Polyvinyl Alcohol Concentration Research Articles

Effect of Polyvinyl Alcohol (PVA) Concentration and Stirring Time on The Mechanical Properties of Biodegradable Plastic from Kepok Banana Peel Starch

One solution is to use bioplastics, which can replace synthetic plastics that are difficult to decompose. Starch is one of the materials used in the manufacture of bioplastics because it is naturally degradable. However, bioplastics made from starch tend to be brittle and easily damaged, so additional materials are needed to overcome this problem. Polyvinyl alcohol (PVA) is one of the materials used in the manufacture of bioplastics because it has properties that can be degraded naturally, is non-toxic, and is able to form good quality plastic films. This study aims to examine the effect of PVA concentration and stirring time on the mechanical properties of biodegradable plastic derived from kepok banana peels. This study used a completely randomized design with three variations of PVA concentration (3%, 4%, and 5%) and three variations of stirring time (25 minutes, 35 minutes, and 45 minutes). The results showed that at a PVA concentration of 5% with a stirring time of 45 minutes, bioplastics showed the best quality with a tensile strength value of 2.25 MPa, the best elongation at break was 416%, and the best elasticity was 0.541. In biodegradation, all samples were completely degraded within 7 days. It can be included that the addition of PVA concentration and the length of stirring effecth the mechanical properties of bioplastics but not on the biodegradation test.

The Influence of Polyvinyl Alcohol Porogen Addition on the Nanostructural Characteristics of Hydroxyapatite.

Hydroxyapatite (HA) is a porous material widely developed in various research fields because of its high biodegradability, biocompatibility, and low toxicity. In this research, HA was synthesized using a hydrothermal method with chicken eggshells as a calcium source and various concentrations of polyvinyl alcohol as a porogen (2.5%, 5.0%, and 7.5% by wt). The structure and morphology of HA were determined by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. HA was obtained with varying concentrations of polyvinyl alcohol (PVA) porogen according to Inorganic Crystal Structure Database (ICSD) standard. Based on analysis using a refinement method, changes in unit cell parameters (cell volume and lattice strain) of HA synthesized using PVA porogen compared to the standard, the chi square (χ2) and index of R values were relatively low, validating the acceptable of the data. In addition, HA [Ca10(PO4)6(OH)2] with hexagonal structure and the P63/m space group was successfully obtained. Morphological analysis of HA by SEM found that HA has a spherical shape, and the porosity of HA increases with increasing concentrations of polyvinyl alcohol. The highest porosity was obtained with an addition of 5.0 wt% of PVA porogen (HAP3), reaching 69.53%.

Construction and Evaluation of Alginate Dialdehyde Grafted RGD Derivatives/Polyvinyl Alcohol/Cellulose Nanocrystals IPN Composite Hydrogels.

To enhance the mechanical strength and cell adhesion of alginate hydrogel, making it satisfy the requirements of an ideal tissue engineering scaffold, the grafting of Arg-Gly-Asp (RGD) polypeptide sequence onto the alginate molecular chain was conducted by oxidation of sodium periodate and subsequent reduction amination of 2-methylpyridine borane complex (2-PBC) to synthesize alginate dialdehyde grafted RGD derivatives (ADA-RGD) with good cellular affinity. The interpenetrating network (IPN) composite hydrogels of alginate/polyvinyl alcohol/cellulose nanocrystals (ALG/PVA/CNCs) were fabricated through a physical mixture of ion cross-linking of sodium alginate (SA) with hydroxyapatite/D-glucono-δ-lactone (HAP/GDL), and physical cross-linking of polyvinyl alcohol (PVA) by a freezing/thawing method, using cellulose nanocrystals (CNCs) as the reinforcement agent. The effects of the addition of CNCs and different contents of PVA on the morphology, thermal stability, mechanical properties, swelling, biodegradability, and cell compatibility of the IPN composite hydrogels were investigated, and the effect of RGD grafting on the biological properties of the IPN composite hydrogels was also studied. The resultant IPN ALG/PVA/CNCs composite hydrogels exhibited good pore structure and regular 3D morphology, whose pore size and porosity could be regulated by adjusting PVA content and the addition of CNCs. By increasing the PVA content, the number of physical cross-linking points in PVA increased, resulting in greater stress support for the IPN composite hydrogels of ALG/PVA/CNCs and consequently improving their mechanical characteristics. The creation of the IPN ALG/PVA/CNCs composite hydrogels' physical cross-linking network through intramolecular or intermolecular hydrogen bonding led to improved thermal resistance and reduced swelling and biodegradation rate. Conversely, the ADA-RGD/PVA/CNCs IPN composite hydrogels exhibited a quicker degradation rate, attributed to the elimination of ADA-RGD by alkali. The results of the in vitro cytocompatibility showed that ALG/0.5PVA/0.3%CNCs and ADA-RGD/PVA/0.3%CNCs composite hydrogels showed better proliferative activity in comparison with other composite hydrogels, while ALG/PVA/0.3%CNCs and ADA-RGD/PVA/0.3%CNCs composite hydrogels displayed obvious proliferation effects, indicating that PVA, CNCs, and ADA-RGD with good biocompatibility were conducive to cell proliferation and differentiation for the IPN composite hydrogels.

Effect of fiber type and content on mechanical properties of microbial solidified sand

Fibers are applied to construction works to improve the strength and brittle failure of the soil. In this paper, fibers with a length of 6 mm are added to the microbial cemented sand, and fiber types and content are research variable. Unconfined compressive strength (UCS), permeability coefficient, water absorption rate, dry density, and calcium carbonate precipitation of the solidified sand were tested. The physical and mechanical properties of fiber types and content on the immobilization of microorganisms were also analyzed from the micro–macro perspective. Results are presented as follows. The UCS of the Microbial induced calcium carbonate precipitation (MICP) treated sand increases first and then decreases with the increasing fiber content. This phenomenon is due to the promotion of calcium carbonate precipitation by short fiber reinforcement, the limited movement of the sand particles caused by the formed network between the fibers, and the enhanced strength of the microbial solidified sand. However, the agglomeration caused by additional fibers leads to the uneven distribution of calcium carbonate and the reduction in strength. The optimum fiber contents of polypropylene, glass, polyvinyl alcohol, and basalt fibers are 0.4%, 0.2%, 0.2%, and 0.1%, respectively.

Captopril Polyvinyl Alcohol/Sodium Alginate/Gelatin-Based Oral Dispersible Films (ODFs) with Modified Release and Advanced Oral Bioavailability for the Treatment of Pediatric Hypertension.

Hypertension can begin in childhood; elevated blood pressure in children is known as pediatric hypertension. Contrary to adult hypertension, there is a scarcity of commercial medications suitable for the treatment of pediatric hypertension. The aim of this study was to develop orally dispersible films (ODFs) loaded with captopril for the treatment of hypertension in children. Captopril-loaded ODFs were composed of different blends of synthetic polymers, such as polyvinyl alcohol (PVA) and polyvinyl pyrrolidone, and natural polymers, such as sodium alginate (SA) and gelatin. The ODFs were characterized based on their mechanical and thermal properties, drug content, surface morphology, in vitro disintegration, in vitro release, and bioavailability. A novel HPLC method with precolumn derivatization was developed to precisely and selectively determine captopril levels in plasma. A low concentration of PVA and a high concentration of SA generated ODFs with faster hydration and disintegration rates. SA-based films exhibited fast disintegration properties (1-2 min). The optimized modified-release film (F2) showed significant (p < 0.05) enhancement in bioavailability (AUC = 1000 ng min/mL), with a value 1.43 times that of Capoten® tablets (701 ng min/mL). While the plasma concentration peaking was in favor of the immediate-release tablet, Tmax was significantly prolonged by 5.4 times for the optimized ODF (3.59 h) compared with that of the tablets (0.66 h). These findings indicate uniform and sustained plasma concentrations, as opposed to the pulsatile and rapid plasma peaking of captopril from the immediate-release tablets. These findings suggest that the modified release of oral films could offer more favorable plasma profiles and better control of hypertension than the conventional release tablets.

Study of Polyvinyl Alcohol Hydrogels Applying Physical-Mechanical Methods and Dynamic Models of Photoacoustic Signals.

This study aims to analyze the physical-mechanical properties and dynamic models of tissue-simulating hydrogels, specifically the photoacoustic (PA) response signals, by varying the concentrations of polyvinyl alcohol (PVA) and molecular weight (MW). A state-space model (SSM) is proposed to study the PVA hydrogels to retrieve the PA-related signal's damping ratio and natural frequency. Nine box-shaped PVA hydrogels containing saline solution were used, with five concentrations of PVA (7, 9, 12, 15, 20%) for MW1 and four for MW2. The results indicated that the concentration of PVA and MW played an important role in the PA wave's amplitude, arrival time, and speed of sound over the hydrogels. The SSM parameters showed that increasing PVA and MW concentrations improved the hydrogels' ability to absorb and transfer energy under the PA effect. These parameters were also found to be correlated with density and modulus of elasticity. Additionally, the concentrations of PVA and MW affected the absorption and optical scattering coefficients. The physical-mechanical properties, including porosity, density, and modulus of elasticity, improved as the concentration of PVA and MW increased. The ultimate goal of this study is to develop hydrogels as phantoms that can be used for tissue simulation and imaging.

Fabrication and In vitro Evaluation of Carbopol/Polyvinyl Alcohol-based pH-sensitive Hydrogels for Controlled Drug Delivery.

Diclofenac sodium has a short half-life (about 1.5 hours), requiring repeated administration, and as a result, serious complications, such as GI bleeding, peptic ulcer, and kidney and liver dysfunction, are generated. Hence, a sustained/controlled drug delivery system is needed to overcome the complications caused by the administration of diclofenac sodium. This study aimed to fabricate and evaluate carbopol/polyvinyl alcohol-based pH-sensitive hydrogels for controlled drug delivery. pH-sensitive carbopol/polyvinyl alcohol graft-poly(acrylic acid) hydrogels (Cp/PVA-g-PAa hydrogels) were developed for the controlled delivery of diclofenac sodium. The combination of carbopol/polyvinyl alcohol, acrylic acid, and ethylene glycol dimethacrylate was used as polymer, monomer, and cross-linker, respectively. The effects of the formulation's composition on porosity, swelling index, and release pattern of diclofenac sodium from the developed hydrogels were investigated. An increase in porosity and swelling was observed with the increasing amounts of carbopol and acrylic acid, whereas polyvinyl alcohol showed the opposite effect. Due to the formation of a highly viscous system, the drug release decreased with the increasing concentrations of carbopol and polyvinyl alcohol while increased with increasing acrylic acid concentration. The pH-responsive properties of the fabricated hydrogels were demonstrated by dynamic swelling and drug release studies at three different pH values. Higher dynamic swelling and diclofenac sodium (model drug) release were found at high pH values compared to low pH values, i.e., pH 7.4 > 4.6 > 1.2, respectively. Cytotoxicity studies reported no toxic effect of the prepared hydrogels, thus indicating that the prepared hydrogels are safe to be used on clinical basis. The prepared carbopol/polyvinyl alcohol crosslinked hydrogel can be used as a promising carrier for the controlled release of drugs.

Development of an in-situ gel from CO2-captured complex solution and inhibiting coal spontaneous combustion: A case study in thermal engineering

The safety of underground coal mining is threatened by coal spontaneous combustion, making it essential to develop effective inhibitors to prevent such incidents. To address this, a new in-situ gel has been proposed, which is formed in coal pores from a fire-prevention aqueous solution (FPAS) that reacts with atmospheric CO2. To determine the appropriate concentrations of polyvinyl alcohol (PVA) and sodium-metasilicate nonahydrate (SN) for FPAS, 24 groups of wire-mesh basket tests were conducted on Baiyinhua coal. The gelling mechanism and performance on fire inhibition of FPAS were then investigated using temperature-programmed tests, scanning electron microscopy, energy dispersive spectrometry, fourier transform infrared tests, thermogravimetric differential thermal analysis tests, and fire-extinguishing tests. The results indicate an inhibition rate of up to 43.3% and effective protection of active groups from oxidation. The in-situ gel demonstrated excellent fire-extinguishing properties. Additionally, the self-ignition temperatures of residual coals with varying thicknesses were estimated using the Frank-Kamenetskii theory. The combined method of CO2 injection and FPAS spraying is recommended for achieving better fire-prevention effectiveness in coal mine gob. The findings are expected to provide guidance on the application of FPAS to address thermal hazards in coal mines.

Effect of soil hydrophobicity on soil-water retention curve of a silt loam soil

Soil wettability is an important property that affects the behaviour of fine-grained soils. Previous studies have shown that hydrophobicity induced by organic or silane additives may affect the soil-water retention curve (SWRC). However, current findings regarding the effect of hydrophobicity on the SWRC are controversial. Previously, organic or silane additives were assumed to change only the soil wettability. Nevertheless, this study shows that polyvinyl alcohol (PVA) can change the hydrophobicity, pore size distribution (PSD), and specific surface area (SSA) of soil, thus affecting the SWRC. PVA-treated soil is hydrophobic when cured at 20 ℃, but hydrophilic when cured at 100 ℃. No thermal degradation is indicated in the PVA at 100 ℃ based on thermogravimetric analysis and a comparison of mass loss, and the sole difference between the PVA-treated soils cured at 20 and 100 ℃ is their wettability. This study managed to make the hydrophobicity caused by PVA to become an independent variable separated from the PSD and SSA by controlling the ambient temperature. The wetting and drying curves are measured under isopiestic humidity control in the high-suction domain (2.7–298.7 MPa), whereas pressure plates are used for the drying curves in the low-suction domain (0–800 kPa). The results obtained indicate that soil hydrophobicity significantly accelerates drainage when the matric suction is between 100 and 400 kPa, and an increase in PVA content increases the water retention capacity of soil. When the matric suction exceeds 2.7 MPa, the effect of soil hydrophobicity on the SWRC of the soil weakens. At this time, the SWRC is dominated by the van der Waals force, and the SSA contributes significantly to the process. Additionally, this study enables some controversial findings from previous studies to be explained, which is of great significance in soil and agriculture sciences.

Tunable biocomposite films fabricated using cellulose nanocrystals and additives for food packaging

Cellulose nanocrystals (CNCs) are considered a prospective packaging material to partially replace petroleum-based plastics attributed to their renewability, sustainability, biodegradability, and desirable attributes including transparency, oxygen, and oil barrier properties. However, neat CNC films are rigid and too brittle to handle or utilize for packaging applications. Hence different additives, including sorbitol, polyvinyl alcohol (PVA), chitin, and κ-carrageenan (CG) were selected to mix with CNCs for packaging film preparation. The influence of additive categories (plasticizer, nonionic polymer, weak cationic and anionic natural polysaccharide), and their concentrations on the performance of CNC suspensions as well as optical, barrier, mechanical, and thermal properties of CNC films were examined. The morphology and physical characterization including density, equilibrium moisture content, contact angle and water durability of the composite films were also determined. Sorbitol and PVA films had the best visible light transparency; mixing with chitin can effectively improve the water durability of CNC films, and CG changed the CNC film from hydrophilic to hydrophobic. Moreover, all CNC films exhibited sufficient oxygen barrier properties, high PVA content films attained the “very high” barrier grade. Thus, durable CNC films can be obtained by adding proper types and amounts of additives, which provides potential scenarios for practical application of CNC films in food packaging.

Mechanical properties of sprayable ultra-high ductility magnesium phosphate cement -based composites

With the aim to investigate the mechanical properties of sprayable ultra-high ductility magnesium phosphate cement-based composites (UHDMC), the effects of starch ether content, water-solid ratio, quartz powder-binder ratio, borax content, fly ash (FA) content and volume content of polyvinyl alcohol (PVA) fibers on the build-up thickness, compressive strength and tensile properties were studied. The mechanism about the change of mechanical properties was explained by Mercury Intrusion Porosimetry (MIP) test. The results showed that the optimum mixture proportion suitable for sprayable UHDMC was as follows: M/P of 4, starch ether content of 0.15%, water-solid ratio of 0.14, quartz powder-binder of 0.3, borax content of 8%, FA content of 40% and PVA content of 2%, presenting the compressive strength of 35.9 MPa, the ultimate tensile strength of 3.7 MPa and the ultimate tensile strain of 4.1%. A linear relationship was established between pore structure parameters and mechanical properties. The macropores and capillary pores had great influence on the compressive strength, while transition pores mainly affected the ultimate tensile strength. Moreover, similar porosity and pore size distribution were presented between the sprayed and cast UHDMC under the optimum mixture proportion.

Intelligent de-icing epoxy coating surface using bionics secreting oil microcapsules

Ice on the surface of outdoor equipment or aircraft under low temperatures often brings serious consequences. Functional coating materials with intelligent de-icing performance have become one of the research hotspots in materials science. Inspired by the bionic de-icing structure of penguin feather secretion oil, the aim of this work was to design and prepare an environmental-friendly intelligent de-icing epoxy coating surface with bionic microcapsule. The core material of the microcapsules is the hydrophobic oily liquid of glyceryl tri(2-ethylhexanoate) (C27H50O6), which can be secreted from and the hexamethoxymethyl melamine resin (HMMM)/polyvinyl alcohol (PVA) shells. Morphology analysis confirmed that the microcapsules were successfully fabricated with core-shell structure and global shape. The microcapsules dispersed homogeneously in epoxy coating with an appropriate ratio of around 3.0–4.0 wt%. No interface debonding appeared between epoxy and microcapsules. Microcapsules had excellent thermal stability and resisted violent repetitive temperature changes without rupture. Chemical analysis of the shell confirmed the existence of gel PVA in pores of the cross-linked HMMM framework structure. Because the core materials penetrated shells through pores, it caused the increase in surface hydrophobicity of coatings. The release capability of the core material was enhanced by increasing the PVA content in shells and higher content of microcapsules in coatings. However, the excessive addition of microcapsules reduced the wear resistance of the epoxy coating. According to the ice shearing force test results, only 1.0 wt% addition of PVA/HMMM microcapsules significantly improved the de-icing performance of epoxy coating even under temperatures of − 20 °C. The reason was that the released oily molecules could dramatically reduce the adhesion between ice and epoxy.

Development of Biodegradable Tableware from Ricestraw by Using Different Plasticizers

The present research work focused on developing Biodegradable tableware composed of rice straw and plasticizers like sorbitol, polyvinyl alcohol (PVA). In the manufacture of the concentration of sorbitol used was 20%, 30%, 35%, and 40% and PVA used was 2%, 5%, and 10% by weight dry ingredients. Mechanical properties such as tensile strength, compressive strength, water absorption, were studied in fabricated BD plate. Maximum compressive strength of 55.79 kgf and tensile strength of 40.79 mpa is obtained at the optimal concentration of sorbitol and PVA is 30% and 5% respectively. The developed biodegradable tableware serves as the alternative solution for plastic tableware such that the developed plate withstands for one month free from fungus

Improving flexural toughness of foamed concrete by mixing polyvinyl alcohol-polypropylene fibers: An experimental study

In this study, the bending properties of polyvinyl alcohol-polypropylene fiber toughened foamed concrete were assessed by the three-point bending test. The flexural properties of specimens were studied in terms of load–deflection curve, failure mode, toughness, and toughening mechanism. The results showed that the mixture of various toughening materials had a synergistic effect on improving the bending property of polyvinyl alcohol-polypropylene fiber toughened foamed concrete. In addition, the increase of the contents of polyvinyl alcohol and polypropylene fibers could lead to the improvement of ductility, strength degradation, bending toughness, and bending degree of foamed concrete after reaching the peak. The influence of polypropylene fiber content on the specimen was greater than that of polyvinyl alcohol content. The toughened specimen had a single crack fracture mode. According to the scanning electron microscopy observations, the polyvinyl alcohol-polypropylene fiber mixture could provide an integrated network with satisfactory cracking resistance and form a variety of energy dissipation modes, thereby improving the bending toughness of the specimen.

Antibacterial Effect of Polyvinyl Alcohol/Biochar–Nano Silver/Sodium Alginate Gel Beads

To date, biochar bacteriostatic material has attracted much attention from researchers. The compact porous structure of fish-scale biochar provides good application prospects. In this study, silver-carrying biochar–polyvinyl alcohol–alginate gel beads (C/PVA/SA) were designed for suppressing bacteria. The biochar was loaded with nano silver particles as the filler, alginate as the substrate, and polyvinyl alcohol (PVA) as the additive to enhance the mechanical properties. The composite gel beads were characterized using Fourier-transform infrared spectrometry (FT-IR). The results indicated that adjusting the PVA concentration could retain the bacteriostatic performance of the gel beads in different pH value solutions. It was found that C/PVA/SA gel beads had a strong inhibitory effect on Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. After ten consecutive antibacterial tests, the antibacterial rate remained high (above 99%) for 15 days. The adhesive effect of SA and PVA resulted in a tight spatial structure of the gel beads. The C/PVA/SA gel composition could effectively prevent water loss and enhance the shrinkage ability of the gel beads. The good degradation performance of C/PVA/SA was also in line with the concept of environmental protection. In general, the C/PVA/SA gel beads showed high potential for application in the treatment of microbial contamination and environmental protection.

Modified Achira (Canna edulis) starch-based adhesives: effect of acid hydrolysis and urea derivatization on physicochemical properties

In recent decades, due to high market demand and multiple environmental concerns, attention has been focused on the use of starch as renewable raw material for adhesives elaboration. Particularly, the origin and film-forming properties of Achira (Canna edulis) starch make it a potential representative for the development of bioadhesives. In this study, achira starch modified by acid hydrolysis and subsequent derivatization with urea was used to prepare adhesives for plywood substrates. For this purpose, the modified starch and polyvinyl alcohol (PVA) were used to prepare several formulations with different proportions of components. Afterwards, they were characterized in terms of physicochemical and mechanical properties. The formation of starch carbamates was confirmed not only by the results of nitrogen content, but also by infrared spectroscopy through the presence of N-H and C=O groups. On the other hand, viscosity increased with PVA content due to the interaction of hydroxyl groups, while starch had the opposite effect. Shear strength showed higher values at higher concentrations of PVA and starch. From the perspective of mechanical behavior, the results showed similarities with a commercial adhesive based on polyvinyl acetate (PVAc), as well as with other bio-based adhesives from studies conducted under comparable conditions.

Development of an anti-infective urinary catheter composed of polyvinyl alcohol/sodium alginate/methylcellulose/polyethylene glycol by using a pressure-assisted 3D-printing technique

Catheter-associated urinary tract infections (CAUTI) are a common complication associated with catheterization, leading to urosepsis, bacteriuria, and septicaemia. The present work focuses on 3D printing a urinary catheter with anti-infective properties using various concentrations of polyvinyl alcohol (PVA, e.g., 6–8 %), sodium alginate (NaAlg, e.g. 1–4 %), methylcellulose (MC, 5 %), polyethylene glycol (PEG, 5 %) impregnated with secnidazole, an antibiotic acting against Gram-negative bacteria. To produce suitable polymer ink for Pressure Assisted Microsyringe (PAM) 3D printing, the cross-linked between NaAlg and calcium chloride is necessary to prepare the catheter. The optimised catheter was found to have an outer diameter of 5 mm, an inner diameter of 3.5 mm, and a length of the catheter of 50 mm. The analysis by various methods confirms the successful incorporation of secnidazole in the 3D-printed catheter. A drug-loaded/coated catheter showed an initial drug release of 79 % following a sustained release to reach 100 % within 5 h. Weibull model fits well with the drug release data. The release models suggest the Quasi-Fickian diffusion mechanism from the system. Moreover, the secnidazole 3D printed catheter disrupted biofilms and suppressed all the Quorum sensing mediated virulence factors of two important keystone pathogens causing urinary tract infections.

Study on the crushing strength improvement of artificial aggregates made with 100% solid wastes using polyvinyl alcohol solution

This study aimed to enhance the crushing strength of artificial aggregates (AAs) made with 100 wt% solid wastes using polyvinyl alcohol (PVA) solution. The effects of treatment methods (namely: mixing and coating) and different PVA dosages/concentrations on the properties of AAs were systematically investigated. The results show that using PVA solution mixing and coating treatment could considerably improve the crushing strength of AAs by about 99% and 69%, respectively. Adopting mixed treatment contributes to the formation of polymer films in AAs, which can fill the pores and enhance the bonding between particles. PVA coating treatment could form a layer of polymer film around AAs and enable the PVA to penetrate into the aggregate, filling the surrounding pores and bridging the aggregate matrix. It is found that the crushing strength of PVA-mixed aggregate with a dosage of 0.5 wt% could achieve comparable crushing strength compared with AAs coated with a high concentration (14%) of PVA. From a cost-effective perspective, the PVA mixing treatment with a dosage of 0.5 wt% is recommended for the crushing strength improvement of AAs. This study provides an effective method for enhancing the mechanical properties of AAs made from 100% solid wastes.

Bioprospecting a Film-Forming System Loaded with Eugenia uniflora L. and Tropaeolum majus L. Leaf Extracts for Topical Application in Treating Skin Lesions.

Natural products can be used as complements or as alternatives to synthetic drugs. Eugenia uniflora and Tropaeolum majus are natives of Brazil and have antimicrobial, anti-inflammatory, and antioxidant activities. This study aimed to develop a film-forming system (FFS) loaded with plant extracts with the potential for treating microbial infections. E. uniflora and T. majus leaf extracts were prepared and characterized, and the individual and combined antioxidant and antimicrobial activities were evaluated. The FFS was developed with different concentrations of polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA) and analyzed for physicochemical characteristics. The combination of extracts showed a superior antioxidant effect compared to the individual extracts, justifying the use of the blend. FFS prepared with 4.5% PVA, 4.5% PVP, 7.81% E. uniflora extract, and 3.90% T. majus extract was adhesive, lacked scale formation, presented good malleability, and had a suitable pH for topical application. In addition, the viscosity at rest was satisfactory for maintaining stability; water solubility was adequate; skin permeation was low; and the antimicrobial effect was superior to that of the individual extracts. Therefore, the developed FFS is promising for the differentiated treatment of skin lesions through topical application.

Dynamics of drop formation and characterization of additive manufactured CS/AgNP/PVA composite membranes

AbstractThis study investigated the dynamics of drop formation and the printability of chitosan/silver nanoparticles composite fluid (CS/AgNP) modified with polyvinyl alcohol (PVA) using an inkjet 3D printer. It specifically investigated the relationship between rheological properties and fluid mechanical properties in determining the minimum drop velocity for 3D printing of modified CS ink. Proper matching of modified CS fluid rheological properties to the established physical parameters generated adequate droplets on glass substrates and formed membrane composites. The dynamic viscosity of the CS ink decreased with an increase in the concentration of PVA, which resulted in the disruption of existing molecular forces within the CS/AgNP polymer chains, suggesting that the solvent (PVA) was responsible for reducing the shear stress, surface tension, and viscosity of the composite membranes and subsequently improving the flow rates of the CS matrix at the nozzle orifice. Optimized drop velocity of 1.77 m/s yielded adequate formation of the CS/AgNP/PVA membrane composite with enhanced surface morphology, while an increase in drop velocity to 2.5 m/s brought about the formation of satellite droplets with irregular surface structures in printed CS composites. Therefore, adherence to minimum fluid drop velocity is fundamental to effective inkjet printing of composite membranes.