Insulating materials for double insulated power tools

The introduction of double insulation into the North American market in the 1960's and its steady growth since then has been due to the following: 1. The increasing use of power tools in locations where proper grounding was not available. It has been estimated that only 15 percent of the homes in the USA have grounding type receptacles throughout.
¹
2. Requests from the U.S. Navy and several other large users of tools for double insulation. 3. Reports from Europe and Australia that electric shock accidents' have been reduced by the use of double insulated tools. 4. Recognition in the 1962 National Electrical Code of double insulation as an alternate to grounding of portable electric tools in residences. Expansion of that recognition in the 1968 Code
²
to include industrial locations. 5. The publication of standards for double insulation by Underwriters' Laboratories.
³
6. The increasing availability of materials which were suitable for protective and reinforced insulation.