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13 pages, 5166 KiB

Open AccessArticle

Degradation Behaviors of Polylactic Acid, Polyglycolic Acid, and Their Copolymer Films in Simulated Marine Environments

by Zeyu Chen, Xi Zhang, Ye Fu, Yujuan Jin, Yunxuan Weng, Xinchao Bian and Xuesi Chen

Polymers 2024, 16(13), 1765; https://doi.org/10.3390/polym16131765 - 21 Jun 2024

Cited by 1 | Viewed by 2217

Abstract

Poly(lactic acid) (PLA) and poly(glycolic acid) (PGA) are extensively studied biodegradable polymers. However, the degradation behavior of their copolymer, poly(lactic-co-glycolic acid) (PLGA), in marine environments has not yet been confirmed. In this study, the changes in macroscopic and microscopic morphology, thermal properties, aggregation, [...] Read more.

Poly(lactic acid) (PLA) and poly(glycolic acid) (PGA) are extensively studied biodegradable polymers. However, the degradation behavior of their copolymer, poly(lactic-co-glycolic acid) (PLGA), in marine environments has not yet been confirmed. In this study, the changes in macroscopic and microscopic morphology, thermal properties, aggregation, and chemical structure of PLA, PGA, PLGA-85, and PLGA-75 (with 85% and 75% LA content) in simulated marine environments were investigated. Results revealed that degradation occurred through hydrolysis of ester bonds, and the degradation rate of PGA was faster than that of PLA. The amorphous region degraded preferentially over the crystalline region, leading to cleavage-induced crystallization and decreased thermal stability of PLA, PLGA-85, and PLGA-75. The crystal structures of PLGAs were similar to those of PLA, and the higher GA content, the faster was the degradation rate. This study provides a deeper understanding of the seawater degradation behaviors of PLA, PGA, and their copolymers, and provides guidance for the preparation of materials with controllable degradation performance. Full article

(This article belongs to the Special Issue Multi-Functional and Intelligent Polymer Composites: Synthesis, Characterization and Applications)

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13 pages, 4026 KiB

Open AccessArticle

Constructing Self-Healing Polydimethylsiloxane through Molecular Structure Design and Metal Ion Bonding

by Lvchao Qiu, Yutong Zhou, Zhoufeng Zhao, Qi Wang, Lijun Chu and Shipeng Wen

Polymers 2024, 16(10), 1309; https://doi.org/10.3390/polym16101309 - 7 May 2024

Cited by 1 | Viewed by 1137

Abstract

Self-healing polydimethylsiloxane (PDMS) has garnered significant attention due to its potential applications across various fields. In this study, a functionalized modification of PDMS containing di-aminos was initially conducted using 2,6-pyridinedicarbonyl chloride to synthesize pyridine-PDMS (Py-PDMS). Subsequently, rare earth metal europium ions (Eu³⁺ [...] Read more.

Self-healing polydimethylsiloxane (PDMS) has garnered significant attention due to its potential applications across various fields. In this study, a functionalized modification of PDMS containing di-aminos was initially conducted using 2,6-pyridinedicarbonyl chloride to synthesize pyridine-PDMS (Py-PDMS). Subsequently, rare earth metal europium ions (Eu³⁺) were incorporated into Py-PDMS. Due to the coordination interaction between Eu³⁺ and organic ligands, a coordination cross-linking network was created within the Py-PDMS matrix, resulting in the fabrication of Eu³⁺-Py-PDMS elastomer. At a molar ratio of Eu³⁺ to ligands of 1:1, the tensile strength of Eu³⁺-Py-PDMS reached 1.4 MPa, with a fracture elongation of 824%. Due to the dynamic reversibility of coordination bonds, Eu³⁺-Py-PDMS with a metal-to-ligand molar ratio of 1:2 exhibited varying self-healing efficiencies at different temperatures. Notably, after 4 h of repair at 60 °C, its self-healing efficiency reached nearly 100%. Furthermore, the gas barrier properties of Eu³⁺-Py-PDMS with a molar ratio of 1:1 was improved compared with that of Eu³⁺-Py-PDMS with a molar ratio of 1:1. This study provides an effective strategy for the design and fabrication of PDMS with high mechanical strength, high gas barrier properties, and exceptional self-healing efficiency. Full article

(This article belongs to the Special Issue Multi-Functional and Intelligent Polymer Composites: Synthesis, Characterization and Applications)

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13 pages, 7332 KiB

Open AccessArticle

Thermal Oxidative Aging and Service Life Prediction of Commercial Ethylene–Propylene–Diene Monomer Spacer Damping Composites for High–Voltage Transmission Lines

by Yutong Zhou, Lvchao Qiu, Zongchao Xu, Shixuan Huang, Jingkai Nie, Hang Yin, Feng Tu and Zhoufeng Zhao

Polymers 2024, 16(9), 1186; https://doi.org/10.3390/polym16091186 - 24 Apr 2024

Viewed by 849

Abstract

The aging behavior and life prediction of rubber composites are crucial for ensuring high-voltage transmission line safety. In this study, commercially available ethylene–propylene–diene monomer (EPDM) spacer composites were chosen and investigated to elucidate the structure and performance changes under various aging conditions. The [...] Read more.

The aging behavior and life prediction of rubber composites are crucial for ensuring high-voltage transmission line safety. In this study, commercially available ethylene–propylene–diene monomer (EPDM) spacer composites were chosen and investigated to elucidate the structure and performance changes under various aging conditions. The results showed an increased C=O peak intensity with increasing aging time, suggesting intensified oxidation of ethylene and propylene units. Furthermore, the surface morphology of commercial EPDM composites displayed increased roughness and aggregation after aging. Furthermore, hardness, modulus at 100% elongation, and tensile strength of commercial EPDM composites exhibited a general increase, while elongation at break decreased. Additionally, the damping performance decreased significantly after aging, with a 20.6% reduction in loss factor (20 °C) after aging at 100 °C for 672 h. With increasing aging time and temperature, the compression set gradually rose due to the irreversible movement of the rubber chains under stress. A life prediction model was developed based on a compression set to estimate the lifetime of rubber composites for spacer bars. The results showed that the product’s life was 8.4 years at 20 °C. Therefore, the establishment of a life prediction model for rubber composites can provide valuable technical support for spacer product services. Full article

(This article belongs to the Special Issue Multi-Functional and Intelligent Polymer Composites: Synthesis, Characterization and Applications)

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12 pages, 1977 KiB

Open AccessArticle

Effect of Chitosan and Its Water-Soluble Derivatives on Antioxidant Activity

by Zhihua Wang, Yongbin Yan, Zhengmao Zhang, Changchun Li, Lanfei Mei, Ruyi Hou, Xiaodan Liu and Hongxia Jiang

Polymers 2024, 16(7), 867; https://doi.org/10.3390/polym16070867 - 22 Mar 2024

Cited by 2 | Viewed by 1425

Abstract

The antioxidant activity of chitosan (CS) and three water-soluble derivatives was analyzed comparatively by in vitro and in vivo experiments, including hydroxypropyl chitosan (HPCS), quaternary ammonium salt of chitosan (HACC), and carboxymethyl chitosan (CMCS). The results show that chitosan and its water-soluble derivatives [...] Read more.

The antioxidant activity of chitosan (CS) and three water-soluble derivatives was analyzed comparatively by in vitro and in vivo experiments, including hydroxypropyl chitosan (HPCS), quaternary ammonium salt of chitosan (HACC), and carboxymethyl chitosan (CMCS). The results show that chitosan and its water-soluble derivatives have a scavenging ability on DPPH radicals, superoxide radicals, and hydroxyl radicals, and a reducing ability. A remarkable difference (p < 0.05) was found for HACC and HPCS compared with CS on DPPH radicals, hydroxyl radicals, and reducing ability. The antioxidant ability of the four chitosan samples was in the order of HPCS > HACC > CMCS > CS. Furthermore, antioxidant activity of all samples increased gradually in a concentration-dependent manner. The in vivo result indicates that oral CS and its derivatives samples result in a decrease in lipid peroxides (LPO) and free fatty acids (FFA) levels in serum with an increase in superoxide dismutase (SOD) activity. Especially for the HPCS and HACC groups, the LPO, FFA, and SOD activity in serum was different significantly in comparison with the high-fat controlgroup (HF) (p < 0.05). These results indicate that chitosan and its derivatives can be used as good antioxidants, and the antioxidant activity might be related to the molecular structure of chitosan derivatives. Full article

(This article belongs to the Special Issue Multi-Functional and Intelligent Polymer Composites: Synthesis, Characterization and Applications)

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12 pages, 3410 KiB

Open AccessArticle

Dual-Shell Microcapsules for High-Response Efficiency Self-Healing of Multi-Scale Damage in Waterborne Polymer–Cement Coatings

by Chenyang Liu, Zhicheng Sun, Shouzheng Jiao, Ting Wang, Yibin Liu, Xianyu Meng, Binbin Zhang, Lu Han, Ruping Liu, Yuanyuan Liu and Yang Zhou

Polymers 2024, 16(1), 105; https://doi.org/10.3390/polym16010105 - 29 Dec 2023

Viewed by 1406

Abstract

Waterborne polymer–cement coatings have been widely applied in building materials due to their organic solvent-free nature, low cost, and eco-friendliness. However, these coatings can easily crack during the drying process as a result of construction environment factors, compromising the barrier performance of the [...] Read more.

Waterborne polymer–cement coatings have been widely applied in building materials due to their organic solvent-free nature, low cost, and eco-friendliness. However, these coatings can easily crack during the drying process as a result of construction environment factors, compromising the barrier performance of the coating and limiting its large-scale application. In this study, a dual-shell self-healing microcapsule was developed, which can effectively heal damage on a macro scale in waterborne polymer–cement coatings. Specifically, this dual-shell self-healing microcapsule was designed with a silica gel shell and a tannic acid–cuprum (TA–Cu) double-shell structure embedded with an epoxy resin (EP) healing agent, which was successfully fabricated via a two-step in situ polymerization. This silica gel shell self-healing microcapsules can effectively load into waterborne polymer–cement coatings. As the coating dries and solidifies, the silica gel shell of the microcapsule also becomes loose and brittle due to dehydration. This improves the mechanical initiation efficiency of the microcapsules in the coating. This study provides a novel approach for the application of self-healing microcapsules in waterborne coating systems, which can significantly reduce cracking during the drying process of waterborne polymer–cement coatings and improve the service life of the coating under complex conditions. Full article

(This article belongs to the Special Issue Multi-Functional and Intelligent Polymer Composites: Synthesis, Characterization and Applications)

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16 pages, 6916 KiB

Open AccessArticle

Strengthened Decellularized Porcine Valves via Polyvinyl Alcohol as a Template Improving Processability

by Qingqing Chen, Chaorong Wang, Han Wang, Jinfeng Xiao, Yingshan Zhou, Shaojin Gu, Weilin Xu and Hongjun Yang

Polymers 2024, 16(1), 16; https://doi.org/10.3390/polym16010016 - 20 Dec 2023

Viewed by 1034

Abstract

The heart valve is crucial for the human body, which directly affects the efficiency of blood transport and the normal functioning of all organs. Generally, decellularization is one method of tissue-engineered heart valve (TEHV), which can deteriorate the mechanical properties and eliminate allograft [...] Read more.

The heart valve is crucial for the human body, which directly affects the efficiency of blood transport and the normal functioning of all organs. Generally, decellularization is one method of tissue-engineered heart valve (TEHV), which can deteriorate the mechanical properties and eliminate allograft immunogenicity. In this study, removable polyvinyl alcohol (PVA) is used to encapsulate decellularized porcine heart valves (DHVs) as a dynamic template to improve the processability of DHVs, such as suturing. Mechanical tests show that the strength and elastic modulus of DHVs treated with different concentrations of PVA significantly improve. Without the PVA layer, the valve would shift during suture puncture and not achieve the desired suture result. The in vitro results indicate that decellularized valves treated with PVA can sustain the adhesion and growth of human umbilical vein endothelial cells (HUVECs). All results above show that the DHVs treated with water-soluble PVA have good mechanical properties and cytocompatibility to ensure post-treatment. On this basis, the improved processability of DHV treated with PVA enables a new paradigm for the manufacturing of scaffolds, making it easy to apply. Full article

(This article belongs to the Special Issue Multi-Functional and Intelligent Polymer Composites: Synthesis, Characterization and Applications)

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Review

Jump to: Research

17 pages, 16329 KiB

Open AccessReview

The Application of Heat-Shrinkable Fibers and Internal Curing Aggregates in the Field of Crack Resistance of High-Strength Marine Structural Mass Concrete: A Review and Prospects

by Jinhui Li, Zi Yu, Jing Wu, Qingjun Ding, Wei Xu and Shaolong Huang

Polymers 2023, 15(19), 3884; https://doi.org/10.3390/polym15193884 - 26 Sep 2023

Cited by 2 | Viewed by 1424

Abstract

High-strength large-volume marine concrete is a critical material required for the construction of large-span sea-crossing bridges. However, the widespread issue of cracking in this concrete type significantly impacts the durability and load-bearing capacity of concrete structures. Dealing with these cracks not only delays [...] Read more.

High-strength large-volume marine concrete is a critical material required for the construction of large-span sea-crossing bridges. However, the widespread issue of cracking in this concrete type significantly impacts the durability and load-bearing capacity of concrete structures. Dealing with these cracks not only delays construction schedules but also increases project costs. Addressing these pressing technical issues, this project proposes the use of newly developed high-modulus heat-shrinkable fibers (polyethylene terephthalate fiber, also known as PET fiber) from the textile industry. These fibers utilize the heat generated during the hydration of large-volume concrete to trigger its contraction, applying three-dimensional micro-prestressing stress to enhance its crack resistance, while simultaneously incorporating prewetted aggregates with high-performance micro-porous structures and utilizing their internal curing effect to reduce concrete shrinkage. This helps to minimize the loss of micro-prestressing stress caused by concrete shrinkage and creep. This synergistic approach aims to improve the crack resistance of high-strength large-volume marine concrete. By employing modern testing and simulation analysis techniques, this study aims to uncover the mechanism by which the heat-shrinkable fibers exert micro-prestressing stress on concrete and the water release mechanism of internal curing aggregates during the temperature rise and fall stages of large-volume concrete. It seeks to elucidate the cooperative regulation of the microstructure and performance enhancement mechanisms of high-strength large-volume marine concrete by the heat-shrinkable fibers and internal curing aggregates. This research will lead to the development of novel methods for the design and crack control of high-strength large-volume marine concrete, which will be validated through engineering demonstrations. The outcomes of this study will provide theoretical foundations and technical support for the preparation of the crack-resistant large-volume marine concrete used in large-span bridges. Full article

(This article belongs to the Special Issue Multi-Functional and Intelligent Polymer Composites: Synthesis, Characterization and Applications)

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37 pages, 11567 KiB

Open AccessReview

The Application of Self-Healing Microcapsule Technology in the Field of Cement-Based Materials: A Review and Prospect

by Bo Liu, Mingli Wu, Wei Du, Lu Jiang, Hongjun Li, Luoxin Wang, Jinhui Li, Danying Zuo and Qingjun Ding

Polymers 2023, 15(12), 2718; https://doi.org/10.3390/polym15122718 - 17 Jun 2023

Cited by 15 | Viewed by 3948

Abstract

This review provides an overview of microcapsule self-healing technology and its application in the field of cement-based materials, as well as future prospects. The presence of cracks and damage in cement-based structures during service has a significant impact on their lifespan and safety [...] Read more.

This review provides an overview of microcapsule self-healing technology and its application in the field of cement-based materials, as well as future prospects. The presence of cracks and damage in cement-based structures during service has a significant impact on their lifespan and safety performance. Microcapsule self-healing technology shows promise in achieving self-healing by encapsulating healing agents within microcapsules, which are released upon damage to the cement-based material. The review starts by explaining the fundamental principles of microcapsule self-healing technology and explores various methods for preparing and characterizing microcapsules. It also investigates the influence of incorporating microcapsules on the initial properties of cement-based materials. Additionally, the self-healing mechanisms and effectiveness of microcapsules are summarized. Finally, the review discusses the future development directions for microcapsule self-healing technology, outlining potential areas for further research and advancement. Full article

(This article belongs to the Special Issue Multi-Functional and Intelligent Polymer Composites: Synthesis, Characterization and Applications)

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