Poly(vinyl alcohol) (PVA)/sodium alginate (SA) blend hydrogels have immense potential for use as functional biomaterials. Understanding of influences of processing parameters and compositions on mechanical and swelling properties of PVA/SA blend hydrogels is very important. In this work, PVA/SA blend hydrogels with different SA contents were prepared by applying freeze-thaw method first to induce physical crosslinking of PVA chains and then followed by Ca 2þ crosslinking SA chains to form interpenetrating networks of PVA and SA. The effects of number of freeze-thaw cycles, SA content and Ca 2þ concentration on mechanical properties, swelling kinetics, and pHsensitivity of the blend hydrogels were investigated. The results showed that the blend hydrogels have porous sponge structure. Gel fraction, which is related to crosslink density of the blend hydrogels, increased with the increase of freeze-thaw cycles and strongly depended on SA content. The SA content exerts a significant effect on mechanical properties, swelling kinetics, and pH-sensitivity of the blend hydrogels. The number of freeze-thaw cycles has marked impact on mechanical properties, but no obvious effect on the pH-sensitivity of the PVA/SA blend hydrogels. Concentration of CaCl 2 aqueous solution also influences mechanical properties and pH-sensitivity of the blend hydrogel. By altering composition and processing parameters such as freeze-thaw cycles and concentration of CaCl 2 aqueous solution, the mechanical properties and pH-sensitivity of PVA/SA blend hydrogels can be tightly controlled.

Thermoplastic starch (TPS)/poly(vinyl alcohol) (PVA) blend films were modified by crosslinking through soaking the films in glutaraldehyde aqueous solution and then heating in an oven. The effects of the concentration of the glutaraldehyde aqueous solution, soaking time, reaction temperature, and time on the crosslinking reaction were investigated. The moisture absorption and mechanical properties of the films were measured to characterize the influence of the crosslinking modification. It was found that the crosslinking modification significantly reduced the moisture sensitivity of the TPS/PVA blend films and increased the tensile strength and Young's modulus but decreased the elongation at break of the TPS/ PVA blend films. The described method could be used for posttreating TPS/PVA-based products to optimize their properties.

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At present, the products of polycarboxylate superplasticizer (PCE) mainly present liquid state. Compared with liquid PCEs, solid PCEs have not only high storage stability, but also high water-reducing rate. Based on acrylic acid (AA) and isobutenyl polyethylene glycol (IPEG) as the main materials, a series of solid PCEs were synthesized under anhydrous condition by employing ammonium persulfate (APS), benzoyl peroxide (BPO), azobisisobutyronitrile (AIBN) and azobisvaleronitrile (ABVN) as initiators, and the effects of different initiators on the application performances of these solid PCEs were also investigated. The molecular characteristics of the synthesized products were determined by Infrared Spectroscopy (IR) and molecular weight measurements to confirm the expected structure. The fluidities, dispersions and micro-observations of cement pastes containing solid PCEs were evaluated. For both liquid PCE and PCE-ABVN, the average particle size reduced from 2373nm to 1147nm. The results showed that the paste fluidity, concrete slump and retentions were significantly enhanced when using ABVN as initiator, with the initial slump up to 225mm. This initiator had high initiating efficiency, exhibiting broad application prospects.