QUANTIFICATION OF THE CONTRIBUTION OF FILLER CHARACTERISTICS TO NATURAL RUBBER REINFORCEMENT USING PRINCIPAL COMPONENT ANALYSIS

Determination of the most significant rubber components influencing the hardness of natural rubber (NR) using various statistical methods

Manufacturers use a large number of components in the production of modern rubber products. The selection of the constituents of the rubber recipe is primarily determined by the purpose of use. The different fields of applications of rubbers require the presence of appropriate mechanical properties. In this respect, it can be useful to know which substances forming the rubber recipe have significant influence on the different mechanical properties. In this study, the statistical analysis of the influence of rubber components on the hardness of natural rubber (NR) is proposed based on literature review. Based on the literature data, various statistical analyses, like linear regression, constrained linear regression, Ridge regression, Ridge sparse regression and binary classification decision trees were performed to determine which rubber components have the most significant effect on the hardness. In the statistical analyses, the effect of a total of 42 constituents of rubber compound on hardness was investigated. Most of the applied statistical methods confirmed that the traditional frequently used rubber components, such as carbon black and sulfur, have a primary effect on the hardness. However, the substances forming the rubber compound that are not widely used in practice or newly developed components appear differently in the lists of significant additives obtained by the different statistical methods.

Characterization and potential valorization of industrial food processing wastes

Valorization and utilization of industrial food processing waste as value added products, platform chemicals and biofuels, are needed to improve sustainability and reduce waste management costs. Various industrial food waste stream samples were characterized with respect to their physico-chemical characteristics and elemental composition. A subset of starchy food wastes and milk dust powder were evaluated in batch fermentation to acetone, a useful platform chemical. Production levels were similar to acetone produced from glucose but were achieved more quickly. Lactose concentration negatively affected fermentation and led to 50 % lower acetone concentration from milk dust powder than from starchy wastes. Uncooked starch waste can produce 20 % more acetone than cooked and modified starch waste. Fatty waste and mineral waste can be digested anaerobically generating biogas. Calorific value of soybean waste was 40 MJ/kg sufficiently high for biodiesel production. Low C/N ratios of wastewater and solids from food processing waste makes them unsuitable for anaerobic digestion but these waste types can be converted thermochemically to hydrochar and used as soil amendments. Low calorific content (10-15 MJ/kg) vegetable wastes also are not ideal for energy production, but are rich in flavonoids, antioxidants and pigments which can be extracted as valuable products. A model mapping food waste characteristics to best valorization pathway was developed to guide waste management and future cost and environmental impact analyses. These findings will help advance food industry knowledge and improve sustainable food production through valorized processing waste management.

Liquid Guayule Natural Rubber, a Sustainable Processing Aid, Enhances the Processability, Durability and Dynamic Mechanical Properties of Rubber Composites

Petroleum-based oils are widely used as processing aids in rubber composites to improve processability but can adversely affect rubber composite performance and increase carbon footprint. In this research, liquid guayule natural rubber (LGNR), produced from guayule natural rubber, was used as a renewable processing aid to replace naphthenic oil (NO) in Hevea natural rubber, styrene-butadiene rubber (SBR) and guayule natural rubber (GNR) composites. The rheological properties, thermal stability, glass transition temperature, dynamic mechanical properties, aging, and ozone resistance of rubber composites with and without NO or LGNR were compared. Natural and synthetic rubber composites made with LGNR had similar processability to those made with NO, but had improved thermal stability, mechanical properties after aging, and ozone resistance. This was due to the strong LGNR–filler interaction and additional crosslinks formed between LGNR and the rubber matrices. The glass transition temperature of SBR composites was reduced by LGNR because of its increased molecular mobility. Thus, unlike NO, LGNR processing aid can simultaneously improve rubber composite durability, dynamic performance and renewability. The commercialization of LGNR has the potential to open a new sustainable processing-aid market.

Characterization of Agricultural and Food Processing Residues for Potential Rubber Filler Applications

Large volumes of agricultural and food processing residues are generated daily around the world. Despite the various potential uses reported for this biomass, most are still treated as waste that requires disposal and negatively impacts the environmental footprint of the primary production process. Increasing attention has been paid toward the use of these residues as alternative fillers for rubber and other large-scale commodity polymers to reduce dependence on petroleum. Nevertheless, characterization of these alternative fillers is required to define compatibility with the specific polymer, identify filler limitations, understand the properties of the resulting composites, and modify the materials to enable the engineering of composites to exploit all the potential advantages of these residue-derived fillers.

REINFORCED MECHANICAL PROPERTIES OF FUNCTIONALIZED SILICA AND EGGSHELL FILLED GUAYULE NATURAL RUBBER COMPOSITES

Replacing synthetic fillers, which are commonly used to reinforce rubber, with bio-fillers has potential to improve the sustainability of rubber products. Eggshell (ES) (a powder with a maximum particle diameter of 9.4 μm and a median of 1.1 μm) was added to guayule natural rubber (GNR) composites to partially or fully replace bifunctionally silanized, high surface area, precipitated silica (BSS). The mixing energy consumption, mechanical properties, cross-link density, filler dispersion and final particle size, fracture surface morphology, and dyeability of GNR composites were characterized. ES filler effectively reinforced vulcanized GNR compared with unfilled vulcanized GNR. Energy consumption, modulus at 300% strain (M300), and hardness generally decreased with increasing ES fraction (decreasing BSS), but tensile strength, gel fraction, and elongation at break increased even where cross-link density and M300 were similar. Thus, composite cross-link density was not solely influenced by silane content as the ratio and loading of ES and BSS changed. The production of the composites reduced particle size to submicron size. Even a small amount of ES improved the dispersion of BSS filler particles in the composites and hence the mechanical properties. The contributions of the two fillers to the composite properties are explained. Linear mixed models were built to predict the mechanical properties of a broader range of GNR–ES–BSS composites, and r2 (the quality of the model predictability) was above 0.9 for all models. ES filled GNR, with or without BSS, can be dyed different colors for specific applications. The lower-cost, renewability, dyeability, and excellent performance of ES–GNR composites addresses the need for sustainable rubber products with low carbon footprint.