Wednesday, 6 October 2010

Protection - Why use a wax on top of a polymer sealant?


Probably the most misunderstood part of the detailing process. Protection refers to the processes that a detailer uses to make sure a customer’s vehicle maintains that ‘just detailed’ look The best way to describe this is that is you have just washed the car, you will see the effects until you hit a puddle of mud, whereas with a complete detail, you will see the effects for weeks or months to come. Protection includes the proper application of waxes and paint sealants to avoid oxidization and the adverse affects of ultra violet radiation, water-based dressings to keep the leather supple and stop it from drying out, and dressing to keep the tires looking matte black.

Some detailers find that a polymer sealant tends have a flat, silvered mirror look. Adding a Carnauba wax to the surface provides depth of shine, gloss, jetting (the so called ‘wet look’) and a warmth to the paint surfaces overall look. Bear in mind that how a paint surface ‘looks’ is very subjective and tends to invoke an emotional reaction rather than a logical one 95% of an applied wax comprises out gassed solvent that is wiped away, whereas 65% of a polymer sealant that is applied remains.

Detailers who prepare show cars will often layer a Carnauba wax on top of a synthetic wax; the synthetic wax acts as a gloss layer, while the carnauba wax adds depth and a so called wet-look (jetting) appearance

Polymer sealants

Need a porous surface to bond to, they initially adhere by surface tension and then after a period in which the solvents /oils in the carrier system vaporize (outgas) the polymers cross-link to form a covalent (molecular) bond to the surface. This process usually requires 12-24 hours, which are time and temperature and / or humidity dependent.

Note that drying and curing are two different processes. Drying generally refers to evaporation of the solvent or thinner, whereas curing (cross-linking) refers to polymerization of the binder, which imparts adhesion, binds the pigments together, and strongly influences such properties as gloss potential, exterior durability, flexibility, and toughness.

When polymer chains are linked together extensively by chemical cross linking - the formation of covalent bonds between chains; the polymer is harder and more difficult to melt. Curing is required to allow the monomers (polymer building blocks) to attach to the surface and to polymerize into a crystal-clear, impervious film.

It is very important to allow polymers to cure for 12 hours after the haze has been wiped off. If the coating is exposed to contamination such as oil, rain, water, cleaners, etc. before it has cross-linked, the contaminants may interfere with the film, preventing the polymer from achieving its maximum performance and durability. A polymer, unlike wax forms a molecular bond with paint once it’s had enough time to cross-linking, usually 12 – 24 hour.

A unique aspect of polyurethane chemistry is that the hydrogen bonding acts as an additional crosslink, but also allows thermoplastic flow, which helps the paint surface to retain its elasticity and its tensile strength to relieve mechanical stress. The basic structure of a polyurethane clear coat features a soft segment (polyol or tetramethylene ether) which gives it flexibility and elasticity. There is also a hard segment (polymerization) that has high urethane density, which gives the coating hardness and tensile strength

Carnauba wax

Carnauba in today's wax formulas functions mostly as a carrier; it’s used to keep the polymers and oils on your car's surface. Only a small portion of your vehicle's shine comes from the wax itself. Carnauba is translucent at best with only minimal light reflection. It is among the hardest of natural waxes, being harder than concrete in its pure form

This sacrificial barrier is all that stands between the environmental contaminants and the paint film surface and this renewable barrier is probably less than 0.1 ยต (100 nm, 0.000 4 Mils or 0.000 004 inch) thick. An applied paint protection product is the barrier that provides protection for automotive paintwork besides the clear coat paint.

An organic wax also provides a sacrificial surface that will resist acid (salt brine, bird excrement, acidic rain, etc) better than a polymer, which forms a molecular bond with the paint, whereas a an organic wax forms a semi-hard protective shell (although it lacks durability)

Paint Surface Protection

Paints that is subject to ultra violet radiation (UV-B) and environmental contaminant (acid rain industrial fallout, brake and rail dust, road salt brine, etc) exposure leads to gloss and colour instability (photosynthesis or photo-oxidation) and surface stains.

Organic wax, contrary to popular opinion, or marketing, does not contain natural UV protection; the wax protects the leaves due to its thickness and the fact that it’s opaque. It does however provide a sacrificial surface that will resist acid (salt brine, bird excrement, acidic rain, etc) better than a polymer, which forms a molecular bond with the paint, whereas a an organic wax forms a semi-hard protective shell (although it lacks durability

Polymer sealants are resistant to UV-B radiation and offer durable protection for a paint surface.

Nanotechnology coatings due to something called the Lotus effect offer resistance to dirt as they do not allow adhesion, they are also scratch resistant.

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