Rubber compounds with bioash filler : a case of circular economy

A circular economy is an economic system aimed at eliminating waste and at continuous using of resources. Circular systems employ reuse, sharing, repair, refurbishment, remanufacturing and recycling to create a close-loop system, minimizing the use of resource inputs and the creation of waste, pollution and carbon emissions. Circular economy takes part in twelfth Sustainable Development Goal of United Nations Member States: the commitment to a responsible consumption and production. Trelleborg Wheel Systems S.p.a. is a leading global supplier of tyres and complete wheels for agricultural machines, material handling and construction vehicles, and two-wheeled vehicles. Its plant in Sri Lanka produce 3 tons per day of bioash as waste from biomass combustion for the generation of hot steam used in rubber mixing. The bioash could have a high added value if it would be used as new filler in the rubber compounding, avoiding its disposal as waste. The problem is the high dimension of bioash grains and the low compatibility between the polar rubber compound and the apolar bioash. In this work, the possible physical and chemical treatments to improve the compatibility between rubber and bioash are investigated. After a preliminary characterization of the bioash, some mechanical and chemical processes are explored by using of different functionalizers and in various percentages. The resulted bioash is characterized by X-ray Diffraction (XRD), Fourier Transform Infra-Red Spectroscopy (FT-IR), Kumagawa Extraction, Thermogravimetric Analysis (TGA), Particle Size Analysis, Scanning Electron Microscope (SEM), Tap Density Testing and Optical Contact Angle (OCA). The standard formulation of rubber compound for tyres has been modified by the addition of some parts of untreated or treated bioash per hundred rubber. The properties of final rubber are investigated by Dynamic Mechanical Analysis (DMA), Tensile Testing and Dispersion Grade Analysis. A comparison among the most significant results from testing of the compounds with modified bioash, is done in conclusion.

L'economia circolare implica un lungo ciclo di vita del prodotto e una minimizzazione degli sprechi, portando ad un minore impatto sull’ambiente e generando nuova ricchezza. In questa ottica è stato condotto il presente studio, per il caso specifico dell’azienda Trelleborg Wheel System S.p.a. Lo scopo di questa tesi è reintrodurre nel ciclo produttivo della fabbricazioni del composto di gomma standard per ruote solide, la cenere prodotta come scarto dall’impianto di generazione del calore necessario per il mescolamento dei materiali che andranno a comporre il prodotto finale. Prima è stata effettuata un’analisi approfondita per caratterizzare la cenere, poi questa è stata inserita in diverse percentuali nella formulazione del composto standard. Il composto finale è stato sottoposto a test dinamico-meccanici, alla prova di trazione e all’analisi della dispersione dei riempi. Diversi trattamenti fisici e chimici sulla cenere sono stati sperimentati, come anche l’aggiunta di agenti compatibilizzanti alla formulazione al fine di mantenere le proprietà del composto standard