Effect of Chemical Foaming Agent in Enhancing Dispersion of Montmorillonite in Polypropylene Nanocomposite - Pages 1-6

Ozan Azguler, Meltem Eryildiz and Mirigul Altan

DOI: https://doi.org/10.6000/1929-5995.2019.08.01

Published: 31 October 2018

Abstract: Homogenous dispersion of the nano particles in the polymer matrix is a key factor in order to achieve enhanced properties of the polymer nanocomposites. Dispersion or exfoliation of nano clay is difficult in the matrix during melt mixing. In this study, dispersion of nano montmorillonite (MMT) in polypropylene (PP) was done by using chemical foaming agent during melt mixing process. Chemical foaming agent (CFA) added (1 %wt.) PP/MMT nanocomposites were prepared on twin screw extruder. Then, injection molding was done to the granulated nanocomposites in order to obtain tensile test samples. Thermal test and morphological investigations were done. Tensile test was applied to observe the difference in mechanical strength of the nanocomposites depending on the presence of the foaming agent during melt mixing process. The results have shown that, dispersion of MMT enhanced in the matrix due to addition of chemical foaming agent. This brought improved tensile strength about 19% for the PP/MMT nanocomposites within same concentrations of nano filler.

Keywords: Nano montmorillonite, polypropylene, melt mixing, dispersion, mechanical strength.

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Fabrication and Characterization of PVA-Gelatin-Nano Crystalline Cellulose based Biodegradable Film: Effect of Gamma Radiation - Pages 7-14

Nanda Karmaker, Farhana Islam, Md. Naimul Islam, Md. Razzak, Farjana A. Koly, A.M. Sararuddin Chowdhury and Ruhul A. Khan

DOI: https://doi.org/10.6000/1929-5995.2019.08.02

Published: 31 October 2018

Abstract: Poly Vinyl Alcohol (PVA) films were prepared using solution casting. The Tensile Strength (TS), Tensile Modulus (TM) and Elongation at break (Eb) of the prepared films were found to be 23.58 MPa, 32 MPa and 302% respectively. Moisture content and water uptake analysis were also checked. Then, gelatin and nano crystalline cellulose (NCC) were incorporated into PVA film and again physchio-mechanical properties were measured. The TS, TM and Eb values of PVA/Gelatin-based films were 23.57 MPa, 114.58 MPa, 48.10% respectively. On the other hand, PVA/Gelatin/NCC-based films showed the TS, TM, and Eb values of 32.92 MPa, 129.8 MPa, 58.5% respectively. Thermal degradation test was accomplished by Thermo-Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Spectroscopic analysis was also done by Fourier Transfer Infra-Red (FTIR). The soil degradation test confirmed the inherent biodegradable nature of the films. The prepared bio-polymeric films were exposed to gamma radiation. It was found that at 6 kGy dose the mechanical properties of the films improved significantly.

Keywords: Polyvinyl Alcohol, Nano Crystalline Cellulose, Biodegradable, Gelatin, Gamma Radiation.

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Study of Catalytic Activity of Lipase and Lipase-Chitosan Complexes in Dynamics - Pages 15-20

Anastasia A. Savina, Olga V. Abramova, Lilia S. Garnashevich, Ilia S. Zaitsev, Oksana A. Voronina, Marina S. Tsarkova and Sergei Yu. Zaitsev

DOI: https://doi.org/10.6000/1929-5995.2019.08.03

Published: 31 October 2018

Abstract: Pancreatic porcine lipase (PPL) is the unique enzyme in numerous biochemical processes for human and animals. Stability in time is the critical point for many enzymes in relation to their further applications. The effect of chitosan on the activity of PPL during 2 months was investigated.

Materials and Methods: Potentiometric method was used to study the catalytic activity of enzymes that based on measuring of the potential an electrode immersed in a triacetin (substrate) solution by titration with 0.01 M NaOH. A laboratory pH-stat with combined pH electrode was used for the measurements of this potential in the presence of PPL or PPL-chitosan complexes. Standard experimental conditions: 40 ºC, pH 7.0.

Results: The following PPL activity values (data given in % to the activity of free lipase) vs. time (in 10 min. intervals) were obtained: 100%, 97.4%, 89.9%, 82.9%, 77.9% and 75.9% after 10, 20, 30, 40, 50 and 60 min., respectively. The PPL catalytic activity decreased at about ¼ to ½ of the initial values after 7 or 14 days, 1 or 2 months storage, although there were differences in the decline dynamics. The complex PPL:Chit=50:1 has better stabilizing properties as compared to other complexes; does not strongly inhibit lipase and requires a small amount of carrier (chitosan) for its formation.

Conclusions: The complex PPL:Chit=25:1 is less effective as the PPL:Chit=50:1 complex, but both can be applicable in some industrial processes.

Keywords: Lipase, chitosan, enzyme immobilization, activity, triacetin.

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Cationic Polymerization Induced by Tris-(p-bromophenyl) Amine Cation-Radical Salts - Pages 21-26

Ideisan I. Abu-Abdoun

DOI: https://doi.org/10.6000/1929-5995.2019.08.04

Published: 31 October 2018

Abstract: Substituted triphenylamine cation radical salts having anions of the type SbF6-, PF6-, BF4- and SbCl6-, were prepared and used to initiate cationic polymerization of cyclohexene oxide (CHO), tetrahydrofuran (THF), and N-vinyl carbazole (NVC), thermally in dichloromethane at room temperature. Experimental results are presented to show the effects of salt counter ion, concentration, and polymerization conditions on the yield and the molecular weight of the obtained polymer. THF polymerization was enhanced by photolysis of the reaction mixture for short time. A general mechanism for the polymerization by cation-radical salts of substituted triphenylamine is proposed.

Keywords: Tris-(p-bromophenyl) amine. Cation radical salts. Cationic polymerization. N-vinyl carbazole. Cyclohexene oxide. Tetrahydrofuran.

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Effects of Different Bridges of A Series of c-Donor-nc-Bridge-cf- Acceptor Type Block Copolymers for Potential Solar Cell Applications - Pages 27-34

Muhammad A. Hasib and Sam-Shajing Sun

DOI: https://doi.org/10.6000/1929-5995.2019.08.05

Published: 05 November 2019

Abstract: A series of c-D-nc-B-cf-A (or DBpfA, p=0,1,2,4,6) type of block copolymers has been designed, synthesized, and systematically studied for photo induced charge separations; where c-D is an electron-donating conjugated block, nc-B is a non-conjugated bridge unit, and cf-A is an electron-accepting conjugated and fluorinated block. A series of photoluminescence quenching measurements with and without different bridge units were evaluated for DBpfA. This study highlights the chemical molecular bridge effects on the optoelectronic property of the DBpfA type block copolymer. Specifically, the DB1fA block copolymer (where only one methylene unit is present in the bridge unit) appears exhibiting the best optoelectronic performance. DfA block copolymer (without any bridge unit) exhibits photoluminescence quenching and optoelectronic property that is between the shortest and longest bridge units, and this can be explained by the calculated four stable state twisting angles (most stable state is at a seventeen degree twist) between conjugated donor and conjugated acceptor blocks. The optoelectronic properties appear following the PL quenching nicely.

Keywords: Conjugated donor and acceptor blocks, bridges, donor-acceptor interfaces, photo induced charge separations, optoelectronics, energy conversion, solar cells.

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