-
Materials (Basel, Switzerland) Oct 2023The effectiveness of 3D concrete printing (3DCP) relies on understanding the rheological properties of cementitious materials and their time-dependent evolution. These...
The effectiveness of 3D concrete printing (3DCP) relies on understanding the rheological properties of cementitious materials and their time-dependent evolution. These materials exhibit shear-thinning viscosity, an elastic region, and both static and dynamic yield stress, which are challenging to balance in 3DCP. Layer deformation can be caused by factors such as self-weight, the weight of subsequently deposited layers, and the stress induced by the nozzle pressing. Starting at the level of a single filament, the final geometrical conformity of a 3D-printed object is the sum of individual filament conformities. Hence, the control of layer deformation during the printing process is critical. The failure of 3D-printed objects can occur due to two primary mechanisms: material failure, which occurs when the material's strength is exceeded, resulting in fracture or uncontrolled deformation; and stability failure, where the object cannot retain equilibrium of forces. These mechanisms often interact; extensive deformations resulting from material failure can lead to stability loss, or conversely, stability loss generates local excessive stresses leading to material failure. The governing mechanism depends on various factors, including material and process characteristics, as well as the transient nature of material properties, print strategy, and object design. With this in mind, this research aimed to broaden the understanding of the connection between rheological material properties-primarily yield stress-and the geometric conformability of printed objects. Experimental tests were conducted on pastes using a rheometer, and correlated mortars, allowing for the evaluation of realistic extrusion properties.
PubMed: 37959461
DOI: 10.3390/ma16216864 -
ACS Sustainable Chemistry & Engineering Apr 2024The cross-linked nature of vulcanized rubbers as used in tire and many other applications prohibits an effective closed-loop mechanical or chemical recycling. Moreover,...
The cross-linked nature of vulcanized rubbers as used in tire and many other applications prohibits an effective closed-loop mechanical or chemical recycling. Moreover, vulcanization significantly retards the material's biodegradation. Here, we report a recyclable and biodegradable rubber that is generated by the vulcanization of amorphous, unsaturated polyesters. The elastic material can be broken down solvolysis into the underlying monomers. After removal of the vulcanized repeat units, the saturated monomers, constituting the major share of the material, can be recovered in overall recycling rates exceeding 90%. Respirometric biodegradation experiments by CO tracking under environmental conditions the polyesters' diol monomer indicated depolymerization and partial mineralization of the vulcanized polyester rubbers.
PubMed: 38665800
DOI: 10.1021/acssuschemeng.3c08435 -
Gels (Basel, Switzerland) Aug 2022Particle image velocimetry (PIV) is an optical and contactless measurement method for analyzing fluid blood dynamics in cardiovascular research. The main challenge to... (Review)
Review
Particle image velocimetry (PIV) is an optical and contactless measurement method for analyzing fluid blood dynamics in cardiovascular research. The main challenge to visualization investigated in the current research was matching the channel material's index of refraction (IOR) to that of the fluid. Silicone is typically used as a channel material for these applications, so optical matching cannot be proven. This review considers hydrogel as a new PIV channel material for IOR matching. The advantages of hydrogels are their optical and mechanical properties. Hydrogels swell more than 90 vol% when hydrated in an aqueous solution and have an elastic behavior. This paper aimed to review single, double, and triple networks and nanocomposite hydrogels with suitable optical and mechanical properties to be used as PIV channel material, with a focus on cardiovascular applications. The properties are summarized in seven hydrogel groups: PAMPS, PAA, PVA, PAAm, PEG and PEO, PSA, and PNIPA. The reliability of the optical properties is related to low IORs, which allow higher light transmission. On the other hand, elastic modulus, tensile/compressive stress, and nominal tensile/compressive strain are higher for multiple-cross-linked and nanocomposite hydrogels than single mono-cross-linked gels. This review describes methods for measuring optical and mechanical properties, e.g., refractometry and mechanical testing.
PubMed: 36005103
DOI: 10.3390/gels8080502 -
Heliyon May 2023Coir is a lignocellulosic natural fiber derived from the coconut's husk, an abundantly found fruit or nut worldwide. This fiber has some unique characteristics, such as... (Review)
Review
Coir is a lignocellulosic natural fiber derived from the coconut's husk, an abundantly found fruit or nut worldwide. This fiber has some unique characteristics, such as its resistance to seawater, microbial attack, high impact, etc. But its low thermal conductivity or high thermal insulating property makes it suitable for being used as insulators in civil engineering sites. On the other hand, the sustainability of a material depends heavily on its environmental impact of the material. For making sustainable materials like biocomposite, there are no options other than using polymers derived from natural renewable sources. Polylactic acid(PLA) is an example of those types of material. And these materials are often being reinforced by fibers like coir for various reasons including improving mechanical properties, reducing the cost of the material, and improving the material's sustainability. Many coir-reinforced sustainable biopolymer composites have already been produced in many pieces of research, which will be discussed in this paper, along with the chemical and physical structure of coir fiber. In addition, this paper will try to focus on the insulating properties of coir and coir-reinforced composites while will also compare some properties of the composites with some commonly used materials based on different parameters to show the suitability of using the coir fiber in heat-insulating applications and to produce sustainable biocomposite materials.
PubMed: 37153406
DOI: 10.1016/j.heliyon.2023.e15597 -
Cureus Sep 2022Hydrogels are thought of as unique polymers utilized to build new materials, and two key factors that impact their features are their hydrophilicity and the degree of... (Review)
Review
Hydrogels are thought of as unique polymers utilized to build new materials, and two key factors that impact their features are their hydrophilicity and the degree of cross-linking of the polymer chains. An injectable hydrogel is based on the hypothesis that certain biomaterials can be injected into the body as a liquid and progressively solidify there. The scientific research community was intrigued and interested by its discovery. The hydrophilic polymers that are used to make hydrogels can typically be split into two groups: natural polymers derived from tissues or other sources of natural materials, and synthetic polymers produced by combining principles from organic chemistry and molecular engineering. A variety of organic and synthetic biomaterials, such as chitosan, collagen or gelatin, alginate, hyaluronic acid, heparin, chondroitin sulfate, polyethylene glycol, and polyvinyl alcohol, are used to generate injectable hydrogels. A promising biomaterial for the therapeutic injection of cells and bioactive chemicals for tissue regeneration in both dentistry and medicine, injectable hydrogels have recently attracted attention. Since injectable scaffolds can be implanted with less invasive surgery, their application is seen as a viable strategy in the regeneration of craniofacial tissue. Treatment for periodontitis that effectively promotes periodontal regeneration involves injecting a hydrogel that contains medications with simultaneous anti-inflammatory and tissue-regenerating capabilities. The advantages of injectable hydrogel for tissue engineering are enhanced by the capability of three-dimensional encapsulation. A material's injectability can be attributed to a variety of mechanisms. The hydrogels work well to reduce inflammation and promote periodontal tissue regeneration.
PubMed: 36277588
DOI: 10.7759/cureus.29248 -
International Journal of Molecular... Sep 2023Tissue engineering for spinal cord injury (SCI) remains a complex and challenging task. Biomaterial scaffolds have been suggested as a potential solution for supporting...
Tissue engineering for spinal cord injury (SCI) remains a complex and challenging task. Biomaterial scaffolds have been suggested as a potential solution for supporting cell survival and differentiation at the injury site. However, different biomaterials display multiple properties that significantly impact neural tissue at a cellular level. Here, we evaluated the behavior of different cell lines seeded on chitosan (CHI), poly (ε-caprolactone) (PCL), and poly (L-lactic acid) (PLLA) scaffolds. We demonstrated that the surface properties of a material play a crucial role in cell morphology and differentiation. While the direct contact of a polymer with the cells did not cause cytotoxicity or inhibit the spread of neural progenitor cells derived from neurospheres (NPCdn), neonatal rat spinal cord cells (SCC) and NPCdn only attached and matured on PCL and PLLA surfaces. Scanning electron microscopy and computational analysis suggested that cells attached to the material's surface emerged into distinct morphological populations. Flow cytometry revealed a higher differentiation of neural progenitor cells derived from human induced pluripotent stem cells (hiPSC-NPC) into glial cells on all biomaterials. Immunofluorescence assays demonstrated that PCL and PLLA guided neuronal differentiation and network development in SCC. Our data emphasize the importance of selecting appropriate biomaterials for tissue engineering in SCI treatment.
Topics: Animals; Rats; Humans; Spinal Cord Regeneration; Biocompatible Materials; Tissue Engineering; Induced Pluripotent Stem Cells; Nerve Tissue; Spinal Cord Injuries
PubMed: 37686446
DOI: 10.3390/ijms241713642 -
Nature Materials Dec 2021The antagonism between strength and resistance to hydrogen embrittlement in metallic materials is an intrinsic obstacle to the design of lightweight yet reliable...
The antagonism between strength and resistance to hydrogen embrittlement in metallic materials is an intrinsic obstacle to the design of lightweight yet reliable structural components operated in hydrogen-containing environments. Economical and scalable microstructural solutions to this challenge must be found. Here, we introduce a counterintuitive strategy to exploit the typically undesired chemical heterogeneity within the material's microstructure that enables local enhancement of crack resistance and local hydrogen trapping. We use this approach in a manganese-containing high-strength steel and produce a high dispersion of manganese-rich zones within the microstructure. These solute-rich buffer regions allow for local micro-tuning of the phase stability, arresting hydrogen-induced microcracks and thus interrupting the percolation of hydrogen-assisted damage. This results in a superior hydrogen embrittlement resistance (better by a factor of two) without sacrificing the material's strength and ductility. The strategy of exploiting chemical heterogeneities, rather than avoiding them, broadens the horizon for microstructure engineering via advanced thermomechanical processing.
Topics: Hydrogen; Steel; Tensile Strength
PubMed: 34239084
DOI: 10.1038/s41563-021-01050-y -
Polymers Oct 2022Composites are macroscopic combinations of chemically dissimilar materials preferred for new high-tech applications where mechanical performance is an area of interest.... (Review)
Review
Composites are macroscopic combinations of chemically dissimilar materials preferred for new high-tech applications where mechanical performance is an area of interest. Mechanical apprehensions chiefly include tensile, creep, and fatigue loadings; each loading comprises different modes. Fatigue is cyclic loading correlated with stress amplitude and the number of cycles while defining the performance of a material. Composite materials are subject to various modes of fatigue loading during service life. Such loadings cause micro invisible to severe visible damage affecting the material's performance. Mode I fatigue crack propagates via opening lamina governing a visible tear. Recently, there has been an increasing concern about finding new ways to reduce delamination failure, a life-reducing aspect of composites. This review focuses on mode I fatigue behaviours of various preforms and factors determining failures considering different reinforcements with respect to fibres and matrix failures. Numerical modelling methods for life prediction of composites while subjected to fatigue loading are reviewed. Testing techniques used to verify the fatigue performance of composite under mode I load are also given. Approaches for composites' life enhancement against mode I fatigue loading have also been summarized, which could aid in developing a well-rounded understanding of mode I fatigue behaviours of composites and thus help engineers to design composites with higher interlaminar strength.
PubMed: 36365551
DOI: 10.3390/polym14214558 -
Polymers Oct 2023Polymer matrix wave transparent composites are used in a variety of high-speed communication applications. One of the applications of these involves making protective...
Polymer matrix wave transparent composites are used in a variety of high-speed communication applications. One of the applications of these involves making protective enclosures for antennas of microwave towers, air vehicles, weather radars, and underwater communication devices. Material performance, structural, thermal, and mechanical degradation are matters of concern as advanced wireless communication needs robust materials for radomes that can withstand mechanical and thermal stresses. These polymer composite radomes are installed externally on antennas and are exposed directly to ambient as well as severe conditions. In this research, epoxy resin was reinforced with a small amount of quartz fibers to yield an improved composite radome material compared to a pure epoxy composite with better thermal and mechanical properties. FTIR spectra, SEM morphology, dielectric constant (Ɛ) and dielectric loss (δ), thermal degradation (weight loss), and mechanical properties were determined. Compared to pure epoxy, the lowest values of Ɛ and δ were 3.26 and 0.021 with 30 wt.% quartz fibers in the composite, while 40% less weight loss was observed which shows its better thermal stability. The mechanical characteristics encompassing tensile and bending strength were improved by 42.8% and 48.3%. In high-speed communication applications, compared to a pure epoxy composite, adding only a small quantity of quartz fiber can improve the composite material's dielectric performance, durability, and thermal and mechanical strength.
PubMed: 37896377
DOI: 10.3390/polym15204133 -
Heliyon Nov 2023The absorption spectrum of a material reveals the absorbed light frequencies, characteristic peaks, and the line width of absorption bands. This information is critical...
The absorption spectrum of a material reveals the absorbed light frequencies, characteristic peaks, and the line width of absorption bands. This information is critical for understanding the energy levels involved in the absorption process as well as the material's electronic structure. In this study, an equation connecting the absorption line width with the static dielectric function is derived for narrow and wide gap materials. It is then compared with the Penn model. It has been found that the constant in the Penn model has a value that is restricted to the range of 0.5 to 1. Application of this equation to various narrow and wide gap materials is then discussed.
PubMed: 37964851
DOI: 10.1016/j.heliyon.2023.e21507