In this section we will discuss detailing of exterior plastic, rubber, and vinyl often used for molding, bumpers (unpainted), trim, weather seals/stripping, cladding, and wheel wells (plastic head/tail lights will be discussed in another section). These materials, otherwise known as polymers, are essential on the modern automobile as their unique properties afford automotive manufacturers the ability to add aesthetics, increased functionality (corrosion resistance, strength, reduced weight, etc.), and flexibility of design. Some cars, such as the Honda CR-V and Nissan Xterra, have a considerable amount of (unpainted) exterior plastic/rubber trim/cladding/molding (to include the whole outer bumper) that require proper care so as to provide the appearance and functionality they were designed to provide. From an aesthetics point of view, polymers allow for some nice touches to a car’s appearance – if properly taken care of. Polymers on the exterior of a car, however, are subjected to the adverse effects of light, oxygen, heat, oil, road tar, grime, ozone, etc., and, even though durable, these elements will cause polymers to age prematurely. We will collectively refer to this premature aging as ‘degradation’. Degradation ultimately results in loss of strength, decreased flexibility, discoloration, ease of scratching, loss of gloss, and cracking that, among other things, creates an unsightly look. Before we address degradation in detail, let’s first understand what makes polymers different from other materials. We will then discuss how to treat and restore them to their near-show-room condition.
The Chemistry of Polymers
To understand the basic degradation mechanisms occurring in polymers we will briefly take a look at their underlying chemistry. Our goal here is to gain a rudimentary understanding of the chemistry in an effort to demonstrate how important maintenance is and to understand degradation so that we can properly clean and protect these materials in the most effective way possible.
At the basic level, materials are comprised of atoms – where the atom is the fundamental ‘unit’ of the material containing neutrons, protons, and electrons. We are not interested in the behavior of the neutrons and protons (that make up the atom’s nucleus) but we are interested in the electrons and in particular the ‘valence’ electrons. The valence electrons are the electrons that are responsible for controlling how an atom will bond to another atom.
Polymers, in general, have six primary atoms responsible for forming bonds: carbon, hydrogen, chlorine, oxygen, nitrogen, and fluorine. All of these atoms lack some valence electrons and, therefore, are chemically reactive – they want to ‘link up’ with other atoms. This fact is what enables chemists to bond atoms into molecules to form polymers (polymers are just long ‘chains’ of monomers. The word ‘mer’ means ‘unit’…thus, we simply have a ‘many unit’ chain of molecules bonded together). Polymers used on the exterior of automobiles (mainly polypropylene) are, as we mentioned above, exposed to sunlight, oxygen, grime, road tar, ozone, temperature, humidity, atmospheric pollutants, etc., and all of these cause the initial chemical structure of the polymer to change – i.e., the polymers starts to degrade – either due to breaking of the polymer chemical bonds (which are covalent bonds) or due to adverse reactions with the additives in polymer materials such as stabilizers, colorants, processing aids, plasticizers, etc.
Polymer Degradation or…Why Does Trim Fade?
It is no secret that polymers degrade. They age, deteriorate, and weather due to three major factors: light (photodegradation), heat (thermal degradation), and oxygen (oxidative degradation). Keep in mind that car designers choose particular polymers based on their ability to resist these types of degradation as well as to meet the unique mechanical properties necessary for functionality. Thus, a material such as ABS (acrylonitrile butadiene styrene), while a great plastic that provides myriad possibilities across a number of application areas, is simply not a great choice for exterior automotive applications as it weathers quite easily.
Photodegradation: This is what we want to prevent!
We will first address ‘photodegradation’ as this is perhaps the most prevalent and easy to understand. As car enthusiasts we generally like to have our cars outside and, for many, the possibility of keeping our cars in a garage is just not an option. Even if kept in a garage, it is often not possible to keep automobiles out of direct sunlight. And, here lies the problem! Sunlight is a major contributor to the degradation of polymers. The spectrum of sunlight consists of infrared, visible, and ultraviolet (UV) radiation (and other radiation that we are not concerned with) distinguished by their wavelengths and, hence, photon (the basic unit of light) energy. Of these three classes of radiation, UV is most responsible for degrading polymers and, as such, most detailing products on the market are designed to protect against UV radiation [UV radiation is typically classified as UV-A (320-400nm wavelength), UV-B (280-320nm wavelength) and UV-C (100-280 nm wavelength). We only have to worry about the effects of UV-A and UV-B as UV-C does not reach the Earth’s surface.] The reason why UV radiation is so detrimental to polymers has to do with the high energy of this type of light and how it interacts with the polymer.
To better understand photodegradation, let’s consider polymers at the atomic level. It turns out that the bonds between the carbon-hydrogen and carbon-carbon atoms in polymers have ‘dissociation’ energies (bond strengths) similar to that of UV radiation energy. Now, think of photons as baseballs with the energy of a photon corresponding to the velocity of a thrown baseball. Imagine that you have a ‘lattice’ of Styrofoam balls held together by sticks and you throw baseballs at them…eventually you will cause the Styrofoam balls to ‘disassociate’. The same thing happens when photons hit the atoms in polymers…the UV-A and UV-B radiation break the bonds in the polymer thereby causing it to degrade! Absorption of UV light starts the degradation process and generally affects the polymer additives first – most pure polymers are not able to absorb UV radiation but the additives in the polymers are and do absorb UV radiation. Bombarding polymers with UV rays causes the breaking of atomic bonds and the formation of what are known as ‘free radicals’ – atoms with unpaired electrons. These free radicals then react with oxygen (oxidation) to form another type of radical which can then remove a hydrogen atom from another part of the polymer and this regenerates another free radical – this process then continues and causes the polymer to degrade. Moving your car out of the sun will not necessarily stop this process. Once this chain reaction has started, sunlight is not needed to cause it to continue. The way to stop photodegradation would be to somehow ‘clean up’ the free radicals caused by the UV rays to make the polymer inert (un-reactive). Polymer manufactures attempt to do this by adding stabilizers (such as antioxidants) to the material…but the stabilizers can only do so much. In the end, if not cared for properly, what we end up with is a material that suffers from cracking, chalking, color changes, bleaching, and loss of its physical properties.
We can go on to look at other types of degradation but the result is going to be the same…so, let’s move on to restoring and protecting. Just as a side note, photodegradation differs from thermal degradation in that it is started by absorption of light and not by heat. Ultraviolet absorbers (e.g. Carbon Black) are often added to polymers to absorb UV radiation and dissipate it as heat in the polymer. This has the positive effect of protecting the bonds from disassociation but the negative effect of adding heat to the polymer (thereby contributing to heat degradation). In addition, UV stabilizers are added to polymers in an effort to slow down the degradation process. The simple fact is, however, that while UV absorbers and stabilizers work in unison to prevent degradation, polymers still degrade over time if not maintained.
How To Care for Plastic, Rubber, and Vinyl
Preventing degradation is actually quite easy if you consistently and continually maintain the plastic/rubber/vinyl surfaces of your car! Maintenance is key! Providing a layer of protection between the exposed polymer and the elements the only way to keep these surfaces looking new – degradation cannot occur if you protect the polymer surfaces so that UV radiation and oxygen cannot generate and link up with the free radicals! But, what if these surfaces haven’t been maintained and they are faded and weathered?
Plastic, Rubber, and Vinyl Detailing
If the plastic, rubber and vinyl surfaces of your car are already faded then there are two possible reasons. One, polish/wax/sealant got on the surface of these materials and dried. Or two, these materials have degraded. Let’s tackle the wax or sealant drying on the polymer first.
For plastic trim/molding/wheel wells/cladding/etc. that is faded due to polish/wax/sealant residue: Most polishes, waxes and sealants, as you may have found out, will stain (with a white chalky appearance) molding/cladding/trim/etc. if allowed to dry on their surfaces (see picture below) – and this happens rather quickly! One way to prevent this is to use masking tape – simply mask off the trim or molding (only usually necessary when using a machine) when you polish or protect your car’s paint finish. Masking off small trim and molding is not a great idea as it is very time consuming and will leave a residue at the tape line that you will need to spend time cleaning. But, for larger pieces of molding/trim/etc., it is worth the investment in time up front to protect these parts of your car. For the smaller pieces of material, you can just go over them afterward to clean the polish/wax/sealant residue. The reason why polymers acquire this chalky white appearance is because the polish/wax/sealant works itself into the pores of the plastic (textured) and then dries. If that’s the case, then all you need is a solvent that can ‘reach’ into the pores to dissolve the wax or sealant. If you are detailing plastic, then you will need to use a product specifically for plastic.
I highly recommend Meguiar’s Hyperdressing, Black Wow, Meguiar’s Gold Class Trim Detailer, Meguiar’s M40, Meguiar’s Ultimate Protectant, 303 Aerospace Protectant, Meguiar’s All Season Dressing and, my favorite, Ultima Tire and Trim Guard Plus. Each of these products will do a good job of removing the polish/wax/sealant residue off of your trim, etc. and provide nice protection. Which of these products to use is up to you and the look you want to achieve. Black Wow is a silicone gel (good silicone) that does a great job at restoring your trim. Black Wow does leaves a ‘wet’ look and, if excess product is not removed, it tends to attract dust (see below). Meguiar’s Trim Detailer leaves more of a matte finish and requires more applications than Black Wow to achieve the same result. Also, Meguiar’s Trim Detailer evaporates very quickly – often before you have had a chance to apply to a small area. Hence, you will have to use quite a bit of Trim Detailer to achieve the same cleaning and protection that Black Wow does with a ‘pea-sized’ drop. Meguiar’s M40 is an excellent product – it is essentially an all-in-one type product as it will clean and protect in one step. M40 can also be used on the interior of your vehicle (likewise with Meguiar’s Ultimate Protectant). Keep in mind that some of these are water-based (Hyperdressing M40, Ultimate Protectant, 303) and some are solvent-based (Black Wow, Megs All Season Dressing, Ultima Tire and Trim Guard Plus)…solvent-based products are more expensive but are going to last much longer. Finally, if the residue just will not come out with one of these products then you can try a dedicated rubber/vinyl cleaner such as Meguiar’s M39 or some vinegar on a microfiber towel or mineral spirits with a tooth brush…one of these methods will surely do the trick. Keep in mind that once you clean the trim, you have to protect it using one of the above. Megs All Season Dressing and Ultima’s Tire and Trim Guard Plus are perhaps the best.
For plastic/trim/molding/cladding/etc. that is faded due to degradation, i.e. the plastic has changed its appearance permanently, you have a few options: You can 1) apply a dressing to temporarily change the appearance – this will darken the polymer and probably last a few weeks before you will have to reapply it, 2) use a dye (e.g. Forever Black), 3) replace the part that has degraded, or 4) paint it with a polymer specific paint. Options 1 and 2, in my opinion, are the best options depending on the size of the part you are trying to restore. Applying dressing is the easiest; dying the polymer will provide a very nice finish, is easy, and will last a long time; replacing the part is costly; and painting it, while a viable option, is difficult to do. Hence, we are conveniently left with options 1 and 2!
Option 1: Apply a Dressing
Whether you have residue or degradation, the process of applying a dressing is the same. Application can be done with a foam pad or a microfiber towel – the choice is yours. I prefer a small microfiber towel for small trim/rubber and a foam pad for larger areas, e.g. bumper cladding. Also, irrespective of product, start with a small amount! Black Wow, e.g., has amazing spreadability as it is a highly concentrated silicone gel – you only need a pea-sized amount to start. Simply wipe the product on and wait a few minutes…then, simply wipe away the residue – being careful not to get the product on the paint – if you do, simply clean it off. In the below photos I demonstrate the differences between unrestored/Trim Detailer and Black Wow/Trim Detailer. Notice how Meguiar’s Trim Detailer leaves a matte finish while Black Wow leaves a ‘wet look’. Again, which product you use depends on the look you are trying to achieve (click on the images to enlarge).
Option 2: Apply a Dye (such as ‘Forever Black’)
Applying a dye to smaller trim pieces is actually quite easy and straight forward (it is akin to applying shoe polish to a shoe). A product like Forever Black comes with a black dye (pigment) and a cleansing solution. The process takes about 20 minutes and leaves a great look. In the picture below, (A) is the unrestored trim, (B) is the trim after cleaning, and (C) is the trim after application of Forever Black. It is recommended that after applying Forever Black you also also apply a protectant such as 303 Aerospace Protectant. Using a dye to restore your trim will provide the best finish for the longest period of time. The only challange occurs when you attempt to restore larger pieces of polymer, e.g. bumper cladding. In this situation it is a bit tricky to apply the dye uniformly – you can use a rag to even out the dye on larger pieces. (click on the below image to enlarge).