Polypropylene Heterophasic Copolymer for Loose Tube Buffers - Material Choice, Processing Conditions and Economy

摘要

Different cable constructions exist to protect optical fibers from all kind of stresses during manufacturing, storage, transport, installation and operation. Traditionally polybutylene terephthalate (PBT) has been used in loose tube buffers to fulfill the requirements. The buffer must hold its dimension, be tough, have good heat aging properties and be flexible. Polypropylene (PP) has many properties that are advantageous such as low density, flexibility at low temperatures, good processability and hydrolytical stability. Furthermore, PP is not sensitive to kinking. The most important aspect of the manufacturing process for loose buffers is the precise matching of the length of the buffer tube with the optical fiber. The tube is extruded around fibers and simultaneously filled with gel. This three-phase system has to be optimized. In this investigation, which is a continuation of a study reported in 2002, we have further optimized heterophasic PP copolymers with different nucleation and the effect on shrinkage, i.e. excess fiber length (EFL) directly after extrusion and after 24 hours in room temperature on coil. Change of certain process parameters and the influence on EFL is also reported. Furthermore, the potential cost saving by using PP in buffer tubes.