Engineered polysaccharide, Alpha-1,3 Glucan, as a Functional Filler of Rubber Composites

Abstract

Rubber products represent an essential and highly functional class of performance materials required in many daily applications. However, the increasing interest in enhancing the overall material sustainability of rubber products has accelerated the focus on compatible, lightweight, and environmentally sustainable fillers. As part of the effort to design sustainable rubber composites, enzymatic polymerization-derived polysaccharide fillers, alpha-1,3 glucan, with designed fibrids, platelet and spherical morphology and high crystallinity was employed as a novel sustainable filler system in natural rubber (NR) films. The alpha-1,3 glucan is supplied by International Fragrances and Flavors (IFF), former E.I. DuPont Industrial Biosciences. Initially, lightly crosslinked NR films reinforced with 0 – 10 phr MCG were fabricated using dipping and casting processes. The effect of MCG on the physicochemical properties, chemical stability, and thermo-mechanical properties of the composite films was investigated. In the subsequent project, colloidal alpha-1,3 glucan with spherical morphology was employed as a functional filler of NR coating films. Coating formulations containing NR latex and 10 – 100 phr colloidal alpha-1,3 glucan were prepared and applied to paper substrates at three different thicknesses. The effect of various coating formulations on the barrier properties against water vapor, oxygen, oil as well as on dry and wet mechanical properties were investigated. In order to study the impact of alpha,1-3 glucan’s morphology on the barrier properties of the paper coating, the following studies were conducted. This study employed enzymatically polymerized microcrystalline glucan (MCG) as a functional additive in natural rubber (NR)-based coating formulations. Typically, NR coating formulations containing 0–50 wt. % MCG were fabricated at a constant coating thickness with a constant solid content. The influence of MCG on the wet and dry strength, rheology, adhesion strength, and barrier properties such as moisture, oxygen, and grease barrier of the formulated coatings was investigated. Also, further study on the effect of solid content and low crosslinking on the barrier properties was conducted. The last stage of the study involved a solvent-free, batch mixer-based reactive process to carry out the reaction of ENR with glucan. In order to enhance the degree of dispersion and bonding of polar filler in a nonpolar natural rubber matrix, in situ melt grafting of epoxidized natural rubber (ENR) onto the polysaccharide was employed to achieve enhanced material properties. The process of temperature and shear-mediated melt grafting, in the presence of two catalysts (sodium hydroxide (NaOH) and dicumyl peroxide (DCP)), was investigated. Analytical characterization techniques, including Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and solvent swelling, were employed to confirm the formation of covalent bonds between alpha1,3-glucan and ENR. The selected ENR-glucan masterbatch samples were then subjected to melt-mixing with NR formulations to produce NR composites. Overall, this study aimed to develop a sustainable rubber composite with the incorporation of alpha-1,3 glucan as a functional filler targeting dipped rubber, packaging, and footwear applications and indicating the potential of this study in alleviating the environmental pollution induced by traditional polymers.