Acrylic Acid Acrylamide Copolymer Research Articles

Swelling Behaviors of Superabsorbent Composites Based on Acrylic Acid/Acrylamide Copolymer and Attapulgite

The swelling behaviors and water retention of superabsorbent sand-fixing materials prepared from acrylic acid/acrylamide copolymer (AA/AM) and acid-modified attapulgite under ultrasonic treatments and different pH conditions were investigated. The results demonstrated that a suitable amount of attapulgite can effectively improve the absorption capacity and saltwater performance. The superabsorbent achieved the highest absorptions of 1257.54 g/g and 209.45 g/g in distilled water and a 0.9 wt% NaCl solution, and a higher water absorbency occurred over a wide pH range of 5~9 when the ultrasonic power was 200 W and the attapulgite content was 10%. The addition of attapulgite could significantly increase the water absorption and retention.

Robust cement composite with low hydration temperature and high mechanical performance achieved by Field's metal and acrylic acid-acrylamide copolymer

Concrete as an artificial stone owns the weakness of high brittleness and poor flexural strength, dramatically restricting its potential. Therefore, it is crucial to reduce the brittleness and increase the flexural strength of concrete to prolong its service life. Herein, we developed a cement composite with low hydration temperature and high mechanical strength (especially in flexural strength) by combining Field’s metal with in situ polymerization of acrylic acid (AA) and acrylamide (AM). A cement composite with compressive and flexural strength increased by 8.2% and 174.2% was achieved by tuning the dosage of Field's metal and AA-AM copolymer. The hydration temperature was significantly reduced with the assistance of Field’s metal and AA-AM copolymer, inhibiting the formation of the thermal crack. In situ polymerization of AA and AM monomers was responsible for improving the intrinsic toughness of cement hydrates by constructing a polymer-cement network, significantly enhancing flexural strength. The in situ polymerized AA-AM copolymer acted as a bridge between Field’s metal and the cement matrix, improving their interface and contributing to the increased mechanical strength. The filling effect of Field’s metal and AA-AM copolymer refined the pore structure of the composite as well. Overall, our findings may offer a promising strategy for developing more robust, resilient, and sustainable cementitious materials.

The copolimeryzation synthesis and swelling capacity of cellulose-poly superabsorbent (acrylic acid-co-acrylamide) based on rice straw

A superabsorbent has been synthesized by copolymerization of rice straw cellulose as the back bone with the composition of 0.724 mol/L acrylamide and 1.429 mol/L acrylic acid as the monomers, 2.32 mmol/L N, N′-methylene-bis-acrylamide as the crosslinker, and 7.94 mmol/L potassium persulfate as the initiator. The rendement of cellulose obtained from rice straw isolation is 33.55% with the size of 34.06 nm nanocrystalline cellulose, obtained from XRD diffraction pattern. The copolymerization results in the spectrum characterization of Cellulose-Poly superabsorbent (AA-co-AM) with FTIR shows OH stretching vibration, NH and C=O stretching of monomer acrylic acid and acrylamide at wave number about 3343 cm-1 and 1600 cm-1. The surface morphology analyzed with SEM shows the superabsorbent has rough surface morphology compared to acrylic acid-acrylamide copolymer. The results of grafting efficiency increases with the increasing amount of the reacted monomer. The characterization of result shows that the grafting process of acrylic acid-acrylamide on cellulose has been formed. The swelling capacity of superabsorbent in water is 691.18 g/g, and 765.58 g/g in urea. This result is quite satisfactory and can be applied for slow release superabsorbent.

Hydration of cement with superabsorbent polymers

Hydration of cement is a complex thermodynamic system where a number of heterogeneous compounds interact with each other to form cement hydrates. Superabsorbent polymers (SAP) can be added to cement systems with many different reasons, so it is relevant that the basic knowledge of this new compound on the development of hydration is well understood. This paper reports basic research on thermal analysis of cement pastes with SAP—a suspension-polymerized poly acrylic acid–acrylamide copolymer. Several parameters were analysed: the concentration of SAP, the effect of particle size distribution and their influence on the hydration process with focus on ordinary Portland cement. The methodology included thermogravimetric analysis and differential scanning calorimetry. Combined water method was employed at different thermodynamic conditions, so the energy of activation in the different systems can be accessed. The introduction of SAP in cement-based materials significantly affects the chemical balance of ordinary Portland cement. The effect is not only in terms of the amount of hydrates, but also the type of hydrates being generated, thermodynamically favourable to precipitation of calcium hydroxide. This paper provides information relevant to hydration modelling and comprehension of cementitious materials when internal curing is active.

Formation of polymer–colloid complexes of aluminoxane particles with poly(acrylic acid) and its copolymers with acrylamide

Formation of polymer–colloid complexes formed by positively charged aluminoxane particles with a size of ~4.6 nm, which constitute the main part of the dispersed phase in aluminum polyhydroxychloride sols with poly(acrylic acid) and acrylic acid copolymers with acrylamide, is studied. Conditions of preparing water-soluble polymer–colloid complexes are determined. It is shown that water-soluble polycomplexes are obtained through the interaction of aluminoxane particles with acrylic acid–acrylamide copolymers containing no more than 0.8 mol% acrylic acid units. In the polymer–colloid complex, aluminoxane particles are uniformly distributed over polyelectrolyte macromolecules and the optimum composition is attained at the molar ratio of components Z equal to 1:1. In semidilute solutions, the addition of aluminoxane particles to the copolymer brings about formation of the gel featuring viscoelastic properties. For all copolymers, the maximally elastic properties of the gels are attained at Z ≈ 1.

Cobalt(II) and nickel(II) complex compounds with the acrylic acid-acrylamide copolymer

A possibility of using transition metal coordination compounds as intermediates in the synthesis of nanostructured composite materials with important practical (electrical, magnetic and optical) properties provokes a great interest to these compounds [1]. We synthesized and studied complexes of cobalt(II) and nickel(II) with the acrylic acid copolymer with acrylamide. The complex compounds of ions Co 2+ and Ni 2+ were prepared by dissolving a freshly prepared metal hydroxide in 0.5% solution of the ligand. The resulting complexes in the solid form are films of bright crimson and green color typical of the cobalt(II) and nickel(II) coordination compounds, respectively. Complexes are well soluble in water and sparingly soluble in organic solvents. In the DTA curves of these complex compounds endothermic effects were observed in the vicinity of 70°C with a total ~6% weight loss that corresponded to the removal of the absorbed water. The exothermic effect at the 420–456°C corresponded to the oxidation of the organic part of the complexes. The endothermic effects at the 470–503°C are associated with the destruction of the complex compounds. The consideration of the data of thermal analysis and the results of atomic absorption studies leads to a conclusion that four ligand donor groups are attached to each metal ion. The complexes empirical formula is ML2·H2O, the coordinated water molecule is in the outer sphere. Changes in the infrared spectra of complex compounds in comparison with the IR spectrum of the ligand indicate bidentate binding of the oxygen atoms of carboxy group and monodentate binding of the oxygen atoms of carbamide group with the metal ion, while the amide nitrogen atom is not involved in the coordination. The electron absorption spectra of the cobalt complex indicate a d → d transition 4 T1g(F) – 4 T1g(P) at 19400 cm –1 . In the nickel complex occur three transitions: ν1 = 4 T1g(F) → 4 T2g; ν2 = 4 T1g(F) → 4 A2g, and ν3 = 4 T1g(F) → 4 T 1g (P), indicating six-coordinated pseudooctahedral environment [2]. We succeeded to obtain nanosized metal particles (5–20 nm) through reduction of the complex compounds with sodium borohydride followed by evaporation of the solutions. The formation of nanoscale metal particles inside the structure of the ligand was confirmed using scanning electron spectroscopy. The nanocomposites are stable in dry air, but decompose at the contact with moisture. The study of magnetic properties of polymer nanocomposites obtained showed that the nanoparticles possess “superparamagnetic” properties.

Production of Exploding Materials for Detonators: Control of Crystal Growth of Lead and Barium 2,4,6‐trinitroresorcinate

AbstractThe production of lead and barium 2,4,6‐trinitroresorcinate in a suitable form for loading by gravity in detonator production has been investigated. During the work, we discovered that the synthesis of the mentioned salts in the presence of some crystal habit additives gives such characteristics of the products. A goal of our work was to investigate the role of some crystal growth additives in the nucleation, growth, size, and shape of lead 2,4,6‐trinitroresorcinate and barium 2,4,6‐trinitroresorcinate crystals. Among several crystal growth additives mentioned in the bibliography, we chose carboxymethylcellulose (sodium salt, viscosity 3–4 Pa⋅s), polyvinyl alcohol, as well as two new ones, cationic acrylamide copolymer salt, polyelectrolyte AS‐3605 and acrylic acid–acrylamide copolymer salt, Haicat (PraestrolR 835BS). As a synthesis pattern, we chose an aqueous procedure of synthesis, using solutions of lead(II) or barium salts and magnesium 2,4,6‐trinitroresorcinate. The crystal growth additives were added to one of the solutions, depending on their nature. During the research, most of the attention was focused on crystal size and shape, on safety handling and manipulation, as well as on the yield and process performing facility. The final products were qualified by chemical (Pb and NO2 group contents) and physical (crystal shape and size, bulk density, flowability, and impact and friction sensitivity) analyses.

Resistance‐based switching humidity property of crosslinked acrylic acid–acrylamide copolymers and their ionization effect against the critical humidity

AbstractThe resistance‐based switching humidity property of crosslinked acrylic acid–acrylamide copolymers was measured with an LCZ meter, and their ionic mobilities, which varied with humidity, were measured by the polar‐inversion method. Their conduction mechanism was discussed, and it was found that the ionization effect of some binding ions against a critical humidity takes place in switchable humidity‐sensitive materials. The effect is that some binding ions in materials turn into free ions when a given ambient humidity, called a critical humidity, is reached. The avalanching‐conduct electricity then occurs in materials. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1057– 1060, 2002

Thermal and radiation chemical stabilities of some polymers after Cu(II) build-up

The interaction of polyacrylic acid (PAA), polysodium acrylate (PAANa), polyacrylamide (PAM) and acrylic acid-acrylamide copolymer P(AM-AA) with copper sulphate was studied to evaluate the thermal and radiation chemical stabilities of the resultant polymers which contained increasing quantities of Cu 2+ . It was found that the efficiency of the polymers toward Cu 2+ interaction, as determined by XRF, follows the order P(AM-AA) > PAM > PAANa. PAA was inactive, and no Cu 2 + ions were detected. Generally, the results obtained from TGA and DSC reveal that there is an improvement in the thermal stability when Cu 2+ is incorporated into the polymer matrix, but the amount of Cu 2 + bound to the polymeric chains does not correlate with their relative thermal stability. The degree of crystallinity estimated by X-ray diffraction also increases as Cu 2 + is incorporated into the polymer. In addition to the thermal stability, the radiation chemical stability of polymer with accumulated Cu 2+ was found to be very high, so that the percentage of Cu 2+ released from the crosslinked polymers was zero at radiation doses of up to 500kGy.

Controlled conversion of polyacrylamide into polyacrylic acid

Interaction of nitrous acid with aqua solution of poly(acrylamide) gives poly(acrylic acid) in quantitative conversion yields. The reaction proceeds smoothly, with simultaneous evolution of nitrogen, provided that the temperature below 5°C. The procedure presented provides a versatile route to prepare acrylic acid-acrylamide copolymers in any desired composition, by adjusting molar ratio of nitrous acid.

Interactions between aluminium ions and acrylic acid-acrylamide copolymers in aqueous solution: 3. Influence of ionic strength on gelation and phase separation

Phase separation and gelation of the aqueous solutions of acrylamide-acrylic acid copolymers in the presence of aluminium chloride are studied as a function of pH and ionic strength. At pH 7, only phase separation is observed as a flocculation of aluminium hydroxide particles by polymer bridges, but because of their small positive residual charge the phenomenon is partially due to electrostatic interactions and consequently depends on the ionic strength of the solution. At pH 5, gelation attributed to the presence of polycations Al 3+ 13 occurs for values of the polymer charge which increase with increasing ionic strength. A qualitative model is proposed to define the conditions and the limits of gelation in such systems.

Deformation of polyelectrolyte gels under the influence of electric field

AbstractDeformation of acrylic acid–acrylamide copolymer gels in an aqueous solution under the influence of a dc electric field was studied. In the electric field, the gel swells, shrinks, or bends. It depends on the concentration of polyion coo− in the gel. When the concentration is low, the gel shrinks, and, when high, it swells. The gel which does not contain polyion is not influenced by the electric field. The long and thin gel is bent in an arc. The bent gel can be recovered to the original shape by removing the applied electric field or by changing the polarity of the applied electric field. The deformation is closely related to two substantial changes. One is the change of the osmotic pressure caused by the ion concentration difference between the inside and the outside of a gel. The other is the conformational change of the polymer network with decreasing of the polyion concentration.

Interactions between aluminium ions and acrylic acid—acrylamide copolymers in aqueous solution: 1. Study by 27Al nuclear magnetic resonance

Aluminium binding to acrylic acid-acrylamide copolymers at different pH values has been studied by 27Al n.m.r. at 104.2 MHz. The study of a pure AlCl 3 solution of 1 × 10 −3 moll −1 concentration (at 25°C) allowed us, using a computer calculation, to define the concentration of different presumed Al species during the Al 3+ hydrolysis, when the OH − Al varied from 0 to 3. A model is proposed which takes into account the electrostatic interaction between trivalent Al species (Al 3+ and Al 13(OH) 3+ 27) and the carboxylate groups of the copolymers. The amount of Al cations bound to the copolymers was then calculated as a function of the pH.

Interactions between aluminium ions and acrylic acid-acrylamide copolymers in aqueous solution: 2. Phase separation

The stability of aqueous solutions of acrylic acid-acrylamide copolymers (with acrylate content τ varying from 0.3 to 27%) towards Al species has been investigated at different pH values. In our previous work, an electrostatic interaction model was proposed which predicted first that the polymer stability is at a minimum at pH 5 (due to the presence of Al polycations) and secondly that there is no interaction between polymer and Al at pH 7 (due to the presence of non-ionic Al(OH) 3 species). The second prediction is incorrect and phase diagrams were established at pH 5 as well as at pH 7, and allowed us to determine: (a) the critical concentration C∗ a of the Al (for which polymer precipitation occurs) as a function of polymer concentration and (b) the C∗ a dependence on τ. The fraction of precipitated polymer was evaluated using two techniques (potentiometric titration of the supernatant and carbon titration in the precipitated phase). This was compared, at low pH (≤5) with the calculated results of the electrostatic interaction model. An interesting result was the finding of gel formation at pH 5, for one of our polymer samples in the presence of Al.

Hydrolysis of polyacrylamide and acrylic acid-acrylamide copolymers at neutral pH and high temperature

The hydrolysis of acrylamide-acrylic acid copolymers has been studied as a function of pH and of the initial composition of the samples. Our experimental results confirm the intramolecular catalysis by neighbouring undissociated carboxylate groups for 3 < pH < 5, as already demonstrated by Smets et al., and the catalysis of OH − ions with autoretarded kinetics for pH > 11. In the range of neutral pH, the observed kinetics cannot be simply explained by the superposition of these two mechanisms. Nevertheless, some empirical laws can be established from experimental data. A simulation based on a Monte Carlo method is proposed in order to predict the hydrolysis of these copolymers in different conditions.

Study of copolymer–copolymer interactions and formation of intermacromolecular complexes

AbstractInterpolymer complex formation has been studied between methacrylic acid‐methacrylamide copolymer and acrylic acid–acrylamide copolymer. The respective co‐monomer units of the two copolymers enter into complex formation through H‐bonding and ion dipole interactions. The unreacted units in the copolymer complex also interact with homopolymers such as PEO and PVP to form ternary complex. Formation of complexes and replacement reactions could be shown through several experimental techniques, e.g., viscometry, conductometry, and potentiometry.

Greffage de chaînons polyethers sur des copolymères acide acrylique-acrylamide

Acrylic acid-acrylamide copolymers were modified in DMSO solution by esterification with polyoxyethylene glycol monomethyl ethers of various chain lengths, via the isourea intermediate (from reaction with dicyclohexylecarbodiimide). A kinetic study shows that both propionic acid (as a model) and high molecular weight copolymers obey a second order law with an activation energy of 86 kJ/mol; the reactivity of the isourea is not dependent on its chain length. The grafted copolymers exhibit different viscometric behaviours in pure water or in CaCl 2 solution, related to the lengths of the graft.

Thermosetting vinyl and acrylic copolymers

AbstractInfrared spectra indicate that carboxyl‐substituted acrylic copolymers react appreci8bly with a butylated melamine–formaldehyde resin when heated at 120°C. for 30 min., but under these conditions acid catalysis is needed before epoxy‐ or amido‐substituted copolymers will crosslink with the melamine–formaldehyde resin. Two methods have been used to synthesize hydroxyl‐substituted acrylic copolymers. First, a glycidyl methacrylate copolymer was reacted with diethplamine. Second, an acrylic acid copolymer was heated under reflux with butylene oxide in the presence of a basic catalyst. This second method was used to esterify a vinyl toluene–acrylic acid–acrylamide copolymer which was subsequently treated with paraformaldehyde. The resulting hydroxy‐methylolamido copolymer intercondensed when heated at 120°C. for 30 min., somewhat as did the hydroxy copolymer with melamine–formaldehyde resin blends.

Hydrolysis of polyacrylamide and acrylic acid–acrylamide copolymers

AbstractThe hydrolysis of polyamides has been studied in buffered acid solution at 110°C. at an amide concentration of 0.05 M. In the case of polyacrylamide, the reaction was carried out in acetate buffer at different values of the ratio r (acetic acid/sodium acetate). The initial velocity is low and is proportional to the concentration of acetic acid; the rate constant is equal to 2.6 × 10−6; this reaction accelerates, however, as soon as the degree of conversion exceeds 3 to 5%. In the case of copolymers of acrylamide and acrylic acid (r1 = 1.38 and r2 = 0.36, respectively), the reaction proceeds in two distinct steps, of which the first is about 50 to 100 times more rapid than the second. By carrying out the reaction with copolymers of different composition (70, 74.5, 85, and 88 mole‐% acid) and varying the degree of neutralization for each (r = 2, 10, and 49), it is shown that the rapid first step results from the interaction between an amide group and an undissociated, directly neighboring acid group, which moreover must be present in a welldetermined stereochemical position. The stereospecificity of the kinetics of this reaction was demonstrated by the difference in the behavior of two copolymers of the same over‐all composition but different internal structure. The slow second step of the hydrolysis of the copolymer corresponds sensibly to the action on polyacrylamide by external acid; the retardation is a consequence of the fact that the requirements of vicinality and stereospecificity are not satisfied for the residual for the amide groups.