Influence of Processing Variables on the Rheological Properties of Lubricating Grease Manufactured in a Stirred Tank

J. M. Franco,J. A. Garc?-Morales,C. Valencia,M. C. S?chez,C. Gallegos 한국공업화학회 2004 Journal of Industrial and Engineering Chemistry Vol.10 No.3

Influence of soap/polymer concentration ratio on the rheological properties of lithium lubricating greases modified with virgin LDPE

J.E. Martin-Alfonso,G. Moreno,C. Valencia,M.C. Sanchez,C. Gallegos,J.M. Franco 한국공업화학회 2009 Journal of Industrial and Engineering Chemistry Vol.15 No.5

The main goal of this work was to study the feasibility of using a low-density polyethylene (LDPE) as additive to improve the rheological properties of lithium lubricating greases. The combined effect that both soap and LDPE concentrations exerts on the rheology of lithium lubricating greases and its relationship with grease microstructure were studied according to an experimental design based on the response surface methodology (RSM). Different lubricating grease formulations were manufactured by modifying lithium 12-hydroxystereate and LDPE concentrations. Small-amplitude oscillatory shear (SAOS) and viscous flow measurements, as well as mechanical stability tests, were performed. In addition to these, environmental scanning electronic microscopy (ESEM) was used to determine grease microstructure. LDPE was found to be a useful additive to modify grease rheology, acting as filler in the entangled soap network. The values of both apparent viscosity and linear viscoelasticity functions increase with soap and LDPE concentration. However, the addition of LDPE distorts soapmicrostructural network, yielding greases with lower relative elastic characteristics.

Influence of Processing Variables on the Rheological Properties of Lubricating Greases Manufactured in a Stirred Tank

Garci´a-Morales, J. A.,Franco, J. M.,Valencia, C.,Sa´nchez, M. C.,Gallegos, C. 한국공업화학회 2004 Journal of Industrial and Engineering Chemistry Vol.10 No.3

This paper deals with the influence that the agitation speed, the temperature of processing, and the cooling profile applied during crystallization of the thickening agent exert on some rheological parameters of lubricating greases. With this aim, the in situ reaction between 12-hydroxystearic acid and lithium hydroxide was conducted to form the lithium soap. After the saponification reaction was completed, the crystallization was induced by adding different batches of the lubricating oil and cooling the stirred tank. Torque was measured during the process using a controlled-rotational-speed mixing rheometer from which the energy consumption during processing was evaluated. The Metner-Otto approach was followed to estimate the viscosity of the incipient and final lubricating greases. Linear viscoelastic and viscous flow measurements were performed on the final product. From the experimental results, we conclude that an increase in the temperature applied after the saponification reaction or a decrease in the cooling rate of the freshly prepared grease generally increases the values of the rheological parameters studied. On the other hand, by increasing the rotational speed, the values of the viscoelastic functions were significantly reduced. In addition to this finding, all of these variables affect the energy consumption during the processing. Discrepancies found in the viscosity values obtained from rotational rheometry and torque measurements during the mixing flow are attributed to the fractured layer observed in the gap between the wall and the impeller.

Rheological and mechanical properties of oleogels based on castor oil and cellulosic derivatives potentially applicable as bio-lubricating greases: Influence of cellulosic derivatives concentration ratio

R. Sanchez,J.M. Franco,M.A. Delgado,C. Valencia,C. Gallegos 한국공업화학회 2011 Journal of Industrial and Engineering Chemistry Vol.17 No.4

Nowadays the lubricating market is demanding new biodegradable or more environmentally acceptable products based on renewable resources as a consequence of progressively more strict environmental regulations. In this framework, this study deals with the design of gel-like dispersions potentially applicable as environmentally friendly lubricating greases. These dispersions were formulated using castor oil and ethyl cellulose/a-cellulose or ethyl cellulose/methyl cellulose blends. In particular, the influence of cellulosic derivatives concentration ratio on the linear viscoelasticity and mechanical stability of the resulting oleogel formulations was studied. The modification of ethyl cellulose/acellulose or ethyl cellulose/methyl cellulose weight ratios allows obtaining some formulations with suitable rheological characteristics and mechanical stability for potential lubricating applications. An important decrease in the values of the linear viscoelasticity functions down to a minimum value was found by increasing ethyl cellulose/a-cellulose or ethyl cellulose/methyl cellulose weight ratios (W) up to a critical value, which depends on both nature of the cellulosic derivatives employed and temperature. Above this critical value, the linear viscoelastic functions increase with W, at temperatures in the range 0–75 8C, and continuously decrease at higher temperatures, i.e. 125 8C. Thermal susceptibility is significantly dampened by reducing ethyl cellulose concentration. Gel-like dispersions formulated with ethyl cellulose/methyl cellulose blends showed appropriate mechanical stabilities to be used as biolubricating greases.

Role of TRPV4 Channel in Human White Adipocytes Metabolic Activity

Julio C. Sánchez,Aníbal Valencia-Vásquez,Andrés M. García 대한내분비학회 2021 Endocrinology and metabolism Vol.36 No.5

Background: Intracellular calcium (Ca2+) homeostasis plays an essential role in adipocyte metabolism and its alteration is associatedwith obesity and related disorders. Transient receptor potential vanilloid 4 (TRPV4) channels are an important Ca2+ pathway in adipocytes and their activity is regulated by metabolic mediators such as insulin. In this study, we evaluated the role of TRPV4 channelsin metabolic activity and adipokine secretion in human white adipocytes. Methods: Human white adipocytes were freshly cultured and the effects of the activation and inhibition of TRPV4 channels on lipolysis, glucose uptake, lactate production, and leptin and adiponectin secretion were evaluated. Results: Under basal and isoproterenol-stimulated conditions, TRPV4 activation by GSK1016709A decreased lipolysis whereasHC067047, an antagonist, increased lipolysis. The activation of TRPV4 resulted in increased glucose uptake and lactate productionunder both basal conditions and insulin-stimulated conditions; in contrast HC067047 decreased both parameters. Leptin productionwas increased, and adiponectin production was diminished by TRPV4 activation and its inhibition had the opposite effect. Conclusion: Our results suggested that TRPV4 channels are metabolic mediators involved in proadipogenic processes and glucosemetabolism in adipocyte biology. TRPV4 channels could be a potential pharmacological target to treat metabolic disorders.

Decellularization and In Vivo Recellularization of Abdominal Porcine Fascial Tissue

Sánchez Julio C.,Díaz Diana M.,Sánchez Leidy V.,Valencia-Vásquez Aníbal,Quintero Juan F.,Muñoz Laura V.,Bernal Andrés F.,Osorio Germán,Guerra Álvaro,Buitrago Juliana 한국조직공학과 재생의학회 2021 조직공학과 재생의학 Vol.18 No.3

BACKGROUND: Tissue decellularization has evolved as a promising approach for tissue engineering applications. METHODS: In this study, we harvested fascial tissue from porcine anterior abdominal wall and the samples were decellularized with a combination of agents such as Triton X-100, trypsin and DNAase. Afterwards, we evaluated cell removal by histological analysis and DNA quantification. Mechanical functionality was evaluated by applying a range of hydrostatic pressures. A sample of decellularized fascia was transplanted into a rabbit and after 15 days a biopsy of this tissue was examined; the animal was observed during 6 months after surgery. RESULTS: The extracellular matrix was retained with a complete decellularization as evidenced by histologic examination. The DNA content was significantly reduced. The scaffold preserved its tensile mechanical properties. The graft was incorporated into a full thickness defect made in the rabbit abdominal wall. This tissue was infiltrated by granulation and inflammatory cells and the histologic structure was preserved 15 days after surgery. The animal did not develop hernias, infections or other complications, after a 6-months of follow up. CONCLUSIONS: The protocol of decellularization of fascial tissue employed in this study proved to be efficient. The mechanical test demonstrated that the samples were not damaged and maintained its physical characteristics; clinical evolution of the rabbit, recipient of the decellularized fascia, demonstrated that the graft was effective as a replacement of native tissue.In conclusion, a biological scaffold derived from porcine fascial tissue may be a suitable candidate for tissue engineering applications. BACKGROUND: Tissue decellularization has evolved as a promising approach for tissue engineering applications. METHODS: In this study, we harvested fascial tissue from porcine anterior abdominal wall and the samples were decellularized with a combination of agents such as Triton X-100, trypsin and DNAase. Afterwards, we evaluated cell removal by histological analysis and DNA quantification. Mechanical functionality was evaluated by applying a range of hydrostatic pressures. A sample of decellularized fascia was transplanted into a rabbit and after 15 days a biopsy of this tissue was examined; the animal was observed during 6 months after surgery. RESULTS: The extracellular matrix was retained with a complete decellularization as evidenced by histologic examination. The DNA content was significantly reduced. The scaffold preserved its tensile mechanical properties. The graft was incorporated into a full thickness defect made in the rabbit abdominal wall. This tissue was infiltrated by granulation and inflammatory cells and the histologic structure was preserved 15 days after surgery. The animal did not develop hernias, infections or other complications, after a 6-months of follow up. CONCLUSIONS: The protocol of decellularization of fascial tissue employed in this study proved to be efficient. The mechanical test demonstrated that the samples were not damaged and maintained its physical characteristics; clinical evolution of the rabbit, recipient of the decellularized fascia, demonstrated that the graft was effective as a replacement of native tissue.In conclusion, a biological scaffold derived from porcine fascial tissue may be a suitable candidate for tissue engineering applications.

Thermo-rheological and tribological properties of novel bio-lubricating greases thickened with epoxidized lignocellulosic materials

E. Cortés-Triviño,C. Valencia,M.A. Delgado,J.M. Franco 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.80 No.-

We examined the rheological and tribological behavior of novel formulations based on castor oil andepoxidized cellulose pulp intended for use as biodegradable lubricating greases. Epoxidized cellulosepulp was found to thicken castor oil to a variable extent depending on its modification degree andthe epoxide compound. Greases were subjected to small-amplitude oscillatory shear tests, evaluating thetemperature-dependence of the plateau modulus. In addition, friction coefficient and wear weredetermined in a steel–steel ball-on-three-plates tribological configuration, at two different temperatures(25 and 95 C), generally obtaining smaller values of both parameters when using aromatic diepoxidesinstead of aliphatic to modify the cellulose pulp.

Formulation and processing of virgin and recycled polyolefin/oil blends for the development of lubricating greases

J.E. Martın-Alfonso,A. Romero,C. Valencia,J.M. Franco 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.2

This work has been focused on the development of polyolefins/oil blends potentially suitable as lubricating greases by studying the effect that some thermo-mechanical processing variables exert on their rheological properties and microstructure. Polyolefin/oil blends have been prepared by dispersing recycled and virgin polyolefins such as high-density polyethylenes (HDPEs) and polypropylenes (PPs) in mineral lubricating oil. Linear viscoelasticity functions have been significantly influenced by processing conditions. The nature of polymers used, specially the content of HDPE, has been found to modify the microstructure of blends yielding lower mechanical stability but, on the other hand, higher values of linear viscoelastic functions.

Formulation of new biodegradable lubricating greases using ethylated cellulose pulp as thickener agent

J.E. Martin-Alfonso,M.J. Diaz,N. Nunez,C. Valencia,J.M. Franco 한국공업화학회 2011 Journal of Industrial and Engineering Chemistry Vol.17 No.6

The influence of cellulose pulp ethylation processing conditions has been evaluated to design suitable renewable and biodegradable lubricating greases from cellulose pulp-based gel-like dispersions. Ethyl/glucose molar ratio (E/G) has a positive effect on the ethyl groups degree of substitution (DS). Gel-like biodegradable dispersions of cellulose pulp in castor oil have been prepared by adding ethylated cellulose samples differing in the substitution degree to modify the rheological properties of castor oil. The rheology of ethyl cellulose/castor oil binary systems is highly influenced by DS. The linear viscoelastic functions and consistency are very similar to those found in traditional lithium lubricating greases.

Reconstruction methodology of a Francis runner blade using numerical tools

Giovanni Delgado,Sergio Galván,Francisco Dominguez-Mota,J. C. García,Esteban Valencia 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.3

In a hydraulic turbine, the search of a better energy exchange with the fluid has led to designs of runner blade of geometrical shapes so complex that they are considered as free-form surfaces. Since such blade characteristics are unable to be expressed by analytic functions, its complete and realistic geometrical reconstruction requires an excessive quantity of design parameters. This study proposes a coherent and robust full 3D blade numerical reconstruction methodology in which the geometrical definition of the blade is independent of its design parameters. A quantitative and qualitative fit evaluation shows that the blade surface reconstruction needs an important quantity of discrete data along the spanwise and streamwise direction to achieve a continuous and smooth definition. The results infer that the shape characteristics of damaged and worn blades without an original CAD model could be recovered, making this methodology attractive for industrial and optimization applications.