Papers by Keyword: Self-Healing

Abstract: Epoxidized natural rubber (ENR) has attracted significant attention due to its outstanding properties, such as mechanical properties and oil resistance. In particular, the development of self-healing properties without external stimuli in ENR has been an important challenge. In this study, the self-healing ENR composites were successfully developed by incorporating microcrystalline cellulose (MCC) as a reinforcing agent and borax as a dynamic cross-linker. The addition of borax resulted in the formation of dynamic borate-ester bonding and hydrogen bonding, enhancing the mechanical properties and self-healing ability of the composites. Structural analysis confirmed good compatibility between borax and MCC. The borax-grafted MCC reinforced ENR composite with 5 wt% borax achieved significant improvements, with self-healing efficiencies reaching 99% in Young’s modulus, 96% in tensile strength, 84% in elongation at break, and 76% in tensile energy after self-healing time 24 h at room temperature, without external stimuli. These results demonstrated the potential of ENR-based composites for sustainable and self-healing rubber applications.

Abstract: Nowadays, the use of rubber products such as tyres, bearings, shoe soles, hoses, and cables are increasing due to its high strain to failure. However, the indestructible cross-linking of sulphur or peroxide chains in vulcanized rubber could complicate the biodegradation, reprocessing, and recycling of rubber products. Due to these crucial problems, the increasing number of rubber-based products worldwide will lead to environmental hazards. An alternative strategy to address this problem is to give elastomers the ability to self-heal, thus promoting their reusability. Zinc diacrylate (ZDA) salt was used as a self-healing agent in NR. The ionic interaction of the self-healing process between natural rubber (NR) and ZDA were investigated, and successful grafting was demonstrated by FTIR analysis. The results showed that NR with 10 phr of ZDA had the highest tensile strength and elongation at break, which was also proved by microscopic images. The image showed no visible gap between the fractured contact surface of NR indicating an efficient self-healing mechanism. Therefore, this study has proven the potential of ZDA as a self-healing agent to NR compound and is expected to pave the way for environmentally friendly rubber products.

Abstract: Thermosets have played crucial roles in different industries, demonstrating versatility in packaging, furniture, electronics, and construction. Nevertheless, due to their permanent chemical bonds, these materials cannot be thermally processed after their shape has been formed. This results in notable environmental consequences as they accumulate in landfills during the product’s end-of-life cycle. Since the introduction of vitrimer, it has become a promising alternative that combines the mechanical strength of thermosets with distinctive characteristics including reprocessability, shape memory, recyclability, and self-healing ability. This review provides a thorough overview of the most recent developments in the vitrimer field, with a particular focus on advancements in self-healing properties and the corresponding techniques. Furthermore, it identifies the potential applications of vitrimer in different industries.

Abstract: Concrete structure are subjected to cracks and it is one of the immanent frailties of concrete thus reduces the life of concrete structure thereby results in high replacement cost. The study was inspired by the technique to find a remedy for cracking using bacteria namely Bacillus subtilis and Bacillus cereus on filling the voids, and the compressive strength, split tensile strength and flexural strength of bacterial impregnated concrete are compared with conventional concrete. The evaluated results of strength revealed that the use of bacteria in combination showed better improvement and SEM, XRD analysis showed that the material growth, increased calcite crystalline when compared to conventional concrete.

Abstract: Reprocessable and recyclable self-healing rubber composites were fabricated by mixing natural rubber (NR) with carbon black (CB) filler in the presence of zinc thiolate (ZT) to form the ionic association in the rubber system. This work investigated and compared the unfilled and natural rubber filled with 5phr of carbon black. The recycling process was repeated three times, and the mechanical performance was measured each time. Tensile strength was increased by more than 430% for unfilled rubber and 520% for NR/5CB composites after the third recycling process. Tear strength was also increased with the number of the recycling process. According to a welding test ability, the developed materials showed potential for repair. Scanning electron micrographs revealed that as the recycling number increased, the white spot of ZT responsible for generating the ionic network reduced as more ZT was converted into Zn²⁺ salt bonding.

Abstract: Hydrogels are polymers with soft and high-water absorption characteristics similar to biological tissues, leading to several potential applications, such as artificial organs, drug delivery, tissue engineering, and strain sensor. Interestingly, hydrogels can be designed to heal themselves after being damaged. In this research, hydrogels with self-healing ability from pectin and polyvinyl alcohol were prepared by simple physical mixing. Borax was used as a crosslinking agent to obtain crosslinked hydrogel structure by the formation of dynamic boron ester bonds. Glycerol was also added to the hydrogels as an anti-freezing agent and a stabilizer. The microstructures, mechanical properties, self-healing ability and swelling properties of the pectin/PVA-borax hydrogels were characterized. The results indicate that the size of microporous structure, modulus, tensile strength, self-healing time, swelling, and equilibrium water content of the pectin/PVA hydrogels increases with the increasing borax contents.

Abstract: The article presents theoretical premises that can be used to describe the mechanism of self-healing of the state of the structure of asphalt concrete containing an encapsulated reducing agent. The article presents the main provisions of the Flory-Huggins theory, according to which the restorative effect can be realized due to the ability of organic binder molecules to spontaneously entangle with each other. The intensity of this process depends on the proximity of the molecules to each other and the rate of spontaneous motion, which increases with increasing temperature. And in accordance with the theory of adhesion, the restoration of the state of the structure of asphalt concrete can be due to the mechanisms of formation of adhesive bonds with the help of an encapsulated modifier. To describe the features of the formation of adhesive bonds during restoration, the approaches described in the mechanical, molecular, chemical, diffuse, relaxation theory of adhesion or the theory of weak boundary layers can be used.

Abstract: Concrete is most widely used as an essential building material in the construction industry all over the globe. Concrete deteriorates over time, and cracks eventually form on its surface for many reasons, such as environmental surroundings and extra. This deterioration and cracks might lead to the ingress of water and chemicals that susceptible steel bars or reinforcements to corrosion. Since this deterioration is inevitable, maintenance and repair are also necessary. This process requires skilled labor and is cost-effective. Thus, researchers suggested alternative techniques to enhance concrete's mechanical properties and search for treatments to be applied to concrete's surface for healing and sealing the cracks by producing calcium carbonate precipitation. Therefore, self-healing concrete was introduced; this method is significant as it's proven environmentally friendly. This research aims to investigate the use of liquid bacteria incorporated in concrete mix and assess whether there would be improvements in the mechanical properties of the bacterial concrete compared to the conventional mix and an autogenous self-healing mix. Two different concentrations of an alkaliphile bacterium called Bacillus Subtilis were incorporated into the concrete mixes to test their ability to repair cracks by producing calcium carbonate and sealing them. This experiment showed a remarkable increase in bacterial concrete's compressive and tensile strengths. A visible partial crack sealing was also observed in specimens containing different concentrations of Bacillus Subtilis. Results also indicate that optimum results were obtained when the bacterial solution of concentration 10⁸ cells/ml was incorporated, especially at early ages.

Abstract: Concrete is extremely vulnerable to crack formation. However, repair and monitoring can be labor-intensive and costly. The investigation focused on the augmentation of natural fiber-silica composite-containing concrete’s mechanical properties. Raw coconut husk fiber (CHF) was used to mix with sodium metasilicate, and the synthesized coir-silica composite (CSC) was mixed in a cementitious matrix to test its self-healing properties. The synthesized composite (CSC) has a sheet-like morphology, whereas the silica has a rough surface morphology based on the SEM-EDX micrographs. The presence of silica improved the thermal stability of the raw coconut husk fiber (CHF). Results demonstrated that both pristine condition and healed samples had enhanced mechanical properties with the addition of the CSC material. Hence, the produced composite embedded in concrete surpassed control specimens in terms of healing capability for compressive and tensile strengths after damage. Finally, a synthesis method was developed to prepare a coconut husk fiber-silica composite, demonstrating a viable upcycling route for coconut husks waste utilization.

Abstract: Concrete is one of the most used construction materials worldwide. It is known to be a strong and durable material at a reasonable price. The most well-known problem in concrete is the cracks, which affect the service life of the concrete structures and leads to consumes higher costs through maintenance. Cracks allow penetrating any ions into the concrete resulting in other big problems such as corrosion of steel reinforcement, sulphate attack, carbonation, alkali-aggregate reaction, etc. It is impossible to prevent the formation of cracks, therefore they can be controlled or repaired using a variety of methods. Nowadays, self-healing is one of the widely recognized techniques to improve concrete's long-term durability. Healing agents such as bacteria, chemical compounds, and polymers are utilized. In this method, with the help of a healing agent, the cracks start to heal autonomously during crack formation. Since Bacteria is the most used material for healing concrete, self-healing concrete is also known as bacterial-concrete or bioconcrete. This article provides an overview of self-healing concrete including describing the system, process, durability, and mechanical properties of healed concrete.