Superabsorbent copolymers, based on acrylamide, 2-acrylamido-2-methyl-propanosulfonic acid and a ... more Superabsorbent copolymers, based on acrylamide, 2-acrylamido-2-methyl-propanosulfonic acid and a divinyl crosslinker, N,N 0 -methylenebisacrylamide, have been synthesized by free radical solution and inverse emulsion polymerization. The copolymerization has been carried at different pH values of the monomer mix reaction medium.
Superabsorbent polymers are environmentally useful as water retention agents, for purposes such a... more Superabsorbent polymers are environmentally useful as water retention agents, for purposes such as agricultural applications and combating desertification. In this work, these polymers were synthesized to study the effects of synthesis parameters and of temperature of the swelling medium on water absorption. The polymers were synthesized by two polymerization techniques, free radical solution and free radical inverse emulsion ("S" and "E", respectively), and some pH values, 4 and 10 for S, and 7 for E. The monomers used were: acrylamide; 2-acrylamido-2-methyl-propano-sulfonic acid; and N,N-methylene-bisacrylamide as a crosslinker. The temperature of the swelling medium was varied in the range 10 to 49°C. The following effects were studied: effect of the polymerization technique and pH on the swelling capacity; and effect of temperature on the time to reach the equilibrium (final) swelling and its extent. The study confirmed expected results: polymers obtained by E at pH 7 reached a swelling almost as large as the polymers obtained by S at a higher pH of 10; and, regarding the swelling conditions, a higher temperature (above 38°C), although significantly decreasing the equilibrium (final) swelling, led to a faster reaching of the equilibrium.
To study the effect of the polymerization conditions on swelling, a copolymer was synthesized fro... more To study the effect of the polymerization conditions on swelling, a copolymer was synthesized from the monomers acrylamide (AA), 2-acrylamido-2-methylpropanosulfonic acid (AMPS) and N,N-methylenobisacrylamide (BA) as crosslinker by an inverse emulsion technique. The conditions were: concentration of organic solvent, s (an isoparaffinic hydrocarbon, commercially Isopar M), concentration of emulsifier, e (sorbitan trioleate, commercially Tween 85), and reaction temperature, T. These three variables (factors) were explored to achieve highest water absorbency, a 2 3 factorial experimental design having been applied to find the main and two-factor interaction effects of those variables on the swelling capacity. A predictive model including the factors for the swelling is proposed, allowing for the estimation of absorbency capacity in this type of copolymers. The results show that the optimum values of the variables given by the experimental design were s ¼ 8.1, e ¼ 1.0, and T ¼ 49 C, with predicted swelling capacity of 1041 and experimental of 1014. The variables are relevant, with a preponderance of s, and the effect of the square of temperature is also significant.
Superabsorbent copolymers, based on acrylamide, 2-acrylamido-2-methyl-propanosulfonic acid and a ... more Superabsorbent copolymers, based on acrylamide, 2-acrylamido-2-methyl-propanosulfonic acid and a divinyl crosslinker, N,N 0 -methylenebisacrylamide, have been synthesized by free radical solution and inverse emulsion polymerization. The copolymerization has been carried at different pH values of the monomer mix reaction medium.
Superabsorbent polymers are environmentally useful as water retention agents, for purposes such a... more Superabsorbent polymers are environmentally useful as water retention agents, for purposes such as agricultural applications and combating desertification. In this work, these polymers were synthesized to study the effects of synthesis parameters and of temperature of the swelling medium on water absorption. The polymers were synthesized by two polymerization techniques, free radical solution and free radical inverse emulsion ("S" and "E", respectively), and some pH values, 4 and 10 for S, and 7 for E. The monomers used were: acrylamide; 2-acrylamido-2-methyl-propano-sulfonic acid; and N,N-methylene-bisacrylamide as a crosslinker. The temperature of the swelling medium was varied in the range 10 to 49°C. The following effects were studied: effect of the polymerization technique and pH on the swelling capacity; and effect of temperature on the time to reach the equilibrium (final) swelling and its extent. The study confirmed expected results: polymers obtained by E at pH 7 reached a swelling almost as large as the polymers obtained by S at a higher pH of 10; and, regarding the swelling conditions, a higher temperature (above 38°C), although significantly decreasing the equilibrium (final) swelling, led to a faster reaching of the equilibrium.
To study the effect of the polymerization conditions on swelling, a copolymer was synthesized fro... more To study the effect of the polymerization conditions on swelling, a copolymer was synthesized from the monomers acrylamide (AA), 2-acrylamido-2-methylpropanosulfonic acid (AMPS) and N,N-methylenobisacrylamide (BA) as crosslinker by an inverse emulsion technique. The conditions were: concentration of organic solvent, s (an isoparaffinic hydrocarbon, commercially Isopar M), concentration of emulsifier, e (sorbitan trioleate, commercially Tween 85), and reaction temperature, T. These three variables (factors) were explored to achieve highest water absorbency, a 2 3 factorial experimental design having been applied to find the main and two-factor interaction effects of those variables on the swelling capacity. A predictive model including the factors for the swelling is proposed, allowing for the estimation of absorbency capacity in this type of copolymers. The results show that the optimum values of the variables given by the experimental design were s ¼ 8.1, e ¼ 1.0, and T ¼ 49 C, with predicted swelling capacity of 1041 and experimental of 1014. The variables are relevant, with a preponderance of s, and the effect of the square of temperature is also significant.
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