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Roadmap for autogenous shrinkage control of UHPC
Published in Hiroshi Yokota, Dan M. Frangopol, Bridge Maintenance, Safety, Management, Life-Cycle Sustainability and Innovations, 2021
Li Yang, Caijun Shi*, Zemei Wu
Superabsorbent polymer has higher water absorption and can be mixed in dry condition compared to porous aggregate. Porous aggregate is often pretreated prior to use and its efficiency is strongly affected by pretreatment methods. It is recommended to use the formwork with porous material lining when casting UHPC.
Physiological and Clinical Considerations of Drug Delivery Systems Containing Carbon Nanotubes and Graphene
Published in Raj K. Keservani, Anil K. Sharma, Rajesh K. Kesharwani, Drug Delivery Approaches and Nanosystems, 2017
Sami Makharza, Giuseppe Cirillo, Orazio Vittorio, Silke Hampel
An example of using a magnetic field to control the drug delivery is reported in (Zhou et al., 2010) where GO/Fe3O4 nanocomposite have been developed and characterized. In a different approach, a noncovalent approach was employed for the preparation of a flexible, electrically conducting hydrogel-based on commercial superabsorbent polymer and hyperbranched polymer. Here, the incorporation of reduced graphene oxide (rGO) resulted in excellent electrical self-healing properties and water-absorption reusability (Peng et al., 2014). Hybrid hydrogel membranes composed of reduced graphene oxide nanosheets and a poly (vinyl alcohol) matrix were proposed as an electrically responsive drug release system for the anesthetic drug lidocaine hydrochloride by Liu et al. (2012). The presence of rGO into the nanohybrids was found to act as a physical barrier to inhibit the drug release, while the exposure to an electrical stimulus highly enhances the release. He and Gao (2010) immobilized different kinds of functional moieties or polymers onto GP sheets via nitrene chemistry to obtain highly engineered composite materials able to delivery therapeutics upon the application of an external stimulus. An electro-responsive delivery vehicles is proposed in (Rana et al., 2011). Here, the chemistry of Chitosan is explored for the GO conjugation via amide bond formation between the carboxylic acid groups of GO and NH2 groups of Chitosan. The delivery of model drugs (Ibuprofen and 5-Fluorouracil in this case) is closely dependent on the ionization properties of the two drugs, with the release reaching a faster rate when the drugs are in the ionized form. External stimulation was also at the basis of the release of the antiinflammatory drug Dexamethasone from electrospinning-based polypyrrole nanohybrids developed in Weaver et al. (2014).
Factors Affecting Concrete Self-Healing Performance
Published in Ghasan Fahim Huseien, Iman Faridmehr, Mohammad Hajmohammadian Baghban, Self-Healing Cementitious Materials, 2022
Ghasan Fahim Huseien, Iman Faridmehr, Mohammad Hajmohammadian Baghban
Healing adhesives contained within microcapsules that are mixed into cementitious materials is another area researched in the literature [12]. Autonomous healing ability is generated by combining cement paste with polystyrene-divinylbenzene (stn-DVB), diglycidyl ether of biphenyl, epoxy resin, and other such adhesive materials. Parameters involving strength were substantially enhanced via this mix. As illustrated in Table 8.2, the flexural strength and compressive strength of standard concrete was 1.3 times and 1.9 time weaker, respectively, than the autonomously healing concrete. The efficacy of superabsorbent polymers functioning as self-recovery agents was examined in another study [13]. The efficacy of autonomous healing was ascertained via a water flow test. Upon exposure to water, superabsorbent polymer has an expansive trait and functions as a cross-linked polymer. Large crack formations have their width significantly reduced via said self-healing procedure. Table 8.2 demonstrates that the flexural strength of standard concrete is 8% weaker than the self-healing concrete, as per the findings. Cementitious composite materials and their autonomous healing capabilities were investigated in a separate academic work [14]. The reaction rate was augmented via the accelerator microencapsulating triethyl borane and methyl methacrylate monomers. A comprehensive mixing of the solution containing a combination of microcapsules and methyl methacrylate occurred within the concrete. The preparation consisted of readying three kinds of carbon microfiber-reinforced mortar samples. The first involves only the control mortar, the second includes sulfonated polystyrene modified mortars, and the third involves the autonomously healing mortar. These three kinds of samples were analyzed to deduce their mechanical performance. As can be seen in Table 8.2, compressive strength improves as per the SHM and SPSM findings. The strength of the healed crack formations in the concrete were examined following flexible polymers being used as healing agents in an academic work [15]. The encapsulation method enabled the incorporation of polymers into the concrete. The tensile strength of the autonomously healing concrete was ascertained via split tensile tests. Following 72 hours of curing at a temperature of 20°C, the analysis took place. The flexural strength of the concrete improved by 35% after the crack formations were healed by the flexible polymers.
Theoretical study on the freeze resistance of concrete mixed with superabsorbent polymer (SAP) considering the reabsorption behavior of SAP
Published in Journal of Sustainable Cement-Based Materials, 2023
Minsoo Kim, Juhyuk Moon, Sung-Gul Hong
Superabsorbent polymer (SAP) is a powdery material capable of absorbing water dozens and hundreds of times its mass. SAP has been attracting attention as a concrete additive—which are materials mixed into concrete to improve its properties—since Jensen and Hansen proposed it as a water-entraining admixture for curing high-performance concrete [4,5]. As an internal curing agent, SAP has been reported to reduce the autogenous shrinkage and water permeability of cement composites [6–8]. As a multifunctional admixture, SAP heals cracks by moisturizing the cement [9–13], and it regulates the rheological properties of fresh cement composites [14].
The study and optimization of the hygroscopic properties of selected natural products with an aim of designing a sanitary pad suitable for low- and middle-income population
Published in Cogent Engineering, 2023
Bett Brian Kipchumba, Augustine Kangogo Kulei, Josphat I. Mwasiagi
The design is engineered in such a manner that it allows the retention of the menstrual fluid for longer hours. The steps are pulping, grinding, formation of mat, spreading of tissue (upper, lower), sectioning of mat, wrap PE Film, hot-melt seal embossing, applying hot melt adhesive, release belt, finished products section, and lastly finished products arranged in parallel. Similarly, cut three shapes from a non-woven, release paper and the stick paper, e.g. the length must be 24 cm by 8 cm (rectangle) (Benshaul-Tolonen et al., 2020). Then, place the absorbent material between two nonwovens and a release paper below it. Lastly, join the three pieces using heat and lamination. The product has a flat shape without wings, making it easy to construct and to secure the pad within the inner cloth. Winged sanitary towels bear the advantage of having more protection against leakages (Kuhlmann et al., 2017). The absorbent portion of the pad is the most crucial layer (van Eijk et al., 2019). They are mostly made of wood pulp that has been mixed with superabsorbent polymers. The absorbent region is first created using a wood pulp (shredded) and a vacuum laid according to the required shape, design, and size. Control of weight is automated. The required thickness is formed through pressing. The pad or pulp is mixed with superabsorbent polymers to enhance its fluid-holding capacity (van Eijk et al., 2019). The superabsorbent polymer is based on an acrylic polymer that absorbs liquid, resulting in the formation of a gel-like substance. This gel is responsible for holding water up to 30 times its weight and consists of potassium acrylate, sodium acrylate, and alkyl acrylate (van Eijk et al., 2019). The absorbent pad is attached to a top sheet of spun lace nonwoven fabric that is permeable. It is then attached to a bottom sheet, a non-permeable material made of polyethylene. All the three layers are consolidated together and sealed to prevent leakage using ultrasonic vibrations and heat. The use of accessories such as glues, tapes, sealing, and others for comfort reasons and fit to the undergarments is also important. To prevent leakage, the superabsorbent polymer mixing with pulp, size and thickness, pulp weight, and seal quality must be precisely controlled. Counting and packaging can be done manually to minimize machine cost, although it may increase the recurring cost and wastage (Githinji et al., 2011).