Polydimethylsiloxane fluid

It has been shown (16) that a stable foam possesses both a high surface dilatational viscosity and elasticity. In principle, defoamers should reduce these properties. Ideally a spread duplex film, one thick enough to have two definite surfaces enclosing a bulk phase, should eliminate dilatational effects because the surface tension of an iasoluble, one-component layer does not depend on its thickness. This effect has been verified (17). SiUcone antifoams reduce both the surface dilatational elasticity and viscosity of cmde oils as iUustrated ia Table 2 (17). The PDMS materials are Dow Coming Ltd. polydimethylsiloxane fluids, SK 3556 is a Th. Goldschmidt Ltd. siUcone oil, and FC 740 is a 3M Co. Ltd. fluorocarbon profoaming surfactant. 

Figure 4. Plot of Ln D versus Ln (molecular weight) for a series of low-molecular-weight linear dimethylsiloxanes in polydimethylsiloxane fluid. Numbers at each data point refer to N, defined by chemical formula. Data from Ref. 10.

The loss index of silicone elastomers made from polydimethyl siloxane, generally speaking, is low due to their low values of dielectric constant and loss tangent. The dielectric constant of polydimethylsiloxane is almost independent of the frequency, where as the tan 6 is highly dependent on the frequency in the micro-wave region (3, 4 ) At 3 x 109 Hz, a 1000 cs polydimethylsiloxane fluid has a tan 6 of about 0.0096 and a dielectric constant of 2.76. This gives a loss index of 0.0264, which puts polydimethyl siloxane in the poor heatability category. 

Table 1. Properties of pre-devolatilized 30 000 cts polydimethylsiloxane fluid prepared using ...

When polydimethylsiloxane fluids are irradiated in the presence of anthracene, the additive is incorporated into the macromolecular system [365]. The kinetics of anthracene disappearance has been studied and interpreted by Jenkins [365] in terms of a theory assuming that the active centres (probably radicals) are produced at random and that they disappear either by reacting with the additive or with neutral molecules, but not with each other. 

Chem. Descrip. Fumed silica, polydimethylsiloxane fluid-surface treated CAS 67762-90-7... 

Table 4 Correlation Between Viscosity and Molecular Weight of Commonly Utilized Polydimethylsiloxane Fluids... 

As mentioned above, the use of cationic surfactants and polymers in a shampoo or conditioner formulation to increase deposition of unmodified polydimethylsiloxane fluids... 

Ducom G, Laubie B, Ohannessian A, Chottier C, Germain P, Chatain V (2013) Hydrolysis of polydimethylsiloxane fluids in controlled aqueous solutions. Water Sci Technol 68 813-820... 

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