Papers by Keyword: Crosslinking

Abstract: Tissue engineering provides a promising approach to addressing the global shortage of organ and tissue donors by developing biological substitutes that can restore or enhance tissue function. This study presents the development and characterization of PEG-PVA biodegradable hydrogels, synthesized through chemical crosslinking with varying concentrations of glutaraldehyde, for tissue engineering applications. Mechanical, thermal, and structural properties were systematically analyzed to determine the optimal formulation for different applications. Hydrogels synthesized with 0.10g and 0.15g of glutaraldehyde were selected for detailed evaluation. The hydrogel with 0.10g glutaraldehyde exhibited a tensile strength of 1200 MPa, a glass transition temperature (Tg) of ～50°C, and a swelling ratio of 7.65, demonstrating superior mechanical robustness and thermal stability for load-bearing applications such as bone and cartilage regeneration. In contrast, the hydrogel with 0.15g glutaraldehyde, with a tensile strength of 1000 MPa, a Tg of 45°C, and a swelling ratio of 4.49, showed greater flexibility and a denser microstructure, making it more suitable for soft tissue applications requiring controlled degradation. These results underscore the importance of tailoring crosslinking density to optimize hydrogel performance for specific biomedical applications. Future studies should explore the behavior of these hydrogels in biologically relevant environments, including enzymatic degradation and in vivo testing. With further development, PEG-PVA hydrogels could play a key role in regenerative medicine, offering customizable mechanical and degradation properties for diverse clinical applications.

Abstract: Materials made from renewable resources offer a promising strategy for reducing environmental problems. Starch is a well-known alternative among several biodegradable materials due to its availability, cheap cost, and degradability. This research aims to develop a degradable film from cassava starch and use citric acid as the crosslinker. Light transmittance measurement reveals that the films produced have high UV barrier capacity in the UV region and above 80% transmittance values in the visible region. Additionally, it was found that the film with 10% citric acid had a favorable balance of tensile strength, elongation, and fracture stress.

Abstract: Using a new heuristic procedure, the influence of graphene reinforcement on Young's modulus of crosslinked epoxy was analyzed. Graphene reinforcement was investigated for 1%, 2%, 3%, and 4% weight ratios. Graphene sheet edges were functionalized with hydrogen atoms and were placed middle of simulation cells. Simulation cell sizes were determined such that the graphene sheets were non-periodic. Thus, the edge effects of graphene sheets could be observed in dynamic simulations. The heuristic protocol is used for the crosslinking process of epoxy. It is less sophisticated than the multi-step iterative approach and is utilized for various components. It also updates higher-order covalent bond and partial charge terms in real-time to prevent inaccurate chemical couplings caused by ignoring angle-based covalent terms. Crosslinked epoxy structures were created by 80% with this new heuristic protocol as a matrix structure. To analyze the multiple variations with the same amount of molecules in each weight ratio, each simulation cell was built as three individual samples, and the standard deviation values were calculated. Young's modulus of the nanocomposite system was then calculated using a constant-strain energy minimization approach. The inter-atomic and intra-atomic interactions were described using the Molecular Potentials for Atomistic Simulation Studies (COMPASS) force field. As expected, the Young Modulus of epoxy resin increased with the addition of graphene reinforcement. This increase in Young's modulus was calculated by 6% for 1% graphene reinforcement, 10% for 2% graphene reinforcement, 14% for 3% graphene reinforcement, and 16% for 4% graphene reinforcement. As the graphene reinforcement ratio increases, the increase in Young's modulus tends to diminish. It's also worth noting that the MD simulation results in this work were in close agreement with the experimental results published in the literature. Both qualitative and quantitative numerical results show the effect of the abovementioned parameters. They will provide gain energy and time for prior synthesizing the new materials and serve as benchmark solutions for future comparisons of numerical and experimental results.

Abstract: Self-assembly and mineralization of type I collagen (Col) with nanocrystalline apatite (nAp), by adding a solution of Ca(OH)₂ to a stirred Col-H₃PO₄ solution by fast dripping, allowed the preparation of Col/nAp fibrils with good crystallographic control of the mineral phase. In this work, in addition, we have cross-linked the mineralized fibers by using different reagents, namely glutaraldehyde (GTA), tannic acid (TA), 1-Ethyl-3-(3-dimethyl aminopropyl)-carbodiimide combined with N-Hydroxysuccinimide (EDC/NHS), and genipin (GP), aimed at producing different types of biopolymeric Col/nAp-based drug delivery scaffolds. In parallel, we have investigated two different methods to impregnate the scaffolds with molecules of the cocrystal diclofenac-metformin (DF-MET). The result, when using TA as a crosslinking reagent, shows the sequence of mineralized fibrils impregnation followed by crosslinking leads to maximum cocrystal molecule loading. The impregnated material is expected to be useful in settings with excessive and prolonged inflammation, since they affect negatively the fracture healing/bone repair processes, especially during the early stages of healing.

Abstract: In this paper, a series of polyvinyl alcohol (PVA) aerogels hybrid with cellulose nanocrystal (CNC) was successfully prepared using freeze-drying process. The influence of different fractions of CNC and crosslinking agent; glutaraldehyde (GA) on the mechanical of PVA/CNC hybrid aerogels property was evaluated by means of compressive strength. Results show that the mechanical property of hybrid aerogels has been improved with the addition of CNC and GA. Variation in the CNC and GA content also led to differences in the porous structure morphologies. Nevertheless, higher content of GA caused adverse effect to the strength of hybrid aerogel which associated to the excessive crosslinking and smaller number of pores formation as evident from scanning electron microscopy (SEM) analysis.

Abstract: Graphene, as a typical zero band gap material, possesses excellent electrical conductivity and mechanical property, but is hardly applied in functional field directly. Hence, how to effectively modify the energy structure of graphene and apply it as functional material in physical signal sensing, information processing and energy management has become a widely attentional research field in recent decades. In this work, a two-dimensional (2D) organic molecular named 5, 10, 15, 20-tetra (4-aminopyenyl) porphyrin is selected to in-situ crosslink with graphene oxide (GO), and the nitrogen-doped graphene (NG) film is prepared through further graphitization. In this paper, the influence of the content of porphyrin molecular on the microstructure and nitrogen content of the NG film is mainly discussed. With the increasing of porphyrin content, the layer space of GO film rises gradually and the GO nanosheets are laid out more smoothly. After graphitization, nitrogen element is well preserved inside the NG film, and the electrical conductivity and Seebeck coefficient is greatly improved. Taking advantage of these properties, a NG film-based temperature sensor is prepared.

Abstract: Generally, only a few especially acrylic monomers have photoabsorption characteristics to allow for effective stereolithography (STL) to take place. Biomaterial product from palm oil, Acrylated Palm Olein (APO), is seen as an ideal alternative to petroleum-based polymers due the diminishing petrochemical supply and abundant of the natural polymer in the market. In this study, APO as a biopolymer is introduced to synthetic polymers Polyethylene Glycol Dimethylacrylate (PEGDMA) and Polyethylene Glycol Diacrylate (PEGDA), separately. All three polymers offer photoabsorption characteristics that enable them to be the resins for ultraviolet (UV) 3D printing. The crosslinking of both copolymers is optimized by comparing two different UV radiation techniques; UV cured machine and UV STL 3D printer. The degree of crosslinking for both APO-co-PEGDMA and APO-co-PEGDA through gel fraction analysis are studied and compared with their prepolymer resins. As predicted, the maximum degree of crosslinking of APO-co-PEGDMA and APO-co-PEGDA samples are achieved from the fabrication of samples by 3D printing and recorded at 67.50% and 59.50% respectively, comparing to the samples cured by UV cure machine, which recorded maximum crosslinking percentage at only 21.31%. Further analysis is done using swelling test to study water absorption capacities of copolymers and results shows that APO-co-PEGDMA able to retain water at maximum of 42.47% and APO-co-PEGDA at 52.02% from the 3D printed samples, and recorded lowest readings at 22.82% and 25.56% respectively. UV cured samples are recorded to have lowest readings at 3.89% for APO-co-PEGDMA, and 4.23% for APO-co-PEGDA. Fourier Transform Infrared (FTIR) Spectroscopy confirmed the successful crosslinked of the copolymers. Analysis of FTIR shows that there are presence of new peaks and shifting of peaks, indicating that APO is crosslinked with PEGDMA backbone as well as PEGDA backbone. These also suggest that both polymers are suitable to be incorporated with APO as new photopolymer resins, fabricated using UV radiation crosslinking, with PEGDMA shown a slightly better result. All results are agreeable with FTIR results.

Abstract: Thermal conductivities of silicone rubber filled with Al₂O₃ were prepared. Thermal conductivity experimental results obtained were analyzed using the Nielsen and Agari models to explain the effect of Al₂O₃ filler on the formation of thermal conductive networks. Thermal conductivities increased with the adding of mixed Al₂O₃ of large and small sizes fillers. The scanning electron microscopy (SEM) showed that it is the optimum particle sizes and quantities that made the filler packing closer, which thus leads to formation of more thermal conductive chains.

Abstract: A carboxymethylcellulose-based encapsulant system for the controlled release of nitrogen-phosphorus-potassium (NPK) fertilizer was synthesized using alginate as a stabilizer, and citric acid as a crosslinking agent. Fourier-transform infrared (FT-IR) spectroscopy, particle size analysis, zeta potential measurement, and scanning electron microscopy showed successful crosslinking, sufficient particle size and colloidal stability, as well as the topography of the formed particles. Fluorescence spectroscopy confirmed successful encapsulation of a model system, 8-anilino-1-napthalenesulfonic acid. Release behavior studies under various pH conditions showed that CMC/Alg NPK conformed to the standards of controlled release fertilizer with a maximum release rate of 50% over the span of 30 days.

Abstract: Polyurethane (PU) gel was synthesized based on methylene diphenyl diisocyanate (MDI) and polyols corporation with 1,1,1-Tris(hydroxymethyl)propane (TMP) as a crosslinking agent. The chemical structure of synthesized polyurethane gel was investigated using Fourier-transform infrared spectroscopy (FTIR). The effects of curing temperature, curing time, and crosslinking concentration on the degree of swelling, gel content and hardness of polyurethane gel are investigated. In addition, the crosslink density and average molecular weight between crosslinking points were determined using the Flory-Rehner equation. The results revealed that the curing temperature had more pronounced effect on degree of swelling and gel content than curing time. As the curing temperature increased the degree of swelling and gel content in polyurethane gel increased. Curing time seem to have a complicated effect on crosslink density and average molecular weight between crosslinking points. The hardness of polyurethane gel tends to increase with increasing crosslinking concentration and curing time.