A Mechanical Foaming Approach To Prepere Porous Superabsorbent PAA-Na Resins And The Study Of Water Absorbent Capacity

Superabsorbent PAA-Na resins with the porous structure was obtained from a large number of foams cladding in PAA-Na network through fast polymerization process, which was formed from a solution containing surfactant under acutely mechanical agitation. The relationship between porous structure and water absorbent capacity was investigated in this paper, and the main content was contained as follows.(1) The effect of polymerization conditions by single factor method on water absorbent capacity of PAA-Na resins was studied in this section, PAA-Na resins were prepared by solution polymerization from partially neutralized acrylic acid under air atmosphere. The results showed that when the polymerization temperature was48℃, the neutralization degree was80%, the amount of distilled water was40mL, the content of oxidation-reduction initiator was0.055wt%, and the water absorbent capacity of PAA-Na resins was the best.(2) A novel system composed of foam stabilizer with surfactant was utilized in preparing porous PAA-Na resins. The effect of types of surfactant and the system of foam stabilizer with surfactant on porous structure and water absorbent capacity of PAA-Na resins was studied in this part. The structure of resulting resins was characterized by FTIR spectroscopy and SEM. The results showed that the porous PAA-Na resins were successfully prepared by the foaming method, and anionic surfactant can obviously enhance water absorbent capacity among three types surfactant. Compared to PAA-Na resins only adding surfactant SDS, adding the system of foam stabilizer NaCl and surfactant SDS can improve the absorbent capacity, and as a result, the packing density decreased from0.78g/mL to0.76g/mL, the water absorption improved from484g/g to521g/g, the0.9%saline absorption improved from53g/g to55g/g and swelling rate enhanced from2.74g/g·s to2.88g/g·s.(3) The porous PAA-Na resins were prepared under air or N2atmosphere using the same polymerization conditions, and the effect of two atmospheres on porous structure and water absorbent capacity was compared. The results showed that the water absorption of PAA-Na resins obtained under air atmosphere was higher, while under N2atmosphere, the resulting resins had lower packing density and higher swelling rate than that under air atmosphere.(4) A novel foaming system composed of surfactant SDS with foam stabilizer NaCl, chemical foaming agent NaHCO3and physical foaming agent CFC-113was utilized in preparing porous PAA-Na resins under N2atmosphere. The effect of types of foaming agent and the combination of three foaming agents on porous structure and water absorbent capacity was investigated in this part. The structure of resulting resins was characterized by FTIR spectroscopy and SEM. The results showed that the combination of these foaming agents could significantly improve the water absorbent capacity, and compared to PAA-Na resins without porous structure, the packing density decreased from0.87g/mL to0.62g/mL, the water absorption improved from356g/g to519g/g, the0.9%saline absorption improved from37g/g to55g/g and swelling rate enhanced from2.54g/g·s to3.90g/g·s.(5) A mixture composed of surface crosslinking agent EGDE, water and methanol was used in surface crosslinking to dried porous PAA-Na resins. The effect of EGDE content on water absorption and gel strength after swelling was studied in this part. The results showed that when EGDE content was15wt%(equivalent to dried PAA-Na resins), compared to PAA-Na resins without surface crosslinking, the water absorption decreased from520g/g to497g/g and the gel strength after swelling increased from528Pa to805Pa.