Development of synthetic fiber-based reinforcements for thermoplastics as alternative to steel-based analogs for industrial applications

Abstract

Despite being robust and inexpensive, steel cords can often become a source of risk to user health and safety when incorporated in industrial applications such as escalator handrails and rubber conveyor belts. Due to their inherent creep accompanied by cyclic thermal expansion and contraction of steel cords, the overall stability and performance of the application can reduce over time. In this context, the present research focuses on an innovative approach to replace steel cords by designing, developing and processing synthetic fibers of high specific strength (based on carbon, glass, and/or Kevlar fibers) to develop Thermoplastic Polyurethane (TPU) composites with superior mechanical properties and enhanced safety characteristics. The experimental work proposed in this thesis is divided into 3 distinct experimental research phases. The experimental results of phase 1 show that the epoxy coating on synthetic fibers significantly increases its load-bearing capacities due to improved compatibility between the fibers and the TPU matrix caused by chemical interaction and enhanced interlocking. Experimental results from phase 2 revealed that the injection molding process parameter related to temperature was the most significant process control variable compared to the injection pressure and the processing time in achieving high tensile properties. The ANOVA test confirmed the significance of temperature at a 99 % confidence level. The mathematical model generated through Response Surface Methodology (RSM) predicted a model with an accuracy of 98.06 %. Phase 3 results emphasized that the electrolytic treatment of carbon fibers created active sites and roughened the surface. When coated with a silane coupling agent, this electrolytically modified carbon fiber (with sulphuric acid electrolyte) increased 39 % in load-bearing capacity against raw carbon/TPU.