TOGWT: Removing Silicon

What is silicone?

Silicon fluid is relatively short chain inorganic polymer called polydimethylsiloxane; please note the prefix poly before the units of dimethylsiloxane. The chain is not long enough to be typically called a polymer but by the technical definition, it is a polymer. Again we see here, the name "polymer" means less and less every time you see it.

The properties of silicon fluids range from very thin, volatile liquids that look and feel like petroleum solvents to thick heavy liquids that look like crystal clear honey. The only difference between the thin liquid and the honey liquid is the number of units in the dimethyl siloxane chain.

Automotive body manufacturing plants and paint shops avoid silicones, as they may cause ‘fish eyes’, small, circular craters in the paint finish

Polymers are used for different reasons they all have differing characteristics, i.e. as a paint sealant that contains four different polymers; two are used for durability, one to make the product easy to remove and one to give a great shine.

Silicon Polymer technology

a) Siloxane (R₂SiO) or Polydimethylsiloxane (PDMS) The word siloxane is derived from the words silicon, oxygen, and alkane and is one of several types of silicon (polymerized siloxane, a resin as opposed to an oil) it’s a water-based amino-functional resin, although it contains silicon atoms, they are not made up exclusively of silicon, and have completely different physical characteristics from elemental silicon.

b) Silicon or Dimethylsiloxane (DMS) usually a petroleum distillate, (PD) solvent-based silicone, which after polymerization (cross-linking) will present an external hydrophobic surface. These penetrating-type, durable silicones oils form a flexible protective shield that prevents penetration of moisture and dirt.

c) Silicon (Ph₂SiO) (Si14) – Silicones are polymers that include silicon together with carbon, hydrogen, oxygen, and sometimes other chemical elements. Some common forms include silicon oil, silicon grease, silicon rubber, and silicon resin

Silicon oils also referred to as dimethyl fluids are generally straight chain poly-dimethyl siloxane fluids ranging in viscosity from 0.65 to 100,000 centipoises. The typical ones used in wax or sealants formulations

However are between 350 to 10,000 centipoises viscosity. These have no reactivity and help with application or initial gloss. There are some modifications to improve characteristics of these oils by adding certain groups for instance aryl groups improve fire resistance and larger alkyl groups make silicon fluids body-shop safe. Some manufacturer’s use these modified silicon fluids only to claim that the product does not contain silicon oils.

Fisheye

[: Silicon Contamination; small circular, crater-like openings that appear during or shortly after the spray application. or wax]

"Photo spotting" or fish eye is caused by contamination of the surface to be sprayed. If the surface to be painted receives the correct preparation it should not cause issues.

Cause

· Spraying over surfaces contaminated with oil, wax, silicone, grease, etc.

· Use of thinner/reducer in place of a solvent cleaner.

· Spraying over previously repaired areas containing "fisheye eliminator" additive.

· Once the surface ’fisheye, the paint should be polished or cleaned with a chemical cleaner (PrepSol) as something has contaminated the surface. There is no point in sanding down the surface and repainting as the problem will not just go away.

Fisheye look like little craters where the paint pulls away from the centre (looks like a fish eye and hence the name)

Surface Preparation (For Polishing)

Why is it important to remove Silicon?

It will have a negative impact on the abrasive as it will tend to make the surface greasy as silicone contains oils, which will affect the abrasives ability to remove defects

The properties that make silicon so popular with car detailers, and some auto manufacturers, also make it a very difficult product for the polisher to remove. During polishing, the silicon mixes with the excess paint that is being removed from the surface to form a smear.

[Can you remove silicon from a clear coat completely? It is impossible to remove silicon from a painted surface without using a chemical process so aggressive that it dissolves the paint. Wax and grease removers will chemically remove one layer of silicon off at a time but are unable to completely remove all the silicon. Tests by Dr Michael Hauber at Menzerna using a spectroscope showed the layers become thinner but the silicon remains. Removing silicon completely can take place over time and involves a lengthy process of oxygen, chemicals, time and sunlight.] Menzerna

Most types of silicone utilized in the auto body and paint industries are water soluble additives used in waxes, polishes and paint protectants. When fatty acids and polydimethylsiloxane derivatives are generated, it creates silicone. Silicone also acts as a lubrication agent, and when added to polish, wax and special coatings, it creates a smooth, slippery finish.

Preparation- If the car has been treated with silicon, use a wax and grease remover to remove as much of the surface silicon as possible before polishing. You will not be able to remove it all but it helps.

When a silicon-free polish works on the surface of paint it uses aluminium oxide spheres, suspended in water and hydrocarbons and a mechanical process to abrade the surface of the paint down to the level of the bottom of the scratch. Silicon cannot be removed this way. Silicon is removed by a chemical means and is designed to resist being removed by mechanical means. Instead the silicon mixes with the blend of paint dust and polish powder and it creates a smear on the paint.

We should differentiate between swirl marks in the silicon layer and swirl marks in the paint underneath. Some polishes may appear to remove the swirl marks in the paint but are really only working on the layer of silicon. So the swirl marks in the paint itself remain unaffected by the polishing and reappear after a few weeks, as the silicon is being removed by time.

Removing Silicone - polishing is a mechanical process; silicon is a product that has been designed not to be removed by mechanical abrasion. When using Menzerna to polish surfaces which have been previously treated with silicon, a smear may result. It is important to understand why this occurs.

There are lots of silicon oils on the market. The high gloss properties that make silicon so popular with car detailers, and some auto manufacturers, also make it a very difficult product for the polisher to remove. During polishing, the silicon mixes with oxidised paint and polish abrasive residue that is being removed from the surface to form a smear. These products and or paint/ polish debris can be removed with a wipe-down process or a specific silicon remover. You may not be able to remove it all but it helps.

· Hi-Temp's Prep Wash - to prepare a paint surface for polishing, compounding, wax and / or polymer sealant application (especially if changing from a wax to a polymer product) this is a water-based paint cleaner designed to remove all traces of silicone, oil, and buffing residue from any exterior paint surface

· DuPont PrepSol II™ or Final-Klean - spray onto a 100% cotton or a micro fibre towel and clean the surface, DuPont now also sells the Sonatra Line, which are essentially wipes/towels, pre-moistened with either Prep-Sol or Final-Klean, ideal for all high tech wiping applications, excellent in use both wet and dry with high absorbent capacity

· Dow Corning® OS-2 Silicon Cleaner and Surface Prep Solvent is a volatile methyl siloxane (VMS) fluid that is compatible with a wide range of materials. It will not harm most substrates, including plastics. OS-2 can be used to remove silicone-based; greases, oils, car wax and car care products, will soften cured silicones to facilitate removal

Current Information

To be of real practical use, a subject like automotive detailing requires a great deal of research, and updating as new products become available. The advent of materials like detailing clay, micro fibre technologies and finely milled micro diminishing abrasives, suitable for ceramic nanotechnology paints are examples of why it’s so important to monitor the industries new products, chemical technologies and ideas that are constantly being introduced, as are the techniques for applying them, hence all of the in-depth articles will be up-dated and revised on a regular basis

Always be willing to learn; because the more you learn, the more you’ll realize what you don’t know. It is said that knowledge is power, with the caveat that it includes access to a reliable information sources. I would like to think that these articles become an asset to anyone who is new to detailing and to professional’s alike, as well as industry experts who seek to advance their knowledge.

I hope these articles are informative. They are based on the current status of technical development as well as my experience with the products.

By having some understanding of the ‘What’ and ‘Why’ as well as the ‘How’ along with a little science to help you understand how the chemicals we use react, you can achieve the results you desire.

I would appreciate it if you would share these articles as it helps other detailers further their knowledge.

As always if you have questions, I’ll do my best to answer; bear in mind the only stupid questions is the one that was unasked. Questions and/ or constructive comments are always appreciated

TOGWT

Friday, 18 September 2015

Removing Silicon

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