrusion cooking. These data, obtained under high strain rate conditions of impact, provide an alternative to the use of low strain rate texture measuring apparatus based on tensile testing devices. The instrumented pendulum records the transient penetration of a hammer into the sample using an angular displacement transducer. The signal is acquired using a microcomputer and may be differentiated to obtain the instantaneous retardation. The restitution of the pendulum hammer is also recorded as a function of time to the point of initial contact with the specimen.     

Fabric Touch Tester: Integrated evaluation of thermal–mechanical sensory properties of polymeric materials

A new test apparatus was designed to evaluate the thermal–mechanical properties of fabric made from polymeric materials in one step. The results of statistical analysis reveal that the sensations of fabric–skin touch under non-sweating conditions like smoothness, softness, prickliness, warmth and dampness can be predicted using the measurements of this apparatus. Heat transfer properties (HF_min) in a fabric play an important role in warmth/dampness perception, which alone accounts for 63.6% and 56.0% of the variance in warmth and dampness perception, respectively. Fabric compression properties (FC_mean) account for 69.5%, 77.0% and 66.7% of the variance in smoothness, softness and prickliness perceptions, respectively.