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Really Long Term Life

March 18, 2011

Really Long Term Life

In my December 29, 2010 post, Wonderer in the Wilderness inquired…

1. How can Novinium get the same cable life extension without a soak period? It would seem to me that Novinium puts less fluid into the cable than one would get with a soak period.

In my first post addressing this question I provided an abbreviated answer. We learned from the abbreviated answer that that when Novinium founders conceived of the first generation of treatment fluid over two decades ago, there was a failure to check the relative diffusion rates of the phenylmethyldimethoxysilane (PMDMS) monomer and the condensation catalyst we had chosen to provide long life. This turned out to be a grave mistake, which we have corrected. In a subsequent post on January 3, 2011, Catalytic Considerations – Component I, I provided a more comprehensive answer, but I promised five new posts that would explain the functional improvement of the five kinds of ingredients in Cablecure 732 [Ultrinium™ 732] and Cablecure 733 [Ultrinium™ 733] fluids. In this last of those five sub-posts, I explain how a component with a really ugly name provides extraordinarily long life. Chemists call the material found in Cablecure 732/733 [Ultrinium™] fluids cyanobutylmethyldimethoxysilane (Pronounced: Sigh-an-Oh•butte-ill•meth-ill•die-meth-ox-ee•sigh-lane); we will call it CBMDMS for short.

3D rendering of CBMDMS or cyanobutylmethyl-dimethoxysilane (and proper pronunciation)

In the graph nearby I explain the first dimension of why CBMDMS works so well for so long. The graph plots the “permeation product” of the three most commercially important rejuvenation silanes. Permeation is the product of the diffusion coefficient and the solubility of the material in cross-linked polyethylene (XLPE). The rate of fluid exudation from a cable is directly proportional to this permeation product. Remember that if a fluid exudes out of the cable, it is not providing any life extension benefit. The lower the permeation value, the longer the fluid will stay in the cable. The permeation of the primary ingredient in Novinium’s Cablecure iXL [Perficio™ 011] fluid and other older technology fluids is illustrated by the light-blue-colored (upper-most) line over the range of 15 to 90°C. This fluid is called phenylmethyldimethoxysilane (Pronounced: Fen-ill•meth-ill•die-meth-ox-ee•sigh-lane) by chemists; we will call it PMDMS. In a recent post, Chain Entanglement, I explained how extending the length of the side chains entangled the silicone in the polyethylene polymer chains and slowed the diffusion. The orange line shows the advantage enjoyed by tolylethylmethyldimethoxysilane (Pronounced: Tall-ill•eth-ill•die-meth-ox-ee•sigh-lane by chemists) or TEMDMS, which is a result of this chain entanglement. The permeation rate and proportional exudation rate of TEMDMS, is always lower than that of PMDMS. At low temperature they are about the same, but at 75°C, the TEMDMS permeates about 5-times slower. But the focus of this post is the amazing CBMDMS, which enjoys a 25-fold to 45-fold permeation advantage over the PMDMS. That’s a really big deal! At 75°C CBMDMS will outlast PMDMS by a factor of 45!

TEMDMS and CBMDMS are available only from Novinium, as their use is protected by U.S. Patent 7,643,977, other pending applications, and their foreign equivalents.

The second really cool thing about CBMDMS, besides its incredibly long persistence in the cable, is how it works. If you look carefully at the CBMDMS molecule just below its permeation line in the graph or in the video, you may notice the feature from which it gets its name  A carbon-nitrogen triple bond and an unbonded pair of electrons make a cyano-group. This cyano-group (alternatively called a nitrile-group) is very polar, that is, it has a positive end and a negative end. Consequently, CBMDMS has a very high dielectric constant. Its dielectric constant is between 50 and 100, which puts it on par with the dielectric constant of pure water. Ultrapure water is used in high voltage electrical laboratories’ water terminations to grade electrical stress.

The cyano-group, found only in Novinium rejuvenation products, grades stress in the same way, but at the nano-scale. Before I explain how this works we need to define a thermonuclear-sized word: dielectrophoresis, pronounced die-EE-lek-trow-for-EE-sis or DEP for short. DEP is a phenomenon in which a force is exerted on a dielectric molecule when it is subjected to a non-uniform electric field—the greater the dielectric constant of the material, the greater the force. The illustration nearby explains how the diverging electrical field near an imperfection imparts a force upon CBMDMS molecules and draws them into the local-region of highest electrical stress. The presence of the high dielectric constant material smoothes the electrical stress and interferes in several ways with dielectric failure mechanisms:

1.    The local AC stress is reduced, and water trees grow more slowly.
2.    The high electrical fields around space charges are reduced, which reduces the likelihood of UV photon creation and the inception of free electrons.
3.    Any free electrons will not be accelerated to the same energy as they would have been in a greater field.
4.    The reduced local field increases both the partial discharge inception and extinction voltages.

Greater persistence in the insulation and stress grading provide longer post-injection life even in demanding applications. Performance at high temperature and performance in cables with constrained geometry that limit the amount of fluid that can be supplied, are greatly enhanced by the presence of CBMDMS.