SIAM: Science and Innovation of Advanced Materials

Effect of Epoxidized Natural Rubber as A Compatibilizer in Thermoplastic Polyurethane/Natural Rubber Blends

2024-08-19T08:54:50+07:00

This study investigates the influence of epoxidized natural rubber (ENR) as a compatibilizer in thermoplastic polyurethane (TPU)/natural rubber (NR) blends, which were prepared through an internal mixer and compression molding. The mixing condition and mechanical properties optimization of the blends were examined following the variation of ENR concentrations. The mixing torque during blending was used to assess the homogeneity degree and processing characteristics based on the incorporation of the ENR. Mechanical properties in terms of tensile properties and impact strength were investigated to elucidate the role of ENR in enhancing the strength of the blends. The modulus and tensile strength increased by adding ENR, reaching an optimal concentration at 3 phr. Also, impact strength confirms the beneficial effects of ENR by exhibiting increased toughness and resistance to impact-induced failure at an appropriate amount of ENR to prevent aggregation when the quantity is excess. These findings highlight the ability of ENR to promote compatibility and enhancing the mechanical properties of TPU/NR blends at 3 phr of ENR loading, offering insights into the development of high-performance elastomeric materials. The presented homogeneous TPU/NR and ENR combination enables the blend for various applications, particularly filament fabrication and 3D printing product development.

Keywords: Epoxidized natural rubber, Compatibilizer, Thermoplastic polyurethane, Natural rubber, Polymer blends

Enhancing Mechanical and Thermal Properties of Natural Rubber Grafted Poly(Ethyl Acrylate) Using Glutaraldehyde as a Curing Agent

2024-09-21T17:22:45+07:00

Ethyl acrylate (EA) monomer was successfully grafted onto natural rubber (NR) via redox polymerization, which enhanced the grafting efficiency to 91%. The grafted-NR was clarified using ATR-FTIR. This study focuses on enhancing the mechanical and thermal properties of the grafted-NR vulcanized by using a low-temperature curing system of glutaraldehyde (GA). It was found that the mechanical properties of grafted-NR were superior to those ungrafted-NR, with a 35% increase in modulus, 145% increase in tensile strength, and 17% increase in elongation at break. Moreover, oil resistance properties and thermal stability of NR were significantly improved after graft copolymerization owing to the presence of functional groups in the molecular chain. It was also demonstrated that the grafted-NR exhibited improved crosslinking, elucidated through swelling and temperature scanning stress relaxation (TSSR) measurements. The relaxation behavior was evaluated through TSSR, revealing two significant peaks in chemical and physical relaxations. According to these findings, it can be summarized that the properties of grafted-NR improved by using a GA curing agent with several possibilities of interaction, including GA-rubber crosslinks, GA-protein crosslinks, GA-ester crosslinks, and polar-polar interactions facilitated by the presence of carbonyl groups on grafted-NR molecules. Therefore, this current work is beneficial for future flexible material applications requiring high mechanical properties, oil resistance, and thermal stability.

Keywords: Natural rubber latex, Graft copolymerization, Glutaraldehyde

Effect of Modified Zinc Oxide-Silica Nanocomposites on Epoxidized Natural Rubber/Tire Waste Composites Properties

2024-09-18T16:36:16+07:00

Epoxidized natural rubber (ENR) was blended with tire waste (TW) and modified zinc oxide-silica nanoparticles (ZnO-SiO₂) using melt mixing, with NR acting as a compatibilizer to link the two incompatible phases—between the polar epoxy groups of ENR and the non-polar rubber in TW. Various ZnO-SiO₂ concentrations of 5, 10, 15, and 20 phr were investigated to determine their effects on cure characteristics, mechanical properties, and antibacterial efficiency of the received composites. It was found that adding ZnO-SiO₂ improved crosslink density, thereby enhancing the acceleration activity of the chemical crosslinking processes, which resulted in longer cure times and scorch times. Optimal loading of 20 phr enhanced the 100% and 300% moduli values to 1.29 and 3.73 MPa, respectively, along with a tensile strength of 10.52 MPa, highlighting the improved mechanical properties of the nanocomposite with ZnO-SiO₂ loadings. This optimal loading also provided superior antibacterial activity, achieving over a 99.0% reduction in bacterial presence within 24 h through releasing Zn²⁺ ions and generating reactive oxygen species (ROS). At this concentration, the optimal values regarding ZnO-SiO₂ particles that can form further agglomerates are reached. These findings support the development of rubber composites with improved performance and durability, as well as enhanced antibacterial protection, for various rubber applications, including footwear, self-pads, and rubber floor mats, highlighting their significance in enhancing product safety and longevity.

Keywords: Natural rubber, Epoxidized natural rubber, Tire waste, Nanocomposites, Antibacterial efficiency

Functionalization of Microcrystalline Cellulose through Integrated Sodium Periodate and TEMPO/Ozone Oxidations

2024-09-12T12:36:53+07:00

Cellulose modification has been a primary focus in developing bio-based degradable functional materials. In this study, an integrated approach combining sodium periodate (NaIO₄) and TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl)-ozone oxidation process is employed to functionalize microcrystalline cellulose (MCC). The resulting materials in water-soluble and precipitate fractions were characterized to understand the influences of each oxidation method on the reaction mechanisms, structures, and physicochemical properties of the oxidized MCC samples. The results demonstrated that the combination of both methods resulted significantly in chemical structures, morphology, and surface reactivity of the samples. FTIR spectra showed an appearance of oxidized functional groups, i.e., carboxyl, ketone, and aldehydes, confirming a successful oxidation process. The use of ozone as a co-oxidant contributes positively to environmental aspects and process economics due to its availability and low cost. These findings illustrate the considerable potential of ozone utilization in improving cellulose properties for various applications. Consequently, the integrated approach offers an effective and sustainable solution for enhancing the quality and performance of cellulose, paving the way for further research and applications in the field of cellulose materials.

Keywords: Microcrystalline cellulose, TEMPO, Periodate, Ozone, Oxidation process

Network Dimension Theory and Its Application to Miniemulsion Vinyl/Divinyl Copolymerization

2024-09-21T16:34:55+07:00

Newly developed network dimension theory is used for rapid estimation of the root-mean-square radius of gyration of each polymer molecule formed during vinyl/divinyl copolymerization. The -value is used for describing the enhancement of intramolecular crosslinking or the cyclization reactions. The model is applied to the miniemulsion copolymerization, and both conventional free-radical polymerization and ideal living polymerization are considered. Some of important characteristics of network architecture formed in these two types of polymerization mechanisms that cannot be predicted based on the classical chemical kinetics can be reproduced by the model successfully. For example, such unique characteristics as the pendant double bonds are consumed from the start of polymerization in conventional free-radical polymerization but not so in living polymerization can be elucidated. The present kinetic model provides useful insights into the size- and structure-dependent network formation.

Keywords: Crosslinking, Emulsion polymerization, Gelation, Graph diameter, Radius of gyration