Charito T. Aranilla

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.

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.