This study investigated the properties of the natural rubber (NR) foam filled with azodicarbonamide (ADC) blowing agents by combination to various ratios of epoxidized NR (ENR) for flexible foam applications. Compound operation was prepared with an open two-roll mill and the production was fabricated by compression molding. The study elucidated properties related to crosslinking behaviors, mechanical and dynamic properties, elasticity, abrasion, weathering resistance, and sound absorption efficiency. The ENR and ADC concentrations affected the tensile testing and also the durability properties of the NR/ENR. The NR and ENR foam of 60/40 filled with 10 phr of ADC demonstrated good properties across various parameters, showing acceptable tensile properties, abrasion resistance, and QVA light resistance. Additionally, the presence of a closed-cell structure in the blends reduced crack propagation in the NR matrix during aging, improving weathering resistance. The absorption coefficient increased with higher ADC content, being optimal at 15 phr, due to the lower density and higher porosity of the opened-cell material, which enhances its ability to interact more effectively with incoming energy at 1600 and 6400 Hz. The findings encourage the use of ENR for blending in NR for improved ENR and ADC concentrations since dipole-dipole interaction from ENR-ADC caused ADC dispersability, providing complexed foam structures for force expansion and aslo sound wave absorption.

This paper extends previous studies by the authors that aimed to describe the effect of apparent cross-link density (CLD) of the rubber polymer networks on the fracture mechanism caused by cut and chip (CC) wear of natural rubber (NR), demonstrating the positive effect of conventional vulcanization (CV). This work is focused on the determination of the effect of CLD while keeping constant the accelerator-to-sulfur ratio A/S = 0.2, typical for CV systems. For this ratio, different sulfur quantities were chosen, and the concentration of the accelerator N-tert-butyl-benzothiazole sulphonamide (TBBS) was calculated to achieve CLDs in a range from 35 to 524 μmol・cm^–3. Standard analyses such as tensile tests, hardness, rebound resilience and DIN abrasion were performed. From these analyses, the optimum physical properties of the NR-based rubber were estimated to be in the CLD range of approximately 60 to 160 μmol・cm^–3. A CC wear analysis was performed with an Instrumented cut and chip analyzer (ICCA) and it was found that the highest CC wear resistance of the NR is in the CLD range of 35 to 100 μmol・cm^–3. Furthermore, the effect of straininduced crystallization (SIC) of NR on CC wear and its dependence on the CLD region was discussed. For the first time, we determine a CLD range for a CV system in which the material achieves both optimal mechanical properties and CC wear resistance.

In this study, a novel methodology for the fabrication of gradient porous structures is introduced, predicated upon the phase evolution characteristics of immiscible polymer blends. Initially, a comprehensive flow-phase field dynamics model is developed. This model couples the principles of phase field theory and the dynamics of fluid flow to the two-phase evolution process, facilitating a numerical simulation of the phase evolution. Subsequently, the phase field parameters of model are determined and combined with the temperature field, thereby enabling a targeted and controlled fabrication of gradient porous structures. Finally, the efficacy and practical applicability of the proposed methodology are substantiated through the construction of illustrative examples. This approach, as delineated herein, provides a robust framework for the efficient design and realization of intricate, interconnected gradient porous structures with potential applications in various scientific and engineering domains.

The present study aimed to prepare prevulcanized latex from modified natural rubber (NR) latex, graft copolymers of natural rubber and poly(vinylbenzyl chloride), NR-g-PVBC. The prevulcanized latex was prepared by heating NR-g-PVBC latex in the presence of adipic acid dihydrazide (ADH). The study showed that the tensile strength of the NR-g-PVBC films with ADH was significantly higher than that without ADH. Interactions of NR-g-PVBC with ADH were further investigated using X-ray photoelectron spectroscopy (XPS). Higher storage modulus (E′) in the rubbery plateau region was also observed for the films with ADH than that without ADH. These results corroborated that the crosslinking reaction occurred in the film with the addition of ADH. It was found that the optimal prevulcanization time was 20 min at 55 °C. After that, the effect of storage on the tensile properties of the prevulcanized latex was studied. Atomic force microscopy (AFM) analysis was performed to follow changes in the surface morphology of films obtained from the prevulcanized latex. A zeta potential value of –37.83 was observed for the prevulcanized latex after being stored for 60 days. Therefore, the present study demonstrated that grafting poly(vinylbenzyl chloride) onto NR particles offered an opportunity to prepare a new type of prevulcanized latex. This new system was accelerator-free and zinc-free, considered more environment-friendly than a sulfur-prevulcanization system.