Lorna S. Relleve

Properties of radiation synthesized PVP-kappa carrageenan hydrogel blends

Abstract Hydrogels have been synthesized from varying concentrations of polyvinyl pyrolidone (PVP) and kappa carrageenan (KC) using gamma radiation. Physical properties such as gel fraction and swelling behavior were determined. Data revealed the presence of a network structure whereby KC is physically entangled into the crosslinked PVP (SIPN). TGA, X-RF and FT–IR analyses of the gel fractions also indicated grafting and crosslinking of the PVP. The degree of grafting and crosslinking depended on the concentrations of KC and PVP. Maximum grafting was obtained at higher KC concentration and lower PVP.

Natural antioxidants for radiation vulcanization of natural rubber latex

The anti-oxidant properties of some non-water soluble amino acids were tested on radiation vulcanized natural rubber latex (RVNRL). Among these were cystine, tyrosine, asparagine phenyl alanine and alanine. The results indicate that all of these amino acids have anti-oxidant properties with cystine, alanine and asparagine, phenyl alanine exhibiting higher anti-aging properties on RVNRL. Combinations of these amino acids improved the antioxidant properties in RVNRL. Keratin from chicken feathers was also tested for its antioxidant properties in RVNRL. Different methods of extraction of keratin gave different aging effects on RVNRL. Reduction of keratin with sodium bisulfite initiated antioxidant activity in RVNRL. Extraction of keratin with alkaline solution however caused pro-oxidant properties in RVNRL.

Radiation-modified hydrogel based on poly(N-vinyl-2-pyrrolidone) and carrageenan

A series of hydrogels based on poly(N-vinyl-2-pyrrolidone)-kappa-carrageenan (KC/PVP) and -iota-carrageenan (IC/PVP) were prepared by γ-irradiation of aqueous solutions of N-vinyl-2-pyrrolidone and the respective carrageenan in air at ambient temperature. The influence of dose and concentration of VP monomer and carrageenan on the gel fraction, swelling and mechanical properties of hydrogels were investigated. To prepare hydrogels with high swelling capacity and strength, a feed composition of 10 wt.-% VP and 4 wt.-% carrageenan and an irradiation dose of 30 kGy were found to be the optimum conditions. Degree of swelling and tensile strength of the hydrogels are improved with increasing carrageenan content compared to pure crosslinked VP. Hydrogels produced are mechanically stable and exhibited a highly pH-and ionic-responsive equilibrium swelling behavior. Eine Reihe von Hydrogelen basierend auf Poly(N-vinyl-2-pyrrolidon)-kappa-Carrageenan (KC/PVP) und -iota-Carrageenan (IC/PVP) wurde durch γ-Bestrahlung wasseriger Losungen von N-Vinyl-2-pyrrolidon (VP) und dem entsprechenden Carrageenan in Luft bei Raumtemperatur hergestellt. Der Einflus von Strahlendosis und Konzentration der Reaktanden auf Gelanteil, Quellvermogen und mechanische Eigenschaften der Hydrogele wurde untersucht. Zur Herstellung von Hydrogelen mit hohem Quellvermogen und guter Festigkeit erwiesen sich Losungen mit 10 Gew.-% VP und 4 Gew.-% Carrageenan sowie eine Strahlendosis von 30 kGy als optimal. Im Vergleich zu reinem PVP nehmen der Quellungsgrad und die Zugfestigkeit mit dem Carrageenangehalt zu. Die hergestellten Hydrogele sind mechanisch stabil und zeigen ein Gleichgewichtsquellverhalten, das auf Anderungen der Ionenstarke und des pH-Wertes empfindlich reagiert.

Antioxidant activity potential of gamma irradiated carrageenan

The antioxidant capacity of irradiated κ-, ι-, λ-carrageenans were investigated using the hydroxyl radical scavenging assay, reducing power assay and DPPH radical scavenging capacity assay. The degree of oxidative inhibition increased with increasing concentration and dose. The type of carrageenan had also an influence on its antioxidant activity which followed the order of lambda<iota<kappa. Increase in oxidative property with radiation dose can be attributed mainly to the depolymerization of the carrageenans with corresponding increase in reducing sugar. The antioxidant properties of these carrageenan oligomers were lower than that of ascorbic acid and galactose sugar.