Polymerization under Centrifugal Force

The last method used to prepare GI preforms employs centrifugal force. This method is divided into two categories based on the role of centrifugal force in forming the GI profiles. 

The first category of the method was developed by Van Duijnhoven et at. in 1999 [13,14]. In their study, distilled MMA and 2,2,3,3-tetrafluoropropylmethacrylate (TFPMA) were utilized as the base material. First, TFPMA was thermally polymerized with benzoyl peroxide (BPO) in bulk in a vacuum-sealed glass tube. 

Lorentz-Lorenz equation. These results show that poly(TFPMA) and PMMA are not completely separated by the centrifugal force, and the composition of the blend polymer gradually changes along the radial direction. The magnitude of the gradients was also confirmed to be dependent on the rotational speed. 

The refractive index profile of Gl POFs prepared by the extrusion method can also be predicted prior to the actual fabrication. The diffusion phenomena of dopants in polymers while passing through the diffusion section can be described by the advection-diffusion equation [20] 

c is the dopant concentration, t is the diffusion time, is the mutual diffusion coefficient, u is the velocity field, and r and z are the positions in the radial and vertical directions of the diffusion section, respectively. The mutual diffusion coefficient is exponentially dependent on the dopant concentration as 

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Solid surfaces, particularly those easily wetted by the dispersed phase, can be major collectors of drops. In the case of a rotating impeller, drops collect and coalesce on blade surfaces to form a condensed film. As this film grows in thickness, it flows under centrifugal forces to the impeller tips and disperses into tiny drops. This process is similar to the breaknp of a cylindrical Uqnid jet. A film of dispersed phase can also collect on free snrfaces, baffles, tank walls, and the impeller shaft, where the surface vortex meets the shaft. In the case of emulsion and suspension polymerization, coalescence also leads to fonUng of heat transfer surfaces. 

Typical cyclic voltammograms were recorded during electropolymerization of aniline at various centrifugal accelerations (Fig. 4). Although their shape seems to be similar, oxidation and reduction peak currents are increased at 315 g (electrode A) and decreased at 290 g (electrode B - with a reversed direction force), compared to electropolymerization performed under 1 g. Using the anodic peak current around 0.5 V as an indicator, polymerization rate appears to be... 

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