Synthesis And Properties Of Superabsor-bent With Interpenetrating Structure

As a new superabsorbent with high performance, the sample of interpenetrating polymer network, i.e., PSA-IP-P(PHA/AMPS), coming from poly(sodium acrylate) (PSA) and the copolymer of hydroxypropyl acrylate (HPA) and 2-acrylamido-2-methy propone sulfonate (AMPS) was prepared by aqueous solution polymerization, in which potassium persulfate (KPS) was used as initiator and N,N'-methylene bis-acrylamid (MBA) as cross-linking agent. The factors influencing the water absorption capacities of the superabsorbent such as the amount of initiator, crossing agent and P(HPA/AMPS), the polymerizing temperature, the neutralizing degree of AA, and the component of P(HPA/AMPS) were discussed. The water absorption capacities of PSA-IP-P(PHA/AMPS) and poly(sodium acrylate) (PSA) were compared, and their infrared spectra and thermal degradation behaviors were characterized.A band of S=O stretching vibration at 1290cm-1 could be observed in the FTIR spectra of PSA-IP-P(PHA/AMPS) before and after absorbing water, while it didn't appear in that of PSA. The thermogravimetric analysis of PSA-IP-P(PHA/AMPS) and PSA showed that their TG curves were similar. However, near 400℃ the former appeared a obvious weight loss, but not PSA. The FTIR and TG results showed that the interpenetrating network of P(HPA/AMPS) and PSA were formed.The research results of water absorbency showed that PSA-IP-P(PHA/AMPS) possessed higher water and 0.9% saline absorption capacities than PSA and terpolymer of SA, HPA and AMPS. The superabsorbent with the best waterabsorption could be synthesized by the following conditions: the polymerizing temperature was 70℃, the neutralizing degree of AA was 70%, the amount of initiator and cross-linking agent was 0.1% and 0.02% weight of monomers, respectively, and the amount of P(HPA/AMPS) (HPA/AMPS=0.5) was 2.4% weight of monomer, the average molecular weight of P(HPA/AMPS) was 2.2×106. The deion-water and 0.9% saline absorbency of PSA-IP-P(PHA/AMPS) superaborbent were 2075ml/g and 115ml/g, 36.1% and 35.3% higher than that of PSA, respectively.The factors influencing the water absorbability of PSA-EP-P(HPA/AMPS) were studied. It was shown that the water absorbency of superabsorbent was strongly affected by the concentration of salts. As the concentration of salt increases, the water absorbency of superabsorbent decreases rapidly. When the concentration of salt was higher than 0.5%, the decreasing trend was not so obvious. Different sort of salts and different valence state of ions influenced the water absorbency in different degree (Na+ < Mg2+ < Ca2+). The water absorbency of the superabsorbent was different when the absorbed water has the different pH value. When pH value was 6, its absorbency arrived the highest amount. However, in the region from pH5 to pH9, the water absorption of the superabsorbent was higher than 1000ml/g. The results also showed that the water absorbency of the superabsorbent was hardly affected by the test temperature.Other properties of the superabsorbent, such as the absorption rate, water-retention and stabilities, were studied. It was shown that the water absorption rate of superabsorbent was influenced by its particle size, in the range of 20-120 mesh, 20<20-60<120. After five frozen-defrozen processes at -10℃, the water absorbency of superabsorbent was no change. The water absorbency of superabsorbent hardly changed after one-hour heat-treatment at 100℃ and decreased 10% after five-hour heat-treatment. It also showed that the water retention of the superabsorbent was very good on the conditions of different temperature and pressure.