Abstract: Buffer tubes are polymeric tubes utilized in the design of fiberoptic cables (FOC) to protect the fibers from mechanical stresses and to prevent moisture from reaching the optical fibers, both of which can cause fiber damage and lead to signal losses. In a wet loose buffer tube design, glass fibers are suspended in a gel filling compound that also provides additional mechanical protection and functions as a barrier to moisture ingress. The gel or grease however can be absorbed into the polymeric buffer tube material over time which causes a loss in modulus and reduces its ability to provide the desired mechanical protection. Modulus retention of the buffer tube material after exposure to tube filling gel is a critical parameter for minimizing mechanical stresses on the fiber. In this paper, high modulus olefin compounds for loose buffer tube applications will be discussed. Properties that are critical for the buffer tube application such as modulus, gel resistance, flexibility, melt strength; low temperature mechanical properties, shrinkage, and extrusion performance are presented. The compounds offer improved retention of modulus after aggressive aging in buffer tube gels compared to a typical polypropylene copolymer (cPP) based material. In addition, higher melt strength is achieved, which is critical to ensure geometrical integrity of the tube after extrusion and before polymer solidification. The compounds maintain comparable shrinkage characteristics to cPP and overall achieve a better balance of critical properties for buffer tube applications.
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