Novel Renewable Materials from Natural Rubber and Agro-Industrial Residues

• Main Author: Barrera Martinez, Cindy Sofia
• Format: Dissertation
• Language: English
• Published: Ann Arbor ProQuest Dissertations & Theses 2016
• Subjects: Engineering
• ISBN: 9781369590951; 1369590954

Natural rubber is currently one of the most important crop-produced industrial bio-based materials in the world. Further improvements in rubber inherent properties are obtained by the addition of fillers, enabling polymeric products suited to highly demanding applications. However, most existing fillers are neither renewable nor sustainable. Agro-industrial residues are highly abundant solid wastes that represent a promising source of alternative fillers. Moreover, the renewable character of these residues could improve the sustainability of natural rubber products while adding value to these waste materials. Fillers obtained from agro-industrial residues, namely, eggshells, carbon fly ash, processing tomato peels and guayule bagasse, were used for the manufacture of composites with both hevea and guayule natural rubber. The effect of amount, type and particle size of waste-derived fillers on power consumption during mixing of the rubber compounds, and on mechanical properties of compression molded test pieces were investigated. Waste-derived fillers were used as partial and complete replacement of petroleum-derived carbon black (industrial reference reinforcing filler). Unfilled compounded rubber and composites containing carbon black with no other filler were used as reference materials. Reinforcement of unfilled hevea and guayule rubber compounds was obtained with most waste-derived fillers used, particularly composites containing micro and nano sized eggshells and tomato peel particles. This can be attributed to different factors related to filler characteristics including particle structure, size, bulk density, alkalinity and surface activity. The introduction of co-filler systems, in this case carbon black with various waste-derived materials at low loadings, generated materials with superior or similar mechanical properties than those of composites made solely with carbon black. This reinforcement may reflect a combined synergistic reinforcing effect of carbon black particles, which possess a strong polymer-filler interaction, with the formation of a unique network between the rubber and the waste-derived materials. This effect was more pronounced in guayule than hevea rubber as a result of differences in rubber structure and composition (non-rubber components) between these two natural rubber matrixes. These differences affect the overall reinforcement achieved with the waste-derived fillers. These results could strengthen ongoing commercialization efforts of guayule products. Unusual combinations of mechanical properties were achieved with both types of rubber. Also, this work showed that micro sized fillers are effective reinforcing fillers. Micro-fillers can be produced at a far lower cost than their nano-sized versions.