Oligoethylsiloxanes

At present, industry produces a wide range of linear oligoorganosiloxanes with the same and different organic groups at the silicon atom however, the most widely used are oligomethylsiloxanes (PMS), oligoethylsiloxanes (PES), oligomethylphenylsiloxanes (PFMS) and their copolymers. 

Oligoethylsiloxanes are a mixture of liquid products, mainly of the linear structure ... 

Oligoethylsiloxanes are obtained by the hydrolytic condensation of ethylethoxysilanes synthesised by Grignard reaction, or by the hydrolytic condensation of diethyldichlorosilane with subsequent catalytic regrouping of the hydrolysis products. 

A. The production of oligoethylsiloxanes by the hydrolytic condensation of ethylethoxysilanes is described below. 

Oligoethylsiloxane production comprises three main stages the synthesis of ethylethoxysilanes the hydrolytic condensation of ethylethoxysi-... 

In the production of oligoethylsiloxanes by the continuous technique (Fig. 40) agitator 5 receives from batch boxes toluene, ethylchloride and tetraethoxysilane. The mixture is agitated for 30 minutes and checked for correct dosage. 

Fig. 40. Production diagram of oligoethylsiloxanes by the continuous technique 1-4, 9, 14, 17 - batch boxes 5, 21 - agitators 6, 36- reactors 7, 10, 11, 19, 26 - coolers 8 - forehydrolyser 12, 18, 23 - settling boxes 13 - neutraliser 15, 20, 24, 29, 40 - collectors 16 - hydrolyser 22 - heat exchanger 25 - distillation tank 27, 30, 33 - receptacles 28 - flusher 31 - purification apparatus 32 - nutsch filter 34 - pressure container 35 - circulation tube 37 - bubble tube 38 - separator 39 - trap 41 - container...

Fig. 41. Diagram of oligoethylsiloxane distillation and completion 1 - vacuum distillation tank 2, 4 - coolers 3 - receptacles 5 - batch box 6-8 - collectors 9 -completion and purification apparatus 10 - nutsch filter...

These liquids are semiproducts used to prepare oligoethylsiloxanes of various viscosity (by fraction distillation and completion). Oligoethylsiloxane combine nicely with organic oils and are also used to prepare heat resistant oils and lubricants. 

Distillation and completion of technical oligoethylsiloxanes In order to extract pure oligoethylsiloxanes the technical products obtained by the listed methods are distilled into fractions. 

The completion of oligoethylsiloxane liquids, which is conducted in apparatus 9, involves the preparation of marketable liquids from the corresponding fractions by mixing, further treatment with active coal (to eliminate residual acidity), decolouring and subsequent filtering in nutsch filter 10. 

Oligoethylsiloxanes and products based on them are as a rule transparent colourless nontoxic liquids. They can be used at operating temperatures ranging from -60-70° C to +180° C. The applications of these liquids are quite varied. They are used as coolants and heat carriers in hydraulic systems, as liquids for diffusion pumps, damping liquids and bodies for instrument oils and lubricants. 

Keywords oligoethylsiloxane, compositions, rheology, free volume theory... 

Summary Rheological properties of compositions containing oligoethylsiloxane, poly-a-olefin, and dioctylsebacinate were studied. Both energetic and structural factors were shown to affect the fluidity of compositions. 

Oligoethylsiloxane-based compositions with various lubricity-promoting additives are currently attracting much attention. Lubricity and behavior at low temperatures of such compositions have been thoroughly investigated [1]. 

Rheological properties of the oligoethylsiloxane-based compositions with additives are of vital importance for the selection of maintenance conditions of various items, but they have not been studied yet. No data on such composition-fluidity relationships (unconfined fluctuating free volume and viscous flow activation energy values) are available. 

Therefore, the study of rheological properties, the determination of the activation energy of viscous flow, composition-fluidity relationships, and key factor effects of the lubricity-promoting additive on the fluidity of oligoethylsiloxane-based compositions were of interest. 

Study of Rheological Properties of Oligoethylsiloxane-Based Compositions 663... 

Figure 2 demonstrates that the viscosity-temperature relationship revealed by plotting Xarj against I T-Tq) is linear for all compositions studied as well as for oligoethylsiloxane and additive. The calculations show that all the analyzed fluid flows within the analyzed temperature range with maximum relative error 2%, obeying the Falcher-Tamman equation (fiee volume concept) [3] ... 

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