Instrumented Macroindentation Techniques for Polymers and Composites – Mechanical Properties,Fracture Toughness and Time-Dependent Behaviour as a Function of the Temperature

An innovative cooling and heating device has been successfully applied to an instrumented macrohardness testing machine in close collaboration with the company Zwick/Roell. The prototype allows the local time-dependent analysis of mechanical properties such as Martens hardness and indentation modulus, as well as fracture toughness and creep and relaxation behaviour at temperatures ranging from −100 °C to +100 °C. On the basis of load–indentation depth, load–time or indentation depth–time diagrams, the indentation behaviour as a function of test speed and/or temperature (which has rarely been done for polymers in the macro-range of loading) depending on matrix and materials composition (amorphous/semicrystalline thermoplastics, epoxy resins, micro- and nanocomposites) has been analysed. Martens-hardness, indentation modulus on the one hand and creep compliance and relaxation modulus on the other have been found to be strongly temperature dependent. Adequate methods of indentation fracture mechanics have been enhanced for polymers and applied to determine the fracture toughness of very different polymer-based materials.     

Investigating the mechanical,thermal and melt flow index properties of HNTs – LLDPE nano composites for the applications of rotational moulding

Linear low density polyethylene (LLDPE) is the one of the most popular polymer used for rotational moulding applications such as storage tanks. But, its inferior mechanical properties and thermal stability restrict the longer service. Hence, this study experimentally demonstrates the effect of Halloysite Nanotube (HNTs) concentration on LLDPE composites for enhancing the mechanical and thermal stability. HNTs were uniformly dispersed with LLDPE matrix through ultra-sonication, followed by compression moulding used to prepare the nano composites plates. The prepared composites are shown 19.2% improved tensile strength for 2 wt% HNTs, whereas 28.9% hike in flexural strength observed for 4 wt% HNTs composite, compare to neat LLDPE. Which shows that higher concentrations of HNTs is favourable in improving the flexural strength rather than tensile properties. In addition to that, higher concentrations of HNTs are also helping in improving the storage modulus of the LLDPE composites. The increase in mechanical properties mainly attributed due to effective load carriers (HNTs) in the composite. Besides, HNTs were also contributing for improving the melting point and residual char of the composites, which is indeed for storage tanks durability. The prepared composite was thermally stable at higher temperature up to 230 °C, because of HNTs chemical structure, the inner layer of HNTs constitute with Al₂O₃ and outermost layer constitute with SiO_2, both are thermally stable. Stated enhancement proves the potential effect of HNTs reinforcement in the LLDPE composite for rotational moulding applications.     

Unambiguous Determination of the Absolute Configurations of Acetylene Alcohols by Combination of the Sonogashira Reaction and the CD Exciton Chirality Method – Exciton Coupling between Phenylacetylene and Benzoate Chromophores

The CD exciton chirality method was applied to various phenylacetylene alcohols to determine their absolute configurations; the long axis polarized –^* transition (_max=252nm) of the 4-methoxyphenylacetylene chromophore couples with the transition (_max=257nm) of the 4-methoxybenzoate group to generate intense exciton split CD Cotton effects, from the signs of which the absolute configurations of phenylacetylene alcohols were unambiguously determined. As an extension of the results, a new methodology for determining the absolute configurations of acetylene alcohols having the HCCCH(OH)-moiety by combination of the Sonogashira reaction and the CD exciton chirality method has been developed and applied. Since the –^* transition of acetylene triple bond is located below 180nm, it is difficult to observe ideal bisignate CD Cotton effects due to the exciton coupling between acetylene and benzoate chromophores. To observe the ideal exciton split Cotton effects necessary for the unambiguous determination of absolute configuration, the terminal acetylene group was converted, by the Sonogashira reaction, to the 4-methoxyphenylacetylene moiety, which exhibits an intense –^* absorption band polarized along the long axis of the chromophore at 252nm. As a partner of exciton coupling, 4-methoxybenzoate showing a –^* band at 257nm was introduced into the alcohol moiety, and the benzoates formed showed intense bisignate CD Cotton effects, from the signs of which the absolute configurations of original acetylene alcohols could be determined in an unambiguous manner.     

Unambiguous Determination of the Absolute Configurations of Acetylene Alcohols by Combination of the <Emphasis Type="Italic">Sonogashira</Emphasis> Reaction and the CD Exciton Chirality Method – Exciton Coupling between Phenylacetylene and Benzoate Chromophores

Summary. The CD exciton chirality method was applied to various phenylacetylene alcohols to determine their absolute configurations; the long axis polarized –^* transition (_max=252nm) of the 4-methoxyphenylacetylene chromophore couples with the transition (_max=257nm) of the 4-methoxybenzoate group to generate intense exciton split CD Cotton effects, from the signs of which the absolute configurations of phenylacetylene alcohols were unambiguously determined. As an extension of the results, a new methodology for determining the absolute configurations of acetylene alcohols having the HCCCH(OH)-moiety by combination of the Sonogashira reaction and the CD exciton chirality method has been developed and applied. Since the –^* transition of acetylene triple bond is located below 180nm, it is difficult to observe ideal bisignate CD Cotton effects due to the exciton coupling between acetylene and benzoate chromophores. To observe the ideal exciton split Cotton effects necessary for the unambiguous determination of absolute configuration, the terminal acetylene group was converted, by the Sonogashira reaction, to the 4-methoxyphenylacetylene moiety, which exhibits an intense –^* absorption band polarized along the long axis of the chromophore at 252nm. As a partner of exciton coupling, 4-methoxybenzoate showing a –^* band at 257nm was introduced into the alcohol moiety, and the benzoates formed showed intense bisignate CD Cotton effects, from the signs of which the absolute configurations of original acetylene alcohols could be determined in an unambiguous manner.     

Metal complexes of gliclazide: Preparation,spectroscopic and thermal characterization. Biological potential study of sulphonylurea gliclazide on the house fly,Musca domestica (Diptera – Muscidae)

Metal complexes of gliclazide (GLZ; HL) drug are prepared and characterized based on elemental analyses, IR, diffused reflectance, magnetic moment, molar conductance and thermal analyses (TG and DTG) technique. From the elemental analyses data, the complexes are proposed to have the general formulae [M(HL)Cl₃(H₂O)]·3H₂O (M = Cr(III) and Fe(III)), [M(HL)Cl₂(H₂O)₂]·yH₂O (M = Co(III), Ni(II) and Cu(II), y = 0–2) and [M(HL)Cl₂]·yH₂O (M = Mn(II) and Zn(II), y = 0–1). The molar conductance data reveal that all the metal chelates are non-electrolytes. IR spectra show that GLZ is coordinated to the metal ions in a neutral bidentate manner with ON donor sites of the amide-O and sulphonamide-OH. From the magnetic and solid reflectance spectra, it is found that the geometrical structures of these complexes are octahedral (Cr(III), Fe(III), Co(II), Ni(II) and Cu(II)) and tetrahedral (Mn(II) and Zn(II)). The thermal behaviour of these chelates is studied using thermogravimetric analysis (TG and DTG) techniques. The results obtained show that the hydrated complexes lose water molecules of hydration followed immediately by decomposition of the anions and ligand molecules in the successive unseparate steps. The activation thermodynamic parameters are calculated using Coats–Redfern method. The GLZ drug, in comparison to its metal complexes also is screened for their biological activity against house fly, Musca domestica (Diptera – Muscidae). Dose of 5 μg/insect of gliclazide is typically applied against 3 days-old larval instar of M. domestica. Survival of pupal and adult stages has been affected by the complexes of gliclazide more than larval instars. Morphogenic abnormalities of larvae, pupae and adults are studied. On the other hand, pupation and adult emergence program is deteriorated by the effect of different chemicals.