This specification covers pressboard for electrical insulating purposes, manufactured from kraft, cotton, or kraft and cotton pulps. This board is intended for dielectrical or structural purposes in transformers and other electrical apparatus.
Electrical insulating boards are most commonly referred to (and will be referred to herein) as pressboard. Other terms used for pressboard include transformer board, fuller board, and presspan.
This specification covers pressboard having a nominal thickness of 0.030 to 0.315 in. (0.8 to 8.0 mm). For thinner material refer to Specification D1305.
The maximum thickness available will differ with the type and the manufacturer. The maximum sheet size will differ with the thickness, type, and manufacturer.
Pressboard shall normally be plied wet without pasting. Unless specified by the purchaser, this specification does not include pressboard comprised of two or more sheets that have been laminated together using an adhesive.
NOTE 1—The materials described in this specification are similar to corresponding types of pressboard described in IEC Specification 641-3, Sheet 1, Types B.0.1, B.2.1, B.2.3, B.3.1, and B.3.3.
The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.