UL 471-BULLETINS:2004 pdf download PROPOSED REQUIREMENTS FOR THE SECOND EDITION OF THE STANDARD FOR INSULATING BUSHINGS, UL 635
5 Materials
5.1 Ceramic materials and some molded compositions such as phenolic and urea formaldehyde arecapable of being used as materials for a separate insulating bushing. Vulcanized fiber is not prohibitedfrom being used when the bushing is not less than 3/64 inch (1.2 mm) thick, and when it is formed andsecured in place so that it is not adversely affected by conditions of typical moisture. Other materials, suchas nylon, are capable of being used after a suitable investigation. See Humidity Test, Section 11, andElevated Temperature Test, Section 12.
5.2 Materials employed in the construction of insulating bushings shall be classified with a flammabilityrating of at least 94 HB as determined by the Standard for Safety for Tests for Flammability of PlasticMaterials for Parts in Devices and Appliances, UL 94.
5.3 Wood, hot-molded shellac, tar compositions, or rubber are not to be used as materials for a separateinsulating bushing.
5.4 The wall thickness of an insulating bushing shall not be less than 3/64 inch (1.2 mm) unless athickness has been determined to be capable of being used as a result of an investigation (see referenceto vulcanized fiber in 5.1). This requirement does not preclude the use of narrow slots or openings in thewall of an insulating bushing when the intended cable, flexible cord, or insulated wire is not capable ofbeing pressed into such slots or openings.
(PROPOSED VERSION OF SECTION 5)
5 Materials
5.1 General
5.1.1 Ceramic materials and some molded compositions such as phenolic and urea formaldehyde arecapable of being used as materials for a separate insulating bushing. Vulcanized fiber is not prohibitedfrom being used when the bushing is not less than 3/64 inch (1.2 mm) thick, and when it is formed andsecured in place so that it is not adversely affected by conditions of typical moisture. Other materials, suchas nylon, are capable of being used after a suitable investigation. See Humidity Test, Section 11, andElevated Temperature Test,Section 12.
5.1.2 Wood, hot-molded shellac, tar compositions, or rubber shall not to be used as materials for aseparate insulating bushing.
5.1.3 The wall thickness of an insulating bushing shall not be less than 3/64 inch (1.2 mm) unless athickness has been determined to be capable of being used as a result of an investigation. See referenceto vulcanized fiber in 5.1.1. This requirement does not preclude the use of narrow slots or openings in thewall of an insulating bushing when the intended cable, flexible cord, or insulated wire is not capable ofbeing pressed into such slots or openings.