Ratio Of Polyvinyl Alcohol Research Articles

Preparation and characterization of poly(vinyl alcohol)/halloysite nanotubes composite sponges with improved mechanical properties

AbstractA novel polyvinyl alcohol (PVA)/halloysite nanotubes (HNTs) composite sponge with preferable properties was fabricated via water solution mixing and casting technique with a fixed PVA ratio and the various contents of nano‐fillers. The morphology and physical properties of all the samples have been studied and characterized extensively. The results showed that HNTs were uniformly aligned along in the PVA matrix depending on good interfacial interactions between HNTs and PVA matrix. The addition of HNTs decreased the pore sizes and porosity of the sponges. Mechanical tests indicated that the incorporation of HNTs contribute to the reinforcement in mechanical properties of composite sponges under both dry and moist conditions. In addition, the composites showed better performances in thermal stability and water absorption capacity than pure PVA sponges. Rhodamine B and ibuprofen were employed to evaluate the control release ability. The results illustrated that increasing HNT contents can enhance the sustained release ability of PVA sponges.

Plasticized poly(vinylalcohol) and poly(vinylpyrrolidone) based patches with tunable mechanical properties for cardiac tissue engineering applications.

Polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) are the two most investigated biopolymers for various tissue engineering applications. However, their poor tensile strength renders them unsuitable for cardiac tissue engineering (CTE). In this study, we developed and evaluated PVA-PVP-based patches, plasticized with glycerol or propylene glycol (0.1%-0.4%; v:v), for their application in CTE. The cardiac patches were evaluated for their physico-chemical (weight, thickness, folding endurance, FT-IR, and swelling behavior) and mechanical properties. The optimized patches were characterized for their ability to support in vitro attachment, viability, proliferation, and beating behavior of neonatal mouse cardiomyocytes (CMs). In vivo evaluation of the cardiac patches was done under the subcutaneous skin pouch and heart of rat models. Results showed that the optimized molar ratio of PVA:PVP with plasticizers (0.3%; v-v) resulted in cardiac patches, which were dry at room temperature and had desirable folding endurance of at least 300, a tensile strength of 6-23 MPa and, percentage elongation at break of more than 250%. Upon contact with phosphate-buffered saline, these PVA-PVP patches formed hydrogel patches having the tensile strength of 1.3-3.0 MPa. The patches supported the attachment, viability, and proliferation of primary neonatal mouse CMs and were nonirritant and noncorrosive to cardiac cells. In vivo transplantation of cardiac patches into a subcutaneous pouch and on the heart of rat models revealed them to be biodegradable, biocompatible, and safe for use in CTE applications.

Gastroretentive Floating Tablets Enclosing Nanosponge Loaded with Lafutidine for Gastric Ulcer: Formulation and Evaluation

Abstract: Aim and Objectives: The present study aimed to formulate and evaluate gastroretentive nanosponge loaded with lafutidine for a gastric ulcer to overcome the drawbacks of oral conventional dosage forms such as the inability to confine and locate within the desired region of the gastrointestinal tract due to variable gastric emptying and motility. The floating tablets of nanosponge were formulated to increase the bioavailability of lafutidine by prolonging retention time in the upper gastric region. Materials and Methods: The emulsion solvent diffusion method was used to prepare the nanosponge and 32 factorial design was employed to assess the influence of two independent variables ethyl cellulose: polyvinyl alcohol ratio and sonication time on particle size, entrapment efficiency and zeta potential of the prepared nanosponges. The optimized nanosponges were compressed into tablets by the direct compression method. Results: Statistical analysis revealed the significant effect of ethyl cellulose: polyvinyl alcohol ratio and sonication time on particle size, entrapment efficiency and zeta potential. The SEM images of the optimized formulation revealed the spherical shape and porous surface of the nanosponges. Pre and post-compression parameters of floating tablets found to be within the limit and the floating tablets of nanosponge remained buoyant for 24 h whereas nanosponges remained buoyant only for 7 h. The F1 formulation showed short lag time, maximum drug content (98.7%), sustained the drug release for 24 h and it was stable for the entire period study. Conclusion: The floating tablet of nanosponge is promising in retaining and controlling drug release for a pronged period of time in the stomach. Key words: Nanosponge, Lafutidine, Design of experiment (DoE), Gastroretentive, Floating tablet.

Novel PVA/Methoxytrimethylsilane elastic composite membranes: preparation, characterization and DFT computation

A modified composite membranes (PVA/SiOH/SiOC) were made via solution-casting process using different 1:1, 1:2, 1:3 and 1:4 volume ratios of polyvinyl alcohol (PVA):methoxytrimethylsilane (MTMS). Moreover, FT-infrared and energy-dispersive X-ray spectroscopy (EDX) were mesured to account for the network structural rearrangements involving silicon within PVA matrices. The addition of MTMS has improved the thermal and mechanical properties of the composite membranes as compared to pristine PVA. In addition, the crystallinity and the morphological changes of PVA/MTMS composites was studied using X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. Three structures were suggested based on trimethyl silanol (I) wet out condensation (II and III) with the dopped PVA followed by and H-bonding interactions (IV). The outcomes of B3LYP/6-31G(d) frequency calculations favors a three-dimensional SiOC linked network (III). Nevertheless, EDX reveals, the 3D SiOC links are not observed on the surface of composite membranes, however, is found dominant in the bulk, [(CH3)3SiOCH2CH2CH2O]n. Moreover, the solubility, density, and refractive index of the synthesized composites were measured and found depended on the ratio of PVA in the composite membranes. The current results are compared with that published earlier including dimethoxydimethylsilane at the same conditions.

Corn starch/PVA bioplastics—The properties and biodegradability study using Chlorella vulgaris cultivation

AbstractIn this study, a biodegradable alternative to synthetic plastics was explored, where gelatinized corn starch was blended with polyvinyl alcohol (PVA) using the solution casting method at different ratios. Tensile tests showed that films made of only starch exhibited the lowest tensile strength at 3.66 MPa, which increased as the ratio of PVA in the blend was raised. The water vapor transmission rate was similar even when the starch content was changed. PVA was shown to increase the solubility of the film in water, and starch demonstrated a better ability to absorb water than that of PVA, with the pure starch film swelled up to 167% of its original weight. Fourier transform infrared (FTIR) analysis revealed that there was no significant chemical interaction between the starch and PVA which could alter their respective functional groups. Bioplastic films made of only starch showed the least amount of degradation after 3 days when buried in soil, while water uptake in films made of PVA caused it to turn into a sticky gel‐like substance. Chlorella vulgaris exhibited a higher preference for PVA as the substrate when compared to starch. This revealed that C. vulgaris showed promise as a candidate for breaking down the bioplastic films when grown as a heterotroph.

Ultra‐low degree of polymerization polyvinyl alcohol products prepared by oxidative chain scission: Method and mechanism

AbstractIn this paper, the high value‐added (ultra‐low degree of polymerization [ULDP]) polyvinyl alcohol (PVA) product was successfully prepared by oxidative chain scission method with sodium hypochlorite as an oxidant. When the molar ratio of PVA to NaClO is not less than 1:1.8, the reaction is stirred for several hours (≥2 h) at a temperature not exceeding 50°C. After precipitation and washing in methanol, PVA with polymerization degree of 38–150 can be obtained after drying. The infrared spectrum (IR) and nuclear magnetic hydrogen spectrum (1H‐NMR) test proved that the product obtained by this method is indeed PVA. The results of 1H‐NMR also showed that the chain broken has no selectivity and the stereoregularity of hydroxyl group did not change significantly. Through radical quenching experiment and electron paramagnetic resonance (EPR) analysis, it is proved that OCl− is the main active oxide, ·Cl makes the oxidative chain scission process can be realized quickly, and ·OH is an indispensable factor for obtaining ULDP PVA. Under the combined action of these three, high value‐added PVA with ULDP was successfully prepared. Additionally, the sodium hypochlorite oxidized the ·OH captured by 5,5‐dimethyl‐1‐pyrroline‐n‐oxide (DMPO‐OH) to 2‐hydroxy‐5,s‐dimethyl‐1‐pyrroline‐N‐oxide (HDMPO‐OH) in an alkaline environment.

Development and Characterization of LBG-PVA Interpenetrating Networks Incorporating Gliclazide for Sustained Release

Background: Controlled oral dosage forms have always been preferred for drugs with variable absorption, and short biological half life and frequent dosing. The prime goal with sustained release systems is to maintain uniform therapeutic blood levels for more extended periods of time. Interpenetrating networks (IPNs) have been evidenced as uniform sustained release systems. In the current study, polyvinyl alcohol (PVA) and locust bean gum (LBG) based IPNs were developed for the oral sustained release drug delivery of gliclazide (shows variable absorption). Methods: The IPNs were synthesized by emulsion cross-linking method using glutaraldehyde (GA) as a cross linking agent. Gliclazide is a potential second generation, and short-acting sulfonylurea oral hypoglycemic agent having a short biological half-life (2-4 h), variable absorption and poor oral bioavailability. Various batches of IPNs were formulated by varying LBG: PVA ratio and evaluated for percentage yield, drug entrapment efficiency (DEE), swelling properties and in vitro drug release studies. Further characterizations were done by Fourier Transform Infrared Spectroscopy (FTIR), C13 Solid state NMR, X-Ray diffraction study (XRD), Scanning electron microscopy (SEM), and Differential scanning microscopy (DSC) studies. Results: The percentage yield, drug entrapment and equilibrium swelling were observed to be dependent on PVA-LBG ratio and GA amount. Sustained release of drug was observed in all IPN formulations (approx 59 - 86% in 8 h in various batches) with variable release kinetics. SEM studies revealed the regular structures of IPNs. FTIR, XRD, C13 Solid state NMR and DSC studies proposed that drug was successfully incorporated into the formed IPNs. Conclusion: IPNs of LBG and PVA can be used as a promising carrier with uniform sustained release characteristics.

Adsorption kinetics for the removal of harmful EBT dye by polyvinyl palmitate as effective adsorbents

Polyvinylpalmitate esters with five different compositions have been prepared with the following ratio of polyvinyl alcohol and palmitic acid, respectively: 1:1 (PVP1), 10:1 (PVP 2), 20:1 (PVP 3), 1:10 (PVP 4) and 1:20 (PVP 5). All these polymers have been characterized by studying their thermal, spectral and morphological properties. These polymers have used as adsorbents for dyes. Eriochrome Black – T is the dye chosen for this study and adsorption characteristics on the five PVPs prepared have been evaluated. The various factors influencing their adsorption such as the initial concentration of the dye, contact time and pH have been varied and the optimum parameters for maximum adsorption have been determined. Almost in all the systems studied, maximum adsorption is observed at pH = 8 for a contact time of about 120 min. Also, kinetically all of them follow second order kinetics, shown by excellent correlation Co-efficient for the plots.The adsorption data fit well in both the Freundlich isotherm and Langmuir adsorption isotherm. From these isotherm profiles, the equilibrium concentration of the dye (corresponding to maximum adsorption) has been evaluated which are in good agreement with those determined experimentally. The desorption studies suggest chemisorption to be responsible for the adsorption of these dyes onto PVPs.

Design and Characterization of Sodium Alginate and Poly(vinyl) Alcohol Hydrogels for Enhanced Skin Delivery of Quercetin.

Nature has led to the discovery of biopolymers with noteworthy pharmaceutical applications. Blended biopolymers have demonstrated promising characteristics when compared with their individual counterparts. Sodium alginate (SA) is a marine polymer that has demonstrated the ability to form hydrogels, an interesting property for the development of cutaneous formulations. Predicting the good performance of blended biopolymers, a novel series of hybrid hydrogels based on SA and poly(vinyl) alcohol (PVA) were prepared. Quercetin, a natural polyphenolic flavonoid commonly found in fruits and vegetables, is widely known for its strong anti-inflammatory and antioxidant activity, thus with potential applications against melanoma, dermatitis, psoriasis, and skin ageing. Here, hydrogels were produced at different ratios of SA and PVA. The surface morphology, structure, interaction of polymers, the capacity to absorb water and the entrapment efficiency of quercetin were evaluated for the blended hydrogels. Targeting the cutaneous application of the formulations, the rheological properties of all unloaded and quercetin-loaded hydrogels revealed pseudoplastic behavior, evidence of non-thixotropy, good resistance to deformation, and profile maintenance with temperatures ranging from 20 °C up to 40 °C. The incorporation of quercetin in the hydrogel retained its antioxidant activity, confirmed by radical scavenging assays (ABTS and DPPH). The permeability of quercetin through the skin showed different penetration/permeation profiles according to the hydrogel’s blend. This behavior will allow the selection of SA-PVA at 2/1 ratio for a local and prolonged skin effect, making the use of these hydrogels a good solution to consider for the treatment of skin ageing and inflammation.

Optical and conductivity studies of polyvinyl alcohol-MXene (PVA-MXene) nanocomposite thin films for electronic applications

A new family of 2D materials known as MXenes (Ti3C2Tx) is combined with polyvinyl alcohol (PVA) to form nanocomposites thin film with a thickness in micrometre range (7.20–7.88 µm) by using a relatively simple way, a drop-casting technique. The multi-layered structure of the MXenes bound together with PVA results in a high degree of structural disorder due to increasing defects in the nanocomposites. Detailed optical studies include UV–Vis absorption, optical absorption coefficient, extinction coefficient, and band gap energy determinations are conducted to investigate electromagnetic wave absorption capability of the nanocomposites. Resistivity measurement is studied as well. Electrical conductivity of the PVA is significantly increased with at least an improvement of 3000 times as compared to pure PVA (1 × 10−13 Sm−1). The highest σ value of 7.25 × 10−3 Sm−1 is found in the nanocomposites with a mass ratio of PVA to MXenes, 80:20 with its calculated optical absorption coefficient value in range 4000–5000 cm−1. The optical findings, as well as the electrical conductivity enhancement exhibited by these nanocomposites, explore the route to apply MXenes in polymer-based multifunctional nanocomposites for various applications such as optoelectronics, conductive filler, and electromagnetic absorbers.

Carboxymethyl cellulose-based polyelectrolyte as cationic exchange membrane for zinc-iodine batteries

The aim of this research is an evaluation of polyelectrolytes. In the application of zinc-iodine batteries (ZIBs), polyelectrolytes have high stability, good cationic exchange properties and high ionic conductivity. Polyelectrolytes are also cost-effective. Important component of ZIBs are cation exchange membranes (CEMs). CEMs prevent the crossover of iodine and polyiodide from zinc (Zn) electrodes. However, available CEMs are costly and have limited ionic conductivity at room temperature. CEMs are low-cost, have high stability and good cationic exchange properties. Herein, polyelectrolyte membranes prepared from carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVA) are examined. It is seen that an increase in the ratio of PVA leads to enhanced ionic conductivity as well as increased iodine and polyiodide crossover. ZIBs using polyelectrolytes having 75:25 wt.% CMC/PVA and 50:50 wt.% CMC/PVA show decent performance and cycling stability. Due to their low-cost and other salient features, CMC/PVA polyelectrolytes prove they have the capacity for use as cation exchange separators in ZIBs.

Development of multicomponent interpenetrating polymer network (IPN) hydrogel films based on 2-hydroxyethyl methacrylate (HEMA), acrylamide (AM), polyvinyl alcohol (PVA) and chitosan (CS) with enhanced mechanical strengths, water swelling and antibacterial properties

The novel poly(2-hydroxyethyl methacrylate-co-acrylamide)/polyvinyl alcohol/chitosan (P(HEMA-co-AM)/PVA/CS) interpenetrating polymer network (IPN-CS) hydrogel films were fabricated by two-step free radical polymerization, aiming to enhance the tensile strength, water swelling and antibacterial activity compared to P(HEMA-co-AM)/PVA hydrogel (IPN-0%CS). The different weight ratios of PVA and CS components were firstly crosslinked by glutaraldehyde. Then P(HEMA-co-AM) copolymers were interpenetrated into the primary networks of PVA/CS and crosslinked by ethylene glycol dimethacrylate to form the IPN-CS hydrogels. The functional group analysis confirmed that the IPN-CS hydrogels were successfully synthesized. The crystallinity, Tg and Tm, microporous and surface area of IPN-CS hydrogels tended to increase significantly with increasing CS content. The swelling equilibrium and surface area of IPN-CS hydrogel exhibited a linearly relationship with CS content. The swelling behavior of IPN-CS hydrogels was best described by the pseudo-first order kinetics and followed a non-Fickian diffusion mechanism. The IPN-5%CS hydrogel film exhibited the highest tensile strength (22.4 MPa) which was increased 2.7 folds of IPN-0%CS. All IPN-CS hydrogels demonstrated an excellent antibacterial activity against E. coli. These results suggest that the IPN-CS hydrogel films have promising potential used as wound dressings.

In vitro evaluation of poly (vinyl alcohol)/collagen blended hydrogels for regulating human periodontal ligament fibroblasts and gingival fibroblasts

Periodontitis is a chronic inflammatory disease that can destroy periodontal tissue. Guided tissue regeneration (GTR) is widely applied to treat periodontitis. However, the challenge is to develop a GTR membrane capable of simultaneously regenerating periodontal tissue and preventing epithelial downgrowth into the defect. Herein, blended hydrogels composed of polyvinyl alcohol (PVA) and fish collagen (Col) were prepared as GTR membranes. The morphology, Col release, and cellular behavior of the blended hydrogels were evaluated. The results showed that the surface porosity and Col release of the PVA/Col blended hydrogels were enhanced by increasing the Col concentration. The adhesion and proliferation of human periodontal ligament fibroblasts (HPDLFs) and human gingival fibroblasts (HGFs) on the PVA/Col blended hydrogels can be regulated by tuning the PVA/Col ratio. The PVA/Col (50:50) blended hydrogel exhibited the highest cell proliferation rate for HPDLFs with spread cell morphology; the lowest viability for HGFs was found on the PVA/Col (100:0) hydrogel. Thus, by controlling the ratio of PVA to Col, multifunctional PVA/Col blended hydrogels able to regulate the cellular behavior of HPDLFs and HGFs can be developed, demonstrating their potential as GTR membrances for guiding periodontal tissue regeneration.

Preparation and characterisation of a high-strength self-healing hydrogel

ABSTRACT In this paper, two-step cross-linking method was used to prepare a composite hydrogel. Explore the effects of the mass ratio of polyvinyl alcohol to sodium alginate, the concentration of cross-linking agent and the times of freeze-thaw cycle on the strength and self-healing properties of hydrogels. The hydrogel were characterized by Infrared Spectroscopy, X-ray Diffraction and Environmental Scanning Electron Microscopy,the water absorption capacity was evaluated bythe swelling rate and the tensile strength was measuered by Electronic Universal Testing Machine. The results indicated that when the mass ratio of PVA and SA was 30:1, the concentration of sodium tetraborate solution was 10wt%, and freeze-thaw cycle once composite hydrogel had the best comprehensive performance: its maximum tensile strength reached 0.90 MPa, and it has good self-healing performance which can be proved by that its tensile strength could return to 75% of initial level 24 hours after being cutting off.

Experimental and analytical investigation of high performance concrete beams reinforced with hybrid bars and polyvinyl alcohol fibers

This paper investigates the flexural performance of engineered cementitious composite (ECC) concrete beams reinforced with innovative hybrid bars. Hybrid bars combine the advantages of both FRP and steel bars in enhancing the ultimate strength, ductility, and corrosion resistance compared with pure FRP or steel bars. Twelve half-scale ECC-concrete beams were tested to study the flexure behaviour under four-points loading test using polyvinyl alcohol (PVA) ECC fibers. Polyvinyl alcohol (PVA) fibers were used in the ECC mix for this purpose. The experimental variables are the hybrid reinforcement ratios (0.85%, 1.26%, and 1.7%), PVA fiber ratio (0.0%, 0.75%, and 1.5%) and hybrid schemes (hybrid and GFRP bars). The test results showed significant enhancement in the capacity of ECC concrete beams reinforced with hybrid bars or hybrid schemes. The achieved enhancements are 12% and 27% for PVA ratio of 0.75% and 1.5% respectively. In the presence of PVA fibers, the ultimate strain of the bars is higher than that registered in the absence of PVA fibers. Non-linear finite element analysis (NLFEA) was carried out to validate the experimental results. The NLFEA is adequately simulating the experimental results. Nominal flexural strength and flexural rigidity were assessed with the experimental test results and validated with 77 available ECC-concrete beams from the literature. The validation proved that the assessments of the nominal flexural strength and flexural rigidity are performed well in the prediction. Finally, a comprehensive sensitivity study is conducted to illustrate the effect of PVA-ECC on the flexural rigidity of the beams. The experimental evidence presented in the current study demonstrates the feasibility and plausible future of the novel hybrid bars and PVA fibers especially for marine and waterfront concrete structures.

Formulation and Evaluation of Iornoxicam as Dissolving Microneedle Patch

The objective of the study was to develop microneedle (MN) patch, with suitable properties to ensure the delivery of a therapeutic level of lornoxicam (LXM) in a period suitable to replace parenteral administration in patients, especially those who fear needles. The used polymers were cold water-soluble polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) of low molecular weight with PEG 400 as plasticizer and Tween 80 (to enhance the release) using micro molding technique. Patches were studied for needle morphology, drug content, axial fracture force measurement and drug release while the optimized formulas were further subjected to pH measurement, folding endurance, ex vivo permeation study, histopathology study, stability study and compatibility study. The patch with 11:1 ratio of PVA to PVP, 30% solid content, 5% PEG 400 and 3% Tween 80 resulted in axial needle fracture force value of (1.35 N) which is suitable for skin penetration. The release was fast with almost 100% of drug released in 60 minutes. The permeation was enhanced significantly with a steady state flux of about 3.1 times that of the solution. The lag time of MN is shorter in comparison with ordinary patch. Histopathology studies demonstrated the safety of the formulation, both stability studies and compatibility studies showed the suitability of the formulation. The results indicated that LXM microneedle patch could enhance drug permeation while achieving fast and painless administration.
 Keywords: Microneedle patch, Polyvinyl alcohol, Polyvinylpyrrolidone, Fracture force, Lornoxicam.

The immobilized Alcaligenes faecalis strain WT14 for removing high strength nitrate and reducing nitrite accumulation

ABSTRACT Microbial immobilization is considered as one of the effective denitrification techniques in the treatment of high load wastewater. In this study, the immobilized cells consisting of polyvinyl alcohol (PVA), sodium alginate (SA), and calcium chloride (CaCl2) were inoculated with Alcaligenes faecalis strain WT14 to treat wastewater with high nitrate-nitrogen (-N) concentrations. After 48 h of wastewater treatment, 26.2–89.4% of total nitrogen (TN) was removed by the immobilized Alcaligenes faecalis strain WT14. The response surface methodology revealed the highest TN removal efficiency by Alcaligenes faecalis strain WT14 occurred at the immobilized ratio of 9.3% of PVA, 2.2% of SA and 1.9% of CaCl2. Under the optimal ratio of PVA, SA, and CaCl2, the conditions for the maximum denitrification efficiency and TN removal were pH of 7, temperature of 40°C, and shaking speed of 60 rpm·min−1. Compared to the free cells, the immobilization cells had no obvious negative effect on denitrification efficiency, additionally reduced the nitrite accumulation, and thus improved the TN removal. Furthermore, the immobilized cells still maintained 95.4% of -N removal after the eighth cycle reuse. These results demonstrated the immobilized Alcaligenes faecalis strain WT14 can remove TN effectively and additionally reduce nitrite accumulation in treating high strength -N wastewater.

Polyacrylic acid and polyvinyl alcohol-based polymer complexes and hydrogels

In aqueous solution, in the acidic environment (pH <3), water-soluble complexes are formed based on polyacrylic acid (PAA) and polyethyleneglycol with a molecular weight of more than 6000 or on polyvinyl alcohol (PVA). The conditions for obtaining hydrogel based on polyacrylic acid and polyvinyl alcohol with a high degree of swelling (about 500 g of water/g of polymer) were determined: pH <3, temperature 120-140 ° С . The degree of interaction of polymers is directly proportional to the content of polyvinyl alcohol in the initial mixture in the range of the molar PVA and PAA ratios from 1 : 1 to 10 : 1, the temperature and duration of heat treatment and is inversely proportional to the molecular weight of polyacrylic acid. The equilibrium degree of hydrogel swelling increases at the pH of the swelling medium above 6, and the swelling rate depends on the solvent diffusion into the hydrogel and is determined by the size of its particles and the swelling conditions (washing, mixing, etc.).

Evaluating the influence of paper characteristics on the efficacy of new poly(vinyl alcohol) based hydrogels for cleaning modern and ancient paper

Wet cleaning of paper artworks by using hydrogels is a recently proposed process in the cultural heritage field. In this contest, on one side, research has focused on more effective and tuned cleaning hydrogels; on the other, the cleaning performances of the proposed hydrogels have been studied on ancient paper and very little on modern paper. This lack of information is not negligible, since the two kinds of paper differ strongly in composition. The difference, in turn could affect the performance of cleaning gels. In this article, new chemical hydrogels were synthetized using an oxidized polyvinyl alcohol (PVA) bearing an aldehyde group at each chain end, as cross-linking agent, i.e. telechelic PVA. PVA hydrogels have been characterized as candidates for paper cleaning applications. The possibility of tuning the mechanical and retentive properties, simply by changing the ratio of two polymer concentrations, their stability and transparency, indeed, render them, potentially suitable in cultural heritage field. The cleaning capability of two hydrogels, with different PVA/telechelic PVA ratios, has been assessed both on ancient paper, than a modern one and the results have been compared. The efficacy of these hydrogels has been demonstrated characterizing the samples before and after the cleaning process by means of a multidisciplinary approach involving spectroscopic and chromatographic tests.

Electrospinning preparation and microstructure characterization of homogeneous diphasic mullite ceramic nanofibers

In this work, diphasic mullite (3Al2O3·2SiO2) nanofibers with good homogeneity were prepared by electrospinning method. Aluminum nitrate (AN) and aluminum isopropoxide (AIP) were used as alumina sources, commercial colloidal silica as silica source, and polyvinyl alcohol (PVA) as polymer additive. Precursor nanofibers with continuous and uniform structures were acquired at mass ratio of PVA to precursor sol from 0.06 to 0.09. γ-Al2O3 phase was obtained at 878 °C and mullite phase formed at 1322 °C upon heating of the precursor under air atmosphere. Calcined samples suggested mullite as dominant phase at 1300 °C and amorphous SiO2 could even exist at 1400 °C. As-prepared nanofibers possessed continuous structures with subequal average diameters at 900–1200 °C. However, such morphological characteristics were lost at temperatures above 1300 °C due to rapid growth of crystal grains. Al and Si elements were uniformly distributed in fibers and mixed at nanoscale, confirming homogeneity and diphasic features of nanofibers.