Inspired by the micro structure of loofah sponge in nature, this article successfully employs a biomimetic approach to develop a novel series of natural Eucommia rubber foamed materials with excellent shape memory properties. This article explores the characteristic features of natural Eucommia ulmoides rubber foamed materials, including the foaming process, mechanical properties, shape memory performance, and adsorption properties. This paper introduces the innovative use of natural Eucommia ulmoides rubber’s shape memory properties to create a temperature-responsive foam adsorbent material. The foamed material’s unique ability to modify its pore structure through simple compression and heating processes offers tailored adsorption speed and capacity for varied practical applications. The adjustable adsorption properties of this foamed material present novel opportunities for its utilization in adsorption applications.

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.

Natural rubber (NR) composites filled with silica and crosslinked with phenolic resin were prepared in this study. The influence of a small sepiolite addition (1–5 part(s) per hundred parts of rubber, phr) on the properties of NR composites was studied. It was found that sepiolite reduced silica aggregate size, allowing improved dispersion in the NR matrix. Sepiolite facilitates silica dispersion by locating at the silica surfaces and acting as a barrier that prevents agglomeration of silica filler. The swelling resistance, crosslink density, tensile strength, and strain-induced crystallization were all strengthened by incorporating sepiolite because of the improved silica dispersion. The greatest tensile strength was achieved at a 2 phr sepiolite addition level. The improvement was about 18% over the reference composite due to the greatest filler-rubber interactions and the finest filler dispersion. The results clearly indicate that sepiolite clay can be applied as a dispersing agent in silica-containing rubber composites.

Dynamic cross-linked networks (DCNs) endow thermoset rubber with self-healability and recyclability to extend its lifetime and alleviate environmental pollution. However, the contradiction between high self-healing and mechanical properties in DCNs rubber is always difficult to be resolved. Herein, we used boronic ester (BO) and Diels-Alder dynamic covalent bonds (DA) to synthesize polybutadiene-based dual networks rubber (PB-BO-DA) via thiol-ene reaction. This approach achieved a tensile strength of 16.46 MPa and 99% self-healing efficiency, facilitated by extensive intermolecular interactions (π-π packing and N-B coordination) and fully dynamic cross-linking. In addition, multiple dynamic cross-linked networks (MDCNs) polybutadiene-based rubber also show excellent shape memory ability and recyclability. This strategy might open a helpful pathway to fabricate intelligent multifunctional polymers with high strength and high self-healing efficiency.

Epoxidized natural rubber with 50 mol% epoxide (ENR-50) was compounded with zinc chloride (ZnCl₂) and subjected to torque response analysis using a moving die rheometer. It was found that different ZnCl₂ concentrations (3, 5, 7, 9, and 12 millimoles (mmol)) mixed in ENR-50 exhibited positive torque responses, prompting further molecular characterization using Fourier transform infrared spectroscopy. The results indicated distinct absorption peaks at wavenumbers of 442 and 809 cm^–1, which signify the presence of –O–Zn–O– coordination linkages. The curing characteristics of ENR and ZnCl₂ compounds showed that increasing ZnCl₂ content resulted in higher minimum and maximum torque values, but also led to a decrease in scorch time and cure rate index (CRI). Moreover, higher ZnCl₂ concentrations enhanced the strength properties (tensile strength, moduli, stiffness, toughness, and hardness), crosslink densities, dynamic shear moduli, initial modulus during relaxation experiments, and thermal resistance, as evidenced by temperature scanning stress relaxation (TSSR), thermogravimetric analysis, and dynamic mechanical analysis. However, an increase in ZnCl₂ content led to a reduction in elongation at break due to the higher crosslink density within the coordination networks in the ENR matrix, which resulted in the movement constraint of the rubber vulcanizate.