State Of Bound Water Research Articles

Quality deterioration of mashed potatoes during the freeze-thaw cycle: From the perspective of moisture and microstructure

This study aimed to simulate cold chain sales temperatures to predict the effects of temperature fluctuations on the physicochemical properties, moisture distribution, microstructure, and flavor of mashed potatoes. The results showed a decline in the hardness and chewability of mashed potatoes alongside the migration of water from bound water states to weakly bound states under freeze-thaw cycles (FTC) conditions. Microstructural analysis indicated that the adhesive forces between proteins and starch granules were weakened, and the structure of mashed potatoes particles was destroyed following FTC. The oxidation and degradation of fat induced by FTC increased the content of key compounds such as octanal and nonanal, thereby contributing to an overall deterioration in the flavor of mashed potatoes. This study elucidates the effects of FTC on water migration, microstructure, and flavor characteristics of mashed potatoes, thereby providing a theoretical foundation for improving the quality of prefabricated frozen mashed potatoes dishes.

Физико-химические свойства суспензий на основе оксида алюминия и перспективы их применения

Cordierite blocks of a honeycomb structure with square cross-section channels are used as ceramic carriers for three-route automotive catalysts. Catalytically active layers are applied from suspensions based on γ-Al2O3, which is introduced into the internal volume of the carrier. The preparation of suspensions included impregnation of Al2O3 powder with solutions of Pt, Eu precursors, dilution with water, grinding to particles with an average size of 4 microns, setting acidity in the required range. The study of the physicochemical properties (point of zero charge, specific surface area, particle size, pore volume, average pore diameter) of a suspension prepared on the basis of aluminium oxide and modified with europium and platinum ions is relevant due to the possibility of using three-path catalysts in technology. The surface and porosity parameters were determined by low-temperature nitrogen adsorption/desorption. pHzcp values were determined by gravimetric titration, the pH of the points were in the range of 6.01-7.1, therefore, the specified acidity range should not be beyond these limits. The processes of thermal destruction of suspensions during heating were studied by thermal analysis. During the heating process from -100 to 250°C, a weight loss was observed throughout the heating process. Endothermic effects were discovered, corresponding to the melting of ice, evaporation of moisture, and decomposition of nitrogen-containing compounds. The greatest weight loss was observed in an aluminium oxide sample modified with europium and platinum ions (Eu,Pt/γ-Al2O3). Quantitative assessment of the forms of moisture bonds in the suspension was carried out using experimental dependences on weight changes of the TG sample and the rate of change in the DTG weight in the temperature range of 270-380 K. Based on the activation energy values, it was established that the mechanism of moisture release from the Eu,Pt/γ-Al2O3 differs from others. The calculated activation energies for the release of moisture was high (41-92 kJ/mol), which indicates the bound state of water in the structure of the solid phase. The suspension was applied to a ceramic catalyst base and annealed at 500 °C, information about the mechanism of moisture release during heating of the suspension will help to avoid a decrease in the specific surface area.

Evaluation of tight waterflooding reservoirs with complex wettability by NMR data: A case study from Chang 6 and 8 members, Ordos Basin, NW China

After long-term water injection, many developed oilfields in the Ordos Basin, China, have entered a period of the high water-cut stage. In waterflooded layers, formation water is a mixture of injected water and primary formation water. The variation of formation water salinity will significantly affect the evaluation of reservoirs using resistivity logging curves while having little effect on the NMR response. It lays a foundation for identifying fluid type and evaluation of waterflooding grade by NMR logging. However, in waterflooding layers with mixed wettability, the NMR T2 responses are still complicated and unclear. In this paper, the tight sandstone samples with different wettability of Chang 6 and Chang 8 members of Triassic Yanchang Formation in the Ordos Basin are used to investigate the NMR experiments under three saturation states: water-saturated state, oil displacing to bound water state (abbreviated as oil flooding) and water flooding to the residual oil state (abbreviated as water flooding). Results show that the distributions of standard T2 spectra, without an external gradient magnetic field, of the water-saturated state in mix-wetted samples is very close to that of after oil flooding. Thus, the standard T2 spectra will be hard to distinguish the oil layer, water layer, and waterflooded layer of mix-wetted reservoirs. The diffusion coefficients of water and oil in pores differ, resulting in different shift T2 spectra results under gradient magnetic field. Therefore, the shift T2 spectra with the external gradient magnetic field and different echo time TEs were calculated and measured. When the echo time TE = 3.6 ms is adopted, the T2 signal of water-saturated tight rock samples will be nearly distributed less than 100 ms with magnetic field gradient G = 18 G/cm, rather the T2 signal greater than 100 ms is the oil signal. This characteristic makes the shift T2 spectra outstanding in the fluid identification of tight reservoirs with complex wettability. Finally, based on this experiment, a residual oil index based on the shift T2 spectrum is constructed to evaluate the flooded grades of tight waterflooding reservoirs. The evaluation results are consistent with the core description and oil test results in the study infilled wells.

Interactions of Linearly Polarized and Unpolarized Light on Kiwifruit Using Aquaphotomics.

Near infrared (NIR) spectroscopy is an important tool for predicting the internal qualities of fruits. Using aquaphotomics, spectral changes between linearly polarized and unpolarized light were assessed on 200 commercially grown yellow-fleshed kiwifruit (Actinidia chinensis var. chinensis ‘Zesy002’). Measurements were performed on different configurations of unpeeled (intact) and peeled (cut) kiwifruit using a commercial handheld NIR instrument. Absorbance after applying standard normal variate (SNV) and second derivative Savitzky–Golay filters produced different spectral features for all configurations. An aquagram depicting all configurations suggests that linearly polarized light activated more free water states and unpolarized light activated more bound water states. At depth (≥1 mm), after several scattering events, all radiation is expected to be fully depolarized and interactions for incident polarized or unpolarized light will be similar, so any observed differences are attributable to the surface layers of the fruit. Aquagrams generated in terms of the fruit soluble solids content (SSC) were similar for all configurations, suggesting the SSC in fruit is not a contributing factor here.

Effects of different hydrocolloids on gelatinization and gels structure of chestnut starch

The effects of carboxymethyl chitosan (CMC), xanthan gum (XG) and sodium alginate (SA) on the gelatinization, rheology, gel properties, crystal form, functional group, water distribution and microstructure of chestnut starch (CS) were studied. The addition of CMC reduced the peak viscosity (PV), trough viscosity (TV) and final viscosity (FV) of CS gel, but increased the setback viscosity (SB) and breakdown viscosity (BD). XG and SA increased all viscosity values (PV, FV, TV, SB, and BD) of CS gel, and XG increased more significantly with the same addition amount. XG and SA were positively correlated with gel strength and viscoelasticity, while CMC was negatively correlated. XG and SA reduced the spin–spin relaxation time (T2), and promoted the water in the sample to gradually change to the bound water state, while CMC increased T2, resulting in more free water content. Results also showed that the addition of CMC, XG and SA did not produce new functional groups and original crystal structure disappeared after CS gelatinization, and the addition of 0.5% XG and 0.1% SA made the structure more orderly. The addition of CMC, XG and SA made the structure of CS uniform. These results will provide a theoretical basis for the production of food and non-food industrial products, and provide new insights for the application of other starches and hydrocolloids.

Predicting hydration and moisturizer ingredient effects on mechanical behavior of human stratum corneum

Hydration of the outermost layer of human skin, the stratum corneum (SC), affects barrier function, physical appearance, and sensory perception of skin. Water loss, ubiquitously associated with dry skin conditions, results in the development of mechanical tensile stresses that lead to the perception of skin tightness and provide a driving force for damage in the form of chapping or cracking. Restorative moisturizing formulations contain molecular components that counteract the effects of water loss. However, the quantitative connection between water loss and SC mechanical behavior together with a predictive model has remained elusive. We develop a diffusional-based mechanics model that accurately predicts the SC mechanical behavior during hydration or dehydration over a wide range of ambient humidity conditions and presence of moisturizing ingredients. The model was validated with published studies including SC water diffusion, quantitative Raman spectroscopy, and mechanical property and stress characterization. The roles of mobile and partially bound water states are included together with one humectant and three cosmetic emollient molecules commonly used in moisturizing formulations. The model accurately predicts the effects of moisture content and moisturizer ingredients on SC mechanical behavior and provides a quantitative predictive capability that can be employed in the design of efficacious treatments.

Polymer-water interactions and damage detection in polymer matrix composites

Polymer matrix composites have a tendency to absorb measurable moisture in nearly all operating environments. This absorbed moisture either becomes bound to the polymer network via secondary bonding interactions or exists as free water with negligible interactions. Damage creates new internal free volume where water molecules can exist in the latter state. This study introduces a novel basis for non-destructive examination in polymer matrix composites which leverages locally-higher concentration of free water in damaged areas. Experiments involved impact-induced sub-surface damage in a laminate prior to moisture exposure. Polymer-water interaction—determining the free or bound state of water—was characterized by near-infrared spectroscopy and microwave-range relative permittivity. Results show a direct correlation between the extent of local damage and higher relative levels of free water at damage sites.

Distribution of water states within Poly(HEMA-co-HPMA)-based hydrogels

The distribution of water states within hydrogels is implicated in their biotechnical performance. Formulated synthetic hydrogels based on poly(2-hydroxyethylmethacrylate-co-N-(2-hydroxypropyl) methacrylamide) [poly(HEMA-co-HPMA)] of varying cross-linker concentration and monomer mole ratio were studied for their degree of hydration and water distribution. Cross-linker concentrations of 0.1, 0.5, 1.0, and 3.0 mol% tetraethylene glycol diacrylate (TEGDA) were studied when the HEMA:HPMA mole ratios were selected to be 1:0 and 4:1. Additionally, the cross-linker concentration of 1.0 mol% TEGDA was studied in detail when the HEMA:HPMA ratio was selected to be 1:1. The degree of hydration was determined by gravimetry. The distribution among water states was determined from Gaussian deconvolution of the DSC thermograms and use of ΔHf(T) for T < 0 °C. Both the cross-linker concentration and the HEMA:HPMA mole ratio served to alter degree of hydration and the distribution among freezable free, freezable bound and non-freezable bound water states. The presence of 20% and 50% HPMA served to increase total hydration relative to poly(HEMA) (0% HPMA) by 25% and 46%, respectively at 1 mol% TEGDA. The freezable free and freezable bound water content increased 21% and 47%, respectively, and non-freezable bound water content decreased 37% when 20% HPMA was added to poly(HEMA). Correlation maps between water content and distribution with previously published properties of elastic modulus (kPa), glass transition temperature (Tg (°C)), void fraction (ϵ), freeze fracture surface roughness (Rq (μm)), the time constant of swelling (τ (min)) and time constant of release of FITC-dextran (40 kDa) (τ (h)) showed that within the freezable water domain, the freezable free water had the larger influence. However, all biotechnical properties of hydrogels were most strongly influenced by the non-freezable bound water content.

Determination of Electrical Parameters in Carbonates with Micro-CT, NMR and Gas Displacement Experiments

Understanding the electrical characteristics of carbonate formation and accurately determining the electrical parameters (cementation exponent m and saturation exponent n in Archie equation) are very important for carbonate formations evaluation. However, the study of electrical characteristics faces great challenge because of the variable pore types, the complicated pore structure and the big heterogeneity in carbonates. We selected representative carbonate cores to carry out experiment research based on newly developed technologies in digital core analysis and resistivity test. Three types of cores were selected: the void space is mainly intergranular and intercrystalline; the vugs are developed; the fractures are developed. Firstly, the porosity and permeability of the selected cores have been tested. Then micro-CT with high resolution is used to scan the cores and NMR T2 spectrums of the cores both in water-saturated state and in bound water state are obtained. Finally, the resistivity of the cores in different water saturation is tested by using gas displacement technology. The analysis results of the experimental data show that the intergranular and intercrystalline pore and the fracture both have great influence on R0 while the influence of secondary vug on R0 is slight. Cementation exponent m and saturation exponent n have great difference between different cores and there is no obvious relation between m, n and reservoir parameters (φ or K). However, if we classify the cores based on the pore type, and the values of both m and n have good relationship with bound water saturation.

Cellular interaction of polygycerol dendrimers and those derivatives

Event Abstract Back to Event Cellular interaction of polygycerol dendrimers and those derivatives Tooru Ooya1 and Yuji Kawashima1 1 Kobe University, Department of Chemical Science and Engineering, Japan Introduction: Understanding of cellular events is crucial for the development of nanomedicine. Polyglycerol dendrimers (PGDs) and hyperbranched polyglycerol (HyPG) have been examined for various biomedical applications due to their positive biocompatibilities and unique physicochemical properties[1]. Although HyPG-based naogels were reported with showing a size-dependent cellular uptake[2], PGDs, which modulate the polarity of water[3]-[5], has not been subjected to cellular interaction. In this study, PGDs and glycerol dendrons (GDs)-modified liposomes were investigated to evaluate modulating cellular functions in terms of cellular uptake, death and activation. Materials and Methods: PGDs of generation 3 and 4 (Fig. 1) were prepared by our previous method. Cytotoxicity test was performed by MTT assay using HeLa cells. Fig. 1 Chemical Structure of PGDs of generations 3 and 4 Mono-stearyl PGD-G4 was mixed with Qdot655 organic quantum dots to obtain PGD-G4-coated Qdot655. Nitric oxide (NO) release from mouse macrophage-like cell line J774.1 stimulated by the addition of the PGD-G4-coated Qdot655 was evaluated by measuring emission intensity of the NO-reacted DAF-FM. GDylated liposomes were prepared and evaluated in terms of cellular uptake (Fig. 2). The obtained conjugates were introduced into bare liposomes, in which doxorubicin (DOX) was preliminarily encapsulated, by a post-insertion method. Cellular uptake amount of each liposomes was evaluated by flow cytometry. Fig. 2 Preparation of GD-modified liposome containing L-α-phosphatidylcholine, cholesterol, and DSPE-GD-G2. Results and Discussion: With increasing the generation of PGDs, T1 was significantly shorten at the same number of hydroxyl groups per one water molecule, whereas the T1 value of PGD-G4 was larger than that of PGD-G3. This result suggests that the amount of bound water located on PGD-G3 molecule was apparently larger than that on PGD-G4. PGD-G3 showed significant cytotoxicity comparing with PGD-G4, suggesting the amount of bound water state affected to the interaction with Hela cells. The results of NO release stimulated by the PGD-G4-coated Qdot655 suggest that the PGD-G4-coatedQdot655 might induce nitric oxide synthase activation. Cellular uptake behavior of DOX-loaded GDylated liposomes was significantly greater than that of PEGylated liposome. Particularly, GD-G2ylated liposomes were internalized into cells as well as PEGylated liposomes, but GD-G1ylated liposome was much greater than the other liposomes. Conclusion: Local density of hydoxy groups provided by PGDs induced possibly both cell death and cellular activation. GDylation of liposome is a valuable approach to modulating cellular uptake of the encapsulated biologically active compounds. This work was partially supported by Grant-in-Aid for Scientific Research on Innovative Areas (New Polymeric Materials Based on Element-Blocks) (No. 15H00748) from JSPS, Japan.

Assessing the Water Migration and Permeability of Large Intact Bituminous and Anthracite Coals Using NMR Relaxation Spectrometry

Although extensive literature has emerged on the use of nuclear magnetic resonance (NMR) relaxation spectrometry for the determination of various petrophysical properties of clastic rocks, relatively few papers have reported the use of NMR to determine the moisture migration process and permeability of large intact coals. In this study, evaporation experiments simultaneously with NMR measurements were conducted for seven coal core plugs. Differences in the relaxation time distribution at the various saturation stages provide both qualitative and quantitative information on the saturation state and migration of moisture in the coal samples. Moisture migration accrues first in the larger pores, whereas the smaller pores appear to remain water-saturated. The evaporation of moisture in large intact coals undergoes three continuous processes: Migration of free water, macro-capillary water, and micro-capillary water, among which, the migration rates of both macro-capillary water and micro-capillary water are related to the coal pore size distribution and porosity. The results of the NMR measurements also indicate that coal permeability has a relationship with the moisture migration characteristics, which make it possible to develop an NMR-derived permeability model. The Timur–Coates and the Schlumberger-Doll Research (SDR) equations, which are commonly used in NMR logging evaluations of the permeability of clastic rock reservoirs, were discussed concerning their application to coals. It is found that a modified SDR permeability evaluation model $$[K_\mathrm{SDR}=0.0224(\hbox {T}_\mathrm{2gm}^\mathrm{b})^{0.182}(\hbox {T}_\mathrm{2gm}^\mathrm{a})^{1.534}]$$ , which is a double-exponential relationship with the $$T_{2}$$ geometric mean in the full water-saturated state and in the bound water state, fits the analyzed coal samples well. The NMR-derived methods provide a framework for the determination of the moisture migration and permeability of coals.

Effect of Different “States” of Sorbed Water on Amorphous Celecoxib

Glass transition temperature (Tg) of an amorphous drug is a vital physical phenomenon that influences its visco-elastic properties, physical, and chemical stability. Water acts as a plasticizer for amorphous drugs thus increasing their recrystallization kinetics. This reduces the solubility advantage of an amorphous drug. Hence, there is an interest in understanding the relationship between water content and Tg of amorphous drug. We have studied the effect of "state" of sorbed water on Tg of amorphous celecoxib (ACLB). ACLB was allowed to sorb water at relative humidity of 33%, 53%, 75%, and 93%. ALCB showed biphasic sorption of water designated as "bound" and "solvent-like" state of water associated with ACLB. Molecular modeling studies provided deeper insights into the interaction of water with ACLB. A distinct co-relationship between the state of water and its plasticization capacity was observed. Bound state of water had a very profound effect on the fall in experimentally observed Tg (T(g-exp)) value. Solvent-like state of water had little impact on T(g-exp) value. Tg of ACLB-water mixture was predicted by Gordon-Taylor equation (T(g-pre)). The deviations in T(g-exp) and Tg-pre were correlated to volume non-additivity and non-ideal mixing. This study has implications on the development of formulations based on amorphous forms.

Coherent Behavior and the Bound State of Water and K+ Imply Another Model of Bioenergetics: Negative Entropy Instead of High-energy Bonds

Observations of coherent cellular behavior cannot be integrated into widely accepted membrane (pump) theory (MT) and its steady state energetics because of the thermal noise of assumed ordinary cell water and freely soluble cytoplasmic K+. However, Ling disproved MT and proposed an alternative based on coherence, showing that rest (R) and action (A) are two different phases of protoplasm with different energy levels. The R-state is a coherent metastable low-entropy state as water and K+ are bound to unfolded proteins. The A-state is the higher-entropy state because water and K+ are free. The R-to-A phase transition is regarded as a mechanism to release energy for biological work, replacing the classical concept of high-energy bonds. Subsequent inactivation during the endergonic A-to-R phase transition needs an input of metabolic energy to restore the low entropy R-state. Matveev’s native aggregation hypothesis allows to integrate the energetic details of globular proteins into this view.

Depletion of water molecules during ethanol wet-bonding with etch and rinse dental adhesives

The treatment of demineralized dentin with ethanol has been proposed as a way to improve hydrophobic monomer penetration into otherwise water saturated collagen fibrils. The ethanol rinse is expected to preserve the fibrils from collapsing while optimizing resin constituent infiltration for better long term adhesion. The physico-chemical investigations of demineralized dentin confirmed objectively these working hypotheses. Namely, Differential Scanning Calorimetry (DSC) measurements of the melting point of water molecules pointed to the presence of free and bound water states. Unfreezable water was the main type of water remaining following a rinsing step with absolute ethanol. Two different liquid water phases were also observed by Magic Angle Spinning (MAS) solid state Nuclear magnetic Resonance (NMR) spectroscopy. Infrared spectra of ethanol treated specimens illustrated differences with the fully hydrated specimens concerning the polar carbonyl vibrations. Optical microscopy observations as well as scanning electron microscopy showed an improved dentin-adhesive interface with ethanol wet bonding. The results indicate that water can be confined to strongly bound structural molecules when excess water is removed with ethanol prior to adhesive application. This should preserve collagen from hydrolysis upon aging of the hybrid layer.

A new imaging method using pulsed neutron sources for visualizing structural and dynamical information

Neutron imaging using pulsed neutron sources coupled with a 2-dimensional position sensitive detector applicable to the time-of-flight method can give information on the crystal texture of coherently scattering materials, dynamical information of incoherently scattering materials such as hydrogen, and magnetic field information. Bragg edges appeared at cold neutron region reflect the preferred orientation, crystallite size, and lattice spacing. To deduce such information from the neutron transmission data depending on the position we have developed a data analysis code, and applied this code to data of a welded iron sample. Furthermore, as examples of more realistic materials we have investigated quenched iron rods. The quenched region was clearly demonstrated by the lattice space distribution. Furthermore, difference in the bound state of water or hydrogen in wet and dry cement pastes have been observed by analyzing the gradient of the neutron transmission cross section at the cold neutron region. The magnetic field has been also measured by using the polarized neutrons, and the strength of the field was estimated easily by analyzing the wave length dependent data.

Effect of microwave irradiation on the hydroxypropyl methylcellulose powder and its hydrogel studied by Magnetic Resonance Imaging

Proton Magnetic Resonance Imaging (MRI) has been used to study the physical changes of hydroxypropyl methylcellulose (HPMC) hydrogels due to microwave irradiation of the polymer. The proton one-dimensional images, derived from relaxation, spin density and diffusion-weighted spin-echo experiments, provide insights on the dynamics of water and the motional state of the polymer inside the hydrogels. The obtained results indicate that the microwave irradiation causes the breaking of the HPMC polymer–hydrogen bonding network in HPMC powder which influences the dynamics of water and polymer chains within its hydrogels. In order to explain the observed spin–spin relaxation time in hydrogels composed of irradiated polymers, we have to assume that in addition to a fast exchange between the free and bound state of water also a rapid proton exchange between the water protons and the hydrogen of hydroxyl groups of side chains of the monomeric units of HPMC polymer is a major transverse relaxation mechanism.

Water States in Perfluorosulfonic Acid Membranes Using Differential Scanning Calorimetry

The water states in perfluorosulfonic acid membranes (Nafion®) were evaluated using low temperature differential scanning calorimetry (DSC) on both vapor and liquid penetrants. At low sorption levels, water sorbed in Nafion existed in the nonfreezable bound state until a critical value was reached. The critical, nonfreezable water content corresponded to 4.8 water molecules per sulfonate group. Beyond that critical value, additional sorbed water was partitioned between freezable and nonfreezable bound states. The freezable water was in intermediate or freezable bound water state with subzero fussion temperatures. The observed water fusion enthalpy for every additional gram of sorbed water was less than that of pure water. The partition coefficient (K) between the nonfreezable bound state and the freezable state water was estimated as 0.755. The critical nonfreezable water content (W c ) and the partition coefficient for vapor permeate in Nafion were similar to those of liquid water penetrant. These findings allow one to estimate the bound and freezable water distribution in Nafion. The K value, in conjunction with the critical water content (W c ), can be used as a quantitative indicator to characterize water states in ionomers. This model may serve as the basis to account for water transport, ionic conductivity, and proton transfer changes in various solid electrolyte membranes.

Formation and Characterization of Fluid Lipid Bilayers on Alumina

Fluid lipid bilayers were deposited on alumina substrates with the use of bubble collapse deposition (BCD). Previous studies using vesicle rupture have required the use of charged lipids or surface functionalization to induce bilayer formation on alumina, but these modifications are not necessary with BCD. Photobleaching experiments reveal that the diffusion coefficient of POPC on alumina is 0.6 microm (2)/s, which is much lower than the 1.4-2.0 microm (2)/s reported on silica. Systematically accounting for roughness, immobile regions and membrane viscosity shows that pinning sites account for about half of this drop in diffusivity. The remainder of the difference is attributed to a more tightly bound water state on the alumina surface, which induces a larger drag on the bilayer.

Bound states of water in poly(vinyl alcohol) hydrogel prepared by repeated freezing and melting method

Bound state of water in poly(vinyl alcohol) (PVA) hydrogel produced by repeated freezing and melting method was investigated by thermal analysis and Raman spectroscopy. Water frozen in PVA hydrogel showed the lowering of the melting temperature depending on PVA concentration. This water can be treated as a supercooled water, of which the melting enthalpy is different from that of normal water frozen at 0 °C. Accurate melting enthalpies of supercooled water estimated by the difference of thermal capacity of supercooled water and ice allowed us to determine the weight content of supercooled bound water. The weight content of supercooled water decreased with increasing PVA concentration, and alternatively that of non-freezable water increased. The maximum content of non-freezable water was 31.4 wt% for the 50 wt% PVA gel. The pore size filled with water was successfully estimated by thermodynamical equation. The diameter is 30.2 nm for 10 wt% gel, which is comparable to that derived from other experimental methods. Raman spectroscopy was used to investigate the hydrogen bond of water. With increasing concentration, the rate of water without hydrogen bond increased. This might be interpreted by the increment of surface area of water as the pore size is reduced. This also supports that the PVA hydrogel takes the pore model filled with water.

Characteristics and Performance of Novel Water-Absorbent Slow Release Nitrogen Fertilizers

In this article, a research on the characteristics and performance of water-absorbent slow release nitrogen fertilizer (WASRNF) using infrared spectroscopy (IR), scanning electronic microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetry analysis (TGA), was present. The results indicate that the water absorbency and nitrogen analysis of WASRNF is 103 g g −1 and 30%, respectively, and WASRNF exhibits approximately neutral pH and very low salt index. WASRNF is a copolymer of nitrogen fertilizer and super absorbent polymer (SAP) monomers which is formed through hydrogen bond interaction, and the molecule contains hydrophilic groups, which is responsible for the absorption and water retention capacity of the molecule. WASRNF is a gel that exhibits the ability to swell, but does not dissolve in water. WASRNF shows non-homogenous nature as a whole, but in local zone it is homogenous, the copolymer molecule shows chain network that is the physical structure responsible for absorption and retention of water in WASRNF. The water retained in WASRNF exists as free and nonfreezing bound and freezing bound water states, with the free and the nonfreezing water accounting for more than 95% of water retained in WASRNF, and the nonfreezing bound water for less than 5%. WASRNF functions in delaying the release of nitrogen from it, thereby serving a novel slow release nitrogenous fertilizer.