Polypropylene heterophasic copolymer for loose tube buffers

摘要

Several different cable constructions exist to protect optical fibres from all kind of stresses during manufacturing, storage, transport, installation and operation. The loose tube cable design has become very popular as the buffer tube can easily be stripped for jointing. A material suitable for loose tube buffers must fulfill several requirements. The buffer must hold its dimension, be tough, have good heat ageing properties and be flexible. Polybutylene tereph-thalate (PBT) and polyamide(PA)havetraditionally buffers. Polypropylene (PP) has many properties that are advantageous such as low density, flexibility at low temperatures, good processability, hydrolytical stability and low cost. 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 fibre. The tube is extruded around fibres and simultaneously filled with gel. This three-phase system has to be optimised. This study was made in order to investigate which structure properties of heterophasic PP copolymers affect one of the main requirements for loose tube buffers, namely the excess fibre length (EFL) and shrinkage.