In the previous article, Chemistry Part 1, we covered alkalinity and acidic chemistry as well as pH and how foam is created. In part 2, we will cover surfactants and how to deal with ever changing road film.
Surfactants make water “wetter”by reducing the surface tension for better penetration. Detergents lift or loosen soil particles from surfaces, creating a foam for a nice visual effect and emulsifying oils.
Surfactants are molecules that are bipolar, with one end of the molecule being Hydrophilic or “water loving”and the other end being hydrophobic or “water fearing”. The “water fearing”end could also be described as “oil loving”. This “oil loving”end can work its way into oily soils and working as a team with other surfactant molecules form a sphere around a drop of oil with all of their “water loving”ends facing out into the water.
Today surfactants are made from a wide variety of substances with many different characteristics. Some are great foamers, others good oil emulsifiers, some are extreme wetting agents; many are developed for functions that are totally unrelated to cleaning.
As manufacturers of car wash detergents, it is our goal to find the best surfactants used in the right combination and with the proper amount and mix of builders to create superior products for all car wash applications.
The builders are fairly inexpensive and favored by low cost providers who rely on the reactivity of the builders to burn away the soils. These ingredients can, however, also react with the surface of the vehicle and, depending upon the soil, they may actually “set”the soil on the surface rather than remove it.
Surfactants range in price from the moderately priced commodity products to very expensive specialty surfactants. It is important to focus on the performance of the surfactants and how they function in combination with other surfactants and the builders to provide the most effective cleaners with the least chance of damage.
Foaming is a critical component of consumer satisfaction. Customers tend to directly equate “clean”to the level of foam they see during the wash process. In general, a wet, thin foam is optimal for cleaning. For triple foam and brush type applications a thick, shaving cream type foam is ideal. Foam can become a negative when it cannot be fully rinsed off the vehicle.
Foam needs to have the proper flow per application. Factors that need to be considered when preparing the right foam per the application are: proper dilution ratio, proper solution and airflow, clean application equipment, rinse capabilities, and the operators expectations.
These are the key principles to consider. Foam is a combination of liquids and gases. Both are fluid. The flow of the fluid is dictated by the application equipment that is used to apply it.
A common issue in many car washes is poor foam level or show. This is often caused by misadjusted fluid and air volumes. If the system is not properly balanced, irregular results will occur. This is because liquid does not compress but gases do. If you exceed the volume of total fluid (liquid and gas) the orifices can realistically pass, you will thin out the foam and/or cause a spurting action. Proper flow and chemical ratios equal fantastic foam.
There are four surfactant categories: anionic, cationic, nonionic and amphoteric.
Anionic is a hydrophilic group with negative charge that tends to repel particles and help detergency. These may be very good foamers.
Cationic is a hydrophobic group with a positive charge that adheres to particles and surfaces and are used in sealants and drying agents.
Nonionic is a hydrophilic group that has no charge and makes a good oil emulsifier.
Amphoteric are cationic in low pH solutions and anionic in high pH solutions.
In general, detergents are formulated with surfactants that make the cleaning solutions hydrophilic. They make the solution better at wetting soils to help lift them into the water for easier removal.
Drying agents and sealants are designed to make the surface of the vehicle very hydrophobic. The water on the hydrophobic surface dislikes the surface so much that it pulls itself away from the surface wherever possible. A drop of water will pull away from the surface in an effort to decrease its footprint forming a bead that wants to roll off of the surface and thus dries the car. In order for these products to work at their optimum, the surface must first be clean as residual dirt can be hydrophilic and hold the water to it resulting in a wetter car.
To produce a fantastic product, you need to have the proper combination of builders and surfactants to get the clean that you desire.
As we advance in technology, we need to consider surfactant based chemistry compared to reactive chemistry. Reactive chemistry is created to react with everything and is unsafe. Surfactant based chemistry looks at safety, how fast it works and the better net value.
In trying to clean road film, the vehicle’s surface and the environment are both factors in the cleaning process.
Vehicle surfaces include metal, plastic, glass, chrome, rubber, vinyl, and new softer paint surfaces.
With the environment, you deal with things such as weather: heat, cold, dry, rain or snow; the road surface: concrete, asphalt, road de-icing chemicals; and organic matter: bugs, sap, etc.
The vehicle’s surface is negatively charged and attracts positively charged soils. The oily soils settle on the top creating a nasty but shiny road film. The small particles have a strong attraction to the vehicle’s surface and are the hardest to clean. Think of a magnet and powdered lead.
To demonstrate how the small particles create a stronger attraction we took a magnet and stuck some different size pieces onto it. The large bolt can easily be removed. As you remove the items from largest to smallest you could see how removing the smaller items gets harder and harder to remove depending on how small the object is.
Another demonstration is the particulate demonstration. There are times when a car wash operator will claim, “The cars are coming out dirtier than when they entered the wash.”Although this is not technically true, appearances can give that impression.
A microscope slide can provide a good demonstration of how this can happen. If the frosted end of this slide represents small particulates that are stuck to the vehicle in a very tough ‘Road Film’including a lot of oils. The oils can even out the surface hiding the small particulates and although the car doesn’t look clean, if the majority of the oil is removed, then the uneven surface of small particles can actually look worse than before it was washed.
This concludes our 5 factors of clean series. In the series we covered water quality, mechanical action, time, temperature and chemistry. All these factors need to work together to be sure to achieve the clean, shiny, dry car that is desired. You can view the video of the 5 factors of clean including the demonstrations on YouTube: http://youtu.be/ke7-JVYJHRs.
Ryan Cook is the assistant vice president of Lustra™Professional Car Care Products.