Major Results of Research and Development in Fiscal 2001

8. Recycling Technologies of Organic Materials used for Rolling Stock

In recent years, environmental problems, such as pollutant gas from incineration and shortage of land filling space, are concerned as one of common issues. In the railway field, disposal process of organic materials used for rolling stock have a lot to do with this issue. When rolling stock was renewed, many kinds of organic materials were wasted. The Railway Technical Research Institute (RTRI) has studied applicable recycling technologies in consideration of properties and disposal amounts of each organic materials.

(1) Recycling technology for FRP
It is found that ordinary recycling methods such as material recycling and thermal recycling (recovery of combustion energy) are applicable to thermoplastic polymer. But FRP is a thermosetting polymer and the disposal amount of FRP is rather small. So, a certain material recycling process, that is simple and is not depend on the amount, is considered suitable for FRP. From this aspect, disposal FRP is crushed into powder and this powder is applied to filler for resin moldings or fine concrete aggregate.
It was found that resin moldings had enough flexural strength up to 40wt% blend of FRP powder (Fig. 1 and 2). This shows resin moldings blended FRP powder is applicable to railway product such as troughs and resin boxes. From a recycling-friendly aspect, it was also suggested that non-halogen thermoplastic polymer was a suitable polymer to be applied to newly manufactured rolling stock.

(2) Recycling technology for Poly (vinyl chloride)
Poly (vinyl chloride) (PVC) used as a floor sheet of rolling stock has a good properties such as weather resistance, durability and flame retardance. However, PVC contains much chlorine in this molecular structure, it is difficult to combust not to produce toxic gas. There has been a strong demand for development of recycling technology of PVC. To meet this demand, RTRI manufactured two types recycled samples using disposal PVC floor sheet, one is fixed by resin binder and the another is re-molded by melting. Through an artificial weathering, degraded property of these samples were investigated. After two thousand hours of artificial weathering (that is equivalent to approx. ten years natural exposure), results of tensile strength and dynamic viscoelasticity were not degraded from initial performances. It was found that these recycled PVC samples had an enough performance as a long-term outdoor use (Fig. 3). And it is found that the degradation mechanism was close related to molecular motion. Therefore, in future, it has a possibility to expect more durability of these samples.

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