Foamable composition and coaxial cable having insulating foam layer

摘要

A foamable composition containing a base polymer containing a polyethylene mixture of a low density-polyethylene having a density of 0.91-0.925 g/cm³ and a high density polyethylene having a density of 0.94-0.97 g/cm³, and a fluororesin powder and/or a boron nitride powder as a nucleator, wherein the high density polyethylene has an swelling ratio smaller than that of the low density polyethylene and a melt flow rate greater than that of the low density polyethylene, and is contained in a proportion of not less than 50 percent by weight of the polyethylene mixture, and the base polymer has a shear viscosity (temperature:170° C., shear rate:1216 sec^−1) of not more than 3150 poise, and a coaxial insulating cable having an electrically insulating layer formed of a foam having an expansion ratio of not less than 70% and obtained by foaming the above foamable composition are provided. The insulating layer formed from the foamable composition has superior attenuation property and can be suitably used for a feeder antenna of a portable communication device.