Addition Of Polyvinyl Alcohol Research Articles

Evaluation of the use of polyvinyl alcohol in the manufacture of pressed samples for X-ray fluorescence analysis

The reliability of the results of X-ray fluorescence analysis (XRF), which is widely used in determination of the elemental composition of various materials, largely depends on the quality of sample preparation. When producing pressed tablets for X-ray fluorescence analysis of trace elements, a binder is often used in a powder form, which requires significant time for thorough homogenization. We present the results of applicating a polyvinyl alcohol solution as a binder in the manufacture of pressed samples without using a substrate in determination of microelements by XRF. The parameters for obtaining a durable tablet with a homogeneous composition that matches the condition of minimum impact on the intensity of the analytical lines of the elements being determined are presented. It is shown that the optimal sample weight for the proposed method of producing pressed tablets is 7 g with the addition of polyvinyl alcohol in a ratio of 7:1, the optimal drying time for the tablet after pressing is 1 hour. The calculated variation coefficients of the analytical signal (<2%) indicate the homogeneity of the produced tablets. The maximum values of standard deviations of pressed tablets for the selected ranges of elements are much less than acceptable, which confirms the validity of the proposed method of sample preparation. It is also shown that during long-term storage and repeated measurements, pressed tablets with the polyvinyl alcohol solution retain their original structure and intensity of analytical lines of elements. The accuracy of measurements in the subsequent determination of rock-forming elements is consistent with their certified contents. The results obtained can be used to reduce the time spent on getting a representative pressed sample when using polyvinyl alcohol, determining elements without additional support (coating films), microelement and silicate analyzes from one sample.

Investigating Cellulose Nanocrystal and Polyvinyl Alcohol Composite Film in Moisture Sensing Application

This study focused on utilizing cellulose nanocrystal (CNC)–polyvinyl alcohol (PVA) composite in optical sensor applications to detect high humidity conditions and determine water concentration in ethanol. We focused on the composite’s effectiveness in moisture absorption to demonstrate visual color change. We demonstrated that the different molecular weights of PVA significantly affect CNC’s chiral nematic structure and moisture absorption capability. PVA with molecular weight 88 k–97 k exhibited the disintegration of its chiral nematic structure at 30 wt%, whereas low molecular weight PVA (n~1750) showed no structural disintegration even at 100 wt% concentration when analyzed through UV-Vis spectroscopy. Further, the thermal crosslinking of the CNC-PVA composite showed no significant loss of moisture sensitivity for all molecular weights of the PVA. We observed that the addition of PVA to the sulfated CNC obtained from sulfuric acid hydrolysis did not facilitate moisture absorption significantly. A CNC-PVA sensor was developed which can detect high humidity with 2 h. of exposure time. 2,2,6,6-tetramethylpiperidin-1-piperidinyloxy oxidized CNC (TEMPO-CNC) having carboxylic functionality was also used to prepare the CNC-PVA composite films for comparing the effect of functional groups on moisture sensitivity. Finally, we demonstrated a facile method for utilizing the composite as an optical sensor to detect water concentration in ethanol efficiently; thus, it can be used in polar organic solvent dehydration applications.

Controllable preparation of metal oxide nanoparticles and Ni/CeO2 catalysts by microdroplets extraction and separation technology in mini-channel

The microreactor coupled mini-channel microdroplets extraction and separation technology (MES) was developed by adding polyvinyl alcohol (PVA) into microdroplets, realizing the controllable synthesis of a series of mono-component and multi-component metal oxide nano particles (MONPs). A double-layer surfactant structure composed of Span20 (oil phase surfactant) and PVA (water phase surfactant) was designed as a barrier to intercept and collect the precipitated salt at the microdroplet interface, the addition of PVA reduces the loss of salt components during the extraction process from 41.7 wt% to 1.1 wt%. The size control of mono-component MONPs (CuO, Co3O4, and NiO) was achieved using MES method. Furthermore, in the application direction of preparing multi-component MONPs, the advantages of MES in preparing multi-component catalysts (Ni/CeO2) were verified. TEM, XRD, H2-TPR, CO2-TPD, XPS, BET et al. characterizations have shown that Ni entered the lattice of CeO2 during precipitation to form a Ni-O-Ce solid solution and was therefore highly dispersed in CeO2. Ni/CeO2-MES showed high CO2 conversion and CO selectivity in reverse water gas shift (RWGS) testing compared to Ni/CeO2 catalysts prepared by impregnation method which has excellent thermal stability and can maintain over 99 % CO selectivity even after 50 h of reaction at 600 °C. The MES method was proved to be an efficient synthesis technology for MONPs and can be extended to a variety of metal oxides catalysts.

Biodegradable Foam from Cassava Starch Blended with Water Hyacinth Fiber: Effects of Polyvinyl Alcohol Content

Abstract Our previous investigation revealed that the addition of water hyacinth fiber (WHF) and polyvinyl alcohol (PVA) enhanced the mechanical properties of cassava starch-based foam. However, the effect of PVA concentration on the mechanical properties of starch foam is still unclear. Therefore, this study examined the effects of various concentrations of PVA on the foam’s quality and production process. Four levels of PVA (0, 1, 2, and 3% w/w) were tested on the mixed dough of cassava starch and 15% of WHF. The foam was made by baking the dough on a thermopressing machine at a temperature of 190 °C for 3 min. The quality level of foams was determined by their physical and mechanical (compressibility, water adsorption, density, color appearance, and biodegradability) properties as well as the practicality of the dough preparation and baking processes. As a result, the addition of PVA significantly affects the mechanical properties and ease of making dough. A higher concentration of PVA contributed to a better mixture of the dough, resulting in a smoother mixing process that led to foams with stronger mechanical properties. Nevertheless, the application of 2% and 3% PVA did not make a significant difference in the mechanical and physical properties. Foam with 2% PVA showed 32 N/mm2 of compressibility, 10% water absorptivity, 12% water content, and good biodegradability, with 87% of the material lost during 30 days of burial in the soil.

Robust construction of polyvinyl alcohol intercalated graphene oxide nanofiltration membrane for desalination via pervaporation

The construction and modification of a Graphene Oxide (GO) membrane, incorporating polyvinyl alcohol (PVA) cross-linked with maleic acid (MA) and supported by a nylon membrane, have been successfully completed. Systematic variations in PVA and MA concentrations were conducted to achieve membranes with favorable characteristics, stability, and excellent desalination performance. Optimization studies utilizing the Central Composite Design (CCD) revealed that the most optimal desalination results were obtained with 10 mL of PVA (0.1 mg mL−1) and 0.9 M of MA (GO-MA0.9-PVA10/Nylon membrane). Experimental findings demonstrated that the inclusion of PVA and MA resulted in an increased interlayer distance of GO and enhanced membrane stability. The addition of PVA increases GO membrane hydrophilicity, while the addition of MA reduces membrane hydrophilicity. The GO-MA0.9-PVA10/Nylon membrane exhibited the highest desalination performance, boasting a rejection value exceeding >99.9% and a permeance of 18.76 kg m−2.h−1 under 1% NaCl feed at a temperature of 50 °C. This membrane demonstrated consistent desalination performance stability over an extended period of up to 70 h. Moreover, it exhibited durability through 8 cycles of 24-h usage with washing treatment. In conclusion, the GO-MA0.9-PVA10/Nylon membrane is strongly recommended for practical applications, outperforming other membrane options based on the comprehensive evaluation of its stability and desalination efficiency.

Stabilization of structure and channel height of two-dimensional montmorillonite membrane for efficient ion separation

As a new type of separation material, two-dimensional membrane has attracted wide attention due to its special transport mechanism. However, due to the hydration swelling of montmorillonite nanosheets, there are still challenges in preparing two-dimensional membrane with stable channel structure and fixed interlayer spacing. In order to overcome the problems caused by swelling, this study used polyvinyl alcohol and polyacrylic acid to stabilize the channel structure of two-dimensional membranes. Moreover, the crosslinking between Fe3+ and montmorillonite nanosheets was proposed to fix the interlayer spacing of two-dimensional membrane. It is found that various polymers had different effects on the mechanical property of two-dimensional membrane. The addition of polyvinyl alcohol and polyacrylic acid can significantly improve the tensile strength of the membrane. And the introduction of them reduces the hydrophilicity of the membrane surface, thus improving the stability of the membrane in water. In addition, the interlayer cations affect the stability of interlayer spacing of the membrane in water. After crosslinking the membrane with Fe3+, the interlayer spacing is fixed and can be maintained at about 0.94 nm in water for a long time. When a certain dosage of polyvinyl alcohol and PAA are added into the membrane and the crosslinking conditions are suitable, two-dimensional membrane has good selectivity to Li+ and Mg2+ in high Mg/Li ratio brine. Inspired by the natural ion exchange properties of montmorillonite, this study found a new method for inhibiting the hydration swelling of two-dimensional membrane and realizing precise control of interlayer spacing.

Fabrication of antibacterial bone scaffold based on carbonate-substituted hydroxyapatite containing magnesium from black sea urchin (Arbacia lixula) shells reinforced with polyvinyl alcohol and gelatin

Carbonate-substituted hydroxyapatite containing magnesium (Mg–C-HAp) was introduced through dissolution-precipitation treatment of hydroxyapatite containing magnesium (Mg-HAp) based on a black sea urchin (arbacia lixula) shells as novel biogenic materials. Based on chemical composition analysis, the Mg–C-HAp formed A- and B-type CHAp, which contained high carbonate ions. The Ca/P ratio of Mg–C-HAp was 1.707, very close to the biological bone apatite of 1.71. The Mg content in Mg–C-HAp was also relatively high, with the Mg/(Ca + Mg) ratio of 0.139, which is beneficial for antibacterial agents. The morphology of Mg–C-HAp showed particles with nanosize that provide a large surface area of ion promotion. The antibacterial test revealed that the Mg–C-HAp performed high antibacterial activity against Pseudomonas aeruginosa. The Mg–C-HAp-based porous scaffolds were then fabricated using the freeze-drying method with variations of polyvinyl alcohol (PVA) and gelatin fraction. According to the physicochemical analysis, the addition of PVA and gelatin in the scaffold structure decreased the crystallinity of the Mg–C-HAp/PVA/Gel scaffold. This lower crystallinity indicates high biodegradability, which is good for new bone growth. The macropores of the Mg–C-HAp/PVA/Gel scaffold were appropriate for new bone and blood vessel formation. The micropores of the Mg–C-HAp/PVA/Gel scaffold can be a medium for cells to grow. The microporosity of the Mg–C-HAp/PVA/Gel scaffold was also suitable for cell nutrient promotion. The compressive strength of the Mg–C-HAp/PVA/Gel scaffold was sufficient for bone regeneration. The Mg–C-HAp/PVA/Gel scaffold demonstrated high antibacterial activity against P. aeruginosa, so the Mg–C-HAp/PVA/Gel scaffold can maintain the role of Mg and carbonate content for antibacterial purposes. The good physicochemical, mechanical, and antibacterial properties of the Mg–C-HAp/PVA/Gel scaffold represented its suitable characteristics for antibacterial bone scaffolds.

The Effect of Polyvinyl Alcohol Addition on the Optical Properties and Oxygen Detection Performance of Titanium Dioxide and Methylene Blue Nanocomposite Colorimetric Indicators.

In this study, we investigated the impact of polyvinyl alcohol (PVA) incorporation on the optical properties and oxygen detection performance of a titanium dioxide/methylene blue (TiO2/MB) nanocomposite colorimetric indicator for packaging applications. The nanocomposite was synthesized via mechanical milling of TiO2 nanoparticles with MB and citric acid. PVA, at varying concentrations (0, 3, 9, and 14 wt%), was introduced during the wet milling process to produce a homogeneous composite film. Spin coating was employed to fabricate TiO2/MB nanocomposite films for oxygen detection evaluation. The influence of PVA loading on the films' chemical functionalities and surface morphologies was assessed using Fourier-transform infrared spectroscopy (FTIR) and field-emission scanning electron microscopy (FE-SEM). The indicator's activation process, involving a color change between bleached and colored states, and its recovery time were monitored via optical imaging and UV-VIS-NIR spectrophotometry. The results revealed that a PVA content of 9 wt% yielded well-defined films with enhanced stability of the TiO2/MB nanocomposite's oxygen detection performance.

Preparation of Filter Paper from Bamboo and Investigating the Effect of Additives.

As air pollution escalates, the need for air filters increases. It is better that the filters used be based on natural fibers, such as non-wood fibers, which cause low damage to the environment. However, the short fiber lengths, low apparent densities, and high volumes of non-wood materials can make it challenging to prepare filter paper with the required mechanical and physical properties. In that context, this study focused on utilizing bamboo fibers to fabricate filter paper by employing the anthraquinone soda pulping method. The pulp underwent bleaching and oxidation processes, with the incorporation of cationic starch (CS) and polyvinyl alcohol (PVA) to enhance resistance properties, resulting in the creation of handmade filter papers. The findings revealed that the tear, burst, and tensile strength of filter paper increased with the oxidation and addition of CS and PVA. Air permeability increased with addition of PVA and combination of CS and PVA. FTIR demonstrated the conversion of hydroxyl groups in cellulose chains to carboxyl groups due to oxidation. SEM images illustrated alterations in the fiber structure post-oxidation treatment, with CS reducing pores while PVA and the CS-PVA combination enlarged pore size and enhanced porosity. The BET surface area surface area expanded with oxidation and the addition of the CS-PVA blend, indicating heightened filter paper porosity. Notably, the combined inclusion of CS and PVA not only augmented mechanical strength but also increased porosity while maintaining pore size.

Tuning Mechanical Characteristics and Permeability of Alginate Hydrogel by Polyvinyl Alcohol and Deep Eutectic Solvent Addition.

Alginate-based hydrogels are widely utilized for various applications, including enzyme immobilization and the development of drug delivery systems, owing to their advantageous characteristics, such as low toxicity, high availability and cost-effectiveness. However, the broad applicability of alginate hydrogels is hindered by their limited mechanical and chemical stability, as well as their poor permeability to hydrophobic molecules. In this study, we addressed the mechanical properties and chemical resistance of alginate hydrogels in a high-pKa environment by the copolymerization of alginate with polyvinyl alcohol (PVA). The addition of PVA resulted in a threefold improvement in the shear modulus of the copolymeric hydrogel, as well as enhanced chemical resistance to (S)-α-methylbenzylamine, a model molecule with a high pKa value. Furthermore, we addressed the permeability challenge by introducing a betaine-propylene glycol deep eutectic solvent (DES) into the PVA-alginate copolymer. This led to an increased permeability for ethyl 3-oxobutanoate, a model molecule used for bioreduction to chiral alcohols. Moreover, the addition of the DES resulted in a notable improvement of the shear modulus of the resulting hydrogel. This dual effect highlights the role of the DES in achieving the desired improvement of the hydrogel as an immobilization carrier.

Use of creep and recovery protocol to assess the printability of fibre-reinforced 3D printed white Portland cement composites

ABSTRACT White Portland cement is an ideal choice for producing 3D printed coloured composites due to its inherent whiteness. However, the uncontrollable rheological properties limit the establishment of printed structures and thus affect the mechanical properties. In this study, the polyvinyl alcohol (PVA) and polypropylene (PP) fibres were utilised as reinforcement materials in 3D printed white Portland cement composites (WPCCs) to improve the printability and toughness by controlling creep properties, aiming to build better printed structures. Experimental results show that the addition of PVA and PP fibres effectively improve the creep properties of WPCCs, and printed structures can be well built by controlling creep properties. Specifically, the thixotropy of WPCCs with PVA and PP fibre is improved within specific content ranges of 0∼1% and 0.4∼0.8%, respectively. Compared with reference sample, the flexural strength increases by approximately 148.8% and 90.2% when the PVA and PP fibre contents reach 1.25% and 1%, respectively.

Proton Exchange Membranes from Sulfonated Lignin Nanocomposites for Redox Flow Battery Applications.

Redox flow batteries (RFBs) are increasingly being considered for a wide range of energy storage applications, and such devices rely on proton exchange membranes (PEMs) to function. PEMs are high-cost, petroleum-derived polymers that often possess limited durability, variable electrochemical performance, and are linked to discharge of perfluorinated compounds. Alternative PEMs that utilize biobased materials, including lignin and sulfonated lignin (SL), low-cost byproducts of the wood pulping process, have struggled to balance electrochemical performance with dimensional stability. Herein, SL nanoparticles are demonstrated for use as a nature-derived, ion-conducting PEM material. SL nanoparticles (NanoSLs) can be synthesized for increased surface area, uniformity, and miscibility compared with macrosized lignin, improving proton conductivity. After addition of polyvinyl alcohol (PVOH) as a structural backbone, membranes with the highest NanoSL concentration demonstrated an ion exchange capacity of 1.26 meqg-1, above that of the commercial PEM Nafion 112 (0.98 meqg-1), along with a conductivity of 80.4 mScm-1 in situ, above that of many biocomposite PEMs, and a coulombic efficiency (CE), energy efficiency (EE) and voltage efficiency (VE) of 91%, 68% and 78%, respectively at 20mAcm-2. These nanocomposite PEMs demonstrate the potential for valorization of forest biomass waste streams for high value clean energy applications.

INFLUENCE OF POLYVINYL ALCOHOL ON THE STABILITY OF AQUEOUS DISPERSIONS OF NANODIAMONDS

The stability of aqueous dispersions of detonation nanodiamonds (ND) in the presence of polyvinyl alcohol (PVA) has been studied. It has been established that PVA additives with a concentration above 0.1 wt.% cause the formation of aggregates. To increase the stability of ND dispersions, it was proposed to add a stabilizer, an anionic surfactant sodium dodecyl sulfate (SDS), into the system. As a result of the simultaneous action of the SDS-PVA mixture, the aggregation stability of aqueous dispersions of ND increases markedly; the particle size in the dispersions does not change for several days.

Preparation and characterization of diclofenac transdermal patch using ethyl cellulose and polyvinyl alcohol by electrospinning

In recent years, the adverse effects linked to the oral administration of diclofenac, a non-steroidal anti-inflammatory drug (NSAID), have urged interest in exploring alternative administration routes, specifically transdermal drug delivery (TDD). Among the techniques emerging for creating nanoscale fibres suitable for TDD systems, electrospinning has attracted attention. The primary objective of this study was to formulate and evaluate nanofibers loaded with diclofenac diethylamine using ethylcellulose (EC) and polyvinyl alcohol (PVA) polymers. The influence of penetration enhancers, namely farnesol and nerolidol, on the properties of these fibres was investigated. Employing the electrospinning technique, nanofibers composed of EC or PVA polymers, with or without penetration enhancers, were fabricated, all maintaining a constant drug-to-polymer ratio. Mechanical strength and release kinetics from a cellophane membrane for the obtained nanofibers were investigated. A Franz diffusion cell was employed to determine the drug penetration rates through rat skin for selected fibre formulations. To gain insights into potential interactions and changes in the drug's solid state, FTIR spectroscopy, DSC, and XRD analyses were conducted. Microscopic examination unveiled that EC-based fibres exhibited homogeneity and lacked bead formations, albeit with larger diameters than other formulations. In contrast, both EC and PVA-based fibres displayed bead formations and nanometer-scale widths. The incorporation of penetration enhancers led to the production of uniform, bead-free nanofibers, with minor impacts on fiber size. EC fibres exhibited the lowest tensile strength and modulus of elasticity, but maximum flexibility. The addition of PVA and penetration enhancers contributed to enhanced fibre toughness and resistance to deformation. These alterations also positively influenced drug release rates, as observed in experiments conducted on cellophane membranes. Notably, when comparing drug release on rat skin to cellophane membranes, a slower initial release followed by a steeper slope was noted, attributed to the beneficial role of penetration enhancers on skin permeation. Analyzing results from DSC revealed the transition of the crystalline form of diclofenac diethylamine to an amorphous state within the nanofiber matrix which was also supported by XRD data. In light of these findings, electrospun nanofibers comprising a combination of EC and PVA polymers, alongside a penetration enhancer and diclofenac diethylamine, exhibit considerable promise for utilization as transdermal patches.

Investigating the Impact of Polyvinyl Alcohol Addition on the Thermal Behavior and Chemical Structure of Electrospun Cellulose Nanofibers

The study aimed to investigate the effect of adding polyvinyl alcohol (PVA) on the chemical and thermal properties of cellulose nanofibers (CNFs). The CNF was prepared using electrospinning with varying amounts of PVA, and the resulting samples were analyzed using Fourier-transform infrared (FTIR) spectroscopy and Thermogravimetric analysis (TGA). The FTIR results showed that adding PVA did not significantly affect the chemical structure of CNF but led to the appearance of new peaks attributed to the characteristic peaks of both CNF and PVA. Moreover, the TGA results revealed that all samples underwent weight degradation after being heated from 350°C. The addition and removal of PVA did not significantly alter the thermal behavior of the CNF. Overall, the results suggested that PVA can be used as a compatible additive to CNF without significant changes to their properties, which could have potential applications in various fields, including biodegradable packaging and drug delivery systems.

Polyvinyl alcohol films incorporated with clove essential oil emulsions stabilized by soy protein isolate-derived amyloid fibrils: Fabrication, characterization, and its application for active packaging

This study aimed to prepare a novel emulsion film with high stability, using soy protein-derived amyloid fibrils (SAFs) as an emulsifier incorporating clove essential oil (CEO) as the active component, and the polyvinyl alcohol (PVA) matrix to stabilize the system. The results demonstrated that SAFs can successfully stabilize CEO. Emulsion prepared by SAFS and CEO (SAC) exhibited a small droplet size and better dispersibility compared with SPI and CEO (SC) emulsion. According to FT-IR results, PVA addition increased the hydrogen bond interactions among emulsion film components, thus further reinforcing the protein matrix, increasing the tensile strength (TS) (41.18 MPa) and elongation at break (E) (121.62 %) of the films. The uniform appearance of SAC-PVA (SACP) emulsion films was confirmed by SEM images. Furthermore, SACP emulsion films show distinctive barrier properties, optical properties, and outstanding antioxidant properties. Finally, emulsion films exhibited excellent preservation of strawberries, resulting in an effective decline of the decay rate.

Effects of steel fiber type and ratio on the one-way bending behavior of hybrid fiber reinforced concrete thin panels

Performance of hybrid fiber reinforced concrete (HyFRC) determined through standardized material tests usually correlates well with the structural performance. However, for thin panels, this correlation may be disturbed due to the fiber orientation and small crack surfaces, and more detailed investigations are required. In this study, effects of steel fiber type and ratio on the one-way bending behavior of HyFRC thin panels was investigated through concrete mixes obtained by using three different steel fiber types and polyvinyl alcohol (PVA) fibers. 45 dog bone shaped, notched specimens were cast and tested under direct tension to investigate the direct tension behavior of used HyFRC. Nine panels of 2500 × 500 × 50 mm in dimension were tested under three-point bending, and nine panels of 1240 × 500 × 50 mm in dimension were tested under four-point bending. An inverse analysis to obtain crack width-stress variation in three- and four-point bending specimens was also performed and behavior of steel fiber reinforced concrete specimens with and without PVA addition were compared. It was found that steel fiber type and ratio was consistently the dominant factor for all types of tests on HyFRC specimens. Addition of PVA fibers in HyFRC specimens either resulted in a similar or worse behavior for direct tension and three-point bending compared to their steel fiber only counterparts. Adverse effect of PVA fibers was more pronounced in three-point bending tests. On the other hand, PVA addition had a more positive effect in four-point bending tests. Inverse analyses performed on three-point bending tests revealed that stress levels develop between crack surfaces in these thin panels were significantly lower compared to direct tension stress levels. However, under four-point bending, these tensile stresses were closer to direct tension stresses, especially for specimens with shorter steel fibers. Loading conditions were found to be an effective factor in the behavior of HyFRC thin panels.

Spectroscopic investigation into the oxidation of polyethylenimine for CO2 capture: Mitigation strategies and mechanism

One of the most critical challenges facing large-scale application of amine-based CO2 adsorbents is their long-term stability, particularly their oxidative degradation, which shortens their lifetime. Numerous oxidation mitigation strategies were proposed, notably functionalization by epoxybutane (EB) and addition of polyvinyl alcohol (PVA). However, neither the amine oxidation mechanism, nor the antioxidation mechanism of these additives are clear. Here, we investigated the oxidation of polyethylenimine (PEI) using electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), mass spectrometry (MS), and thermogravimetric analysis (TGA). EPR data provided for the first time direct evidence for the occurrence of radical species during PEI oxidation, and their increased content in the presence of transition metal catalysts. Moreover, significant amounts of CO2, water and ammonia were detected by MS. Surprisingly, although EB and PVA enhanced the oxidation resistance of PEI, they did not reduce the amount of radical species. Theoretical calculations by DFT indicated that PEI is more prone to oxidation than EB-functionalized PEI and PVA, because its CH bonds are weaker. Consistent with experimental data, a mechanistic explanation to the slower amine oxidation in the presence of EB and PVA, was put forward, and clues for further improvement were proposed.

Synthesis of Nano Silver From Melastoma malabathricum Leaf Extracts Modified PVA and its Antibacterial Activity Test

Synthesis of silver nanoparticles from the extract of senduduk leaf (Melastoma malabathricum) with modified polyvinyl alcohol (PVA) has been carried out. The purpose of this study was to determine the effect of the addition of PVA on the characteristics of silver nanoparticles formed using the extract of sensaat leaf (Melastoma malabathricum). Variations in the concentration of PVA used were 0%; 0.75%; 1.5%; and 3%. Synthesis was carried out in a ratio of 1:10:1 (Extract: AgNO3: PVA) for 2 hours. The characteristics of the synthesis of nanoparticles using a UV-Vis spectrophotometer resulted in a consecutive wavelength of 414 nm; 435 nm; 438 nm; and 420 nm. To determine the particle size using Particle Size Analyzer (PSA) analysis at 0% PVA and 3% PVA with sizes obtained 61.9 nm and 216.2 nm. The average particle size using X-Ray Diffraction (XRD) analysis showed the results in the form of crystals and using the Debye-Scherrer equation to obtain the average particle size of PVA 0% 22.97 nm and PVA 3% 10.15 nm. Antibacterial activity test on silver nanoparticles used disc diffusion method, which showed that silver nanoparticles had moderate to strong antibacterial activity against Staphylococcus aureus and Escherichia coli bacteria.Keywords: Bioreductor, senduduk leaf extract, silver nanoparticles, and polyvinyl alcohol

Effect of polyvinyl alcohol powder on the impermeability, frost resistance and pore structure of calcium sulfoaluminate cement concrete

The pore structure has close tie with the performances of concrete, especially the impermeability and frost resistance. In this paper, Polyvinyl alcohol (PVA) powder was added into calcium sulfoaluminate cement (CSA) concrete to improve the pore structure. The effect of PVA on the impermeability, frost resistance and pore structure of CSA concrete were studied, and the relationship between impermeability and pore structure was revealed. The results show that PVA significantly improves the impermeability and frost resistance of CSA concrete. The seepage height reduces from 3.06 mm to 1.43 mm, the relative permeability coefficient reduces from 4.82 × 10-6 mm·h−1 to 1.05 × 10-6 mm·h−1, and the frost resistance increases from F100 to F150. PVA can reduce the porosity of CSA concrete, and the critical pore size and pore connectivity also gradually decrease, while the fractal dimension gradually increases. The relative permeability coefficient of CSA concrete has a good linear relationship with porosity and capillary porosity, an exponential relationship with critical pore size, a negative linear relationship with fractal dimension, and a logarithmic relationship with pore connectivity. Therefore, the addition of PVA reduces the porosity of CSA concrete and improves the impermeability and frost resistance.