Papers by Keyword: Poly(vinyl alcohol)

Abstract: Polymer-based hydrogels are suitable for development as wound dressings because the hydrogel can regulate the amount of fluid and moisture in the wound area, exhibit a network structure, and be compatible with the human body. Therefore, this work focused on the preparation of 2% w/v (Chitosan:CS)/2%,4%,6% w/v (Poly(vinyl alcohol):PVA) gel containing silver nanoparticles for antibacterial use, synthesized by the chemical crosslinking method with glutaraldehyde. Silver nanoparticles were prepared at a concentration of 1 mmol with black lemon extract as a reducing agent and a stabilizer packaged in the gel. From the study of absorbance, particle size, and morphology, it was found that silver nanoparticles were 10.60± 2.20 nm, with good dispersion and spherical shape. The swelling behavior of 2% w/v CS/2% w/v PVA gel showed the highest swelling at 95.74±21.29%. In addition, 2% w/v CS/2% w/v PVA gel containing silver nanoparticles could inhibit the growth of gram-positive and gram-negative bacterial microorganisms. Thus 2% w/v CS/2% w/v PVA gel containing silver nanoparticles is suitable for medical applications.

Abstract: Due to the growing demand of the textile market, the production of synthetic fibers like polyester (PET), has been increasing compared to any other existing fiber group. However, this type of fiber has its own disadvantages, the main one being its hydrophobic nature. To improve its properties, it was sought to develop a chemical functionalization. This process consisted of three steps, the first one being the cleaning of the polyester with hydrochloric acid, followed by a subsequent hydrolysis of the textile substrate in an alkaline medium in the presence of sodium hydroxide. The last phase, that concerns the textile substrate functionalization with poly (vinyl alcohol), more commonly known as PVA, was made by a process of exhaustion at different pH values (3, 6, and 10), followed by a curing, which allowed the formation of bonds between the PVA and the polyester fibers and consequently improve polyester properties, namely the hydrophilicity, presenting a contact angle of 0º. This process of functionalization of the polyester with PVA at acidic pH, led to very promising results since a significant improvement of its properties was obtained. The functionalized and original polyester samples were further characterized through the application of several techniques, such as SEM, FTIR-ATR and differential scanning calorimetry DSC. These characterization techniques allowed to prove that the textile substrates were effectively modified. It can be concluded that, properties such as, contact angle, tensile strength, air permeability, coefficient of friction and water vapor permeability, were substantially improved by the functionalization of the polyester fabric with PVA.

Abstract: The ultrafine fibers of Poly Vinyl Alcohol (PVA) /Graphene Oxide (GO) composite were prepared by using a homemade electrospinning set-up at 12.5 kV and 12 cm with different concentrations of GO (1g/L, 0.75g/L, and 0.5g/L) in PVA. The effect of GO concentrations in 10% PVA solution on the diameter of fibers was investigated. Fourier Transform Infrared (FTIR) Spectroscopy was used to analyze the functional groups. Ultraviolet (UV)-visible spectra of GO suspension showed the absorption peak at 232 nm. The morphology of the nanofibers was analyzed by Scanning Electron Microscopy (SEM). The X-ray diffraction (XRD) technique was used to analyze the crystalline nature of this material. The diameter of nanofibers decreased with improved crystallinity, thus, increasing the concentration of GO in PVA.

Abstract: This work is focused on the preparation and characterization of poly (vinyl alcohol)/silica gel/Nano-TiO₂, and the study of titanium dioxide (TiO₂) nanoparticles (from 1 to 5%) on the properties of poly (vinyl alcohol) (PVA)/silica films. This new material was prepared by the sol-gel method using poly (vinyl alcohol) powder with Tetraethyl Orthosilicate (TEOS) as a precursor source of silica. TEOS was hydrolyzed and condensed in water and ethanol in the presence of hydrochloric acid (HCl) used as a catalyst. Fourier transform infrared (FT-IR), water absorption, water contact angle, ultraviolet-visible spectrometry (UV-VIS), and thermogravimetric analysis (TGA) were used to characterize the hybrid films obtained. The PVA/SiO₂/Nano-TiO₂ films were successfully synthesized. Owing to the FT-IR Analysis, the chemical bonds have clearly shown that the PVA backbone is linked to the (SiO₂-TiO₂) network. UV-VIS tests indicated that the hybrid films' UV shielding properties were drastically enhanced as a result of the addition of TiO₂. According to the TGA tests, the hybrid films are more heat tolerant than neat PVA films. The water contact angle results revealed that TiO₂ nanoparticles used as a doping compound possess an important influence on the hydrophilicity of PVA/SiO₂ as thin films. The film's water resistance has also been enhanced.

Abstract: Poly (ethylene terephthalate) (PET), also commonly called as polyester, is the most widely used polymer for the production of synthetic fibres over the past fifty years. The frequent use of this PET is due to its high mechanical strength combined with other properties such as the resistance to chemical products, stretching and abrasion. The fibre’s hydrophobicity also impacts the difficulty of cleaning these materials [1, 2]. Previous works shows that treatment with concentrated NaOH solutions can greatly improve hydrophilicity of PET fibre [1, 2, 3, 4]. However a significant decrease of mechanical properties takes place during this process. In this work, chemical strategies to counteract this negative effect and further increase the hydrophilicity of PET fibre’s has been tested. In particular, the effect of polyvinyl alcohol (PVA) and N, N ́-dimethylol-4, 5-dihydroxyethyleneurea (DMDHEU) chemically modified resin in the functionalization of saponified PET was carefully analysed. The treated fabrics were characterized by scanning electron microscopy (SEM), contact angle, ATR-FTIR spectroscopy and differential scanning calorimetry (DSC). When the best process conditions were considered for PVA-DMDHEU application, the modified PET presented a contact angle of 33.9o, stain release grade of 4 and a 45.6% increase in its mechanical properties when compared to saponified PET.

Abstract: The search for new materials that serve as dressings and promote the proper means for wound healing, without yielding toxic waste to the wound bed and at low cost, is currently the subject of research. In this sense, the present study aimed to develop a prototype of a poly(vinyl alcohol) (PVA) polymeric film, sodium carboxymethylcellulose (NaCMC). PVA and NaCMC as miscible polymer blend films for wound dressings was developed using internal mixing chamber processing in a mix torque rheometer (MTR) without the use of binders or crosslinks in different mixing conditions that were investigated by thermal characteristics (differential scanning calorimetry (DSC)) and thermogravimetric analysis (TGA) and crystallinity (X-ray Diffraction Technique (XRD)). The films obtained by pouring from this starting material were characterized by DSC, TGA, Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), optical microscopy and swelling assay. All stages of development of this prototype are discussed, from the quality control of the raw materials, through the development of the preparation technique of the blends in 14 different processing conditions. The processed PVA/NaCMC film showed physical crosslinking which may have promoted its ability to resist dissolution in water (unprocessed PVA/NaCMC films’ characteristic). The results demonstrated that the processing of the PVA and NaCMC polymers in the MTR constitutes a viable technique to obtain membranes for use as dressings.

Abstract: Response surface methodology (RSM) was used to determine the optimal blend of alginate (ALG), poly (vinyl alcohol) (PVA) and graphene oxide (GO), as well as glutaraldehyde (GA) crosslinking solution concentration for the synthesis of dual-crosslinked ALG/PVA/GO nanocomposite hydrogel adsorbent beads for methylene blue (MB) removal. Statistical analyses show that PVA concentration contributes the largest effect to the adsorption capacity response, attributed to improved accessibility of MB molecules to adsorption sites. The optimal blend was determined to be 3% polymer with 50% PVA, 383.8384 ppm GO, crosslinked in 1% CaCl₂ and 5% GA. These results were validated, and the experimental value of the adsorption capacity deviated by only 1.702% from the RSM model prediction, suggesting good model predictability. Adsorption isotherm models were tested to provide a description of the adsorption process. The Sips isotherm model, suggesting monolayer adsorption over heterogeneous surface with action of cooperative adsorbate-adsorbate interactions, was the best fit to the experimental equilibrium data, with an R² of 0.9782. Furthermore, the ALG/PVA/GO beads demonstrated a maximum monolayer adsorption capacity of 1081.62 mg/g, showing superior performance compared to known biosorbents of MB.

Abstract: Bacterial cellulose (BC) was synthesized using Gluconacetobacter xylinus (BCRC 14182). Synthesized BC was powdered and dissolved in Bis(ethylenediamine) copper (II) hydroxide (Cuen) solution to introduce the amine (NH₂) group onto the BC network to yield modified BC (mBC) which was then blended with poly (vinyl alcohol) (PVA) and subsequently crosslinked with genipin (Gp). Pristine, modified and crosslinked hydrogels were studied using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and swelling behavior in water. FTIR revealed a distortion on the BC network chain via a reduction in the absorption of OH peak of mBC and the emergence of peaks at 1587 and 1560 cm^-1 attributed to N-H stretching of the induced NH₂ group. SEM confirmed the 3-D fibril and porous structure of BC which became distorted after modification and crosslinking. The hydrogels showed equilibrium water content of 86.5%, 67.5%, 66.7% and 33.0 % for BC, PVA, mBC-PVA and mBC-PVA-Gp, respectively. The decreased swelling in mBC-PVA-Gp indicated that genipin was able to crosslink the modified BC.

Abstract: Interest in the nanotechnology invention has been increased among the researcher and industries which lead to many investigations and studies to develop a product with better performance. In this research, hydroxypropyl methylcellulose (HPMC) and poly (vinyl) alcohol (PVA) nanofiber with the ratio 1:1 and the concentration of 5 wt% and 7 wt%, respectively, were successfully fabricated by using electrospinning technique. The HPMC/ PVA was then blended with the different concentration of cellulose nanocrystal (CNC) at 2 wt%, 4 wt%, 6 wt% and 8 wt%. The SEM results of HPMC/PVA/CNC nanofibers shown random orientation fibers with average diameters of 62.28 nm - 252.80 nm. The TGA results showed three major weight loss that prove the decomposotion of HPMC/PVA/CNC was occured with three maximum temperature peaks around 69 °C, 290 °C and 392 °C. As for DSC, the peak intensity of the T_g in the electrospun nanofiber are decreasing as the concentration of CNCs increased might be due to the interfering of the CNC with the crystallization of the polymer causing mobility of the amorphous regions to be higher. Therefore, the study on the thermal properties of HPMC/PVA incorporated with CNCs nanofibers could be a reference for various potential applications.

Abstract: In this study, biodegradable scaffolds based on hydroxyethyl cellulose (HEC) (5 wt%) and poly (vinyl alcohol) (PVA) (15 wt%) with different percentages of celullose nanocrystal (CNC) (1 and 7 wt%) were fabricated by lyophilization method to get highly porous scaffolds. These scaffolds were made water insoluble by cross-linking via heat treatment. The morphology and thermal properties of HEC/PVA/CNCs scaffolds were characterized by using Scanning Electron Microscope (SEM) and Thermogravimetric Analysis (TGA). The morphological study showed that both prepared scaffold have highly porous structures with good pore interconnected structure. It was observed that thermal properties of scaffolds increased significantly as the concentration of CNCs increased. Cytotoxicity studies on scaffolds were carried out by utilizing human fetal osteoblast (hFOB) cells using DAPI nuclear stain and then confirmed using SEM. hFOB cells were able to attach and spread on all scaffolds. Incorporated CNCs as reinforcing nanofiller on scaffolds promising a superior functionality in bone tissue engineering.