Surekha Devi

Studies on biodegradability, morphology and thermo-mechanical properties of LDPE/modified starch blends

Abstract Starch was converted to a hydrophobic derivative by phthalation. The starch phthalate (stath) thus obtained was found to show highly crystalline nature and sharp melting point. The potential of stath as a substitute for starch in the development of biodegradable blends was investigated. Blends of LDPE containing upto 30% starch were prepared and the latter was gradually replaced by stath. It was observed that the tensile strength and elongation at break increased while the modulus decreased as the starch was substituted by stath. Morphology of binary LDPE/stath blends showed improved adhesion leading to enhanced mechanical properties compared to LDPE/starch blends. DSC analysis showed no significant change in the Tm of LDPE by incorporation of 30% stath in spite of a wide difference in the Tm of the two components. Biodegradation of starch was found to decrease on esterification. However, the LDPE/stath blends showed greater degradation in soil compared to LDPE/starch blends.

Effect of polyols and diisocyanates on thermo-mechanical and morphological properties of polyurethanes

Abstract Polyurethanes based on two polyols PPG (polypropylene glycol) and HTPB (hydroxy terminated polybutadiene) and diisocyanates TDI (toluene diisocyanate) and MDI (methylene diphenyl diisocyanate) were synthesised using three different concentrations of the crosslinker 1,1,1-trimethylolpropane (TMP) at NCO : OH equivalent ratio 1.2 and 1.3. The mechanical, thermal and morphological properties were investigated. HTPB/TDI system showed highest tensile strength whereas PPG/MDI system exhibited highest elongation at break. In differential scanning calorimetry (DSC) thermograms transition for soft segment was observed to be considerably higher in PPG based polyurethanes (PUs). The dielectric constant was also found to be higher in PPG based PUs. The tan δ max was found to lie in the range 0.7–1.0. From swelling behaviour the solubility parameter for PPG and HTPB based PUs was found to be 9.7 and 8.6 (cal/cm3)1/2, respectively. The molecular weight between crosslinks were determined by using the Flory–Rehner equation.

Relationship between morphology and mechanical properties of binary and compatibilized ternary blends of polypropylene and nylon 6

The effect of compatibilization on the morphology, mechanical properties, and dynamic mechanical properties of isotactic polypropylene (IPP)/nylon-6 (Ny-6) binary blends was investigated. Maleic anhydride (MAH) functionalized IPP was used as a compatibilizer in binary blends. The morphological, mechanical, and dynamic mechanical properties of binary and ternary blends were compared. The blends containing IPP-g-MAH showed more regular and finer dispersion of phases, different dynamic properties, and improved mechanical properties due to better adhesion between the two phases. The blends were also characterized for their flow properties and extent of water absorption. The melting peak temperature and percent crystallinity of IPP and Ny-6 phases were decreased in compatibilized blends.

Preconcentration and separation of palladium(II) and platinum(IV) on a dithizone anchored poly(vinylpyridine)-based chelating resin

Abstract A chelating resin was prepared through the reaction between chloromethylated poly(vinylpyridine) and dithizone. The resin shows high affinity for noble metal ions such as palladium(II), platinum(IV) and gold(III). At batch and column levels, the preconcentration of palladium and platinum was studied. Various conditions such as pH, temperature, flow rate and column parameters were optimized for the maximum extent of palladium and platinum loading. Palladium and platinum loadings of 100 and 250 mg g−1, respectively, were achieved at optimized conditions. Mixtures of 0.1 M HCl and 1.0% thiourea or 0.1 M HCl and 5.0% thiourea solution could elute palladium and platinum quantitatively. Separation of palladium(II) and platinum(IV) from gold(III) and nickel(II) was achieved quantitatively.

Relationship between morphology and properties of polyamide-6 low-density polyethylene blends: effect of the addition of functionalized low-density polyethylene

Binary and ternary blends of polyamide-6/low-density polyethylene (PA-6/LDPE) and PA-6/LDPE/LDPE-g-butyl acrylate were prepared by melt mixing. The blends were characterized for their various mechanical properties and extent of water absorption. Morphology of the prepared blends was studied by scanning electron microscopy. It was observed that the use of LDPE-g-butyl acrylate as an interfacial agent improves the impact strength of PA-6 and decreases the water absorption remarkably.

Preconcentration of mercury(II) on dithizone anchored poly(vinyl pyridine) support

Dithizone, a selective and sensitive reagent for mercury, was anchored on cross-linked poly(vinyl pyridine) and was used for the preconcentration of nanogram levels of mercury. The polymeric support was characterised for the extent of coupled dithizone and thermal properties. The support was used in batch and column experiments for the preconcentration of mercury. Various conditions such as pH, temperature, flow rate and column parameters were optimised for the maximum extent of mercury loading. Figures exceeding 140 mg/g support were achieved at optimised conditions. Mixture of 0.2 M nitric acid and 2.0% ammonium nitrate in 1 : 1 proportion elutes mercury quantitatively. Separation of mercury from binary and ternary mixtures of mercury, palladium, zinc and cadmium was achieved without any cross-contamination.

Chelating resin containing s-bonded dithizone for the separation of copper(II), nickel(II) and zinc(II)

Analytical and physicochemical properties of a crosslinked poly (vinyl pyridine) based resin containing dithizone were examined. The resin was further used for the preconcentration of copper, nickel and zinc at batch and column level. Various conditions such as pH, equilibration time, temperature were optimised for the maximum loading of copper, nickel and zinc. The loading capacities of the resin for copper, nickel and zinc were observed to be 0.51, 0.59 and 0.65 mmol g(-1) of dry resin respectively. Elution of loaded copper, nickel and zinc from the resin was done by using 0.1 M HCl, 0.1 M H(2)SO(4) and 0.1 M HNO(3) respectively. Separation of copper, nickel and zinc in binary and ternary mixtures was achieved without any cross contamination.

Effect of crosslink density on transport of industrial solvents through polyether based polyurethanes

Polyurethanes based on PPG 2000 with variable concentrations of TDI and TMP were prepared and used for sorption studies, employing homologous series of hydrocarbons such as benzene, toluene and xylene. The sorption was observed to be non-Fickian in nature. The solubility parameter of the polyurethane series was observed to be 9·7(calcm-3)1/2. The polymer solvent interaction parameter χ was found to be lowest in benzene, suggesting higher interaction with it. The sorption and diffusion coefficients were observed to increase with a decrease in the degree of crosslinking. Molecular weights between crosslinks were calculated using the Flory–Rehner equation and compared with those obtained theoretically.

High solids content semicontinuous microemulsion copolymerization of methylmethacrylate and butylacrylate

The possibility of obtaining high-solids-content microlatexes was investigated. It was found that, for the semicontinuous copolymerization of methylmethacrylate and butylacrylate coagulum-free 45.20% solid content latexes can be obtained through microemulsion polymerization using Dowfax 2A-1 surfactant. The effect of the amount of surfactant, type of cosurfactant, type and concentration of initiator and temperature on solid content was studied. The chemical, freeze-thaw, storage and mechanical stabilities of the latexes were determined.

Mechanism of microemulsion polymerization of methyl methacrylate: Experimental evidence

Free radical polymerization of methyl methacrylate in emulsion and microemulsion media was studied for the understanding of the mechanism of the polymerization process. Average particle size of the poly(methyl methacrylate) (PMMA) latex formed during microemulsion polymerization was observed to be ≈ 45 nm. Nuclear magnetic resonance data indicated a larger number of interactions for β-methylene protons of PMMA synthesized in microemulsion, indicating dominant isotaciticity in the polymer. Activation energy of degradation of the products was calculated by Broidos method and was found to be 44.70 kJ/mol and 65.47 kJ/mol for PMMA synthesized from microemulsion and emulsion media, respectively. Solution properties of the above polymers were also studied. Intramolecular expansion factors indicate a more rigid structure for PMMA synthesized from microemulsion medium.