Addition Of PVA Research Articles

Simple and controllable preparation of SBA-15 microspheres by poly(vinyl alcohol)-assisted P123 templating system

Abstract This work reports a simple two-step synthesis method for the preparation of SBA-15 microspheres using poly (vinyl alcohol) (PVA) as a solo additive based on classic P123 templating system. Both spherical particle morphology and long-range 2D-hexagonally ordered mesostructures can be achieved. It is demonstrated that the particle sizes and mesopore sizes of SBA-15 microspheres can be facilely tuned by varying synthesis parameters, including standstill temperatures, hydrothermal treatment temperatures, etc. It is proposed that the addition of PVA in combination with the standstill step at low temperatures (1st step) suppress the rapid growth and aggregation behavior of silicate/P123 primary particles and favor their aggregation into spherical SBA-15 particles, while the meso-ordering and particle uniformity are improved by stirring step at relatively high temperatures (2nd step). This two-step synthesis method based on the PVA-assisted TEOS/P123/HCl(aq.) templating system thus represents a novel and simple pathway to preparing SBA-15 microspheres. Instead of HCl, other mineral acids, including sulfuric acid and nitric acid, can also be used to prepare SBA-15 microspheres. Via sulfuric acid catalyzed system, the carbonization of P123 also enables more direct preparation of mesoporous carbon microspheres.

Synthesis of Bio-composite CHA/PVA/Alginate as Bone Substitute Material

The main inorganic constituent of human bone is carbonated-hydroxyapatite (CHA). The CHA powder had been successfully synthesized by using chicken eggshell through microwave assisted precipitation methods. In the application, the biomaterials needed by orthopaedic doctors were in the form of scaffold. The addition of PVA and alginate to CHA can improve mechanical properties and affect the pores. The freeze-drying method was used to synthesize bio-composite scaffold. The FTIR result showed that spectrums correspond to functional group of PO4 3−, OH−, CO3 2− which were the characteristic of CHA. The elastic scaffold was produced in this research. The scaffold mechanical test results showed that the higher PVA content showed the higher mechanical properties. The phase composition was evaluated by XRD and indicated the presence of CHA. The morphology of the sample was evaluated by SEM which formed pores. These scaffolds showed good prospects for bone substitute material.

Synthesis of porous hydroxyapatite scaffolds from waste cockle shells by polyurethane sponge replication method

Researchers have synthesized hydroxyapatite-based porous scaffolds by the polyurethane sponge replication methods. Hydroxyapatite was derived from waste cockle shells through the co-precipitation method. The synthesis of porous scaffolds through the sponge replication methods is carried out by absorbing hydroxyapatite slurry through the addition of PVA and then followed by heating at 900 o C to decompose the polyurethane and PVA. The best of slurry that can produce a porous scaffold in this study is the slurry that prepared through the ratio of hydroxyapatite:PVA = 80:20. The decomposition of the two polymers will leave macropores on the scaffold with an average size of 460 μm. Based on the thermogravimetric analysis, X-ray diffraction and FTIR spectrophotometer revealed that the PVA and polyurethane sponge were correctly decomposed, except for scaffolds with 40% PVA. Thus, the porous scaffolds synthesized in this study satisfies the requirements of porous scaffolds for the bone therapy process.

Synthesis of high surface area mesoporous silica SBA-15 by adjusting hydrothermal treatment time and the amount of polyvinyl alcohol

AbstractThe high surface area of mesoporous silica SBA-15 has been synthesized successfully by hydrothermal treatment with direct addition of PVA, triblock copolymer (P123) as a direct structure agent and tetraethyl orthosilicate (TEOS) as a precursor. The mesoporous silica SBA-15 have been characterized with nitrogen physisorption, scanning electron microscopy, Fourier transformed infrared spectroscopy, and x-ray diffraction. Measurement of nitrogen sorption indicated that with the addition of PVA, the surface area is increased but the pore volume and pore diameter is not significantly. The short time of hydrothermal treatment (20 h) and using x-ray diffraction, showed that the morphological structure of silica SBA-15 can be changed to a orthorhombic crystal system. The result of the FTIR and SEM-EDX characteristic indicated the functional groups and morphology of the SBA-15 with a narrow pore size distribution. The BET method has exhibited the largest surface area 1726 m2/g, pore volume 1.4 cm3/g, and pore diameter 3.2 nm. It can be suggested that the silica mesoporous SBA-15 will have potential application prospect in catalysis, storage, and adsorbent.

Influence of Activator on the strength of Ultra Fine Natural Steatite Powder based on Geopolymer Mortar

In this study the detailed analysis was made on alkali activated ultra fine natural steatite powder (UFNSP) mortars. The activating alkali was prepared through sodium hydroxide and sodium silicate with different molarities concentration of NaOH. The molarities of NaoH are various from 8, 10, 12, 14 and 16. The proportion of sodium hydroxide and sodium silicate proportion are fixed 1:2.5. Further the strength gained was accelerated through polyvinyl alcohol [PVA]. And various water binder ratio of 0.5, 0.6, 0.7, 0.8 and 0.9 with addition of PVA. For workability purpose super plasticizer was used, here Poly carboxylic ether was used as a superplasticizer. These various ratios concentration of alkali activators were tried on compressive strength of polymer mortar and the results were discussed. The watched outcomes demonstrate that, increment in sodium hydroxide content in soluble base fluid expands the strength. Exhibit the outcome was effect of Si/Al proportion on compressive strength of the specimen with various water binder proportions. In general, the study shows that integrating low ratio of Si/Al content in UFNSP with PVA can fetch low binding property on alkali activator UFNSP material.

Organizing Crystalline Functionalized Pentacene Using Periodicity of Poly(Vinyl Alcohol).

Nanoparticles of acenes exhibit highly efficient intermolecular singlet fission (SF). Recent reports indicate that altering the morphology of 6,13-bis-(triisopropylsilylethynyl)pentacene (TIPS-Pn) nanoparticles has a profound influence on their SF dynamics. Here, we show that poly(vinyl alcohol) (PVA) induces a phase transition in preformed TIPS-Pn nanoparticles. These nanoparticles are amorphous when initially formed but crystalline after addition of PVA. Surface characterization indicates that a diffuse PVA layer surrounds the nanoparticles. We propose that a periodic interaction between the hydroxyl groups of PVA and TIPS groups of TIPS-Pn on the nanoparticle surface induces a large-scale structural rearrangement to yield crystalline TIPS-Pn. Such reorganization in preformed organic nanoparticles is unprecedented, and we believe that this is the first report of such an effect induced by polymer adsorption. Transient absorption spectroscopic results reveal that SF within these nanoparticles is accelerated by an order of magnitude upon structural rearrangement.

Antibacterial nanofibers based on poly(l-lactide-co-d, l-lactide) and poly(vinyl alcohol) used in wound dressings potentially: a comparison between hybrid and blend properties

Morphology, hydrophilicity, degradation, mechanical properties, drug release, bacterial resistance, and cell viability are indispensable parameters for a bioactive wound dressing. In this work, the aforementioned terms between hybrid and blend nanofibrous samples based on poly (L-lactide-co-D, L-lactide) (PLDLLA) and poly (vinyl alcohol) (PVA) containing triclosan (Tri) as an antibacterial drug were investigated. The FE-SEM images showed that the presence of Tri in the hybrid and blend samples led to bimodal, and unimodal diameter size distributions. The FTIR spectra revealed that the addition of PVA caused to shift the carbonyl bond of PLDLLA in the blend sample, and DSC thermograms exhibited the immiscibility of PVA and PLDLLA polymers in the blend. Moreover, the hybrid sample showed higher hydrophilicity with water contact angle (WCA) of 53 than the blend ones with WCA of 73 which proved by water up-take test. In the following, the antibacterial evaluation showed better results for hybrid-Tri with the maximum growth inhibitory zones of 35 mm and 48 mm for E. coli and S. aureus, respectively. On the other hand, the hybrid nanofibrous sample showed remarkable mechanical properties (tensile stress ∼19 MPa, and Young’s modulus ∼532 MPa). Finally, the SNL 76/7 fibroblast cell line culture confirmed that the hybrid-Tri nanofibrous sample had better proliferation performance than the blend-Tri sample because of the minimal cytotoxicity and maximal cell viability by MTT and acridine orange/ethidium bromide staining.

Bioplastic Properties of Sago-PVA Starch with Glycerol and Sorbitol Plasticizers

This study describes the making of sago starch bioplastics using glycerol and sorbitol plasticizers with the addition of PVA and chitosan filler. It purposes to compare the effect between the addition of glycerol and sorbitol plasticizers. Bioplastic samples of sago-PVA starch have been made from a mixture of sago starch and chitosan solution that had been dissolved with acetic acid, glycerol/sorbitol plasticizer, and PVA was printed and left in the air for 24 hours, then dried in the oven for 12 hours. Testing the mechanical properties of tensile strength refers to ASTM D882 then tearing strength testing based on method C in JIS K 7128 standard. In addition to testing mechanical properties, morphological tests were also referred to as the JSM-6390A standard and biodegradability tests were carried out qualitatively with DIN EN ISO standards 846, and this Water Uptake test was referred to the ASTM-D570-98 standard. This study found that the glycerol plasticizers have a better value than other comparable materials in biodegradation testing with a value of 82.38%, However, in tensile strength test, sorbitol has better value than other material, namely with the best tensile strength value of 16.12 MPa, 142.05% in elongation, tear strength of 12,729 kgf/mm, and water uptake value of 10.34%.

Porous granules by freeze granulation of Pickering emulsions stabilized with halloysite particles

Pickering emulsions stabilized with a natural silicate mineral, halloysite, were dried by freeze granulation in order to prepare porous granules. Different formulations were studied, by varying the pH of the suspension, the ionic strength and with the addition of organic binders (poly(vinyl alcohol) (PVA) and poly(ethylene glycol) (PEG)). To get a better understanding and control on the process, the objective was to correlate the formulation and the emulsion behavior to the morphology and size of the granules. This study highlights the predominant role of electrostatic interactions on the emulsions. Their stability is improved if the dispersion of solid particles in the continuous phase is relatively limited, with medium zeta potential absolute values. Freeze granulation of emulsions prepared at different ionic strength and pH led to similar granules, with an internal porosity attributed to the low solid fraction. The addition of organic additives PVA and PEG led to a better conservation of the structure, with fewer broken fragments and a larger porosity, attributed to a higher cohesion of these emulsions during the spray freezing and the lyophilisation steps.

Long-term stabilization of hydrogen peroxide by poly(vinyl alcohol) on paper-based analytical devices

Stabilizing reagents that can be deposited onto paper is an important issue for researchers who depend on paper-based analytical devices (PADs), because long-term stability of the devices is essential in point-of-care testing. Here, we found that poly(vinyl alcohol) (PVA) would stabilize hydrogen peroxide placed on a paper substrate following exposure to air. Horseradish peroxidase was employed as a sample in colorimetric measurements of PADs after hydrogen peroxide and 3,3′,5,5′-tetramethylbenzidine were deposited as substrates in an enzymatic reaction. The addition of PVA to hydrogen peroxide significantly suppressed its degradation. Concentrations of PVA that ranged from 0.5 to 2%, increased the duration of the stability of hydrogen peroxide, and the results for a PVA concentration of 1% approximated those of 2% PVA. Storage of the PADs at 4 °C in a refrigerator extended the stability of the hydrogen peroxide containing 2% PVA by as much as 30 days. The stability of hydrogen peroxide without PVA was degraded after one day under room temperature.

Effect of binder addition on optimum additive amount of dispersant for aqueous BaTiO3 slurry

Abstract In ceramic wet-shaping processes, the effects of the addition of binder is seldom taken into account when determining the optimum amount of dispersant to be used. Hence, in this study, the effect of the addition of PVA, which is commonly used as a binder, on the particle dispersion state of aqueous BaTiO 3 slurry was investigated. Dispersant adsorption, rheological characteristics evaluation, and sedimentation tests were conducted on slurries with and without PVA addition. The slurry with 2 mg･g −1 PCA but no PVA was well dispersed; however, the addition of PVA caused significant aggregation. Although slurries containing more than 4 mg･g −1 PCA plus PVA were more aggregated than those without PVA, the amount of aggregation was less than that with 2 mg･g −1 PCA. The aggregation mechanism was the interaction between PCA as a dispersant and PVA, with the degree of aggregation depending on the amount of non-adsorbed PCA.

Double network anion exchange membrane with excellent flexibility and stability

A double-network anion exchange membrane (TA/AT-PEK/PVA-x) was prepared by Br-PEK and PVA, 3-amino-1,2,4 triazole forms a cross-linking structure with PVA under the action of 1,4-phthalaldehyde and then triazole can be linked with Br-PEK. The structure of membranes was verified by FT-IR. The composite membrane is uniform and smooth can be seen from the scanning electron microscope (SEM) and exhibit good hydrophilic/hydrophobic micro-phase separation structure proved by Transmission electron micrograph (TEM). The ionic conductivity of TA/AT-PEK/PVA-0.15 is 0.062 S/cm at 80 °C. With the addition of PVA within a certain range, the water uptake, swelling ratio hydroxide conductivity and alkaline stability are increase. The membranes are more flexible. After immersing in 4 M NaOH solutions for 240 h at 80 °C, it remains at least 65% of its initial hydroxide ion conductivity of TA/AT-PEK/PVA-0.3 membrane. With the increasing number of water molecules solvating the hydroxide, its nucleophilicity and basicity were hindered, which enhance alkaline stability of anion exchange membranes.

The influence of polyvinyl acetate and rice starch binders on molded rice straw filled rice bran: comparative study

The main objective of this study is to evaluate the effect of rice starch and polyvinyl acetate (PVAc) as binding agents on mechanical, thermal and water absorption properties of molded rice bran/rice straw (RB/RS). Rice bran (RB) and rice straw (RS) were molded in form of paper sheet using compression-molding technique. Tearing resistance of RB/RS was enhanced by 135%–140% after the addition of PVA and rice starch binders. Thermal stability of RB/RS was affected positively by PVAc and negatively by rice starch binders. Fractured surface analysis of inverted optical microscope indicated that RB/RS samples have clear visible phase separation without binding agent compared to RB/RS with binders of PVAc and rice starch.

Stiffness-Changing of Polymer Nanocomposites with Cellulose Nanocrystals and Polymeric Dispersant.

Bio-inspired, water-responsive, mechanically adaptive nanocomposites are reported based on cellulose nanocrystals (CNCs), poly(ethylene oxide-co-epichlorohydrin) (EO-EPI), and a small amount of poly(vinyl alcohol) (PVA), which is added to aid the dispersion of the CNCs. In the dry state, the CNCs form a reinforcing network within the polymer matrix, and the substantial stiffness increase relative to the neat polymer is thought to be the result of hydrogen-bonding interactions between the nanocrystals. Exposure to water, however, causes a large stiffness reduction, due to competitive hydrogen bonding of water molecules and the CNCs. It is shown here that the addition of PVA to the EO-EPI/CNC nanocomposite increases the modulus difference between the dry and the wet state by a factor of up to four compared to the nanocomposites without the PVA. The main reason is that the PVA leads to a substantial increase of the stiffness in the dry state; for example, the storage modulus E ' increased from 2.7MPa (neat EO-EPI) to 50MPa upon introduction of 10% CNCs, and to 200MPa when additionally 5% of PVA was added. By contrast, the incorporation of PVA only led to moderate increases of the equilibrium water swelling and the E ' in the wet state.

PENGARUH PENAMBAHAN SEKAM PADI DAN POLIMER EMULSI POLY VINYL ACECATE CO ACRYLIC PADA TANAH LEMPUNG DENGAN OBJEK PENGUJIAN KEKUATAN BATU BATA MENGGUNAKAN METODE UNIAXIAL

Research on the effect of the addition of rice husk and poly vinyl acetate emulsion polymer co acrylic (PVA) on clay have been conducted to see the strength of brick. Calculation of strength compared to brick by rice husks and polymer emulsion and given rice husk without any emulsion polymer. Provision of rice husk to batter was fixed at 9:1, while the provision of PVA polymer mixture for each batter with varying percentage are 1%-7%. Based on the results of the research, showed that: uniaxial compressive strength test resultsbricks to mix rice husk without PVA emulsion polymer was 28,7kg/cm2(L0), compressive strength test results bricks to mix rice husk with PVA emulsion polymer to a mixture of 1%-7%, respectively: (PVA 1% of 28,7 kg/cm2 (L1);(PVA 2% of 28,7 kg/cm2 (L2); (PVA 3% of 28,7 kg/cm2 (L3); (PVA 4% of 28,7 kg/cm2 (L4); (PVA 5% of 28,7 kg/cm2 (L5); (PVA 6% of 28,7 kg/cm2 (L6); and (PVA 7% of 28,7 kg/cm2 (L7). From the above results show that the compressive strength test results bricks to mix rice husk with PVA emulsion polymer mix increased from 1% to 3% mix, while starting from a mixture of 4% to 7% of the compressive strength of bricks dropped dramatically. The addition of PVA 3% of additions that the most effective way to improve the compressive strength of the bricks with compressive strength reached 53,5 kg/cm2, or increase of 46,4% from a brick with a mixture ofrice husk.

MODIFIED POLYSACCHARIDES APPLICATION FOR ANTISEPTIC LEATHER PROCESSING

Urgency of the research. The leather is very sensitive to microbial degradation during processing, storage, transportation and use. Therefore, it is important to search for preparations and methods of leather treatment, providing specific fungicidal properties, depending on the purpose. Target setting. To establish the possibility of using a composition based on modified polysaccharides with the addition of PVA and Quaternary ammonium salts for leather treatment to give fungicidal properties. Actual scientific researches and issues analysis. Recent open access publications have been reviewed regarding polymeric materials, antiseptic and fungicidal preparations used to obtain of insole leather with special properties. Uninvestigated parts of general matters defining. The principle of action of many fungicidal or bactericidal products when used together has not been established. In particular, in the case of the simultaneous use of modified polysaccharides and quaternary ammonium salts for antiseptic treatment of the leather. The research objective. The purpose of the work is to research antiseptic properties of the coating based on modified polysaccharides with the addition of quaternary ammonium salts (QASc) for insole leather. The statement of basic materials. It is established that the polymer composition based on modified starch and polyvinyl alcohol with the addition of a quarter of ammonium salts gives the leather antiseptic properties, this is proved by the delay of growth of microorganisms by 3-4 mm from the edge of the sample. The relative air permeability of the leather is reduced by almost half (from 1.18 · 103 to 0.54 · 103 cm3 / cm2 • h), the leather porosity is also reduced by 5-10 % and the stiffness is increased by 40 %. Conclusions. As a result of the conducted researches it is established that although treatment of leather surface by a solution CMS: PVA and QASс reduction of the tensile strength of leather but in its physical and mechanical properties the treated leather meets the requirements for the lining, has antiseptic properties and can be used for the manufacture of insoles.

Poly(vinyl alcohol)-induced thixotropy of an l-carnosine-based cytocompatible, tripeptidic hydrogel.

The generally poor mechanical stability of hydrogels limits their use as functional materials for many biomedical applications. In this work, a poly(vinyl alcohol) (PVA) embedded hybrid hydrogel of a β-amino acid-containing Fmoc-protected tripeptide was produced at physiological pH (7.4) and room temperature. The hydrogel system was characterized by a number of techniques, including UV-vis, fluorescence, circular dichroism, FT-IR spectroscopy, electron microscopy, and rheology. While the tripeptide-based pure hydrogel was found to be unstable after ca. half an hour, addition of PVA, a water soluble polymer, increased the temporal and mechanical stability of the hydrogel. A rheological step-strain experiment demonstrates that the peptide-polymer hydrogel is thixotropic. Results from a fluorescence probe study and transmission electron microscopy reveal that addition of PVA increases both the fibre diameter and entanglement. Circular dichroism spectra of the hydrogels confirm the formation of aggregates with supramolecular chirality. The thixotropic nature of the hydrogel has been exploited to entrap and release doxorubicin, an anticancer drug, under physiological conditions. Furthermore, an MTT assay of the Fmoc-tripeptide using AH927 cells confirmed its cytocompatibility, which broadens the utility of the hybrid gel for biomedical applications.

Particle Size Control by the Addition of PVA and HNO 3 in γ-Al 2 O 3 Synthesis Using by Sol-Gel Method

Particle Size Control by the Addition of PVA and HNO 3 in γ-Al 2 O 3 Synthesis Using by Sol-Gel Method

Investigation of the Optimal Percentage from Polyvinyl Alcohol on Flexural Strength of Cement Mortar Composite

Polyvinyl alcohol solution(PVA) proveded potential enhancement of the properties of cement mortar composite. This work investigated the effect of (w/c) and polymer-cement ratios (p/c) on the flexural strength of type I Portland cement mortar. A sand-cement ratio (s/c) of 1.25 and 0.5 by mass was used, and PVA powder was dispersed in water at (0.7%, 1%, 2%, and 3%) by weight of cement. The p/c solution was adjusted at five different values of 0.008, 0.012, 0.016, 0.020 and 30% covering relatively low and high values. Two types of curing were used; wet and dry curing. The study results demonstrated that flexural strength and significant water absorption properties of Portland cement mortar, as well as workability can be basically enhanced by the addition of PVA. Composite was prepared with optimum (p/c) 1.6% at concentration of 1% by mass under dry curing. The highest flexural strength was above twice the flexural strength of unmodified mortar. Also modified mortar samples illustrated that increasing of (p/c) causes reducing water absorption due to the packing effect caused by PVA, while mortar prepared at 0.1 and 0.3 w/c and (p/c) respectively, exhibited an increase in flexural strength which was more than the strength of unmodified mortar.

A molecular dynamics simulation of the structure of sodium lauryl ether sulfate and poly(vinyl alcohol) at the air/water interface

The influence of a poly(vinyl alcohol) (PVA) molecule on the air/water interfacial structure of adsorbed sodium lauryl ether sulfate with one polyethylene oxide group (SLE1S) was investigated using molecular dynamics simulations. Increasing SLE1S surface density increases the interface thickness and forces both SLE1S and PVA molecules to migrate towards the air (actually vacuum) to different degrees. While most surfactants, when dilute, align parallel with the interface, increasing surfactant surface density forces tail groups gradually to align more perpendicularly to the interface. The three types of oxygen atoms in the SLE1S head group, i.e. the ionic, ester and ether oxygen atoms, form three distinct hydration shells, with PVA monomers appearing both within these shells and between the second and third shell due to its own hydrogen bonding with water and excluded volume of surfactant and water. The ionic oxygen atoms form more hydrogen bonds with water molecules and PVA than do the ester and ether oxygen atoms. The addition of PVA decreases slightly the number of hydrogen bonds between the surfactant oxygen atoms and the water molecules, as PVA chains form new hydrogen bonds with both of them. With increasing surfactant concentration, the PVA is pushed away from the bulk water, decreasing the number of the hydrogen bonds between it and water. These results are relevant to the use of polymers to aid surfactant in aqueous foaming applications.