Mechanical property of strain-hardening cementitious composites modified with superabsorbent polymers

In order to improve the tensile property, flexuralproperty and drying shrinkage of strain-hardening cementitiouscomposites （SHCC）, mixtures quantitatively modified withsuperabsorbent polymer （SAP） were investigated. Theuniaxial tensile test, the four-point bending test, thecompressive test, the drying shrinkage test and theenvironmental scanning electron microscope （ESEM） wereemployed to investigate the tensile strain capacity, flexuraldeformation capacity, compressive strength, drying shrinkage,crack width and self-healing of SHCC. The experimentalresults show that SHCC modified with SAP particles exhibitsexcellent ductility and deformability, and the tensile strain isup to about 4.5% and the average crack width is controlledaround 40 μm. Meanwhile, the drying shrinkage of SHCCmodified with SAP particles can reduce by about 60%.Furthermore, the self-healing behavior is observed in thecracks of specimen after three cycles of high-low relativehumidity curing, and the self-healing products can completelyfill the cracks of SHCC specimens modified with SAPparticles. It is, therefore, feasible to produce SHCC materialmodified with SAP particles, while simultaneously retaininghigher material ductility.

Preparation and Charcterization of Konjac Superabsorbent Polymer

A superabsorbent polymer was prepared by grafting sodium acrylate （ SA ） onto Konjac flour using potassium persulfate （KPS） and N, N＇-methylene bis acrylamide （ MBA ） as an initiator and crosslinker , respectively. The effect of various preparation conditions on its water absorbency was investigated. When the Konjac Flour content was 3.0g, the acrylic acid （AA） content was 30.0 g, the amount of initiator was 0. 150 g, the neutralization degree of monomer was 85% , the reaction temperature was 60 ℃ and the amount of crosslinker was 0.025 g, the polymer＇s absorbency was 750 times in pure water and 279 times in tap water at ambient temperature. It had also high water retention. The graft efficiency reached 67% . The analyses of FT-IR and SEM indicate that sodium acrylate is grafted on the polysaccharides of Konjac flour.

Superabsorbent polymer for water management in forestry

The effectiveness of a superabsorbent polymer of sodium polyacrylate was studied, with emphasis on water management, i.e., absorption, retention and desorption in the soil. The polymer was applied in plots with a sandy soil near Grandola (southern Portugal). Characterization of the most relevant physical and chemical properties of the polymer was made, namely, its specific gravity, particle diameter, capacity of water absorption and desorption. In the plots with and without the polymer, soil moisture was continuously monitored, and grassland biomass samples were collected and weighed. The results reflected the effective role of the polymer both in the improvement of the water regime in the soil and in the substantial increment of grassland productivity.

Preparation of Superabsorbent Polymers with Increased Saline Absorbency

Superabsorbent having enhanced absorbency of 0.9%NaCl solution was synthesized on one basis of incorporating zwitterionic (sulfobetaine) monomer into the previous monomer mixture, which comprises ionic (AA) and nonionic monomers, and another basis of introducing inorganic salt B. As far as saline absorbency is concerned, introduction of inorganic salt B is more useful than the sulfobetaine monomer.

Properties and Structure of Microcrystal Muscovite Composite Superabsorbent

Microcrystal muscovite composite superabsorbents（MMCSA） were prepared by water solution polymerization using acrylic acid, acrylamide and itaconic acid as comonomers and microcrystal muscovite as an inorganic additive. Properties, such as water absorbency, salt absorbency, gel strength, water retention capacity and structure of MMCSA characterized by SEM and XRD, were investigated. Water absorbency, salt absorbency, gel strength, water retention capacity and thermostability were enhanced by incorporation of suitable amount of microcrystal muscovite. Water absorption of MMCSA was rapid, requiring 24.55 min to reach 63% of equilibrium absorbency（1218 g/g）. Microcrystal muscovite was physically combined into the polymeric network without destroying its polycrystalline structure and microcrystal muscovite composite superabsorbent had some irregular, undulant, and small microporous holes with sheet-like microcrystal muscovite distributed in the polymeric matrix.

A Novel Method for Studying the Re-Swelling Capacity of Superabsorbent Polymers in An Artificial Crack

Re-swelling capacity is a key factor influencing the self-sealing efficiency of superabsorbent polymers (SAPs) in concrete.In this paper,a new parameter (re-swelling ratio,η),the volume ratio of the crack which was filled with the expansive SAPs and the dry SAPs,was given to quantify the re-swelling capacity of a single SAPs particle.An innovative immersion test was used to study the η value of SAPs in the hardened cement paste with an artificial crack.Moreover,the influence of the crack width and particle size on the sealing efficiency of SAPs in the cracked paste was investigated by a water permeability test.The results showed that the mass ratios of the expansive SAPs in an artificial crack were less than those in a free state.The η value of SAPs in the hardened paste with an artificial crack increased with the increase of the crack width due to the restricting effects of the crack.The expansive SAPs in the cracked paste could totally seal or partly seal the crack within the original void.Moreover,the sealing efficiency of SAPs slightly increased with the rise of the crack width (0.25 to 0.5 mm) and the reduction of the particle size.This research demonstrates that the crack width in concrete and the particle size of SAPs are the key factors influencing the re-swelling behavior of SAPs which should be taken into consideration when designing the self-sealing concrete containing SAPs.

Influence of Reaction Parameters on Water Absorbency of Starch Grafted Superabsorbents

Superabsorbents starch grafted sodium polyacrylate was synthesized by inverse suspension polymerization, using toluene as the continuous phase, potassium persulfate as the initiator. The effect of reaction parameters, such as starch pretreatment temperature, neutralization degree of monomer, reaction time and temperature, concentration of initiator, molar ratio of monomer and starch, on water absorbency of the starch grafted polymer was studied. The effects of the last two parameters were investigated by uniform design method, and the prediction equation was obtained.

Experimental Synthesis of Polyacrylic-Type Superabsorbent Polymer and Analysis of Its Internal Curing Performances

A solution polymerization method has been used to synthesize a polyacrylic-type superabsorbent polymer(SAP).The influence of various influential factors,such as the temperature,neutralization degree,cross-linking agent,and initiator,on the water absorption capacity of SAP has been investigated.The results show that the absorption can display a non-monotonic behavior depending on the synthesis conditions.The absorption can also change according to the pH,ion types and ion concentration.As the pH value increases,the water absorption capacity decreases significantly.It also decreases if the N^(a+)concentration becomes higher and becomes particularly low in solutions containing Mg^(2+).With the addition of SAP,the compressive strength of cement mortar decreases;the internal relative humidity can be maintained at 96%within 200 hours;and autogenous shrinkage can be reduced by nearly 69%.

Synthesis and Swelling Behaviors of Microcrystal Muscovite Composite Superabsorbent by Photopolymerization

A new microcrystal muscovite composite superabsorbent was synthesized by UV photopolymerization using 2-hydroxy-2-methylpropiophenone（1 173） as photoinitiator,N,N-methylene bisacrylamide（MBA） as crosslinker,acrylic acid（AA）,acrylamide（AM） and sodium 4-styrenesulfonate（SSS） as comonomers.Factors affecting water and salt absorption of the microcrystal muscovite composite superabsorbent,such as crosslinker amount,microcrystal muscovite concentration,photoinitiator content,and SSS concentration,were systematically studied.Water retention capacity of the composite superabsorbent was also investigated.The results show that microcrystal muscovite composite superabsorbent has water absorbency of 550 g/g,salt absorbency of 62 g/g,and water retention of 60% after heating at 70 ℃ for 40 h.The microcrystal muscovite is physically combined into the polymeric network without destroying its polycrystalline structure and the surface of the microcrystal muscovite composite superabsorbent has some deep and small holes.

Preparation, Swelling and Antibacterial Behaviors of N-Succinyl Chitosan-g-Poly(Acrylic Acid-co-Acrylamide) Superabsorbent Hydrogels

Superabsorbent hydrogels were prepared successfully from N-succinyl chitosan grafted poly（acrylic acid-co-acrylamide）. The potassium persulfate（KPS）, N, N＇-methylenebisacrylamide（MBA） were used as the initiator and crosslinker, respectively. Fourier transform infrared spectroscopy（FTIR） and scanning electron microscopy（SEM） were used to confirm the porous network structure of superabsorbent hydrogel. The effects of reaction parameters on the swelling behaviors of the superabsorbent hydrogels were investigated. The results indicated that water absorbency increased first, and then decreased gradually with the increase in the contents of monomer（AA＋AM）, KPS, MBA or acrylamide. The product had excellent water absorbency of 1375 g/g in distilled water and 83 g/g in 0.9wt% NaCl solution. Simultaneously, the superabsorbent hydrogels were p H sensitive. The antibacterial activities of the hydrogels against Escherichia coli（E. coli） were improved effectively because of polyamidoamine（PAMAM） dendrimer absorbed in the hydrogels.

Synthesis of Acrylic Acid/Kaoline Powder Superabsorbent Composite by Inverse-suspending Polymerization

An acrylic acid/kaoline powder superabsorbent composite with a water absorbency of the superabsorbent composite about 1/800 was synthesized by inverse\|suspending polymerization reaction between acrylic acid monomer and kaoline ultrafine powder. The influence of the dispersant agent on the configuration of the products in the inverse suspension polymerization is investigated. The influences of the kaoline powder,cross\|linker,initiator,neutralization degree and the volume ratio of oil to water phase on the water absorbency of the superabsorbent composites are discussed in the paper.

Microwave Assisted Synthesis of Guar Gum Grafted Acrylic Acid/Nanoclay Superabsorbent Composites and Its Use in Crystal Violet Dye Absorption

Natural gums can be tailored and used for the removal of toxic dyes like crystal violet via grafting techniques. However, grafting via microwave irradiation showed both higher yield and fast reaction kinetics as compared to conventional grafting. Silane modified nanoclay has been used to prepare acrylic acid grafted guar gum nanocomposites via microwave irradiation technique. The grafting was confirmed via infrared spectroscopy while XRD diffractograms suggested exfoliation of modified nanoclay in guar gum grafted acrylic acid. The reaction kinetic parameters have been optimized. The effect of nanoclay on swelling characteristics has been examined. The sensitivity of pH on swelling capabilities has also been assessed. The efficiency of the superabsorbent nanocomposite on the absorption of crystal violet dye has been studied. The superabsorbent nanocomposite loaded with 1.75% modified nanocaly was found to be optimal concentration for the removal of crystal violet dye.

An Investigation into the Performances of Cement Mortar Incorporating Superabsorbent Polymer Synthesized with Kaolin

Cement-based materials are fundamental in the construction industry,and enhancing their properties is an ongoing challenge.The use of superabsorbent polymers(SAP)has gained significant attention as a possible way to improve the performance of cement-based materials due to their unique water-absorption and retention properties.This study investigates the multifaceted impact of kaolin intercalation-modified superabsorbent polymers(K-SAP)on the properties of cement mortar.The results show that K-SAP significantly affects the cement mortar’s rheological behavior,with distinct phases of water absorption and release,leading to changes in workability over time.Furthermore,K-SAP alters the hydration kinetics,delaying the exothermic peak of hydration and subsequently modifying the heat release kinetics.Notably,K-SAP effectively maintains a higher internal relative humidity within the mortar,reducing the autogenous shrinkage behavior.Moreover,K-SAP can have a beneficial effect on pore structure and this can be ascribed to the internal curing effect of released water from K-SAP.

Smart superabsorbent alginate/carboxymethyl chitosan composite hydrogel beads as efficient biosorbents for methylene blue dye removal

The presence of toxic dyes in the aqueous medium has threatened environmental safety, and thereby re- moving them from wastewater in an efficient way is highly desired. Herein, the efficient biosorbents were successfully fabricated via a facile physical gelation process of sodium alginate (SA) and carboxymethyl chitosan (CMCTS) in an acidic aqueous solution. The as-prepared hydrogel beads not only displayed water superabsorbent properties and pH-responsive swelling characters but also exhibited excellent methylene blue (MB) adsorption capacity removal efficiency with experimental maximum MB adsorption capacity of 2518 and 1005 mg g -1 , which are comparable with most reported lignocellulosic and alginate-based hydrogels. The MB adsorption process fitted well in different kinetic and isotherm models and became more heterogeneous in concentrated MB solutions as verified by principal component analysis results. The adsorption mechanism was proposed, and the high dye absorbency was attributed to the strong electro- static forces between adsorbents and adsorbates. Our current study provides a promising and sustainable composite hydrogels platform targeted to dye decontamination.

Superabsorbent Fibers for Comfortable Disposable Medical Protective Clothing

Disposable medical protective clothing for 2019-nCoV mainly consists of stacked layers with nanopore films,polymer coated nonwoven fabrics and melt-blown nonwoven fabrics against anti-microbial and anti-liquid penetration.However,such structures lack moisture permeability and breathability leading to an uncomfortable,stuffy wearing experience.Here,we propose a novel medical protective clothing material with a superabsorbent layer to enhance moisture absorption.Poly(acrylic acid-co-acrylamide)/polyvinyl alcohol superabsorbent fibers(PAAAM/PVA fibers)were prepared via wet spinning.And the superabsorbent composite layer was stacked from PAAAM/PVA fibers,bamboo pulp fibers(BPF)and ethylene-propyl-ene side by side fibers(ESF).The novel disposable medical protective composite fabric was obtained through gluing the superabsorbent layer to the inner surface of strong antistatic polypropylene nonwoven fabric.The resultant composite fabric possesses excellent absorption and retention capacity for sweat,up to 12.3 g/g and 63.8%,and a maximum hygroscopic rate of 1.04 g/h,higher than that of the conventional material(only 0.53 g/h).The moisture permeability of the novel material reached 12,638.5 g/(m^(2) d),which was 307.6%of the conventional material.The novel material can effectively reduce the humidity inside the protective clothing and significantly improve the comfort of medical staff.

Green Fabrication of Multifunctional Three‑Dimensional Superabsorbent Nonwovens with Thermo‑Bonding Fibers

Disposable hygiene products have evolved into the important parts for millions of people around the world,enhancing the convenience of daily lives.However,development of the disposable hygiene products is restricted by unsustainable production technology,complicated operation process,and poor liquid absorption performance of the absorbent core.Herein,integrated and three-dimensional(3D)multifunctional superabsorbent nonwovens with liquid-triggered fragrance release was prepared via green,fast and scalable multi efect hot-air anchoring method which physically crosslinking the joint thermobonding fbers and anchoring fragrance microcapsules/super absorbent polymer(SAP)onto adjacent thermo-bonding fbers simultaneously.The resulting composite nonwovens could three-dimensionally absorb water 33.14 times of its own weight without gel blockage between SAP,and correspondingly release increased intensity fragrance along with enhancing amount of water absorption.Absorption rate t1 and t2 is 83.62%and 50.62%higher than the commercial specimen respectively,and the air permeability is increased by 226.88%compared with the commercial specimen.The superabsorbent nonwovens with controllable fragrance release and odorant synergistic has the potential to be practically applied to functional textiles felds because of the excellent liquid absorption and controlled fragrance release performance,and is easy to be produced on a sustainable,pollution-free and large-scale industrial production.

Hydration, microstructure and autogenous shrinkage behaviors of cement mortars by addition of superabsorbent polymers

Superabsorbent Polymer(SAP)has emerged as a topic of considerable interest in recent years.The present study systematically and quantitively investigated the effect of SAP on hydration,autogenous shrinkage,mechanical properties,and microstructure of cement mortars.Influences of SAP on hydration heat and autogenous shrinkage were studied by utilizing TAM AIR technology and a non-contact autogenous shrinkage test method.Scanning Electron Microscope(SEM)was employed to assess the microstructure evolution.Although SAP decreased the peak rate of hydration heat and retarded the hydration,it significantly increased the cumulative heat,indicating SAP helps promote the hydration.Hydration promotion caused by SAP mainly occurred in the deceleration period and attenuation period.SAP can significantly mitigate the autogenous shrinkage when the content ranged from 0 to 0.5%.Microstructure characteristics showed that pores and gaps were introduced when SAP was added.The microstructure difference caused by SAP contributed to the inferior mechanical behaviors of cement mortars treated by SAP.

Preparation of Cassava Starch-based Superabsorbent Polymer Using a Twin-roll Mixer as Reactor

Cassava starch-based superabsorbent polymer was successfully synthesized using a new technology that based on modification of a Haake twin-roll mixer as reactor. The cassava starch was first gelatinized then modified by grafting under external shear stress in the reactor. The torque and temperature curves as a function of time can reflect the variations in the reactor and also offer some information about the copolymerization reaction. The advantages of this system include starch modification can be carried out （l） with high starch concentration, （2） under controlled ticne and （3） smaller amount of sample （60 g） required. The technology provides useful guides for reactive extrusion. The starch grafted composites were characterized by Fourier transform infrared spectroscopy （FTIR）, nuclear magnetic resonance （NMR） and thermal gravimetric analysis （TGA）. The TGA was also used for determining the percentage of grafting ratio. The results show that the cassava starch has been successfully grafted with acrylamide then crosslinked by N,N＇-methylene-bisacrylamide using this reactor. The ultimate water absorbent capacity of the cassava-based superabsorbent polymer impacted by various pH values illustrated that the acid and basic solutions inhibit the ability of imbibing water. Additionally, gel properties of the cassava-based superabsorbent polymer were investigated. It can be concluded that the structure of cassava gel is stable, while the three dimensional network of cassava-based superabsorbent polymer is rigid but its structure could not resist external force effectively and everlastingly since G＇ was decreased with increasing amplitude.

A new fast swelling poly[DAPB-co-DMAAm-co-AASS] superabsorbent hydrogel for removal of anionic dyes from water

The objective of this research is to utilize a new poly[N,N-diallyl pyrrolidinium bromide-co-N,Ndimethyl acrylamide-co-acrylic acid sodium salt]superabsorbent hydrogel（SAH）for the removal of two anionic dyes,e.g.,Reactive Red 5B（RR5B）and Reactive Orange M2R（ROM2R）,from water.The SAH was characterized by swelling in water,FTIR,TGA and SEM.The SAH DDA6showed good swelling property and thermal stability.We have also investigated the parameters affecting dye adsorption such as pH,adsorbent dose,adsorption rate and initial dye concentration.The experimental data were also analyzed by applying the well known Langmuir and Freundlich isotherm models.