Better Living with Chemistry- Windshield Wipers

The recent deluge of rain in the Houston area has me considering trading my car for an airboat.  Except for February, each month of 2015 has exceeded the normal monthly rainfall average.  Several very heavy rains in the last week of  April, have been followed with several ‘monsoons‘ already here in early May.  In the interim, the annoying sound of my windshield wipers approached exceeding the functional limit of their purpose.  In other words, the sound was so distracting, I started manually turning them on and off repeatedly to avoid listening to the squeak.  As my mind often does, I started thinking about the chemistry of the rubber blades.  My car is only 2.5 years old, so what has changed in the blades to resulting in the distracting racket.  As the rain can only pour in Houston, so does the sun.  From the UV light to the cleaning agents in the wiper fluid, the blades changed.  Read below for the chemistry, keep reading for the solution.

Rain Rain Go Away

A little ArmorAll(TM) does the trick.  While it may be an off label application, spray a generous amount of the product onto a paper towel, then slowly work into the rubber.  For best application, let is soak in for a few minutes and repeat.  Works like a charm- and keeps your passengers happy.

The chemistry of why this works:  Environmental stresses such as sunlight attack the rubber and may make it slightly shrink, so that it the fit is actually with greater tension.   Sunlight comprises many forms of electromagnetic radiation in addition to the visible light we enjoy.  The spectral region consisting of light from 100 nm to 400 nm, known as the ultraviolet region produces damaging effects on organic molecules.  Whether it is human skin, or natural rubber, UV radiation causes electronic changes in the molecules.  These molecular changes make rubber, or skin more susceptible to reactions with oxygen.  For rubber, the layer of oxidation causes changes that result in decreased performance of physical, chemical and mechanical properties.  Modern wiper blades include many advanced materials, and it is difficult to truly find a pure rubber blade, but the oxidation occurs on all the molecules.  Modern blades whether synthetic, or natural rubbers are impregnated with surfactants.  Surfactant is just a fancy name for soap, but really means that a molecules can make dissimilar surfaces work together.  On your windshield, this is less friction between blade and the glass.  For sunlight and oxygen damage, the surfactants built into the product have degraded over time.

Alternatively, windshield cleansers can leach out compounds over time.  For those of you that generously apply the windshield washer, many of those contain alcohol.   The alcohol slowly dissolve out the surfactants, increasing the friction on your windshield.  Alternatively, other plastics additives called plasticizers make the rubber stay soft, can also leach out with the cleaners that keep the windshield clear.

Either way, the ArmorAll penetrates the surface of the rubber and moisturizes it, helping to soften.  The active ingredient in Armorall is listed as a class of chemical compound called siloxane and is often referred to as PDMS. It simply works as a surfactant or plasticizer, replacing the original blade additive that was chemically changed by the sun, or leached out with cleaners.  The compounds in the formulation decrease the friction by lubricating the blade as it swipes over the glass.  While this won’t fix wipers that leave streaks from uneven surfaces caused by excessive wear, if your blades are effective, but squeak, give it a shot.  CAUTION, a little goes a long way, so spray the towel, then rub into the wiper blade.  Remember, do not spray the glass, you don’t want to create a hazy field of view!


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