WD‑40 is a ubiquitous household spray that many of us rely on without much thought, yet its creation was the result of decades of experimentation and ingenuity.
In 1953, San Diego‑based Rocket Chemical Company began developing rust‑preventing solvents and degreasers for the aerospace industry. The team eventually landed on a water‑displacement oil that would become WD‑40 after testing 40 different formulations. The “WD‑40” name—Water Displacement perfected on the 40th try—quickly resonated with both industry professionals and the general public.
Throughout the years, WD‑40 evolved from a protective coating for missiles to a widely adopted consumer product with a surprisingly diverse history. The spray was shipped to soldiers in Vietnam to keep weapons operational, to Floridians after Hurricane Carla in 1961 to recondition damaged machinery and vehicles, and the company maintains a list of more than 2,000 uses. From a bus driver removing a python that had wrapped itself around the underside of a bus to police officers using it to dislodge a “naked burglar” from an air‑conditioning vent, WD‑40’s versatility is legendary.
Despite its many applications, WD‑40 is not a universal solvent. When it comes to plastics, the spray can be a serious mistake, especially with certain types.
Adam McCullough/Shutterstock
While WD‑40 can be applied to many plastic materials, it does not work well with all of them. Spraying it on PVC (polyvinyl chloride) pipe may seem like a quick way to lubricate joints, but the hydrocarbons in WD‑40 actually degrade the polymer chains in PVC, polycarbonate, and polystyrene. The result is weakening or discoloration of the material.
Polymers are long‑chain macromolecules that can be either amorphous or crystalline. Amorphous polymers—such as polymethylmethacrylate, polycarbonate, PVC, and polystyrene—have a loose, random molecular arrangement. These types are particularly vulnerable to aliphatic hydrocarbons found in WD‑40, which erode their structure. Consequently, it is best to avoid WD‑40 on polycarbonate (commonly used in eyeglass lenses), PVC pipe, polystyrene, and other amorphous plastics like baby bottles, optical discs, and LCD screens.
Crystalline plastics—including polypropylene, polyethylene, polyester, and nylon—tend to resist WD‑40’s solvent action more effectively. Even so, it is prudent to limit WD‑40 use on most plastics and opt for products specifically formulated for plastic surfaces when needed.
