Evaluation on the Service Life of a Plastic Covering Material of Steel Wire Cable for the Long Bridge

Abstract

Firstly, the service life of the 28-year-old plastic covering material of cables for the long bridge was evaluated. Mechanical degradation such as crack generation and remarkable bending strength reduction on the plastic covering material was not found because of the past adequate maintenance for coating film layer covered on the plastic covering material. However, by means of chemical evaluation method such as FT-IR, the slight chemical degradation was confirmed and shown as follows. (1) Main molecular chains of the coating film (polyester) and side chains of base resin (PMMA) were detached by hydrolysis. (2) The glass transition temperature of the base resin was raised by polymerization. Secondly, to examine effective degradation detection methods, the degradation experiment was conducted on PMMA test samples without containing anti-oxidants and pigments in the autoclave at 70°C with saturated water and pure O₂. Effective degradation detection methods were as follows: inspection with optical microscope, measurement for bending strength, dynamic hardness, dynamic viscoelasticity, FT-IR, DSC, and solid ¹³CNMR.