Poly Vinyl Alcohol Acrylic Acid Research Articles

The enhanced thermal and mechanical properties of graphite foams with a higher crystallinity and apparent density

Graphite powder, which has a highly graphitic structure, is used as filler material in the preparation of graphite foams (GFms) and enhances the foams’ thermal–mechanical properties. GFms are prepared using the hydrogel template method with mesophase pitch, polyvinyl alcohol-acrylic acid (PVA-AAc) solution and graphite powder. GFms containing 0.3 w/w% added graphite exhibit as much as an 11.18% increase in crystalline thickness (Lc) compared to that of the sample without graphite powder. These increased crystalline thicknesses of GFms result in thermal conductivity increases as high as 59.30%. Furthermore, the compressive strength is increased by as much as 120.52% compared to that of the sample without graphite powder, and the apparent density is increased by as much as 4.05%. The average pore size of the GFms is controlled by the amount of graphite powder, which affects the GFms’ cell growth mechanism. These results revealed that the thermal–mechanical properties of GFms containing graphite powder with a highly graphitic structure were strongly affected by the GFms’ crystalline thickness and apparent density.

Improvement on efficiencies of dilute alkaline water electrolyzer using membranes

Electrolysis of 0.50% (w/v) aqueous KOH solution with novel packed bed electrodes made of SS 316 solid cylindrical packing has been carried out using membranes with three different combinations, namely Poly vinyl alcohol-acrylamide (PVA-AAm), Poly vinyl alcohol-Acrylic acid (PVA-AAc) and Poly vinyl alcohol-Acrylic acid-acrylamide (PVA-AAc-AAm).For production of hydrogen, nearly 100% current efficiency and about 50% energy efficiency have been achieved by using PVA-AAc and PVA-AAc-AAm membranes. FTIR analyses of fresh and used membranes as well as AAS analyses of anolyte and catholyte confirm that membranes prevent transportation of Fe ions from anode to cathode resulting in better current and energy efficiencies for production of hydrogen and oxygen. PVA-AAm membrane has been found to be unsuitable as AAm reacts and decomposes to AAc during electrolysis in dilute KOH solution. The ratios of production rates of hydrogen to oxygen reach the steady state value of 2 in 2 h which confirms the consumption of oxygen by undesired reactions at initial stages.

PVA-AAc 용액을 사용한 메조페이스 핏치기반 그라파이트 폼의 제조 및 특성

Graphite foams (GFs) were prepared by adding different amounts of mesophase pitch (MP) into polyvinyl alcohol-acrylic acid (PVA-AAc) solution followed by the heat treatment. It was confirmed that the pore diameters of GFs were controlled by the slurry concentration, which was the mesophase content added in polymer solution, and their thermal conductivity and com- pressive strength were also controlled by porosities of GFs formed at different conditions. The resulting GFs in this study had the highest thermal conductivity of 53.414 ± 0.002 W/mK and compressive strength of 1.348 ± 0.864 MPa at 0.69 in porosity. The thermal conductivity of MP based GFs increased approximately 23 times higher than that of using isotropic pitch based GFs due to the developed graphitic structure.

Functional Modification of Poly Vinyl Alcohol/Acrylic Acid Hydrogels Prepared by γ-Radiation Through Some Amine Compounds

Radiation-induced poly vinyl alcohol/acrylic acid (PVA/AAc) hydrogels were modified through condensation reaction with various aliphatic and aromatic amines to form amine-treated polymers. The amine compounds are 2-amino-3-(4-hydroxyphenyl) propanoic acid (P1), propane-1,2-diamine (P2), 4-amino-1,5-dimethyl-2-phenyl-1,2-dihydropyrazol-3-one (4-aminoantipyrine) (P3), 2-aminothiazole (P4), 4-amino-N-(1-phenyl-1H-pyrazol-5-yl) benzene sulfonamide (P5) and 4-amino-N-(4-methoxy-1,2,5-thiadiazol-3-yl) benzene sulfonamide (P6). The degree of swelling of amine-modified polymers increased with increasing AAc contents in the PVA/AAc copolymer and lowered irradiation doses, reaching its maximum at PVA:AAc composition, 50:50 wt%. The characterization of all synthesized polymeric compounds was carried out by using IR, NMR and UV spectral analysis, in addition to thermal studies which predicted by thermal gravimetric analysis and differential scanning calorimetry. Thermal studies display that the amine-treated polymers have more thermal stability than untreated ones. All the newly synthesized polymeric compounds were evaluated for their antibacterial and antifungal activities in vitro against two gram-positive bacteria and two gram-negative bacteria as well as two fungi by the disk diffusion method. In general, the newly synthesized polymeric compounds exhibited higher promising biological activities and can be used in medical applications.

Characteristics of a high compressive strength graphite foam prepared from pitches using a PVA–AAc solution

A facile method applied for preparing high-compressive-strength graphite foams in which pitch was added to a PVA–AAc (polyvinyl alcohol–acrylic acid) solution. Various amounts of pitch were added to a polymer solution to control the pore sizes and apparent densities of resulting foams. The pore size of graphite foam was reduced by increasing the slurry concentration, and its apparent density ranged from 0.12 to 0.61g/cm3. The graphite foam prepared using a hydrogel template had a high-compressive-strength of 7.90±1.02MPa and a thermal conductivity of 5.17±0.02W/mK. The proposed method was applied successfully for high-compressive-strength graphite foams.

Nano-Ag Doping Induced Changes in the Optical Behavior and Thermal Stability of Acrylic Acid-Grafted Poly Vinyl Alcohol Copolymer Films

Metal–polymer nanocomposites have been prepared from an aqueous solution of polyvinyl alcohol/acrylic acid (PVA/AAc) and silver nitrate (AgNO3). The functionalized PVA/AAc was copolymerized and cross-linked using electron beam irradiation. The prepared nanocomposites were characterized by FTIR, TEM and TGA. The average grain size is in the range of 15–44 nm, depending on Ag concentration. The thermal stability was found to increase and the optical band gap decreased with the increase of dopant concentration. The real and imaginary parts of the dielectric constant, optical conductivity, volume energy loss (VELF) and surface energy loss (SELF) of the films were also determined.

Photo-catalytic degradation of Metanil Yellow dye using TiO2 immobilized into polyvinyl alcohol/acrylic acid microgels prepared by ionizing radiation

Polyvinyl alcohol (PVA) microgels were prepared using electron beam irradiation. To improve the PVA microgel functionality and gel fraction, chains of polyacrylic acid (PAA) were incorporated into PVA microgel by radiation grafting technique. The increase in the acrylic acid (AA) content as well as PVA Mwt is accompanied by a mutual increase in the gel fraction and a decrease in the swelling%. Immobilization of different TiO2 concentrations on the surface of the prepared PVA–AA microgel was carried out. The structural changes in the prepared PVA–AA microgel immobilized with TiO2/were investigated using FTIR, EDX and XRD. Photodegradation efficiency of TiO2/PVA–AA microgel against metnil yellow dyes was studied. TiO2/PVA–AA microgel activity increases with the increase of the amount of TiO2 and results in an increase in the rate of the photodegradation reaction. Easily recovery and reusability made TiO2/PVA/AA of great important in practice use as a photocatalytic degradation composite, for dye removal from wastewater.