The Automotive Aftermarket Industry Week trade show—North America's version of Automechanika—took place recently in Las Vegas. DrivingVisionNews was there; watch for forthcoming articles about what we found. Perhaps of most pressing concern was the sudden appearance of kits offered for the purpose of restoring plastic headlamp lenses that have opacified and yellowed in the sun.
Plastic headlamp lens materials brought great new styling freedom and weight savings. However, the sad but persistent truth is that with the exception of impact resistance, plastic lenses—all of them—have proved much less durable than glass in terms of optical performance. Cars now develop cataracts; their headlamps go opaque and yellow. It happens a little faster in sunny climes and a little slower in dark places, but it eventually happens to virtually all plastic headlamps.
The kits come from longtime suppliers of car washing and waxing supplies like Meguiar's, established lighting suppliers like Osram-Sylvania, and outfits specialising in consumable supplies for independent auto workshops. The kits generally consist of several grades of sandpaper and polishing compound. All claim to restore clarity to aged lenses, and we can assume most of them do that reasonably well. But what about protection from UV and abrasion? It's the protective hardcoat—applied and cured during lens manufacture under cleanroom conditions—that degrades with age, heat, and sunshine. Polishing the lenses scrubs away the hardcoat, exposing the polycarbonate lens itself to rapid and severe degradation. At that point the lens is permanently spoiled and cannot be restored. Because U.S. regulations tend to favour non-replaceable lenses and many ECE headlamps now also have the same, a ruined lens means the whole headlamp must be replaced. What degree of lasting lens protection do these kits offer?
