This research involves the synthesis of cross-linked sodium polyacrylate hydrogels by solution polymerization technique. Three products were selected from different types of synthesized crosslinked sodium polyacrylate polymers to investigate the physicomechanical properties of sodium polyacrylate hydrogels. Reaction parameters such as time, temperature, concentration of initiators, concentration of activator, concentration of sodium acrylate solution and concentration of cross-linking agents were investigated for crosslinked sodium polyacrylate hydrogels. FT-IR spectroscopic analysis was done for the synthesized hydrogel and the results showed the evidence of positive reactions. Density, viscosity, solubility test, solid content and melting point were measured for all products. Polymer films of the synthesized polymers were made by solution casting method and the mechanical properties were studied. Mechanical properties (ultimate tensile strength, tensile modulus and elongation at break) were measured for all synthesized cross-linked sodium polyacrylate polymers. Swelling properties of cross-linked sodium polyacrylate hydrogels were measured in distilled water, tap water and aqueous sodium chloride solution respectively. Water absorbencies results indicate that this polymer was water-swellable but not watersoluble like super absorbent polymers.
…………………………………………………………………………………………………….... Introduction:-Hydrogels are crosslinked network polymeric materials that have received considerable attention in the past 50 years, due to their exceptional promise in wide range of applications. Researchers have defined hydrogels in many different ways. It is a water insoluble polymeric material that exhibits the ability to swell in aqueous conditions and retain a significant fraction of dispersed water within its structure (1) . The dissolution of a hydrophilic polymer in water can be prevented by adding cross-links via either a physical or a chemical process. Physical cross-linking gives reversible hydrogels. Chemical cross-linking gives permanent hydrogels. These cross-linked polymers are soft and rubbery in nature and referred to as "Super Absorbents".Highly swelling polymers, superabsorbent hydrogels are hydrophilic, three dimensional networks that can absorb water in the amount from 10% up to thousands of times their dry weight. They are widely used in hygienics, foods, cosmetics and agriculture. Hydrogels have vast potential applications, including biomedical applications, soil/water stabilization layers in farming, civil engineering
Post-consumer polyethylene terephthalate (PET) plastic bottles, after some pre-processing, were chemically depolymerized for the production of terephthalic acid (TPA), an important monomer of PET resin. The optimized condition of PET hydrolysis was 100°C with 80% v/v aqueous sulfuric acid liquor for 30 min reaction time. The terephthalic acids (TPAs) were filtered out from the reaction mixtures with a sintered glass filter. The viscosity of recycled hydrolysis liquor was measured before it was used in a successive batch of PET depolymerization. The viscosity of hydrolysis liquor increased gradually from 5 mm2/s to 87 mm2/s. TPA yields were obtained from 85.03 ± 0.03% to 99.20 ± 0.06% and the color of TPA changed from bright white to off-white in the final batches. The structure of TPA was confirmed by FTIR, mass analysis, and 1H-NMR spectroscopy. The purity of TPA was found to be 95–98% from the HPLC study via external calibration technique. Thermogravimetric analysis (TGA) determined the thermal degradation patterns of TPAs and residual weights. This experiment reveals that repeated use of sulfuric acid hydrolysis liquor would be a good option for PET depolymerization in terms of resource utilization, TPA quality as well as sustainability.
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