Investigating the thermal stability of thermoplastic polymer composite materials containing recycled rubber for railway rail pad applications

Abstract

Railway rail pads are critical components of rail fastening systems, ensuring vibration damping, load distribution, and structural stability of the track. During operation, these elements are subjected to significant temperature fluctuations and cyclic mechanical loads, which require materials with high thermal stability and durability. In this study, the thermal behavior of newly developed thermoplastic polymer composite materials containing recycled rubber powder was investigated for potential application in railway rail pad systems. Six composite formulations based on high-density polyethylene (HDPE), polypropylene (PP), ultra-high molecular weight polyethylene (UHMWPE), polyvinyl chloride (PVC), ethylene-vinyl acetate (EVA), plasticizer, modifier, and recycled rubber particles were prepared and analyzed. Thermogravimetric analysis (TGA), derivative thermogravimetry (DTG), and differential scanning calorimetry (DSC) were used to evaluate the thermal degradation mechanisms, onset decomposition temperature, and residual mass characteristics of the developed materials. The obtained results demonstrate that the incorporation of recycled rubber particles leads to increased char residue and modifies the degradation kinetics of the polymer matrices. Among the investigated compositions, the UHMWPE–HDPE-based composite exhibited the highest thermal stability, with the main degradation stage occurring at temperatures above 400 °C, indicating enhanced resistance to thermal degradation. Conversely, the PVC-based composite showed early mass loss associated with the dehydrochlorination process. Comparative analysis with a commercially used railway rail pad material revealed that the developed composites exhibit comparable or improved thermal resistance within the operational temperature range of railway fastening systems. The findings suggest that thermoplastic composites containing UHMWPE and recycled rubber powder represent promising candidates for the development of durable and thermally stable railway rail pad materials.