Cellular Polymers

This paper presents an experimental study on manufacture and characterization of an insulating foam coating in the coaxial cables where a physical blowing agent (butane) is used. Coaxial cables with foam insulator are widely used in communication industries. The insulating foam plays a key role in the attenuation properties of the coaxial cables. In this research work, an extrusion setup was prepared to produce foam insulated coaxial cable using butane as the physical foaming agent. The effect of die geometry (die gap and die outlet diameter) on foam morphology and loss-attenuation were investigated using a blend of LDPE (90%)-HDPE (10%) as the main material. The results show that an acceptable low loss-attenuation is achievable via using a polyethylene compound and adjusting processing parameters.

Three UK manufacturers of flexible polyurethane foam collaborated in a study in which cushion sized samples made from different formulations were stored for a period of ten years. Samples were monitored at approximately 6 monthly intervals for retained flame retardant. Two chlorinated phosphate ester flame retardants were investigated - TCPP and TDCP. Neither of these was prone to migration losses during the study period and foam ignition resistance was maintained.