Values Of Surface Roughness Parameters Research Articles

Blocked polyisocyanates containing monofunctional polyhedral oligomeric silsesquioxane (POSS) as crosslinking agents for polyurethane powder coatings

Blocked polyisocyanate crosslinkers for powder coatings were synthesized using alicyclic diisocyanates (TMDI and IPDI), formic acid, (methylaminopropyl)hepta(isobutyl)Si8O12 (POSS), ɛ-caprolactam, dibutyltin dilaurate as well as triethylamine as catalysts. The chemical structures of these compounds were characterized by means of IR, 1H NMR and 13C NMR spectroscopy. The three-dimensional surface topography and surface chemical structure of the resulting powder coatings were investigated by using confocal microscope and ATR FT-IR. The values of surface roughness parameters were calculated. The surface topography was correlated with the chemical structure of the coatings and macroscopic surface behaviour: surface free energy, abrasion resistance, hardness, adhesion to the steel surface and impact resistance. Thermogravimetric analysis was employed to assess the hardening property of powder coatings and the thermal decomposition processes.

Examination of the Enzyme Resistance of Polyurethane Powder Coatings

Polyurethanes powder lacquers were obtained in a reaction hydroxy terminated polyester resin RUCOTE 102 and blocked polyisocyanate crosslinkers. The polyisocyanates were synthesized using alicyclic diisocyanates (IPDI and H12MDI) and monohydric aliphatic alcohols as well as dibutyltin dilaurate and triethylamine as a catalysts. The biodegradation experiments were realized in solution consisted of lipase (Novozym 735, Novozym 51,032, Lipolase 100L or Palatase 20,000) and phosphate buffer during 42 days at 37 °C. The biodegradation progress was controlled by using optical microscopy method, thermal analysis TG/DTA, DSC method, surface free energy parameters, total organic carbon measurements and sample weight loss. The three-dimensional surface topography of the powder lacquers by means of confocal microscope was investigated. The values of surface roughness parameters were calculated.

Blocked polyisocyanates containing fluorine atoms as crosslinking agents for polyurethane powder coatings

AbstractUsing alicyclic diisocyanates (HDI, TMDI, IPDI, H12MDI), aliphatic unfluorinated and fluorinated alcohols, dibutyltin dilaurate as well as triethylamine as catalysts, blocked polyisocyanate crosslinkers for powder lacquers were synthesized. The chemical structure of these compounds was characterized by means of IR, 1H‐NMR, 13C‐NMR, and 19F‐NMR spectroscopy. Their molecular weight distribution parameters were determined by gel permeation chromatography. These blocked polyisocyanates were used for the production of powder lacquer compositions and coatings. The three‐dimensional surface topography and surface chemical structure of the resulting powder lacquers were investigated by means of confocal microscope and ATR FT‐IR. The values of surface roughness parameters were calculated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Estudio del mojado y caracterización superficial por microscopía de barrido laser confocal de chapas de madera obtenidas por desenrollo

The aim of this work was to study the surface properties of rotary-peeled veneers of five species of hardwoods: okume, ayous, poplar, fromager and eucalyptus and to compare the behavior of both sides of the veneers. The equilibrium contact angles were determined together with the wood surface free energy and its polar and disperse components. Additionally, surface roughness was evaluated using confocal laser scanning microscopy. Surface free energy ranged from 49-64 mJ/m 2 and decreased in the order okume> fromager> poplar> eucalyptus ~ ayous, indicating a decrease in wettability in that order. Okume wood with the highest value of the surface free energy and the lowest values of the equilibrium contact angle was confirmed as the species with the best wetting properties, and also presented the highest values of surface roughness parameters. In general, there were not significant differences between the properties of both sides of the veneers, except for roughness. The largest differences were obtained for okume veneers whose interior side showed higher wettability.

Ge growth on self-affine fractal Si surfaces: influence of surface roughness

We have studied the influence of substrate surface roughness on the growth of Ge on self-affine fractal Si surfaces. Self-affine fractal surfaces can be prepared by irradiating surfaces of solid materials with an energetic ion beam, which modifies the surface morphology predominantly via an erosion process. By tuning the ion beam energy, surface parameters such as surface roughness (σ0) and correlation length (ξ), can be controlled. Values of σ0 and σ0/ξ affect the effective free energy of the surface. When materials are grown on surfaces with different values of surface roughness parameters, the morphology of the deposited layer is expected to be influenced. In comparison with an earlier study where 2 MeV Si ion irradiation was used, we have produced surfaces with larger values of σ0 and σ0/ξ by irradiating the surfaces with 45 keV Si ions. We have made a comparison for Ge growth on Si surfaces irradiated with 2 MeV and 45 keV Si ions and have observed remarkably different growth behaviour. Upon Ge deposition, in the former case, the surface roughness decreases at smaller length scales and remains practically unchanged at larger length scales. This indicates that Ge has grown preferentially within the valleys of the rough surface. In the latter case, where σ0 is large and ξ is small on the substrate surface, the roughness increases at all length scales by almost a factor of 2, upon Ge deposition, indicating the lack of preferential growth within the surface valleys. Following Ge deposition, in the former case the roughness exponent increases from 0.82 to 0.99, while in the latter case it remains practically unchanged (∼0.83). Roughness parameters of the substrate surface are found to have a significant influence on the morphology of the overlayers.

Study of orifice compensated hole-entry hybrid journal bearing considering surface roughness and flexibility effects

The present work describes a theoretical study to demonstrate the combined influence of surface roughness and bearing flexibility on the performance of an orifice compensated hole-entry hybrid journal bearing system. The average Reynold equation governing the flow of lubricant in the clearance space between rough journal and bearing surfaces and 3-dimensional elasticity equation governing the displacement field in the bearing shell have been solved simultaneously using finite element method. The influence of transverse, isotropic and longitudinal roughness patterns on the performance of orifice compensated hole-entry journal bearing configuration have been studied for the various values of surface roughness parameter ( Λ), surface pattern parameter ( γ) and bearing shell deformation coefficient ( D ¯ c ) . The study indicate that the reduction in the bearing characteristic parameters such as load carrying capacity, fluid-film stiffness and damping coefficients due to the bearing shell flexibility effect can be partially compensated in roughened hole-entry flexible journal bearing system by making a proper selection of roughness patterns. The results presented in the study demonstrates that for an accurate prediction of bearing characteristic data, the consideration of combined influence of surface roughness and bearing flexibility effects in the analysis may be more appropriate to use.

The effects of cut-off length on surface roughness parameters and their correlation with transition friction

Surface roughness affects friction, but it is not clear which surface roughness characteristics are better correlated with friction. The surface roughness parameters generated from quarry tiles were correlated with the transition friction between the tiles and a commonly used sole testing material, Neolite, with three different mixtures of glycerol and water as contaminants at the interface. Measurement of surface roughness usually requires removing the waviness portion from the measured profiles in order to focus on the surface features of interest through the selection of different cut-off lengths for filtering. The effect of cut-off length on the values of surface roughness parameters and their correlation with transition friction were investigated. The correlation coefficient between the surface roughness parameters and the measured friction was affected by the glycerol contents. The cut-off lengths of 2.5 and 8 mm resulted in stronger correlated surface roughness parameters than that of 0.8 mm. The surface parameters Δ a, R pm, R k, R 3 z and R a had a stronger correlation with the transition friction than other surface parameters examined in this study.

Influence of surface roughness effects on the performance of non-recessed hybrid journal bearings

The effect of journal and bearing surface roughness on the performance of a capillary compensated hole-entry hybrid journal bearing system has been theoretically studied. The analysis considers the average Reynold’s equation for the solution of lubricant flow field in the clearance space of a rough surface journal bearing system. The finite element method and Galarkin’s technique has been used to derive the system equation for the lubricant flow field. The non-dimensional parameters Λ (surface roughness parameter) and γ (surface pattern parameter) have been defined to represent the magnitude of height distribution of surface irregularities and their orientation, respectively. The influence of surface roughness on the bearing performance has been studied for the transverse, isotropic and longitudinal surface patterns. The bearing performance characteristics have been computed for both symmetric and asymmetric capillary compensated hole-entry journal bearing configurations for the various values of surface roughness parameter (Λ), surface pattern parameter ( γ) and restrictor design parameter ( C ̄ S2 ). The computed results indicate that the inclusion of surface roughness effects in the analysis affects the performance of a bearing quite significantly vis-à-vis smooth surface bearing. The study indicates that for generation of accurate bearing characteristic data, the inclusion of surface roughness effects in the analysis is essential.

Combined Influence of Journal Misalignment and Surface Roughness on the Performance of an Orifice Compensated Non-Recessed Hybrid Journal Bearing

The combined influence of surface roughness and journal misalignment on the performance of an orifice compensated hole-entry hybrid journal bearing system is theoretically studied. The analysis considers the average Reynolds equation for a rough surface for the solution of the lubricant flow field in the clearance space of a journal bearing system. The bearing performance characteristics are presented for the various representative values of surface roughness parameter (Λ) and surface pattern parameter (γ) for a concentric design pressure ratio β* = 0.5. Performance is also compared to capillary and constant flow valve compensated bearings. The computed results indicate that the effect of journal misalignment is to lower the value of the minimum fluid-film thickness of the journal bearing system while the effect of surface roughness is to partially compensate this loss. For the chosen values of journal misalignment parameters (ϕ, δ), the constant flow valve compensated symmetric journal bearing configuration with longitudinal roughness pattern (γ = 6) shows an improvement of around 20% in the value of stability threshold speed margin. Presented at the 57th Annual Meeting in Houston, Texas May 19–23, 2002

Atomic force microscopy of dense and asymmetric cellulose-based membranes

The surface structures of dense and integrally skinned cellulose acetate (CA) and cellulose acetate butyrate (CAB) membranes, prepared by phase inversion under different casting conditions, are investigated by tapping mode atomic force microscopy (TM AFM). The results obtained show that: (i) The top and bottom surfaces of the dense CA membrane were quite uniform in comparison with the corresponding faces of asymmetric CA and CAB membranes. Despite the casting conditions the active and support layers of the asymmetric membranes display large differences on the roughness parameters. (ii) The asymmetric membranes prepared with an organic system as a non-solvent pore-former (method IV) display smaller nodule aggregates and lower values of the roughness parameters than the ones prepared using an inorganic system as swelling agent (method I). This is more pronounced for the CA membranes than for the CAB membranes. (iii) In the active layer of asymmetric CA membranes casted at longer evaporation times, the measured values of surface roughness parameters tend to decrease. Also, for these CA membranes, as the evaporation time increases the average size of the depression areas observed on the surface decreases. The laboratory-made CA and CAB membranes display a wide range of nanofiltration and reverse osmosis permeation characteristics. These characteristics are correlated to surface roughness parameters of the active layers.

An Enhanced End Milling Surface Texture Model Including the Effects of Radial Rake and Primary Relief Angles

An enhanced surface texture model for predicting the two- and three-dimensional structure of the surface generated by the end cutting edges on the bottom of an end mill is presented. This model includes the effects of the radial rake and the primary end tooth relief angles which have been neglected in the models available to date. Non-ideal effects such as cutter runout and back-cutting are explicitly modeled. An algorithm to simulate the two- and three-dimensional milled surface is presented. It is shown that the main effect of the radial rake and the primary end tooth relief angles is to increase the surface roughness parameter values. The effectiveness of the enhanced model in accurately capturing the major features of the machined surface texture and in closely predicting the roughness parameter values is demonstrated through experiments and model simulations. It is shown that the enhanced model predicts both the shape of the surface profile and the surface roughness parameters more accurately than the existing models in the literature.