Soil Burial Tests: Effect of Soil Burial Exposure on the Properties of Rubber, Crosslinked Polyethylene, and Vulcanized Wire Coatings

R u b b e r and other vulcanized polymers play an important role in the construction of a great deal of the hardware and equipment used in the Bell System. The uses range from wire and cable jackets and insulations to molded goods, such as the floor tiles in phone booths, splicing tape, underground conduit and couplings, waveguide supports, and manhole seals. Through the years more and more of the plant. 87 88 T H E BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1972 equipment has been and will be buried, necessitating the development of vulcanizate compounds t h a t can withstand the rigors of different soil environments to provide twenty to t h i r t y years service life. 0. DeVries reported the destruction of 22 percent of the hydrocarbons of "fresh raw r u b b e r " by fungi in two years and 30 percent in five years. 1 B u t one m u s t question t h e purity of any sample of n a t u r a l rubber ( N R ) and assume t h a t the diluents therein have promoted this degree of consumption, for it has been found t h a t most pure synthetic polymers, by themselves, are generally resistant to fungi, i.e., polymers do not serve as a source of carbon for the growth of fungi. 2 , 3 However, they do not inhibit their growth. For this reason, the assorted ingredients t h a t are added in making up a useable compound must be selected with care to be sure t h a t they are not biologically susceptible. Although individual components m a y be resistant, in combination with others they m a y be susceptible to deterioration.