Initial Swelling Rate Research Articles

New Oil-Absorbent Fiber Absorb the Oil of Water

Experiment uses the Suspension Polymerization, under the dual oxidation-reduction system of H2O2-xanthate and H2O2-FeSO4 initiating, the lipophilic- monomer of BMA is grafted on the frame of cotton fiber which prepares oil-absorbent fiber. It has studied the adsorption kinetics, adsorption transfer and isothermal absorption model of the oil-absorbent fiber for the oily wastewater under 25°C. The result shows that the adsorption kinetics of the oil-absorbent fiber for the oily wastewater accords with pseudo second order kinetic model, it could get that the initial swelling rate is increase with stirring speed increasing from fitting. Particles internal diffusion model analyzing shows that the diffusion rate of external diffusion and particles internal diffusion are similar, increasing the stirring speed could increase the internal diffusion rate and external diffusion rate. Increasing the stirring speed could increase capacity mass transfer rate and it benefits to absorb. The absorbing of oil-absorbent fiber for oily wastewater accords with Langmuir and Freundlich isothermal absorption model.

Synthesis, swelling and responsive properties of a new composite hydrogel based on hydroxyethyl cellulose and medicinal stone

In this study, a series of pH- and saline-responsive composite hydrogels were prepared by a facile free-radical graft copolymerization amongst hydroxyethyl cellulose (HEC), sodium acrylate (NaA) and medicinal stone (MS). Fourier transform infrared spectroscopy (FTIR) and Thermogravimetric/Differential thermal analysis (TG/DTA) confirmed NaA was grafted onto HEC and MS participate in polymerization, and presented the improved thermal stability. Field emission scanning electron micro-scope (FESEM), Energy dispersive spectroscopy (EDS), Elemental map (EM) and Transmission electron microscopy (TEM) analyses revealed a better distribution of MS in the HEC- g-PNaA matrix. Introducing 10 wt% MS greatly enhanced the swelling capacity by 400% (from 162 to 810 g/g), and also enhanced by 117% (from 162 to 352 g/g) even MS content reached 50 wt%. Also, the initial swelling rate was improved by incorporating MS, but decreased with enhancing the ion strength. The highly reversible On–Off switching pH- and saline-responsive region of the hydrogel was clearly extended after forming composite. In addition, the intriguing “overflowing” swelling behaviour was observed in aqueous solution of dimethyl sulfoxide (DMSO).

Swelling of pure vanadium and V-5Cr at ∼430 °C in response to variations in neutron flux-spectra in FFTF

When irradiated at ∼400–436°C in the FFTF fast reactor, pure vanadium swells more than does V-5Cr, a behavior opposite of that observed at 500–600°C. The tendency of V to swell more than V-5Cr increases as the dpa rate increases. The swelling of both metals appears to be exceptionally sensitive to the dpa rate, with the initial swelling rate increasing strongly as the dpa rate decreases. If this sensitivity is not factored into the analysis of swelling data it will appear that swelling is completely unpredictable. When this sensitivity to dpa rate is recognized along with the tendency of both alloys toward self-organization via void lattice formation, then swelling of V and V-5Cr in response to irradiation becomes better understandable.

Synthesis, Characterization and Swelling Behaviour of Poly(sodium acrylate)/Palygorskite Superabsorbent Composites based on Palygorskite and Organo-palygorskite

Novel superabsorbent composites based on partially neutralized acrylic acid (SA) and palygorskite (PLG) were synthesized by aqueous solution polymerization. The effects of PLG, organo-PLG (O-PLG) and the content of PLG in the copolymeric gels on the water sorption and the initial swelling rate in deionized water and saline solution (0.2 wt% NaCl (aq) ) were studied. Experimental results indicate that the absorption in saline solution is smaller than that in deionized water. In comparison with a polymer prepared under clay-free conditions (415 gg -1 ), no considerable change in absorption is observed with incorporating 20.0 wt% PLG or 20.0 wt% O-PLG (368 gg -1 or 356 gg -1 ), which significantly reduces in the cost of preparing superabsorbents. Plots of swelling against time have been found to fit mathematical relationships which are based on spring and dashpot models and are applied in the polymer field to viscoelastic systems. The thermal stability of the composites was found to be increased, and this was associated with the addition of palygorskite. In addition, the XRD patterns of poly(SA)/PLG and poly(SA)/O-PLG indicate the formation of a traditional microcomposite.

Poly(acrylamide/maleic acid)–sepiolite composite hydrogels for immobilization of invertase

Poly(acrylamide/maleic acid) and sepiolite (PAMS) composite hydrogel was prepared and used for the immobilization of invertase. In FTIR analysis, the characteristic bands of composite such as –OH, –COOH, Si–OH show the evidence of sepiolite and maleic acid. In TGA analysis, water loss, decomposition of amide side groups and breakdown of main chain regions of the composite were found. The parameters of equilibrium swelling, initial swelling rate, diffusional exponent, and diffusion coefficient were calculated and evaluated from swelling experiments in distilled water. Invertase was immobilized onto PAMS by adsorption and poly(acrylamide/maleic acid)–sepiolite–invertase (PAMSI) was prepared. Optimum pH, optimum temperature values for free invertase and PAMSI were found. It was found that K m values of free invertase and PAMSI were 11.3 and 34.1 mM, respectively. V max value was found that 2.0 μmol min−1 for free invertase and 13.9 μmol min−1 for PAMSI, respectively. PAMSI showed excellent temperature, operational and storage stability.

Study on superabsorbent composite XXV. Synthesis, characterization, and swelling behaviors of poly(acrylic acid‐co‐N‐acryloylmorpholine)/attapulgite superabsorbent composites

AbstractIn this work, a novel poly(acrylic acid‐co‐N‐acryloylmorpholine)/attapulgite superabsorbent composite was prepared by graft copolymerization among acrylic acid, N‐acryloylmorpholine and attapulgite in aqueous solution, using N,N′‐methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. The result from FTIR spectra showed that OH of attapulgite participated in graft copolymerization with acrylic acid and N‐acryloylmorpholine. Proper monomer ratio and atapulgite content could form a loose surface, and improve reswelling ability and initial swelling rate. The buffer action of the COOH and COO− groups in the superabsorbent composite keeps the water absorbency a rough constant in the pH range of 4.4–9.6. Both polarity and structure of an organic solvent are responsible for the phase transition point of the superabsorbent composite. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

Effect of synthesis parameters on polymethacrylic acid xerogel structures and equilibrium swelling

Hydrogels based on crosslinked polymethacrylic acid were synthesized via free-radical polymerization in aqueous solution, using N,N′-methylene bisacrylamide as a crosslinking agent and 2,2′-azobis-[2-(2-imidazolin-2-yl)propane] dihydrochloride as an initiator. The influence of the reaction parameters (the neutralization degree of methacrylic acid and the initial monomer concentration) on the equilibrium swelling degree, the swelling kinetic parameters and the basic structural properties of xerogels was investigated. The change of synthesis parameters leads to the change of the basic structural parameters of xerogel, as well as the equilibrium swelling degree and the initial swelling rate of the hydrogels. It is found that there are power form relationships between the equilibrium swelling degree, the initial swelling rate and the structural xerogel’s properties and the change of the neutralization degree of monomer, i.e. the monomer concentration. The examined correlations proved that the crosslinking density is the crucial parameter which determines all the other investigated structural and swelling parameters.

Kinetics and thermodynamics of the water sorption of 2‐hydroxyethyl methacrylate/styrene copolymer hydrogels

AbstractA series of polymer hydrogels based on 2‐hydroxylethyl methacrylate and styrene were synthesized by bulk polymerization. The kinetic and thermodynamic swelling properties of these hydrogels were studied. The swelling mechanism of the hydrogels followed Fickian behavior. The diffusion coefficients, initial swelling rate, and maximum water uptake all decreased with the styrene content increasing because of the hydrophobicity of styrene. The swelling process was exothermic from 278 to 315 K, and the greater the styrene content was, the lower the enthalpy of mixing was in magnitude. The polymer–water interaction parameter, reflecting thermodynamic interactions, increased with increasing styrene content in the polymers. The negative values and trend of the actual partial molar enthalpy and entropy of dilution could be explained by the structuring of water through enhanced hydrogen bonding and hydrophobic interactions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Swelling and drug releasing properties of poly(N-isopropylacrylamide) thermo-sensitive copolymer gels

A series of N-isopropylacrylamide (NIPAAm) copolymer gels with different hydrophilicities were prepared from NIPAAm, hydrophilic acrylamide (AAm) and hydrophobic butyl methacrylate (BMA). The swelling and thermo-responsive properties of PNIPAAm P (NIPAm-co-BMA) and P(NIPAm-co-AAm) copolymer hydrogels were investigated. The drug loading and releasing behaviors for two kinds of model drug with different hydrophilicities were studied. The result shows that the copolymer gels present negative thermo-sensitivities. The lower critical solution temperature (LCST), equilibrium swelling degree and the initial swelling rate increase as the hydrophilicity of gels increases when the temperature is below the LCST. With increasing gel hydrophilicity the loading ratio for sodium salicylate increases, while for salicylic acid, the reverse is observed. The initial drug releasing rate of sodium salicylate and salicylic acid also increase with increasing gel hydrophilicity. The initial drug releasing rate of sodium salicylate is significantly higher than that of salicylic acid. For salicylic acid which is less hydrophilic, the equilibrium releasing ratio at high temperature is lower than that at low temperature while for sodium salicylate which is more hydrophilic, the equilibrium releasing ratio at high temperature is almost the same as that at low temperature. Equilibrium releasing ratios of the three gels are significantly different from each other for salicylic acid when the temperature is below LCST while the equilibrium releasing ratios of the three gels are all 100% for sodium salicylate.

Radiation synthesis and characterization of 2‐hydroxyethyl‐methacrylate‐based hydrogels containing di‐ and tri‐protic acid and its application on wastewater treatment

AbstractRadiation‐crosslinked 2‐hydroxyethylmethacrylate/citric acid (HEMA/CAc), 2‐hydroxyethylmethacrylate/tartaric acid (HEMA/TA), and 2‐hydroxyethylmethacrylate/succinic acid (HEMA/Sc) copolymers were prepared by using 60Co γ‐rays. The gel fraction yield and the swelling behavior of the prepared hydrogels were studied. It was shown that increasing irradiation doses was accompanied by an increase in yield of gel fraction and a decrease in swelling degree. The parameters of equilibrium swelling, maximum swelling, initial swelling rate, swelling exponent, and diffusion coefficient of the hydrogels were determined by studying the swelling behavior of the hydrogels prepared. It was seen that the equilibrium swelling degree increases as the content of acid increases, as a result of introducing more hydrophilic groups. When the hydrophilic polymer (acids) varies in the content range of 40–80 mg, swelling exponents (n) decreases, thereby indicating a shift in the water‐transport mechanism from the anomalous (non‐Fickian)‐type to the Fickian‐type. Characterization and some selected properties of the prepared hydrogels were studied, and accordingly the possibility of its practical use in the treatment of industrial wastes such as dyes and heavy metals (Fe, Ni, Co, and Cu) were also studied. The effect of treatment time, pH of feed solution, initial feed concentration, and temperature on the dye and heavy metals uptake was determined. The uptake order for a given metal was HEMA/TA hydrogel > HEMA/CAc > HEMA/Sc hydrogel. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Synthesis and water sorption studies of pH sensitive poly(acrylamide- co-itaconic acid) hydrogels

Superabsorbent copolymers of acrylamide (Am) and itaconic acid (ItA) were prepared by free radical solution polymerization using sodium persulfate and N, N, N′, N′-tetramethylenediamine (TMEDA) as initiating system at 35 °C. Two series were prepared. The first series (SA series) used varied amount of itaconic acid and fixed amount of N, N′-methylenebisacrylamide (MBAm), while in the second series (SB series) the amount of (MBAM) changed and the amount of itaconic acid was fixed. The swelling behavior was studied at room temperature and the swelling percentage, swelling kinetics parameters such as initial swelling rate, swelling rate constant, and diffusion parameters were determined. The effect of pH and saline sensitivity on swelling behavior was also studied.

Comparison of the swelling kinetics of a partially neutralized poly(acrylic acid) hydrogel in distilled water and physiological solution

The isothermal kinetics curves of the swelling of a poly(acrylic acid) hydrogel in distilled water and physiological solution at temperatures ranging from 20 to 40 ?C were determined. The possibility of applying both the Fick?s kinetics model and kinetics model of the first order chemical reaction to the swelling kinetics of the PAA hydrogel in distilled water and physiological solution were examined. It was found that the possibilities of applying these models were limited. The new model of the kinetics of swelling in distilled water and physiological solution was established. The kinetic parameters (Ea, ln A) for the swelling in distilled water and physiological solution were determined. The decrease of the equilibrium degree of swelling and the saturation swelling rate of the swelling of the PAA hydrogel in physiological solution compared to swelling in distilled water could be explained by the decreased differences in the ionic osmotic pressures between the hydrogel and the swelling medium. The increase of the initial swelling rate in the physiological solution might be caused by an increased density of charges at the network and by an increased affinity of the network towards the water molecules. The increase of the activation energy of the swelling of the PAA hydrogel in the physiological solution is a consequence of its additional "ionic crosslinking".

Controlled release NPK compound fertilizer with the function of water retention

Controlled release nitrogen, phosphorus and potassium (CRNPK) compound fertilizer with the function of water retention was prepared, which possessed the core/shell structure. Its core was urea formaldehyde (UF) and polyphosphate potassium (PAK) fertilizer, and the shell was P(acrylic acid-co-acrylamide)/kaolin (P(AA-co-AM)/kaolin) superabsorbent composite. Analysis results showed that the N, P and K contents were 11.3, 21.1 (shown by P 2O 5) and 8.6 (shown by K 2O) wt%, respectively. The synthesis conditions of inversion suspension polymerization were studied systematically. The water absorbency of the product was 91 g/g in tap water. The swelling rate, slow release and water retention properties of CRNPK were also investigated. Additionally, the effect of temperature on the nutrients release behaviors was studied. The results showed that the product had high initial swelling rate, and the product not only had a good slow release property but also excellent water retention ability, which could effectively improve the utilization of fertilizer and water resource at the same time.

Preparation and Properties of Coated Nitrogen Fertilizer with Slow Release and Water Retention

A coated nitrogen fertilizer with slow release and water retention (CNSW) was prepared by cross-linked poly(acrylic acid)/organo-attapulgite (outer coating), urea-formaldehyde (UF) (inner coating), and urea granule (core). The synthesis conditions of inversion suspension polymerization were studied systematically. The water absorbency of CNSW was 80 times its own weight in tap water. Elemental analysis showed that the nitrogen content of the product was 28.3%. Swelling rate, slow release, and water retention properties of CNSW were also investigated, and a possible slow release mechanism was proposed. The results showed that the product had a high initial swelling rate, and the product had not only a good slow release property but also excellent water retention capacity, which could effectively improve the utilization of fertilizer and water resource. The results of the present work indicated that CNSW would find good application in agriculture and horticulture, especially in drought-prone areas.

Synthesis of copolymeric hydrogels using gamma radiation and their utilization in the removal of some dyes in wastwater

AbstractCopolymer hydrogels were prepared by γ‐radiation copolymerization of maleic acid (MA) and 2‐hydroxyethylacrylate (HEA) or acrylamide (AAm). The effect of AAm/MA and HEA/MA composition and irradiation dose on the gel fraction yield in the prepared hydrogels was determined. It was found that as the content of MA increased, the gel fraction yield decreased. The increase of irradiation dose resulted in increasing the crosslinked network structure and consequently the gel percent. The parameters of equilibrium swelling, maximum swelling, initial swelling rate, diffusion exponent, and diffusion coefficient of the hydrogels were calculated and evaluated, and it was found that water diffusion to the hydrogels generally was a non‐Fickian diffusion type. Characterization of the prepared hydrogels was studied and accordingly the possibility of its practical use in the treatment of waste dyes from aqueous solution was studied. The effect of treatment time, the pH of the feed solution, initial feed concentration, and temperature on the dye uptake was also investigated. The maximum uptake of the investigated dyes was higher for HEA/MA hydrogel than that for AAm/MA hydrogel. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:3720–3731, 2006

Swelling Characterization of Polyelectrolyte Poly(Hydroxamic Acid) Hydrogels in Aqueous Thiazin Dye Solutions

In this study, swelling behavior of polyelectrolyte poly(hydroxamic acid) (PHA) hydrogels have been investigated in aqueous thiazin dye solutions. PHA hydrogels were prepared by free radical polymerizations of acrylamide with some cross-linkers such as N,N′ methylenebisacrylamide (NBisA) and ethylene glycol dimethacrylate (EGDMA); then they were used in experiments on swelling and diffusion of some water-soluble cationic dyes such as methylene blue (MB), thionin (T), and toluidin blue (TB). Swelling experiments were performed in water at 25°C, gravimetrically. The equilibrium swelling percent (S%) values of PHA hydrogels were calculated as 238–2705%. Some swelling kinetic parameters such as initial swelling rate, swelling rate constant, and maximum (theoretical) swelling percent were found. Diffusional behavior of dye solutions was investigated. Dye diffusion into hydrogels was found to be non-Fickian in character. Diffusion exponent (n) is over 0.50. For sorption of thiazin cationic dyes, MB, T, and TB to PHA hydrogels were studied by batch sorption technique at 25°C. PHA hydrogels in the dye solutions showed the dark coloration. In the experiments of the adsorption, S-type adsorption in the Giles classification system was found.

Preparation and swelling behavior of macroporous poly(acrylamide‐co‐sodium methacrylate) superabsorbent hydrogels

AbstractMacroporous superabsorbent hydrogels (SAHs) composed of acrylamide (AAm) and sodium methacrylate (NMA) were prepared by aqueous solution polymerization in the presence of a glucose solution. Their swelling capacity was investigated as a function of the concentrations of the glucose solution, sodium methacrylate, crosslinker, initiator, and activator. The porosity of the poly(acrylamide‐co‐sodium methacrylate) superabsorbent hydrogels was confirmed using scanning electron microscopy. The SAHs were characterized by IR spectroscopy. To estimate the effect on the swelling behavior, three types of crosslinkers were employed: N,N′‐methylenebisacrylamide, 1,4‐butanediol diacrylate, and diallyl phthalate. Network structural parameters such as initial swelling rate, swelling rate constant, and maximum equilibrium swelling were evaluated by water absorption measurement. The equilibrium water content (EWC%) of the AAm–NMA macroporous SAHs was found to be in the range of 93.31–99.68, indicating that these SAHs may have applications as biomaterials in the medicinal, pharmaceutical, and veterinary fields. Most of the SAHs prepared in this investigation followed non‐Fickian‐type diffusion, and few followed a case II– or super–case II‐type diffusion. The diffusion coefficients of these macroporous SAHs were investigated. Further, the swelling behavior of these SAHs also was investigated at different pHs and in different salt solutions and simulated biological fluids. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3202–3214, 2006

Influence of poly(acrylic acid) xerogel structure on swelling kinetics in distilled water

The basic structural properties of xerogels of crosslinked poly(acrylic acid) were defined and determined: xerogel density (ρxg), xerogel volume fraction in the equilibrium-swollen state (v2), the number average molar mass between network crosslinks $(\bar{M}_{c})$ , the crosslink density (ρc) and the distance between macromolecular chains (d). A crosslinking ratio (X) increase leads to a linear increase in the values for ρxg and ρc, while the values $\bar{M}_{c}$ and d decrease. The isothermal swelling kinetic curves of four samples of structurally different poly(acrylic acid) xerogels in bidistilled water at different temperatures ranging from 25 to 45 °C were determined. It is shown that isothermal kinetic swelling curves could not be described with the model of first-order reaction kinetics in entire. It was found that these curves could be described by the Johanson-Mampel-Avrami (JMA) equation. For all of the investigated xerogel samples, the initial swelling rate (vin), effective reaction rate constant (k) and equilibrium swelling degree increased with swelling temperature increase. Based on the determined values of the vin and k, the activation energy (Ea) and pre-exponential factor (lnA) were determined. It was concluded that the activation energy linearly increased with increasing distance between macromolecular chains (d) and molar mass between the network crosslinks $(\bar{M}_{c})$ . The relationship between the activation energy changes with pre-exponential factor (compensation effect) caused by xerogel structural properties was established. Isothermal swelling kinetics could be completely described by the kinetics of phase transition of the xerogel transformation from glassy to rubbery state, i.e. with the JMA kinetic equation.

Semi-IPNs of starch and poly(acrylamide-co-sodium methacrylate): Preparation, swelling and diffusion characteristics evaluation

Semi-interpenetrating polymer network (IPN) hydrogels composed of starch and random copolymer of poly(acrylamide-co-sodium methacrylate) [poly(AAm-co-NMA)] were prepared by polymerizing an aqueous solution of acrylamide (AAm), sodium methacrylate (NMA) using ammonium persulphate (APS)/ N, N, N 1, N 1-tetramethylethylenediamine (TMEDA) as redox initiating system in presence of a crosslinker and starch solution. IR spectroscopy was used to identify the presence of different repeating units in the IPN networks. The swelling and diffusion characteristics, such as initial swelling rate ( r i), swelling rate constant ( k s), equilibrium swelling ratio ( S eq), diffusion constant ( n) and diffusion coefficients ( D) were evaluated for different semi-IPN hydrogels prepared under various formulations. For better understanding of network structure formation of these semi-IPNs, three different crosslinkers namely, N, N-methylenebisacrylamide (MBA), 1,4-butanediol diacrylate (BDDA) and diallyl phthalate (DP) were employed. Further, the swelling pattern of semi-IPN hydrogels was studied in different physiological, pH and ionic/salt solutions and showed great responsiveness due to their ionic character. The morphological features of these IPNs were observed using scanning electron microscopy (SEM).

Study on superabsorbent composite. III. Swelling behaviors of polyacrylamide/attapulgite composite based on acidified attapulgite and organo-attapulgite

A novel kind of salt-resistant superabsorbent composite, polyacrylamide/attapulgite, from acrylamide (AM) and attapulgite (APT) was prepared by free-radical aqueous polymerization, using N, N′-methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator. The organification of APT with hexadecyltrimethyl ammonium bromide (HDTMABr) was proved by FTIR and XRD. The effects of acidified APT (H +-APT), organo-APT (HDTMABr-APT) and the content of APT in the superabsorbent composite on the water absorbency and the initial swelling rate for the superabsorbent composite in distilled water and in various saline solutions were studied. The effects of incorporated HDTMABr-APT and H +-APT on the reswelling ability of the superabsorbent composites were investigated. The results indicate that the incorporation of APT had remarkable influence on the improvement of water absorbency and swelling rate of the composites. Comparing with the composite doped with H +-APT, the water absorbency for the composite doped with 10 wt% HDTMABr-APT was enhanced from 2140 g g −1 to 2800 g g −1 in distilled water and from 100 g g −1 to 121 g g −1 in 0.9 wt% NaCl solution, respectively. The water absorbency of the composites in various saline solutions decreased with the increasing concentration, especially for the multivalent cations. In addition, the reswelling ability of the superabsorbent composites is also improved evidently by adding a small amount of HDTMABr-APT into the composite, comparing with that of incorporated with H +-APT.