Types Of Polyvinyl Alcohol Research Articles

Pilot Study on a Liquid Mineral Foliar Fertilizer Mixed with Herbicides for Maize Protection and Nutrition

The purpose of this study was to develop a complex composition of a foliar liquid mineral fertilizer containing NPK macroelements and microelements including Fe, Mg, B, S, Zn, Cu, Mo, Ni, V, and Cr. This complex fertilizer aims to support the optimal development and maturation of maize crops, thereby enhancing both the quality and quantity of production. In our study, an original recipe was established for a complex composition of foliar liquid mineral fertilizer, and a technological process was developed in order to obtain the recipe at the laboratory level. The designed fertilizer was a complex mixture of fertilizers with herbicides with multiple purposes, which can be used in different pedo-climatic areas and which present, at the same time, low toxicity and minimal ecological impact. A wide-spectrum mixture DICOPUR TOP containing 2,4-D acid and Dicamba was chosen as a systemic herbicide which is absorbed by plants both in the root system and also on the leaves. For conditioning the complex mixture of fertilizers with herbicides, different types of polyvinyl alcohol with different degrees of hydrolysis were used. The liquid fertilizer mixture with DICOPUR TOP was applied over two years (2021 and 2022) to the Felix maize hybrid, demonstrating significant positive effects on grain yield while effectively controlling both dicotyledonous and monocotyledonous weeds.

Use of aqueous polyvinyl alcohol in binder jetting of Inconel 718

Binders used in binder jetting often pose health and environmental risks during processing and post processing operations. The print-heads which are used to deposit binder selectively on the feedstock are prone to clogging, despite the trend of print-heads being highly customised to suit different kinds of binders. These factors often hide the advantages of binder jetting as an additive manufacturing process, especially its scalability and its faster printing rates in comparison to powder bed fusion methods. The work presented here takes a step back and focuses on the development of an aqueous, polyvinyl alcohol (PVA)-based liquid binder that is easy to manufacture and store, safe to handle, and can be reliably jetted to print parts. The feedstock considered was Inconel 718, a nickel-based super alloy which can be effectively processed by binder jetting without niobium segregation. PVA was added to the Inconel 718 powder in dry, granular form to manufacture a modified feedstock. The study also investigated the role of molecular weight of the PVA used, sintering environments and post-processing methods like hot isostatic pressing (HIP) on process responses like part densification, tensile strength, and hardness. Three different types of PVA were chosen which had molecular weights 10,000 g/mol (low molecular weight or LMW), 26,000 g/mol (medium molecular weight or MMW), and 84,000 g/mol (high molecular weight or HMW). The compatibility of the liquid, aqueous PVA-based binders with virgin Inconel 718 was examined by measuring the contact angle. The liquid, aqueous binder having MMW PVA reported better wetting with the Inconel 718 powder with a wetting angle of 26.6 which was lower than the wetting angle of 42.4°, seen in case of a commercial resin-based binder. The green strength reported by the MMW PVA liquid binder was 220 kPa which was higher than the other two PVA-based liquid binders. Green parts, upon successful printing, were sintered at 1260 °C. It was observed that a part printed using MMW PVA had a densification of 96.16% when sintered in 99.98% by volume argon gas, which increased to 98.96% after undergoing HIP. The same part reported a densification of 88.69% when sintered in a 95% by volume N2 and 5% by volume H2 gaseous environment, which was later attributed to the uptake of nitrogen by the chromium present in Inconel 718, which prevented necking between particles. Tensile specimens printed using MMW PVA, sintered in a 99.98% argon environment, showed the highest ultimate tensile strength of 220 MPa, which increased to 1010 MPa after the HIP process, which can be compared to commercially available Inconel 718.

Synthesis of PVA–MWCNTs–UMCNOs–starch crosslinked nanocomposite biodegradable films for the removal of methylene blue and Congo red dyes from wastewater

AbstractPlastic waste and wastewater are indeed significant environmental issues that have wide‐ranging impacts on ecosystems, human health, and the economy. This study outlines the synthesis of biodegradable polyvinyl alcohol (PVA)–starch polymeric films incorporating multiwalled carbon nanotubes (MWCNTs) derived from plastic waste and unzipped carbon nanotubes oxides (UMCNOs) as co‐filled nanomaterials. These films were formulated based on data generated using a mixture design method in Design Expert 13 software, resulting in the synthesis of 19 films utilizing five types of PVA–starch polymer solutions (Types A–E). The synthesized films underwent characterization to study their surface morphology via scanning electron microscope and Fourier transform infrared spectroscopy analysis. Subsequently, the films were individually subjected to vacuum filtration, through which cationic dyes such as methylene blue (MB) and anionic dye Congo red (CR) were passed in batches. The highest removal efficiency of 96.43% for MB dye was achieved, accompanied by an exceptionally high flux of 3146.78 LMH. Similarly, the maximum removal of 88.08% for CR was observed with a flux of 1512.66 LMH. The renewable active sites mechanism resulted in increased dye removal with every cycle. Results indicated efficient reusability, particularly when washed with ethanol–water solution.

Charge-patterned nanofiltration membranes with polystyrene sulfonate particles and polyethyleneimine in cross-linked polyvinyl alcohol

Removing salinity has always been a challenge for wastewater treatment. Utilizing nanofiltration (NF) membranes is a promising approach. However, currently available NF membranes are less effective in monovalent salt removal. In this study, work toward the initial aim of fabricating charge mosaic membranes led to charge-patterned NF-selective films on polyether sulfone (PES) or polyacrylonitrile (PAN) support membranes, with similar rejection for mono- and divalent salts. The membranes were fabricated by a two-step layer assembly of first negatively charged polystyrene sulfonate (PSS) particles immobilized in a polyvinyl alcohol (PVA) layer, followed by coating a positively charged polyethyleneimine (PEI) layer. Both PVA and PEI were crosslinked using glutaraldehyde that had initially been impregnated into the support membrane. The type of support membrane, nanoparticle, PVA, and PEI concentrations during fabrication, as well as feed pH and salt concentration, play significant roles in separation performance of obtained composite membranes. Charge-patterned NF membranes fabricated using 0.5 wt.% PVA and 0.05 wt.% PSS for assembly of the first layer followed by coating 0.5 wt.% PEI solution had even somewhat higher rejection for monovalent salt (NaCl; ∼82%) compared to multivalent salts (Na2SO4, MgSO4, and MgCl2; ∼74%), at a permeance of 5.5 LMH/bar on the PES and 3.1 LMH/bar on the PAN support membrane.

Two-photon polymerization based reusable master template to fabricate polymer microneedles for drug delivery

Microneedle patches have been widely used in a minimally invasive manner for various drug delivery applications. However, for developing these microneedle patches, master molds are required, which are generally made of metal and are very expensive. Two-photon polymerization (2PP) technique can be used for fabricating microneedles more precisely and at a much lower cost. This study reports a novel strategy for developing microneedle master templates using the 2PP method. The main advantage of this technique is that there is no requirement for post-processing after laser writing, and that for the fabrication of polydimethylsiloxane (PDMS) molds, harsh chemical treatments such as silanization are not required. This is a one-step process for manufacturing of microneedle templates which allows easy replication of negative PDMS molds. This is done by adding resin to the master-template and annealing at a specific temperature, thereby making the PDMS peel-off easy and allowing re-use of the master template multiple times. Using this PDMS mold, two types of polyvinyl alcohol (PVA)-rhodamine (RD) microneedle patches were developed, namely, dissolving (D-PVA) and hydrogel (H-PVA) patches and were characterized using suitable techniques. This technique is affordable, efficient and does not require post-processing for development of microneedle templates required for drug delivery applications.•Two photon polymerization can be used for cost-effective fabrication of polymer microneedles for transdermal drug delivery.•Post-processing or surface-modification procedures are not required for these master templates.•Using a simple annealing step, the master template becomes reusable and robust for peeling off polymers like PDMS.

Synthesis and Characterization of New Polymeric-Schiff Bases and Their Complexes

Complexations of three new polymeric Schiff base ligands to transition metals (Ni and Zn) were synthesized via the preparation of a Schiff base ligand on Styrene-allyl alcohol (SAA) and two types of polyvinyl alcohol (PVA). These polymers were a supporting agent for preparing Schiff base ligand on it, followed by complexation with transition metals. Modified SAA and PVA polymers with Ni (II) and Zn (II) have been synthesized in order to investigate some transition metal complexes roles in these polymer modifications. The prepared polymeric complexes were confirmed and characterized by FTIR spectroscopy and TGA instrument respectively. The transition metals (Ni and Zn) content was estimated using SEM-EDX analysis

The effect of the PVA hydrolysis degree on the electrical properties of organic resistive memories based on PVA + CNT composites

This work studies the interaction effect between functionalized multiwall carbon nanotubes (f-CNTs) and a polymeric matrix in the electrical behavior of resistive memories. f-CNTs were synthesized by spray pyrolysis using xylene-ethanol (1:0.8 v/v) as the reaction mixture, allowing the in-situ functionalization (OH, COOH, CH, C–OH groups) on the f-CNT surface and, then, improving their solubility in polar solvents as well as their dispersion in a polymeric matrix. Two types of polyvinyl alcohol (PVA) with different hydrolysis degrees were used, PVA with high hydrolysis (HD) degree (Mw 89,000-98,000, 99 + % hydrolyzed) and PVA with low hydrolysis (LD) degree (Mw 9000-10,000, 80% hydrolyzed), for the fabrication of the organic resistive memories. The PVA + f-CNT composites show significant differences in the morphology, thickness and current-voltage (I-V) electrical behavior as a function of the hydrolysis degree of the PVA matrix. In the case of IV measurements, our results are broadly different from those reported in the literature, PVA-LD + f-CNT composites at 1, 3 and 5 wt% f-CNTs show rewritable behavior, whereas PVA-HD + f-CNT composites the rewritable behavior started at 5 wt%. From here, we conclude that the polymeric matrix can play an essential role in the resistive memory behavior.

Development and evaluation of novel hydrogel for preventing postoperative pancreatic fistula

AbstractPancreatic fistula is a complication that frequently occurs after pancreatic surgery. Although various attempts have been made to prevent pancreatic fistula after pancreatic surgery, no effective methods have been developed thus far. In this study, to prevent the pancreatic fistula, we attempted to prepare the hydrogels consisting of two types of polyvinyl alcohol (PVAs), Poval® and Exceval® by the freezing–thawing (F/T) method. As the concentration and the number of F/T cycles increased, it was revealed that the swelling degree tended to decrease, and tensile strength tended to increase. Especially, Exceval® formed more robust hydrogels than that of Poval® hydrogel prepared by the same conditions. Furthermore, the release behavior of tartrazine from 10% Exceval® hydrogels differed depending on the number of F/T cycles. It was also revealed that the diffusion pattern of the drug in the hydrogel differed along with the release, and the entire amount of tartrazine in the hydrogel was released by 120 min. As nafamostat mesylate was loaded, in vivo study, Pancreatic enzyme values were obtained after 48 h, which allowed comparison of the preventive effects against pancreatic fistula between the untreated group, the Exceval® hydrogel group, and nafamostat mesylate‐containing Exceval®‐applied group. Furthermore, there was a significant difference between the untreated group and the hydrogel‐applied group. Besides, PVA hydrogels prepared by the F/T method could probably absorb pancreatic enzymes. This study found that Exceval® hydrogel prepared by the F/T method was considered a novel hydrogel formulation to prevent pancreatic fistula.

Genipin‐crosslinking polyvinyl alcohol hollow braids degradable tissue engineering scaffolds: Manufacturing techniques and property evaluations

AbstractTissue engineering has been developed with the aim of improving the regeneration and recovery of impaired tissues and organs. Biodegraded scaffolds serve the aforementioned functions and can also be decomposed by means of metabolism. They have no biological toxicity and save patients from injuries by the second surgery, which makes biodegradable scaffolds a new development trend in the tissue engineering. In this study, the textile engineering and chemical crosslinking techniques are employed to produce biodegradable polyvinyl alcohol (PVA) hollow braids, serving as the tissue engineering scaffolds. The process involves two types of products, including the twisted yarns and hollow braids. The twist number of PVA twisted yarns is changed to form different PVA twisted yarns, which are then used to braided into hollow braids via the braiding technology. Therefore, the hollow braids are basically composed three types of PVA twisted yarns. Next, the surface observation, mechanical properties, and degradation of the products are then evaluated. The test results indicate that PVA twisted yarns exhibit the optimal mechanical properties when being twisted with 3 turns/inch. Any higher twist counts result in over twist in the twisted yarns. The optimal hollow braids are composed of PVA twisted yarns with a twist counts being 3 turns/inch. Afterwards, hollow braids are crosslinking with genipin, thereby obtaining greater mechanical strength of 23.6 N and higher decomposition rate of 0.8. The specified hollow braids are suitable for the use as tissue engineering scaffolds.

New Hydrogen Bonding Enhanced Polyvinyl Alcohol Based Self‐Charged Medical Mask with Superior Charge Retention and Moisture Resistance Performances

AbstractThe water vapor exhaled by the human body can severely accelerate the charge dissipation of a polypropylene (PP)‐based medical mask, thereby reducing the electrostatic adsorption efficiency to cause infection. To solve this problem, a new type of polyvinyl alcohol (PVA)‐based medical mask through electrostatic spinning to replace the PP melt‐blown layer, which has self‐charging and charge retention performance in a high humidity environment is fabricated. The PVA is rich in hydroxyl groups, which can spontaneously form hydrogen bonds with water vapor molecules exhaled by the human body and fix water molecules to increase the triboelectricity. By analyzing the electrical output performance of PVA‐based triboelectric nanogenerator (TENG), it is shown that the short circuit current is ≈26 times larger than that of PP‐based TENG in 95% relative humidity (RH). Moreover, PVA has a strong charge storage capacity and self‐charging performance, as determined by hand touching under a high humidity environment. The static dissipation rate of PVA is 1.4 times lower than that of PP at a 95% RH. In comparison with PP‐based medical masks, PVA‐based medical masks have a high humidity resistance and self‐charging performance and can be easily recharged in situ by hand slapping without taking it off for many times.

Establishment of fiber factor for rheological and mechanical performance of polyvinyl alcohol (PVA) fiber reinforced mortar

In this paper, two types of polyvinyl alcohol (PVA) fibers with three kinds of aspect ratios were added to reinforce mortar. Rheological properties, density loss, ultrasonic pulse velocity (UPV), compressive strength and flexural strength were evaluated and the relationship between system viscosity and fiber volume fraction was developed based on a simplified two-phase system of fiber reinforced cementitious composites (FRCCs). In addition, the rheological and hardened properties of 29 PVA-FRCCs groups were divided into three grades by two specific fiber factors (FF) values that were associated with fiber content, i.e. critical fiber factor Fc and dense fiber factor Fd (Fc < Fd). When the FF is lower than Fc = 100, the fibers have insignificant effect on rheological properties and exerts some damage on the matrix. When the FF exceeds Fd = 400, a large amount of fibers formed clusters and almost deteriorate the rheological and hardened properties of mortar. When the value of FF is between Fc = 100 and Fd = 400, the content of fibers is proposed to produce desirable PVA-FRCCs with proper rheological properties and excellent mechanical properties. Conclusively, it is found that rheological properties can significantly affect the hardened properties of PVA-FRCCs by means of variation in fiber dispersion and microstructure. The obtained values of Fc and Fd assisted in determination of fiber content for mix design proportion. The optimum PVA fiber type as well as aspect ratio were proposed in each region, which would help for design of PVA-FRCCs with favorable rheological and hardened properties in practical applications.

Constructing a tetraphenylethene (TPE) derivative-decorated polyvinyl alcohol (PVA)/lanthanide nanoparticle composite system for tunable luminescence.

A novel tetraphenylethene (TPE) derivative-decorated lanthanide nanomaterial NaLnF4 (denoted as TPEBA-Ln, Ln = Gd3+, Tb3+ and Eu3+) was hydrothermally synthesized using (4-(1,2,2-triphenylvinyl)phenyl) boronic acid (TPEBA)-modified polyvinyl alcohol (PVA) as a coating ligand. Interestingly, the aggregation-induced emission (AIE) of the TPE moiety was activated because the intramolecular rotation of TPEBA was restricted via the esterification of TPEBA with PVA. More excitingly, it was found for the first time that the TPEBA-based ligand could further act as a donor and transfer energy to the lanthanide nanoparticle (Ln = Eu3+ and Tb3+) acceptor in this TPEBA-Ln system. Encouragingly, TPEBA had advantageous effects on the emission of the composite material, in which a more effective energy transfer process from the ligand to lanthanide ions was observed when TPEBA tended to be isolated on the surface of the nanoparticles. Furthermore, the material combining different ratios of TPEBA, Tb3+ and Eu3+ displayed tunable luminescence properties covering the wavelength range from 400 nm to 700 nm in the visible region due to the established energy transfer path (tetraphenylethene derivative-Tb3+-Eu3+), which provided a facile and effective strategy to obtain potential full-color emitters. Strikingly, distinct luminescence properties were induced by adding different PVA samples. When PVA with a higher hydrodynamic radius (Rh) and more curly structure was added, it substituted some TPEBA molecules and then twined around the surface to lock and isolate the remaining TPEBA molecules, resulting in a blueshift in the peak together with increased intensity in the emission spectrum. However, only attenuated aggregate emission was observed upon the addition of PVA with a lower Rh and more stretched chains because the arrangement of the TPEBA left on the surface was not significantly affected by the displacement of this type of PVA. This discovery may provide a facile approach to design and prepare more promising candidates as tunable optical composite materials and TPE-based fluorescent sensors.

Polyvinyl alcohol films with different degrees of hydrolysis and polymerization

O objetivo deste trabalho foi produzir filmes biodegradáveis à base de álcool polivinílico (PVA) e, também avaliar o efeito dos diferentes graus de hidrólise (DH) e graus de polimerização (DP) do PVA nas propriedades desses filmes. Quatro tipos diferentes de PVA com DH variando de 88,0 a 98,4% e DP variando de 150 a 2000 foram utilizados para produzir os filmes por casting, e o glicerol foi usado como plastificante. Os filmes formulados com PVA com menor DH (SelvolTM 540 e 203) apresentaram maior solubilidade, permeabilidade ao vapor de água e capacidade de absorção de água, além de serem menos rígidos e apresentarem menores temperaturas de transição vítrea e de fusão quando comparados aos filmes obtidos com PVA com maior DH (SelvolTM 325 e 107). O DP afetou a solubilidade dos filmes, o filme produzido com PVA com maior DP (SelvolTM 325 - DP = 1000????1500) apresentou menor valor de solubilidade. Os filmes formulados com PVA com maior DP (SelvolTM 540 e 325) apresentaram maiores valores de elongação na ruptura. Tanto o DH quanto o DP afetaram as propriedades dos filmes de PVA, resultando em materiais com diferentes possibilidades de aplicação, no entanto, observou-se que o efeito do DH foi mais importante para as propriedades dos filmes de PVA do que o efeito DP.

Process development of fabricating ceramic core using 3D printing technique

Previous 3D printers developed for the fabrication of ceramic cores have been limited to implement mechanical properties and provide shapes that meet the requirements, since the type and size of powder, and the type of binder are standardized according to the printer. Therefore, in this study, the composition and manufacturing process of ceramic powder and binder were studied to fabricate ceramic cores with high mechanical properties without depending on the type of 3D printer. Fine mullite powder (average particle size: 16 μm) and zircon flour (average particle size: 43 μm) with conventional mullite bead. In addition, two types of polyvinyl alcohol (PVA) were used to enhance the coating ratio of an inorganic binder. Green bodies were formed by a three-dimensional (3D) printer employing three kinds of starting powders and PVAs mixed at the proper ratio. The green bodies were then heat-treated at 250 °C to evaporate the PVA with a lower boiling point. Then, the heat-treated core samples were dipped into the inorganic precursor, dried, and heat-treated at 1000 °C for the organic–inorganic conversion process. Through using a combination of different starting powders, the compact density of the sample was increased and the pore size was reduced, resulting in an increase in the coating efficiency of the inorganic binder. This study demonstrates the feasibility of the fabrication of a ceramic core with excellent strength through the 3D-printing process.

Egg shell-derived calcium phosphate/carbon dot nanofibrous scaffolds for bone tissue engineering: Fabrication and characterization

Recent exciting findings of the particular properties of Carbon dot (CDs) have shed light on potential biomedical applications of CDs-containing composites. While CDs so far have been widely used as biosensors and bioimaging agents, in the present study for the first time, we evaluate the osteoconductivity of CDs in poly (ε-caprolactone) (PCL)/polyvinyl alcohol (PVA) [PCL/PVA] nanofibrous scaffolds. Moreover, further studies were performed to evaluate egg shell-derived calcium phosphate (TCP3) and its cellular responses, biocompatibility and in vitro osteogenesis. Scaffolds were fabricated by simultaneous electrospinning of PCL with three different types of calcium phosphate, PVA and CDs. Fabricated scaffolds were characterized by Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), contact angle measurement and degradation assessment. SEM, the methyl thiazolyl tetrazolium (MTT) assay, and alkaline phosphatase (ALP) activity test were performed to evaluate cell morphology, proliferation and osteogenic differentiation, respectively. The results demonstrated that while the addition of just 1 wt% CDs and TCP3 individually into PCL/PVA nanocomposite enhanced ALP activity and cell proliferation rate (p < 0.05), the synergetic effect of CDs/TCP3 led to highest osteogenic differentiation and proliferation rate compared to other scaffolds (p < 0.05). Hence, CDs and PCL/PVA-TCP3 could serve as a potential candidate for bone tissue regeneration.

Packing structures and formation of cracks in particulate films obtained by drying colloid–polymer suspensions

We investigated the effects of polymer addition on crack formation in particulate films of colloidal silica. Two types of polyvinyl alcohol (PVA) with different degrees of saponification were compared. Partially saponified PVA (PVA-1) suppressed crack formation. In contrast, weaker suppression was observed when we used fully saponified PVA (PVA-2). Centrifugation experiments of colloid–polymer suspensions revealed that PVA-1 adsorbed on particles well whereas PVA-2 was not adsorbed effectively, suggesting that the polymer–particle interactions strongly depended on the content of polymer functional groups. In addition, we observed segregation of PVA-2 between packed particles, which contributed to a sparse packing structure. We did not observe such segregation of PVA-1 and particles were packed more tightly than for PVA-2. These results clearly showed that the affinity between polymer molecules and suspended particles affected both crack formation and packing structures. We also found that adsorption of polymer molecules did not necessarily suppress crack formation. When we added polyvinyl pyrrolidone (PVP) to silica suspensions, we observed much more cracks than in the sample without polymer even though PVP molecules adsorbed on the silica particles. We conclude that adsorption of polymer molecules on suspended particles is preferable, but does not necessarily suppress crack formation. Miscibility between polymer molecules and particles would be a key issue in crack formation and packing structure of colloid-polymer films.

Investigation of the properties of Ni(OH)2 electrochrome films obtained in the presence of different types of polyvinyl alcohol

Electrochromic films were prepared by cathodic template synthesis in the presence of two types of polyvinyl alcohol: with the hydrolysis degree of 99 % and 85 %. The prepared films show differences in structural, morphological, electrochromic and electrochemical characteristics. Both films were X-ray amorphous and had different shapes of the curve on the XRD patterns in the region of small 2q angles, which corresponds to differences in the direction of 001. Comparison of the morphology of the films prepared from solutions containing PVA with different hydrolysis degrees revealed that the film prepared in the presence of 99 % hydrolyzed PVA has a relatively flat relief with small sizes of bumps. On the other hand, the film prepared in the presence of 85 % hydrolyzed PVA had worse uniformity. Its relief had wavy lines, the height of which reached 1.2 µm. Cyclic voltammograms of both films were also different. CVA of the film prepared in the presence of 85 % hydrolyzed PVA had sharp anodic and cathodic peaks that are similar in height. The potentials of the peaks were +600 and +700 mV. The film prepared in the presence of 99 % hydrolyzed PVA showed broader peaks, with the anodic peak shifted to more positive values (+900 mV). Electrochromic characteristics of both films also differed significantly. The film deposited in the presence 85 % hydrolyzed PVA had a high coloration rate (60 s), but lower coloration degree (18 %). On the other hand, the film deposited in the presence of 99 % hydrolyzed PVA had a coloration rate that is three times slower (200 s), but higher absolute coloration degree (24 %). Several mechanisms that explain such differences in the behavior of the films prepared in the presence of different PVA types have been proposed.

New conversion process for fabricating a ceramic core by a 3D printing technique

A new conversion process combined with a three-dimensional (3D) printing technique has been developed for application in the fabrication of a ceramic core. The new process allows the provision of a sufficient amount of inorganic binder on the particle surface and at the interface between particles. Two types of polyvinyl alcohol (PVA) with a similar molecular structure, but with a large difference in decomposition temperature were used as an organic binder. A green body was prepared with two kinds of PVA using a 3D printer, which was heat-treated at 250°C to evaporate the PVA with the lower decomposition point. The heat-treated core samples were dipped into the inorganic precursor, and then dried and heat-treated at 1000°C for the organic–inorganic conversion process. In the new conversion process, the formability of the core sample was controlled through the remaining organic compounds and the inorganic binder penetrating between particles and/or coated on the particle surface, and the firing strength was attributed to the glass phase generated by the inorganic precursor. The firing strength of the core prepared through the new process was improved because of the increase in the inorganic precursor that infiltrated the spaces/sites of the decomposed PVA, and it could be readily applied to the production of a core using 3D printing techniques without further shrinkage in a high-temperature heat treatment.

Baked Foams Based on Cassava Starch Coated with Polyvinyl Alcohol with a Higher Degree of Hydrolysis

The aims of this work were to produce trays based on cassava starch, coated with polyvinyl alcohol (PVA) with a higher degree of hydrolysis (98%), and to study the effects of the coating on the mechanical and water sorption properties of the trays. Two types of PVA were tested: SELVOL™ 325 (degree of polymerization = 1000–1500) and SELVOL™ 107 (degree of polymerization = 350–650). A decrease in the water absorption capacity of 50% was observed when the coated samples were compared with the control sample after 30 min of immersion in water. It was observed in both coated samples a reduction of the initial rate of water adsorption sorption and a decrease in hydrophilicity compared with the control sample. Tensile strength and elongation were increased with application of the coatings. The use of the two types of PVA resulted in materials with similar mechanical and water sorption properties.

Preparation and characterization of bee venom-loaded PLGA particles for sustained release

Bee venom-loaded poly(lactic-co-glycolic acid) (PLGA) particles were prepared by double emulsion-solvent evaporation, and characterized for a sustained-release system. Factors such as the type of organic solvent, the amount of bee venom and PLGA, the type of PLGA, the type of polyvinyl alcohol, and the emulsification method were considered. Physicochemical properties, including the encapsulation efficiency, drug loading, particle size, zeta-potential and surface morphology were examined by Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC), and X-ray diffraction (XRD). The size of the bee venom-loaded PLGA particles was 500 nm (measured using sonication). Zeta-potentials of the bee venom-loaded PLGA particles were negative owing to the PLGA. FT-IR results demonstrated that the bee venom was completely encapsulated in the PLGA particles, indicated by the disappearance of the amine and amide peaks. In addition, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis indicated that the bee venom in the bee venom-loaded PLGA particles was intact. In vitro release of the bee venom from the bee venom-loaded PLGA particles showed a sustained-release profile over 1 month. Bee venom-loaded PLGA particles can help improve patients’ quality of life by reducing the number of injections required.