Preparation And Performance Research Of Modified Poly(Aspartic Acid) Composite Absorbent Resin

The super absorbent resin is a kind of polymer materials that can absorb hundred times of its own weight, it was popular in many areas because of its good water absorption and retention. However, the conventional water-absorbent polymer has poor salt tolerance, oneness capability, non-degradable and slowly absorption rate and so on. Thus, exploring the superior performance of composite water-absorbing polymer has important application value. The modified poly(aspartic acid)/ poly(acrylic acid)(MKPAsp/PAA) and modified poly(aspartic acid)/sodium alginate(MKPAsp/KSA) were synthesized by aqueous solution polymerization, respectively. The synthesis parameters of absorbent polymer, absorbent properties and of temperature-, pH-, salt- sensitive and other aspects were discussed. Then, the structure of absorbent polymer was characterized. The main contents are as follows:(1) A novel modified poly(aspartic acid)/poly(acrylic acid) composite absorbent resin was prepared with Acrylic acid(AA) as the monomer, potassium persulfate(KPS) as the initiator and modified poly(aspartic acid)(MKPAsp) as the crosslinking agent in an aqueous system. The influence of synthesis parameters on the water absorbency of the resin was investigated. The results indicated that when the mass ratio of AA to polysuccinimide grafted with γ-aminpropyltriethoxysilane(KPSI) was 5:1, the neutralization degree of AA was 75%, the triethoxyvinylsilane(A151) amount was 0.42mol%(based on AA), the KPS content was 0.2wt%(based on AA), the γ-aminopropyl triethoxysilane(KH550) amount was 1.1mol%(based on PSI), the monomer concentration of AA was 15%, the water absorbency of MKPAsp/PAA composite absorbent resins was optimum with the swelling ratio of 886.7 g/g and 120.3 g/g in distilled water and 0.9% NaCl solution, which were enhanced by 3.8 and 1.1 times when compared with KPAsp resin, respectively.(2) The absorbent resin was characterized by Fourier transform infrared spectroscopy(FT-IR), scanning electron microscopy(SEM) and thermal gravimetric analysis(TGA). SEM confirmed that the introduction of AA into the network structure can optimize the pore channel structure, increase the pore density and make the pore sizes become uniform. The thermal stability of the resin has improved. The swelling properties of the composite resin in different temperature, pH and salt solutions were investigated, the results showed that the lower critical solution temperature(LCST) of MKPAsp/PAA composite absorbent resin was 10 ℃ high than that of poly(aspartic acid)(KPAsp), which suggested that MKPAsp/PAA composite absorbent resin had a better temperature sensitivity. The composite absorbent resin had the best swelling ratios at pH=6 and 10; the salt tolerance of the composite resin was significantly enhanced and the absorbency order in different chloride salt solutions was: Na+> Fe3+ > Ca2+.(3) Novel biodegradable modified poly(aspartic acid)/sodium alginate(MKPAsp/KSA) composite resin was prepared by hydrolysis polymerization in alkaline solution with the polysuccinimide(PSI) grafted with KH550 and A151 grafted with SA. The imfluence of synthesis parameters of MKPAsp/KSA absorbent resin on the water absorbency was discussed. The results manifested that when the dosage of SA was 7wt%, the KH550 amount was 1.44mol%(based on PSI), the A151 amount was 2.7wt%(based on PSI), the KPS content was 0.75wt%(based on the SA and A151), the graft reaction temperature of KSA was 60 ℃, the ratio of ethanol to water on hydrolysis reaction was 16: 14, the water absorbency of MKPAsp/PAA composite resin was optimum with the swelling ratio of 228.6 g/g and 57.2 g/g in distilled water and 0.9% NaCl solution, respectively.(4) The swelling kinetics of MKPAsp/KSA resin showed that there was about 100 min when the resin reached swelling equilibrium, the water absorption rate was fast and the process of diffusion belonged to Fick diffusion. It exhibited excellent sensitivity to temperature, pH and salt. SEM analysis showed that the introduction of SA into the network structure can optimize the pore channel structure, increase the pore density and make the pore sizes become uniform.TGA analysis showed that the thermal stability of the resin was improved after the introduction of the SA.