Investigação do processo de absorção de água de hidrogéis de polissacarídeo: efeito da carga iônica, presença de sais, concentrações de monômero e polissacarídeo

Bortolin, Adriel; Aouada, Fauze A.; Longo, Elson; Mattoso, Luiz H. C.

doi:10.1590/s0104-14282012005000046

Cited by 17 publications

(18 citation statements)

References 27 publications

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“…Several authors consider that the Fickian model is not able to describe the complete water absorption behavior of several polymers and/or polymer composites [14][15][16][17] . In fact, in many instances it was found that the Fickian behavior can fit the experimental data points only at the early stages of the absorption process, failing, however, to describe the behavior when the absorption time increases.…”

Section: Non-fickian Behaviormentioning

confidence: 99%

Effect of the hardener to epoxy monomer ratio on the water absorption behavior of the DGEBA/TETA epoxy system

Pereira

d’Almeida

2016

Polímeros

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SbstractThe water absorption behavior of the DGEBA/TETA epoxy system was evaluated as a function of the epoxy monomer to amine hardener ratio. Weight gain versus immersion time curves were obtained and the experimental points were fitted using Fickian and Non-Fickian diffusion models. The results obtained showed that for all epoxy monomer to hardener ratios analyzed water diffusion followed non-Fickian behavior. It was possible to correlate the water absorption behavior to the macromolecular structure developed when the epoxy/ hardener ratio was varied. All epoxy/hardener ratios present a two-phase macromolecular structure, composed of regions with high crosslink density and regions with lower crosslinking. Epoxy rich systems have a more open macromolecular structure with a lower fraction of the dense phase than the amine rich systems, which present a more compact two-phase structure.

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Section: Non-fickian Behaviormentioning

confidence: 99%

Effect of the hardener to epoxy monomer ratio on the water absorption behavior of the DGEBA/TETA epoxy system

Pereira

d’Almeida

2016

Polímeros

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“…Some physical factors, such as the presence of hydrophilic groups (-OH, -NH 2 , -COOH, -CONH 2 , -SO 3 H) in the polymer chain structure (laterally or in the main chain), lower crosslink density and high flexibility of the polymer network, can contribute positively to a greater swelling of the material. Bortolin et al (2012) explain that higher concentrations of acrylamide increase the stiffness of the polymer chains, resulting in less water absorption capacity. Generally, polymer networks formed with high AAm concentration are more strongly crosslinked and this reflects in less expansion, causing lower volume of water diffused into the matrix.…”

Section: Resultsmentioning

confidence: 99%

Cowpea bean production under water stress using hydrogels

Lopes

Tavares

Veloso

et al. 2017

Pesqui. Agropecu. Trop.

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The population increase and the need of intensifying food production, coupled with the scarcity of water resources, have led to the search of alternatives that reduce consumption and optimize the water use during cultivation. In this context, hydrogels become a strategy in agricultural management, due to their water retention capacity in the soil and availability to plants. This study aimed at evaluating the efficiency of hydrogels on the development and production of cowpea bean ('Sempre-verde' cultivar) under water stress, in a greenhouse. The experiment was performed in a randomized block design, with five replications, in a 4 x 5 factorial scheme, consisting of four types of hydrogel (Hydroplan-EB HyA, with granulometry of 1-3 mm; Hydroplan-EB HyB, with granulometry of 0.5-1 mm; Hydroplan-EB HyC, with granulometry < 0.5 mm; Polim-Agri, with granulometry of 1-0.5 mm) and five concentrations (0 g pot-1; 1.5 g pot-1; 3 g pot-1; 4.5 g pot-1; 6 g pot-1). The following traits were evaluated: number of pods per plant, number of grains per pod and grain yield. The highest concentration (6 g pot-1) resulted in a higher number of pods and yield for all the hydrogels, especially for HyC and Polim-Agro, which presented 7.4 pods plant-1 and 7.0 pods plant-1, with yield of 15.43 g plant-1 and 16.68 g plant-1, respectively. The use of hydrogel shows to be efficient for reducing yield losses under water stress.

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“…O que pode estar relacionado com a quantidade de cargas positivas dispersas na solução de intumescimento, proporcionando uma maior diferença de pressão osmótica entre a solução e a matriz polimérica. 2,38 Tais resultados estão coerentes com os resultados de Q. O comportamento de n e k em função das diferentes soluções salinas e água destilada é representado na Figura 10. Por último, os valores de n e k obtidos em soluções com diferentes valores de pH apresentaram mecanismo de transporte anômalo no limite do transporte Fickiano. Não foi observado variação significativa dos valores de n e k para a faixa de pH estudada.…”

Section: Parâmetros Cinéticosunclassified

Efeito Do Ph, Espécie E Concentração Iônica Na Absorção De Água De Hidrogéis Bionanocompósitos Constituídos De CMC/Paam/Laponita RDS

Garcia¹,

Moura²,

Aouada³

2019

Quím. Nova

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Recebido em 23/01/2019; aceito em 13/05/2019; publicado na web em 20/08/2019 EFFECT OF PH, IONIC CONCENTRATION AND SPECIES ON THE ABSORPTION OF WATER BY HYDROGEL BIONANOCOMPOSITS CONSTITUTED FROM CMC/PAAm/ LAPONITE RDS. The objective of this paper was to study the effect of pH, concentration and ionic species on the water absorption of the bionanocomposite hydrogels based on carboxymethylcellulose polysaccharide and laponite nanoclay. Bionanocomposite hydrogels were obtained via free radical polymerization. It was possible to observe that the swelling degree (Q) and kinetic properties were strongly influenced, and controlled, by the presence and quantity of ionic species, decreasing their water uptake when compared to the same values obtained in distilled water. Furthermore, the addition of nanoclay decreased the water uptake sensibility of the hydrogel in ionic media. It was also observed that the presence of the nanoclay decreased the Q eq distilled water values from 32.5 g g-1 to 22.5 g g-1. The pKa variation of the bionanocomposites was a good indication of the possible interaction of the nanoclay-polymeric chains. The possibility of the control of water absorption (velocity and quantity) whereas these nanocomposites are pH-and salt-responsive may potentiate their application in agriculture. Agronomical studies are in progress, which can confirm its applicability in this area.

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Investigação do processo de absorção de água de hidrogéis de polissacarídeo: efeito da carga iônica, presença de sais, concentrações de monômero e polissacarídeo

Cited by 17 publications

References 27 publications

Effect of the hardener to epoxy monomer ratio on the water absorption behavior of the DGEBA/TETA epoxy system

Effect of the hardener to epoxy monomer ratio on the water absorption behavior of the DGEBA/TETA epoxy system

Cowpea bean production under water stress using hydrogels

Efeito Do Ph, Espécie E Concentração Iônica Na Absorção De Água De Hidrogéis Bionanocompósitos Constituídos De CMC/Paam/Laponita RDS

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