Release efficiencies of potassium permanganate controlled-release biodegradable polymer (CRBP) pellets embedded in polyvinyl acetate (CRBP-PVAc) and polyethylene oxide (CRBP- PEO) for groundwater treatment

In-situ chemical oxidation (ISCO) is a commonly used method for the remediation of environmental contaminants in groundwater systems. However, traditional ISCO methods are associated with several limitations, including safety and handling concerns, rebound of groundwater contaminants, and difficulty in reaching all areas of contamination. To overcome these limitations, novel Controlled-Release Biodegradable Polymer (CRBP) pellets containing the oxidant KMnO₄ were designed and tested. The CRBP pellets were encapsulated in Polyvinyl Acetate (CRBP-PVAc) and Polyethylene Oxide (CRBP-PEO) at different weight percentages, baking temperatures, and time. Their release efficiency was tested in water, soil, and water and soil mixture media. Results showed that CRBP-PVAc pellets with 60 % KMnO₄ and baked at 120 °C for 2 min had the highest release percentage and rate across different conditions tested. Natural organic matter was also found to be an important factor to consider for in-field applications due to its potential reducing effect with Mn O 4 - . Overall, the use of CRBP pellets offers an innovative and sustainable solution to remediate contaminated groundwater systems, with the potential to overcome traditional ISCO limitations. These findings suggest that CRBP pellets could provide sustained and controlled release of the oxidant, reducing the need for multiple injections and minimizing safety and handling concerns. This study represents an important step towards developing a new and effective approach for ISCO remediation.

Blend membranes comprising polyetherimide and polyvinyl acetate with improved methane enrichment performance

A clean and sustainable energy source, biogas is widely accessible worldwide. The caloric value of biogas is related to its methane content, and therefore removal of other gases is essential for reaping the benefits of this cleaner resource. In contrast to other classical techniques, membrane technology is relatively new yet extremely promising for methane enrichment. The methane enrichment performance of polymeric membranes is constrained, hence newer material combinations have been investigated to enhance membrane performance. In this study, blend membranes comprised of polyetherimide (PEI) and polyvinyl acetate (PVAc) in varying proportions were prepared by adopting the wet-phase inversion technique. The generated pure, and blend membranes were characterized for the morphological, thermal, and structural study. The interactions of PEI and PVAc in blend samples were verified by FTIR analysis. On the other hand, SEM investigation indicated that the membranes have an anisotropic porous structure with a dense skin layer at the top. Subsequently, a single glass transition temperature (T_g), as validated by DSC analysis, indicates that the blended polymers are miscible. Furthermore, membranes' performance for gas separation was assessed regarding selectivity and permeance at feed pressures ranging from 2 to 6 bar. The permeation results showed that the CO₂ permeance has increased by 40.47% with the addition of 4 wt % PVAc at 2 bar pressure. Furthermore, ideal selectivity improves as the blend ratio increases; nonetheless, the highest value for CO₂/CH₄ ideal selectivity was attained with a 2 wt % PVAc addition and at 2 bar pressure, which is approximately 26% greater than the pure PEI membrane. At 4 bar pressure, optimum CO₂/N₂ selectivity value of 22.50 was achieved. The findings indicate that PVAc is an excellent option for expanding the separation performance of blended polymeric membranes for biogas enrichment.

Thermal runaway evaluation on batch polyvinyl acetate emulsion polymerization from calorimetric measurement

Emulsion polymerization is the most applied method in the vinyl acetate monomer (VAM)-polyvinyl acetate (PVAc) process. However, the flammable property and unexpected bulk polymerization for the reactant and product may occur in the batch reactor or storage tank. VAM is reactive enough to decompose readily into free radicals and then, initiate the polymerization, which may contribute to heat accumulation due to the monomer, initiator, and solvent mixtures. This study attempts to analyze the exothermic reaction and compare the thermal runaway potential for various VAM solutions during PVAc polymerizations. Summarily, 50%, 70%, and 100% of VAM solutions reacting with 2,2'-azobis(2-methylpropionitrile) readily increase the self-heating rate with their concentration from adiabatic calorimetric tests. Furthermore, kinetic parameters of 50, 70, and 100 mass% VAM solutions were evaluated to elucidate the self-heating model associated with thermal analysis and to determine heat production mechanisms that are practical to proactive safety protocol for the PVAc emulsion process.

Effect of polyvinyl acetate (PVAc) based coating on quality characteristics of capsicum during storage

The effect of PVAc (Polyvinyl acetate) coating on various characteristics of capsicum was determined during postharvest storage at room temperature (30 ± 1 °C) and refrigeration temperature (10 ± 1 °C). Food grade PVAc was used to make different coating formulations (2.5, 5, 7.5, 10 and 12.5%) by dissolving alcohol-water mixtures. After coating, the samples were stored at room temperature (30 ± 1 °C) and refrigeration temperature (10 ± 1 °C) for a comparative study. Various physicochemical parameters viz. weight loss, TSS, acidity, chlorophyll, pH, ascorbic acid, and color were analyzed every three days of storage till spoilage. Results revealed that the physicochemical characteristics and the quality of the bell peppers were improved by coating treatments at both the storage conditions. PVAc concentrations of 10 and 12.5% performed better than other PVAc coatings in retaining the chlorophyll and water content, which ultimately increased the shelf life of capsicum without significantly affecting its green color. The coating reduced the weight loss and color change, maintained total soluble solids, titratable acidity, pH over the storage period. About 40-50% less weight loss was observed in case of higher PVAc coating concentrations (10 and 12%). Therefore, the present study results suggested that PVAc coating can maintain postharvest storage quality of capsicum at 30 ± 1 °C and 10 ± 1 °C storage conditions.

Graphical abstract

Polyvinyl acetate-based soil stabilization for rock slope ecological restoration

External-soil spray seeding (ESSS) is a method often used for the ecological restoration of bare rock slopes. However, the direct use of ESSS is normally less satisfactory due to the erosion of sprayed soil and low survival rate of the plants on rock slopes. This study proposes a novel approach to addressing this issue through the combined use of ESSS with polyvinyl acetate (PVA) based soil stabilization. The PVA solutions are added to the soil to stabilize soil and improve soil strength while possessing high water and nutrient retention favorable for plant growth. A series of experimental tests on the mechanical properties, water stability, erosion resistance, water retention, and plant growth of the PVA-stabilized soil were conducted to assess the efficacy of the proposed method. The results showed that the proposed method could be promising for rock slope ecological restoration. A proper curing time (e.g., >3 days) was required to achieve beneficial effects of PVA on the soil properties. A shorter curing time would otherwise result in the decrease in the strength with the increased PVA content. It was found that the optimum PVA content was 3% for achieving the maximum water stability, erosion resistance, water retention, and plant growth. The cohesion increased by up to 50% and the internal friction angle increased by 3.5° compared to the natural soil. The disintegration rate of the stabilized soil was generally < 3e-3%/min. The maximum reduction in erosion was up to 83% when the PVA content ≥3%. The mechanisms behind the findings are also discussed.

Enhanced rainfall erosion durability of enzymatically induced carbonate precipitation for dust control

Globally, most cities are facing severe challenges caused by dust pollution. Recently, the significant dust control application potential of the environmentally friendly enzymatically induced carbonate precipitation (EICP) has been demonstrated. However, repeated rainfall erosion negatively affects the long-term durability of several EICP treated areas. This study applied EICP and added either polyvinyl acetate (PVAc) or polyethylene glycol (PEG) to the cementation solution. The results showed that both PVAc and PEG could improve the shear resistance and rainfall-erosion resistance of treated dust soils. However, for repeated rainfall erosion, the surface strength and calcium carbonate (CaCO₃) contents of samples still decreased to less than 250 kPa and 1.1%, respectively. Therefore, combined EICP-PVAc-PEG treatment was proposed and the rainfall-erosion durability of treated dust soils was further studied. With the EICP-PVAc-PEG treatment, the dust samples achieved better shear resistance, higher surface strength, and better repeated rainfall-erosion resistance. Considering cost, cementation effects, and the effects of repeated rainfalls, EICP-PVAc-PEG treatment with 50 g/L PVAc and 30 g/L PEG was most suitable for dust control. The combined EICP-PVAc-PEG treatment significantly suppressed the generation of dust and improved the rainfall-erosion durability.

Application of enzymatic calcification for dust control and rainfall erosion resistance improvement

Globally, most cities are facing severe challenges associated with dust pollution and it is of great significance to propose an effective and environmentally friendly dust control method. This study used enzymatically induced calcite precipitation (EICP) technology for dust control. Moreover, polyvinyl acetate (PVAc) was added to the cementation solution to improve its rainfall erosion resistance. The results showed that the optimum ratio of urease solution to cementation solution differed according to the concentrations of reactants in the cementation solution. Under combined EICP and PVAc (50 g/L) treatment, the stability of the dust-slope significantly improved. Moreover, little dust soil loss was washed out by simulated rainfall because of the more stable spatial structure of CaCO₃ precipitation. Furthermore, PVAc addition increased the surface strength of slopes, while the cemented layer became thinner. With this combined EICP and PVAc (50 g/L) treatment, in a field test, the treated area of the slope had higher surface strengths and stronger erosion resistance than untreated areas. These higher surface strengths were attributed to the smaller particle size, and the stronger cementing effect of grass seeds. These results demonstrated that EICP-PVAc treatment significantly controlled dust and mitigated surface erosion of dust-slopes. This represents promising potential for the prevention of dust pollution.

Preparation of Chitosan-grafted-Polyvinyl acetate Metal Nanocomposite for producing Multifunctional Textile Cotton Fabrics

Chitosan-g-polyvinyl acetate (Cs-g-PVAc) was synthesized successfully using redox copolymerization using potassium persulfate as initiator. TiO₂ and TiO₂ doped ZnO which previously prepared by sol-gel technique added for preparing emulsion from polymer - metal oxide nanocomposites. Cotton fabrics were treated with prepared emulsions using citric acid and sodium hypophosphite. XRD measurements prove that the prepared TiO₂ nanoparticles corresponded to anatase phase with average crystallite size d = 15.98 nm where the crystallinity and crystallite size decreased for Zn doped TiO₂ where d = 11.7 nm. FTIR indicates that the exhibition of grafting process and formation polymer metal oxide nanocomposite. Samples treated with Copolymer showed the highest antibacterial properties. However, the copolymer doped with TiO₂ and TiO₂/ZnO showed lowest contact angle and affects positively on its photocatalytic performance. SEM and TEM micrographs confirmed that the prepared metal oxides are in nano scales, where TiO₂ is smaller than TiO₂/ZnO which effects on the band gap of TiO₂/ZnO to be larger than TiO₂ and consequently decreased on the photocatalytic properties TiO₂/ZnO of samples compared to TiO₂ sample under the halogen lamp.

Development of controlled release amorphous solid dispersions (CRASD) using polyvinyl acetate-based release retarding materials: Effect of dosage form design

The amorphous solid dispersion (ASD) technique has been employed to formulate poorly-soluble drugs, however, development of solid dosage forms with ASD is challenging due to the high propensity of amorphous drug to precipitate upon dissolution. Thus this work aimed to explore the potential of controlled release amorphous solid dispersion (CRASD) systems using polyvinyl acetate (PVAc) as a release-retarding excipient to mitigate the drug precipitation during dissolution of poorly water-soluble drugs. A number of solid oral CRASD dosage forms in different shapes and structures were prepared to contain spray-dried SD powders of a model BCS Class II drug, celecoxib (CEL), polyvinylpyrrolidone (PVP) and polyvinyl acetate (PVAc) which was incorporated in varying ways. In vitro dissolution tests were performed to investigate the effect of dosage form design on the dissolution/recrystallization profiles. The results indicated that despite nearly identical formulation compositions, the dissolution/recrystallization profiles could be tailored by changing the dosage form design. Matrix-form granules demonstrated greatest improvement of solubility appropriate for rapid drug release, while membrane-coated beads appeared to have the greatest potential for sustained release and thereby the least possibility of precipitation during dissolution. These results suggest that appropriate dosage form design of CRASD systems is of potential to reduce the problem of precipitation during dissolution of poorly soluble drugs.

Effectiveness of hemostatic gelatin sponge as a packing material after septoplasty: A prospective, randomized, multicenter study

OBJECTIVE

Although hemostatic gelatin sponge is a gelatin-based packing material with a powerful hemostatic effect, there were no studies in regard to its efficacy for packing material after septoplasty. The purpose of this study was to investigate the efficacy of hemostatic gelatin sponge nasal packing on patient's subjective symptoms, hemostasis, and wound healing following septoplasty.

SUBJECTS AND METHODS

Seventy six adult patients with nasal septum deviation requiring septoplasty were included. Following surgery, one nasal cavity was packed with hemostatic gelatin sponge and the other one with polyvinyl acetate. Patients' subjective symptoms while the packing was in situ, hemostatic properties, patients' pain on removal, degree of bleeding on removal of the packing, time for hemostasis after removal, postoperative wound healing, and the cost of the pack were evaluated.

RESULTS

Both packs were equally effective in the control of postoperative bleeding following septoplasty. However, hemostatic gelatin sponge packing was significantly more comfortable while in situ and less painful on removal of the pack. The polyvinyl acetate packing was associated with significantly more bleeding on removal, therefore much time was needed to control hemorrhage. There was no significant difference in the cost of the pack used and outcome of wound healing.

CONCLUSION

The use of hemostatic gelatin sponge after septoplasty results in significantly less discomfort and greater patient satisfaction with no adverse reactions when compared with polyvinyl acetate packing. Therefore, hemostatic gelatin sponge may be a useful packing material after septoplasty.

Improvement of vibrodamping properties of polyvinyl acetate-graphite composites by electron beam processing of the filler

The effect of electron beam processing (energy 900 keV, absorbed dose in the range from 25 to 600 kGy) of graphite upon the efficiency of its use as a filler in polyvinyl acetate (PVA) based vibrodamping composites is studied. Graphite treatment at optimal doses above 200 kGy is found to provide a significant increase of damping loss factor for these composites at ambient and especially at elevated temperatures. The observed improvement of vibrodamping properties correlates with the increase in the content of Broensted centers (hydroxyl groups) on modified graphite surface probably due to the additional bonding of the filler particles with each other and PVA binder.

Effects of the intermittent injection with super-low pressure on the postoperative pain control during the uterine artery embolization for uterine myoma

OBJECTIVE

Uterine artery embolization (UAE) has been commonly used for uterine myoma with satisfactory effects, but the pain during and following the procedure with an occurrence rate in 100%. The aim of this study was to observe the effects of intermittent injection with super-low pressure on pain control during the UAE for uterine myoma.

METHODS

67 subjects were divided into 2 groups with 47 in-group A and 20 in group B. A underwent UAE with the intermittent injection at super-low pressure, while B underwent routine UAE. Pain was assessed according to WHO analgesic ladder. Meanwhile, all were scored with the visual analogue scale (VAS).

RESULTS

The numbers of first, second and third step analgesic user in Group A were 21, 18 and 6, respectively, with 2 non-analgesic users, while in Group B were 4, 6 and 10, respectively without non-analgesic user (chi-square = 7.043, P = 0.008). VAS showed good pain control in 23 cases, satisfactory in 18 and poor in 6 in Group A, while in Group B, were 4, 8 and 8, respectively (chi-square = 7.329, P = 0.007). Mean follow-up was 16.5 months (range, 6-32 months). The abnormal menstruation was improved and the ultrasound examination 6 months later demonstrated a significant decrease in the diameter of myoma (from 6.65 ± 2.40 cm to 5.22 ± 1.86 cm, t = 3.186, P = 0.002).

CONCLUSION

The application of intermittent injection with super-low pressure during UAE can decrease and possibly eliminate post-operative pain. But the procedure time was increased.

Formulation and characterization of modified release tablets containing isoniazid using swellable polymers

The aim of this work was to develop swellable modified release (MR) isoniazid tablets using different combinations of polyvinyl acetate (PVAc) and sodium-carboxymethylcellulose (Na-CMC). Granules were prepared by moist granulation technique and then compressed into tablets. In vitro release studies for 12 hr were carried out in dissolution media of varying pH i.e. pH 1.2, 4.5, 7.0 and 7.5. Tablets of all formulations were found to be of good physical quality with respect to appearance (width and thickness), content uniformity, hardness, weight variation and friability. In vitro release data showed that increasing total polymer content resulted in more retarding effect. Formulation with 35% polymer content exhibited zero order release profile and it released 35% of the drug in first hr, later on, controlled drug release was observed upto the 12(th) hour. Formulations with PVAc to Na-CMC ratio 20:80 exhibited zero order release pattern at levels of studied concentrations, which suggested that this combination can be used to formulate zero order release tablets of water soluble drugs like isoniazid. Korsmeyer-Peppas modeling of drug release showed that non-Fickian transport is the primary mechanism of isoniazid release from PVAc and Na-CMC based tablets. The value of mean dissolution time decreased with the increase in the release rate of drug clearly showing the retarding behavior of the swellable polymers. The application of a mixture of PVAc to Na-CMC in a specific ratio may be feasible to formulate zero order release tablets of water soluble drugs like isoniazid.