Orange-peel-derived carbon dots embedded in polyvinyl alcohol films for transparent and flexible UV-blocking applications

Towards the toughness-strength balance of poly(vinyl alcohol) films via synergic plasticization

With the advantages of excellent processability and biodegradability, polyvinyl alcohol (PVA) becomes an environmentally friendly and biocompatible material in many fields currently. To further improve the mechanical properties of thermoplastic PVA films, the orientation was adopted and studied. In this work, the uniaxial stretched PVA films with ethylene glycol as plasticizer were prepared to explore the influence of stretching temperature and draw ratio on the structure and properties of oriented PVA films. The introduction of ethylene glycol improves the thermoplastic processing capacity of PVA. When the stretching temperature was lower than 100 °C, the strength of the film increased with the increase of temperature. However, as the temperature continued to increase, the strength decreased since the process of disorientation accelerated. In addition, with the increase of draw ratio, an increase in the tensile strength and Young’s modulus of the films and a decrease in the elongation at break were observed. When the draw ratio at 5, the tensile strength and Young’s modulus of the PVA films reached the maximum of 219.7 MPa and 219.6 MPa respectively. Thus through controlling the orientation conditions and plasticizers, the PVA films with enhanced performance could be obtained.

Investigations on Fe 3+ doped polyvinyl alcohol films with and without gamma (γ)-irradiation

To increase the amount of pirfenidone (PFD) loaded in polyvinyl alcohol (PVA) film embedded soft contact lens (SCL), and evaluate its function of sustaining delivery of drug in vitro and in vivo. Drug loading efficiency within PVA film and SCLs, drug release from SCLs in vitro, and the effects of parameters of SCLs and external environment on drug release in vitro were evaluated by ultraviolet–visible spectrophotometer at 312 nm. Safety of SCLs was evaluated in vitro by transformed human corneal epithelial cell. Safety in vivo was determined by optical coherence tomography and histology of anterior segment of rabbits. Drug release study in tear fluid and aqueous humor were measured by ultra-performance liquid chromatography. SCLs had smooth surface and were fit for experimental rabbits. Amount of PFD in PVA film and SCLs were 153.515 μg ± 12.508 and 127.438 μg ± 19.674, respectively, PFD in PVA film was significantly higher than SCLs (p=.006) and closed to 150 μg (targeting amount of PFD to be loaded). Thickness of SCLs, molecular weight of PVA, and amount of PVA used in SCLs affected drug release in vitro significantly. Thickness of PVA film and amount of drug in SCLs had no effect on drug release rate in vitro. SCLs were safe in vitro and in vivo, PFD released from SCLs could be detected around 12 hours in tears and aqueous humor, and the concentration of drug was higher than eye drop at all detected time points while amount of PFD in SCLs was lower than eye drop. Drug loaded PVA film embedded SCLs may be a promising ocular drug delivery system.

We report on the simultaneous generation of phase-conjugate signals by degenerate four-wave mixing (DFWM) and holographic processes using a nanosecond pulse and a CW lasers in polyvinyl alcohol (PVA) films doped with four kinds of saturable absorbing dyes. For the pulse laser, of the four kinds of dye-doped PVA films, the erythrosine B-doped PVA and uranine doped-PVA films generate PC signals only by the DFWM process, while the other dye-doped PVA films generate PC signals simultaneously by not only the DFWM process but also the holographic process. Especially, the safranin T-doped PVA film generates strong PC signals by the holographic process. In contrast, all of the dye-doped PVA films generate the two types of PC signals for the CW laser. The fading of dye molecules is found to result in the generation of the holographic component of PC signals which governs the temporal behavior of the total PC signals.

This article reports the systematic photoluminescence study of the various contents of gold nanocomposites in polyvinyl alcohol (PVA) films. The variations in the gold content in PVA film were 0.2, 0.5, 1.0, and 1.5wt%. All the samples were excited at two selected wavelengths; those are at 400 nm and 532 nm. On exciting the gold-PVA nanocomposite films at 400 nm the photoluminescence was observed in the region of 430-500 nm in comparison to pure PVA films that show an emission at 400 nm. However, on exciting the gold-PVA nanocomposites at 532 nm, the emission was observed at 560-650 nm with a long tail till 700 nm that is unlike the pure PVA films that do not show any emission peak in this region. This suggests that emission between 430 and 500 nm regions is due to the coordination of PVA with gold nanoparticles because PVA has an emission at 400 nm. However, the emission peak between 560 and 650 nm is entirely due to the gold nanocomposite particle. The peak also shows a smaller red-shift that is usually with the increasing nanoparticles size with the increasing content in the PVA films. The formation of gold nanoparticles was justified by X-ray diffraction (XRD) analysis which is further supported by X-ray photoelectron spectroscopy (XPS) analysis.

Effect of gamma irradiation on the color, structure and morphology of nickel-doped polyvinyl alcohol films: Alternative use as dosimeter or irradiation indicator

Laser surface alloying of commercial pure titanium pre-coated polyvinyl alcohol (PVA) film was carried out to improve wear resistance. The laser beam is absorbed at the surface of titanium substrate because the PVA film is transparent to the wavelength of a Yb-fiber laser. Thermal decomposition of the PVA occurred at the interface of the titanium substrate and PVA film. A crack free modified layer was obtained by the reaction of these thermal decomposition products and a titanium melt pool at the interface of the film and the substrate. A Ti(C,O) precipitation layer was formed on the surface layer of the laser alloyed zone. The laser alloyed zone exhibits superior wear resistance.Laser surface alloying of commercial pure titanium pre-coated polyvinyl alcohol (PVA) film was carried out to improve wear resistance. The laser beam is absorbed at the surface of titanium substrate because the PVA film is transparent to the wavelength of a Yb-fiber laser. Thermal decomposition of the PVA occurred at the interface of the titanium substrate and PVA film. A crack free modified layer was obtained by the reaction of these thermal decomposition products and a titanium melt pool at the interface of the film and the substrate. A Ti(C,O) precipitation layer was formed on the surface layer of the laser alloyed zone. The laser alloyed zone exhibits superior wear resistance.

Poly (vinyl alcohol) supported thermally reduced graphene oxide (TRGO) nanosheets exhibit enhanced electrical and mechanical behavior

The detection of infrared radiation (IR) with pure and doped Polyvinylidene difluoride (PVDF) films has been well documented using the mechanism of pyroelectricity. Alternatively, the electrical properties of films made from Polyvinyl Alcohol (PVA) have received considerable attention in recent years. The investigation of surface resistivities of both such films, to this point, has received far less consideration in comparison to pyroelectric effects. In this research, we report temperature dependent surface resistivity measurements of commercial, and of multiwall carbon nanotubes (MWCNT), or Ag-nanoparticle doped PVA films. Without any variation in the temperature range from 22°C to 40°C with controlled humidity, we found that the surface resistivity decreases initially, reaches a minimum, but rises steadily as the temperature continues to increase. This research was conducted with the combined instrumentation of the Keithley Model 6517 Electrometer and Keithley Model 8009 resistivity test fixture using both commercial and in-house produced organic thin films. With the objective to quantify the suitability of PVDF and PVA films as IR detector materials, when using the surface resistivity phenomenon, instead of or in addition to the pyroelectricity, surface resistivity measurements are reported when considering bolometry. We find the surface resistivity of PVDF films to be in the range, which extends beyond the upper limit of our Keithley electrometer, but our measurements on PVA films were readily implemented.

Physical and microstructural properties of biodegradable films based on pea starch and PVA

Reusing uncured Fiber-reinforced thermoset composite Prepreg waste with water-soluble PVA backing film

Polyvinyl alcohol (PVA) has been widely applied in industries for its low cost, nontoxicity, biodegradability, and renewable advantages. However, its unstable structure may not meet some strong physical and mechanical needs. In order to enhance the performances of the PVA film, cellulose nanocrystals (CNCs), tannic acid (TA), and chitosan (CS), working as a reinforcer, a crosslinker, and an antimicrobial agent, respectively, were introduced into the PVA matrix. The results indicated that CNCs, TA, and CS were evenly distributed and cohesively incorporated within the PVA matrix, which contributed to the good mechanical properties and thermal stabilities of biocomposite PVA films. Besides, the addition of TA remarkably improved the antiultraviolet and antioxidant capabilities of PVA films, although the light transmittance declined slightly. It was also observed that the pure PVA film and PVA reinforced with CNCs were incapable of protecting against bacteria, while the ones with CS had prominent antibacterial properties to Escherichia coli and Staphylococcus aureus. Overall, the resulting film presented a high potential utilization as a food packaging material for its outstanding physical and mechanical performances.

Preparation and conductivity of polyvinyl alcohol (PVA) films composited with molybdotungstovanadogermanic heteropoly acid

Flame retardancy performance and mechanism of polyvinyl alcohol films grafted amino acid ionic liquids with high transparency and excellent flexibility