Synthesis and characterization of polyvinyl alcohol/corn starch/linseed polyol-based hydrogel loaded with biosynthesized silver nanoparticles.

Nanocomposite hydrogel film was prepared from Polyvinyl alcohol [PVA], Corn Starch [CS], Linseed oil polyol [LP], and silver nanoparticles [NP]. LP was prepared by epoxidation and hydration of Linseed oil [LO]. IR and NMR supported the insertion of hydroxyl groups in LP by epoxide ring opening reaction at epoxidized LO. Silver NP were biosynthesized using aqueous leaves' extract from locally grown Ocimum forsskaolii Benth [LEO] plant. FTIR, XRD, UV and TEM confirmed the synthesis of NP (size 30 to 39 nm). Transparent and foldable hydrogel film resulted by blending the constituents (PVA, CS, LP and NP), crosslinking by glutaraldehyde, at room temperature, and showed expansion in water, different pH solutions, biodegradation and good antibacterial and antifungal activity against tested microbes. Linseed polyol influenced the structure, morphology, hydrophilicity, improved swelling ability and thermal stability and accelerated biodegradation of hydrogel films. NP were well adhered to LP globules that were embedded in PVA/CS matrix as strung set of beads (LP globules) decorated with black pearls (spherical NP). Silver NP conferred antimicrobial behavior to hydrogel film as observed by antimicrobial screening on different microbes. The results were encouraging and showed that such hydrogel films may find prospective applications in antimicrobial packaging.

Synthesis, characterization, antibacterial and corrosion protective properties of epoxies, epoxy-polyols and epoxy-polyurethane coatings from linseed and Pongamia glabra seed oils.

The aim of this paper is to investigate the structures and properties of epoxidized linseed and Pongamia glabra oils (LOE/POE), their derived products-epoxy-polyols (HLOE/HPOE), epoxy-polyurethanes (EU=LOPU/POPU) and EU coatings. Changes in epoxy equivalent, iodine value, hydroxyl value and percent saturation of oil backbone in due course of epoxidation and hydroxylation reactions, were plotted as a function of time. Spectral (IR, (1)H NMR and (13)C NMR), physico-chemical and thermal (TGA and DSC) analyses of aforementioned resins were performed by standard methods. Physico-mechanical and chemical resistance tests reveal that coatings of LOPUs perform better than those of POPUs. It was found that properties of oil epoxy-polyurethane coatings are mainly governed by: (i) fatty acid composition and nature of starting oils, (ii) extent of epoxidation, (iii) number and location of hydroxyls and residual double bonds in the final product and (iv) the presence of long dangling chains. PO, HLOE and LOPUs exhibit good antibacterial activity against Escherichia coli at very small MIC. These EU systems can be safely employed unto 220 degrees C.