This is a heads-up from FMCA!
Tech Tip: RV Handrail Cleaning Warning
September 24, 2020
I have some urgent information to share with owners of RVs that have clear plastic handrails, especially illuminated ones. This is especially relevant in view of increased sanitation related to the COVID-19 situation. DO NOT clean these with hand sanitizer or wipes that contain alcohol. This can cause them to crack and craze because of a phenomenon called environmental stress corrosion in plastics. Use only plain or antimicrobial soap and water, or wipes that do NOT contain alcohol or other hydrocarbon solvents.
Environmental stress corrosion is similar to what happens in metals. Some chemicals that are not necessarily considered solvents to certain plastics and do not affect them under normal circumstances will cause them to crack if exposure occurs while the material is under stress. Combinations that are at issue include polycarbonates and acrylics — commonly used to manufacture clear RV handrails and others — when exposed to alcohol and acetone. The weight you place on the handrail when using it, or thermal expansions that result from internal illuminating lights or sun exposure, are prime sources of mechanical stress. These stresses do not normally affect the material in the absence of such chemicals.
I witnessed this recently when friends asked me, a retired engineer, why I thought the illuminated clear plastic handle on their RV had cracked and crazed. After seeing it, my first question to them was, “Did you clean it with alcohol?” They said they had just cleaned it that morning with alcohol wipes. While I was able to explain why it happened, it was obviously too late to prevent it.
Apparently, drying off these impervious plastics immediately after exposure is not a guarantee of preventing this, because they typically absorb moisture or other liquids.
The phenomenon was known in metals but first discovered in plastics when a major appliance manufacturer attempted to make blender bowls from polycarbonate instead of glass, giving a pilot run to employees for field testing. Someone took their blender bowl out of the dishwasher just after it finished. They put their cocktail ingredients in the blender; turned it on; and, fortunately, walked away. The blender bowl exploded all over their kitchen. The bowl had absorbed water and swelled very slightly during the washing cycle; then the drying cycle dried and shrank the outer layer, leaving high internal stresses. This explains why, even with today’s improved plastic materials, many blender bowls are still made from expensive tempered glass.
You can demonstrate this dramatically by a well-known experiment using two small strips from a polycarbonate sheet (Lexan, etc.). Rub some alcohol on one. It will have no effect. Then bend the other one in an arc and drop a little alcohol on it. It will immediately crack and fail.
If you have a handrail that shows heavy cracks and crazes, be very careful that it does not fail when being used and cause injury. You would be well advised to replace it.
— John Richards, F365753
West Richland, Washington