New slow-release agrochemical formulations based on cross-linked poly(acrylic acid) hydrogels and liquid fertilizers (LF) were prepared by free radical copolymerization of acrylic acid (AA) and N,N′-methylenebisacrylamide directly in the LF solution. Two NPK liquid fertilizer compositions containing urea and potassium and ammonium phosphates were employed. For comparison, AA was also polymerized under identical conditions in distilled water. The resulting products were characterized by FTIR spectroscopy and scanning electron microscopy, and their water absorption and slow-release properties were determined. The results showed that the swelling degree (SD) of the hydrogels synthesized depended on the overall concentration of reactants (monomers and initiator), LF composition and cross-linking agent, and initiator concentrations. By appropriately combining these reaction parameters, superabsorbent hydrogels with SDs in distilled water ranging from a few hundred to 1000 g of water/g of xerogel can be obtained. The fertilizer-containing hydrogels displayed slow-release properties in still distilled water at room temperature. These slow-release formulations will be tested in the future for their effect on corn and sunflower crops.

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New polymer composites were synthesized by a new approach: radical polymerization in an ultrasonic field of the vinyl acetate inside the silica pores. The systems were extensively characterized by different techniques: X-ray photoelectron spectroscopy (XPS), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), derivative thermogravimetry (DTG), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). The formation of hybrid materials was proved by XPS. The molecular weight of the entrapped polymer in the cavities of the inorganic structure was assessed by GPC. The thermal properties of the composites were determined by TGA/DTG and DMA.

The parameters of a generalized rheological model for the description of the flow characteristics of some fluid polymeric systems are determined. Nonlinear regression analysis is used for the fitting of the experimental viscosimetric data. The behaviour of the investigated polymer melts, suspensions and solutions obeys the general equation a"" = a,,"" + (pi)'/"', where n, nor p , and m are parameters which characterize the different types of flow behaviour. Die Anwendung rheologischer Modelle auf die Beschreibung der FlieJcharakteristik einiger PolymersystemeDie Parameter eines verallgemeinerten rheologischen Modells zur Beschreibung der FlieBcharakteristik einiger fliissiger Polymersysteme wurden bestimmt. Die Anpassung der experimentellen viskosimetrischen MeBwerte erfolgte durch nichtlineare Regressionsanalyse. Das Verhalten der untersuchten Polymerschmelzen, -suspensionen und -1osungen folgt der allgemeinen Gleichung al/"=aol/" +(pi)""', worin n, oo,p und rn Parameter darstellen,die die unterschiedlichen Arten des FlieRverhaltens charakterisieren.