摘要:

AbstractUsed oils constitute a potential health hazard. Every year several million tons of used oils are released into the environment. At present, environmentally friendly synthetic oils, e.g., esters, are used as alternatives to conventional oils produced from petroleum. The aim of the present work has been to synthesise ester oils and determine their properties, particularly in terms of their biodegradability. Using dimethyl adipate, dimethyl sebacate, and neopentyl glycol as starting materials, oligomer esters with different ranges of molecular mass were synthesised. The syntheses were based on transesterification reactions catalysed by calcium methoxide. The degree of oligomerisation was closely correlated with the molar ratio of the esterification substrates. The esters showed physicochemical properties appropriate for use as synthetic lubricants. Both adipic acid esters and sebacic acid esters are characterised by high biodegradability. The biodegradability depends only slightly on the degree of oligomerisation of the ester molecules. The esters studied were considered as environmentally friendly high‐performance functional fluid

ISSN:0265-6582    

DOI:10.1002/jsl.3000200402

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractMost lubricants and functional fluids worldwide are based on mineral oil. These fluids contain up to 10% of a wide variety of additives for the improvement of their tribological properties. Several of these are still ecologically hazardous.From an environmental point of view, the use of renewable feedstock is of great interest. In Europe rape seed oil is available in substantial amounts and its esters (triglycerides, esters with saturated or partly unsaturated acids) to some extent display better tribological properties than conventional lubricants. The aim of the work which is presented here has been to improve the stability of these types of ester and their derivatives with regard to oxidation and hydrolysis. This can be done by the addition of different carboxylic acids and alcohols, of various complexities, to the double bonds. This paper deals with the indirect addition of different alcohols, such as methanol, isobutanol, and neopentanol, to the double bond of methyl oleate, and the addition of methanol to the double bonds of glycerin trioleate using the corresponding epoxides as intermediates. The reactions were carried out with environmentally friendly heterogeneous catalysts. Several tests, such as for viscosity, oxidation stability, and biodegradability, were carried out to demonstrate the potential of these newly developed fluids for use as lubricants.

ISSN:0265-6582    

DOI:10.1002/jsl.3000200403

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractSilahydrocarbons are members of a relatively new class of liquid lubricants with great potential for use in space mechanisms. They are unimolecular species consisting of silicon, carbon, and hydrogen. They possess unique wear, viscosity, and volatility properties while retaining the ability to solubilise conventional additives. The tribological properties of several members of this class, including tri‐, tetra‐, and penta‐compounds, are presented. These properties include viscosity‐temperature, viscosity—pressure, vapour pressure, lubricant life, traction, and reciprocating and four‐ball wear rates. Lubricant lifetimes were determined using a vacuum ball bearing simulator, the spiral orbit tribometer. Wear was measured using a Cameron Plint reciprocating tribometer and wear rates with a vacuum four‐ball tribometer. Conventional viscometry was used for viscosity—temperature measurements and a Knudsen cell for vapour pressure. Thermogravimetric analysis was also used for volatility measurements. Pressure—viscosity coefficients (α—values) were estimated from elastohydrodynamic lubrication film thickness measurements. These properties are compared to those of existing state‐of‐

ISSN:0265-6582    

DOI:10.1002/jsl.3000200404

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractNew sets of equations have been constructed from the density‐pressure‐temperature and viscosity‐pressure‐temperature relationships to determine the rheology of synthetic lubricants at high pressure. A phase diagram was first plotted for the oils up to a pressure of 1.2 GPa and temperatures from 303 to 353 K using high‐pressure density experimental results and others. For the oils at temperatures of 313, 333, and 353 K, the high‐pressure viscosity experiment was done up to a viscosity of 104Pa s and up to a pressure of 0.4 GPa. A relationship, based on free volume theory, between pressure and temperature with varying density and viscosity was proposed. It was found that the new equations from these relationships could predict the high‐pressure rheology more closely than those of previous researchers. Moreover, it was shown that the Ehrenfest equation or the gradient of the phase diagram is closely related to the expansion coefficient o

ISSN:0265-6582    

DOI:10.1002/jsl.3000200405

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

摘要:

AbstractGearings and bearings are machine elements that are subjected to heavy tribological stresses. The pressures are high in the rolling contacts of these machine elements, and this leads to slippage between the surfaces of the contact partners. Correspondingly, the demands on the lubricants are also quite high. Nowadays, additives are used to reduce the friction and wear. However, the biodegradability of additivated lubricants is often not known, although the use of such lubricants can be critical for the environment. The objective of the investigations described in the present paper is to find a way of using lubricants with as few additives as possible but without decreasing the capability, reliability, and life of the machine elements. Thin coatings seem to be a good solution to substitute for the additives. The wear protection of coatings is investigated here with respect to gearings and spindle bearings for machine tools.

ISSN:0265-6582    

DOI:10.1002/jsl.3000200406

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

ISSN:0265-6582    

DOI:10.1002/jsl.3000200407

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

ISSN:0265-6582    

DOI:10.1002/jsl.3000200408

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

ISSN:0265-6582    

DOI:10.1002/jsl.3000200409

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY

ISSN:0265-6582    

DOI:10.1002/jsl.3000200401

出版商:John Wiley&Sons, Ltd    

年代:2004

数据来源: WILEY