Preparation And Swelling Behavior Of Psyllium-g-poly(Acrylic Acid)/Clays Superabsorbent Composites

Recently, natural plant gum-based superabsorbent composites become the hot research subject in the field of superabsorbent materials, and the relevant academic research and application development have gained remarkable progress. In allusion to the drawbacks of the commercial superabsorbent products such as high production cost, poor salt-resistant properties, bad biocompatibility and biodegradability, in this thesis, we synthesized a series of novel superabsorbent composites by free radical graft copolymerization in aqueous solution, using biodegradable natural psyllium gum (PSY) as the matrix polymer, partially neutralized acrylic acid (AA) as the monomer, clasys such as attapulgite (APT), biotite (BT), muscovite (MVT), sodium montmorillonite (Na-MMT) and medicinal stone (MFS) as the inorganic components, ammonium persulfate (APS) as the initiator and N,N'-methylene-bis-acrylamide (MBA) as the crosslinker. The structure of the developed superabsorbent composites was characterized by Fourier transform infrared spectra (FTIR) and scanning electronic microscope (SEM) technique, and the effect of inorganic clays on the properties of the composites was investigated. In addition, the swelling properties of the composites in various media were also systematically evaluated. The main research results are as follows:1. A series of PSY-g-PAA/APT superabsorbent composites were synthesized by solution graft polymerization reaction. FTIR results confirmed that PAA has grafted onto the macromolecular chains of PSY, and APT participated in polymerization reaction by its active silanol groups. SEM observation proved that APT nano-rod crystal was uniformly dispersed in the polymeric matrix, and the homogeneous composite was formed. The introduction of moderate amount of APT clearly improved the water absorption capability and rate of the developed superabsorbent composites.2. The moderate modification of APT may further enhance the performance of the superabsorbent composites. After APT was treated by grinding, freeze-thawing, high pressure homogenization, mechanical high-speed dispersion and organification using sodium oleate. the resultant superabsorbent composites showed relatively higher swelling properties than ones based on raw APT.3. The series of PSY-g-PAA/clays superabsorbent composites with different clays (BT, MVT, Na-MMT and MFS) and contents of clays were prepared. FTIR results indicate that the graft copolymerization reaction occurred among PSY, AA and clays. By comparing the above four clays with APT, the required amounts of clays for achieving the best water absorption are 10 wt% for APT, BT and MFS,20 wt% for MVT and 30 wt% for Na-MMT. In addition, the introduction of clays may enhance the salt-resistant performance of the superabsorbent, but has litter influence on the pH-sensitivity.