Viscosity Improver

Butyl mbber, a copolymer of isobutjiene with 0.5—2.5% isoprene to make vulcanization possible, is the most important commercial polymer made by cationic polymerization (see Elastomers, synthetic-butyl rubber). The polymerization is initiated by water in conjunction with AlCl and carried out at low temperature (—90 to —100° C) to prevent chain transfer that limits the molecular weight (1). Another important commercial appHcation of cationic polymerization is the manufacture of polybutenes, low molecular weight copolymers of isobutylene and a smaller amount of other butenes (1) used in adhesives, sealants, lubricants, viscosity improvers, etc. 

Viscosity improvers are primarily used in multigrade automotive engine oils, automatic transmission oils, power steering fluids, and gear oils. They also find use in aircraft and some industrial hydrauHc fluids for low temperature use. 

Spray-dried powders find application in adhesives to build solids, increase viscosity, improve tack, and decrease drying time (145). A primary use is in joint compounds with other applications in mastics and grouts, and patching compounds (146). 

Metal- Working and Hydraulic Fluids. In the preparation of fluids for metal-working and hydrauflcs, the trend has been to replace organic-based materials with aqueous-based materials. Neodecanoic acid has found apphcation in these newer fluids as a corrosion inhibitor and a viscosity improver. For example, neodecanoic acid is used in an aqueous hydrauflc fluid concentrate for corrosion inhibition and improved antiwear properties (101), in the preparation of a thickened aqueous hydrauflc fluid to reduce viscosity loss (102), and in a water-soluble metal working oil to reduce corrosion (103). In a similar vein, neodecanoic acid has been used in antifreeze concentrates for corrosion inhibition (104). 

Resin Low MW (<5000) Tg usually > RT Amorphous Lower viscosity Improve wet out Adjust Tg of system... 

Paraffin crystalline waxes Apart from asphaltenes, a number of differing molecular weight paraffinic waxes are also present. These progressively crystallize at lowering temperatures (their respective pour points). These waxes increase friction and resistance to flow, so that the viscosity of the fuel is raised. This type of problem is controlled by the use of pour-point depressants (viscosity improvers), which limit the growth of the crystals at their nucleation sites within the fuel. They also have a dispersing effect. 

Cold flow improvers (pour point depressants) These viscosity improvers are often specified in cold climates for unheated gas oil or where existing residual oil heaters are inadequate. The use of these paraffin crystal modifiers permits fuel to continue to flow at temperatures of 30 to 40 °F lower than the point at which wax crystallization would normally occur. 

All these capabilities enable to address the search for new enzymes for specialty applications, such as thermostable and solvent resistance enzymes. A viscosity improving thermostable enzyme family (Pyrolase 160 and Pyrolase 200, the later working at higher temperatures) was designed for use in deep and high temperature oil wells. Sales of this product commenced in January 1999, but were discontinued later. 

The importance of temperature control of the GPC column cannot be overstated. The use of temperatures above ambient results in lower mobile-phase viscosity, which in turn reduces the back pressure generated by the column. Column life is prolonged, and in some cases higher flow rates may be employed. The reduction in mobile-phase viscosity improves both the rate and efficiency of mass transfer processes, enhancing column performance. While... 

Like dissolves like, and this is true with both polymers and smaller molecules. Thus linear amorphous polymers with nonpolar groups are typically soluble in nonpolar solvents with solubility parameter values within 1.8 H of that of the polymer. Thus polyisobutylene (PIB) is soluble in hot lubricating oils, and small amounts of high-molecular-weight PIB are used as viscosity improvers. 

If PIB or other related polymers are not soluble in the oil at room temperature, they have little effect on the viscosity of the oil under these conditions. However, if these polymers are soluble in hot oil, they will typically increase the viscosity of the hot oil and can be used as viscosity improvers. 

Research Focus Preparation of poly acrylate viscosity improvers containing grafted iV-phenyl-p-phenylenediamine as an antioxidant. 

Originality Departure from using oil viscosity improvers based on poly(ethylene-co-... 

Observations Most automotive oil viscosity improvers are based on shear stable... 

The WTD is a cumulative rating based on observation of deposits in the groove and land areas of the piston and lacquer on piston skirts which have been weighted and calculated in accordance with the test procedure. The evalated lubricating oils also contained, where required, conventional viscosity improver, a metal detergent and ZDDP in mineral base oil. The WTD ratings were as follows ... 

Environmental demands and are as follows (a) improved fuel economy (reduced viscosities, reduced friction, special viscosity improvers), (b) reduced oil consumption (unconventional base oils, improved seal compatibility), (c) extended oil life (improved thermo-oxidative stability), (d) extended engine life (improved detergents and antiwear additives), (e) beneficial effects on emission/after treatment hardware (new additives), (f) technological and environmental sensitivity (no halogens, limited metal types/concentrations, new organic compounds), (g) recyclability (limitations the polycyclic aromatic hydrocarbons content and high chlorine levels (Havet et al., 2001 Waara et al., 2001). 

Total removal of phosphorus and sulfur would require the use of synthetic base-oils and new additive systems to provide antiwear antioxidation protection. Synthetic base-oil PAOs or esters have high values of viscosity improver VI and low temperature operating properties. The lubricants in diesel engines require a reduction in Ca carbonate-sulfonate concentrations. This may be less of a problem when ultra low sulfur diesel fuel is widely deployed, since a significant part of the requirement for these additives arises from the need to neutralize sulfur oxides from combustion processes. 

Reduced hot-paste viscosity, improved gelling59 Improved batter adhesion61... 

Since the viscosity of ionic liquids is large in some cases and concomitantly the diffusion is slow, ionic liquids generally exhibit a lower conductivity than aqueous electrolytes. To improve the mass transport it has been suggested to add diluents like benzene, toluene or acetonitrile. Water may also be a suitable diluent in some cases, acting as both a ligand and a viscosity improver. 

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