Solvent crazing

In detail

A solvent applied to a polymer under mechanical stress can produce environmental stress cracking, seen as a network of very fine cracks spreading across the surface. Two features make it a distinctive hazard in cleaning. It needs stress as well as chemistry, so the crazing appears at moulded corners, around screw bosses and at snap-fits — the places a plastic part is already strained — rather than uniformly where the solvent was applied. And it is delayed: the surface can look unaffected when it is wiped and craze over the following hours or days, by which time nobody connects the two. Domestic solvents are entirely capable of it. A regulator's fact sheets record that acetone attacks plastics and that white spirit attacks plastic, rubber and coatings, and alcohol-based cleaners craze several common transparent plastics. That is why device and lighting manufacturers specify what may touch their housings rather than leaving it open, and why nail varnish remover on a laminate worktop, a spectacle lens or an acrylic bath is one of the most reliably destructive things in a household cupboard. The damage is structural and cannot be polished out.

Why

• Acetone is explained by Solvent crazing
• Household plastics is explained by Solvent crazing
• Laminate worktop is explained by Solvent crazing
• Phenolic plastic is explained by Solvent crazing

  The stable plastic. Its realistic failure is somebody trying to restore the shine with a solvent.

• Bicycle helmet is explained by Solvent crazing