UV-A infrared radiation resin binder oxidation
UV-B photosynthesis or photo-oxidation (fading)
[: electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV. It is so named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the colour violet] 
Ultra violet light is an electromagnetic wave of radiation that can penetrate and damage sensitive materials; it is also known to contribute to the chemical modification of exposed paint surfaces resulting in loss of gloss, colour change, chalking, flaking and eventually destruction of the clear coat paint film by oxidation.
Ultra violet protection is a sacrificial / renewable component; this is due to the UV protection layer (stabilizers) being degraded by exposure to the elements (sun, sand, road or sea salt, and etc) it is also water miscible, so it is imperative that you renew it and needs to be re-applied on a regular basis (dependent upon location climatic condition)
There is no such thing as a permanent UV stabilizer, it a matter of physics, not chemistry. Ultra violet protection is a sacrificial and necessarily renewable protection. Acrylic polymers and polyurethane polymer are slow to absorb UV light and accordingly somewhat resistant to photo degradation.
Many natural and synthetic materials are attacked by ultra-violet radiation and products made using these materials may crack or disintegrate. This problem is known as ultra violet degradation, and is a common problem in products exposed to sunlight.
1. UV-A radiation dries out the binder system causing structural failure (delamination); it will dry the resin in paint; leading to oxidation. A paint surface will often show cracking as the resin binder dries out the paint draws up on itself forming ‘crow’s feet’. It will also dry out the oils and plasticizers in vinyl and other materials and may lead to structural damage (this is especially relevant to open top convertibles)
2. UV-B radiation exposure leads to gloss and colour instability (photosynthesis or photo-oxidation) and surface fading stains. But before UV light can cause harm, it must first be absorbed. If it is not turned into heat or transferred to a nearby stabilizer molecule called a quencher, it breaks weak chemical bonds. This is the beginning of UV damage. Oxidation really amounts to a weakening of the resins that bind paint, which results in the micro-pores becoming exposed and a larger area of paint becomes oxidized. The paint top surface loses its reflective ability and becomes ‘chalky ‘and it delaminates from the substrate; this is a sign that the structural integrity (mechanical strength) of the paints matrix has become compromised.
Some materials absorb UV radiation more readily than other materials. Materials that readily absorb (UV-B) radiation are quickly damaged; rubber, vinyl, gel coat fiberglass, and many other plastics.
Ultra violet radiation (UV-A) oxidation
Ultra Violet (UV) Protection
Many natural and synthetic materials are attacked by ultra-violet radiation and products made using these materials may crack or disintegrate. This problem is known as ultra violet (UV-B) degradation, and is a common problem in products exposed to sunlight.
Some waxes and polymer sealants have ultra violet (UV-B) protection agents added when they are formulated, but be cognizant that the protection a microscopically thin layer can provide is limited. This renewable barrier is probably less than 0.1 µ (4 Mils) thick. The primary paint surface protection against UV light is the clear coat; which protects the colour coat from fading by adding anti-UV-B chemicals to the polymer when mixing the clear coat ingredients.
The rate of environmental exposure that negatively effects (clear coat) paint varies widely with ambient conditions (Ultra violet (UV-B) radiation, Environmental Fall-out, paint protection used, etc) but an approximation of 0.005Mil (0.13µ) per annum is about average. A protective coating i.e. a polymer sealants, wax, etc, being renewable are meant to be sacrificial (it is subjected to oxidation, thereby by saving the clear coat)
It's better to have dust, road tar, tree sap, bug and bird excrement stuck to wax than your paint, wax also provides a limited paint (sacrificial) protection against acid (i.e. acid rain, environmental fallout and bird excrement. It is of paramount importance that once a sacrificial protection is attacked by an acid it be removed immediately and then replaced with a fresh coating
An applied paint protection product is the barrier that provides protection for automotive paintwork besides the clear coat paint. Clear coat paint (polyurethane) provides the colour and base coats with protection, and usually has UV protection added in the final coating; this tends to migrate towards the upper level of the clear coat (this is why it’s important to check how much of the paint surface you are removing with an abrasive polish). It should be noted that Carnauba wax does not contain a natural ultra violet radiation protection
Be cognizant that there are no polymers, nanotechnology coatings or waxes that are ultra violet radiation -proof; they will only offer short-time resistance. The most pertinent factor is to have a layer of (sacrificial) protection between the sun’s rays and your paint surface.
Two important points-
a. UV protection is a sacrificial / renewable component; this is due to the UV protection layer being degraded by exposure to the elements (sun, sand, road or sea salt, and etc) so it is imperative that you renew it or your surfaces will degrade.
b. UV stabilizers have to be periodically renewed or replenished if continuing protection is to be achieved, there is no such thing as a permanent UV stabilizer, it a matter of physics, not chemistry.
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