Papers by Keyword: Poly(Vinyl Alcohol) (PVA)

Abstract: In this paper, a series of polyvinyl alcohol (PVA) aerogels hybrid with cellulose nanocrystal (CNC) was successfully prepared using freeze-drying process. The influence of different fractions of CNC and crosslinking agent; glutaraldehyde (GA) on the mechanical of PVA/CNC hybrid aerogels property was evaluated by means of compressive strength. Results show that the mechanical property of hybrid aerogels has been improved with the addition of CNC and GA. Variation in the CNC and GA content also led to differences in the porous structure morphologies. Nevertheless, higher content of GA caused adverse effect to the strength of hybrid aerogel which associated to the excessive crosslinking and smaller number of pores formation as evident from scanning electron microscopy (SEM) analysis.

Abstract: This study aimed to evaluate the optimal conditions for crosslinked of PAMA/PVA microneedle (MN) arrays. Poly (acrylic acid-co-maleic acid) (PAMA)/poly (vinyl alcohol) (PVA) MN arrays were fabricated for the first time using the micromolding technique. The PAMA/PVA MN arrays at the polymer ratio of 1:4 were sharp, homogenous and perfectly formed with an elegant appearance. The successfully crosslinking MN arrays were determined using FTIR and water insolubilization. The results showed that increasing the crosslinking temperature and time, the degree of crosslinking also improved, which results in a decline in water uptake. The optimal crosslinking condition for PAMA/PVA MN arrays was 130°C for 1 h. Moreover, the highest swelling was observed from crosslinked PAMA/PVA MN arrays at 90°C for 0.5 h. These studies suggest that the combination of PAMA and PVA for fabrication of MN arrays could have a great potential to develop both hydrogel and dissolving MN devices for transdermal drug delivery.

Abstract: The objective of this study was to optimize fabrication variables that affected desirable properties of dressings. Boesenbergia rotunda extract incorporated PVA hydrogels for wound dressings were fabricated by freeze-thaw method. The fabrication variables including PVA concentration (15, 17.5 and 20 % w/w), freeze-thaw cycle (2, 3 and 4 cycles) and extract loading (30, 40 and 50 % w/w) were studied and optimized. Effects of variables on the hydrogel wound dressing properties were determined by using Box-Behnken design and response surface method. Hydrogel properties such as tensile strength, elongation at break, Young’s Modulus, water content, swelling and erosion were measured and used as the designed responses. From statistical data analysis (p <0.05), the polynomial quadratic equation which indicated the significant effects of fabrication variables on the hydrogel properties was generated. In conclusion, desirable B. rotunda extract loaded PVA hydrogel dressing was favorably designed. The optimized PVA concentration, freeze-thaw cycle and extract loading were 17.07 % w/w, 3.86 cycles and 50 % w/w, respectively.

Abstract: Nanofibers have been widely used for tissue engineering. Using charged polymers for the preparation of nanofibers can be useful for the loading of substances or macromolecules. Dual charge nanofiber mats are expected to be able to immobilize both positively charged and negatively charged substances in one versatile nanofiber mat. The purpose of this study was to prepare and characterize dual-charge nanofibers generated from poly (vinyl alcohol) (PVA)/poly-(acrylic acid-co-maleic acid) (PAMA) and chitosan (CS)/PVA. The polymer solutions of PAMA/PVA (1:1.63 w/w) and CS/PVA (1:2.33 w/w) were electrospun to form the nanofibers using dual-jet electrospinning process. The obtained dual-charge nanofibers were thermally crosslinked by leaving the nanofibers in the oven at 110-130 °C for 0.5, 1, 3, 5 h. The appearance of the nanofiber mat was characterized by a scanning electron microscope (SEM), and the diameter of nanofibers were determined by an image analysis software (J-micro vision^®). The percentage water insolubilization and FT-IR spectra were also determined. The dual-size nanofiber mats with smooth and bead-free fibers were obtained. The diameter of the PAMA/PVA and CS/PVA fibers was 574.54 ± 142.98 nm and 225.69 ± 41.92 nm, respectively. The desirable temperature and time for the crosslink of the dual-charge nanofiber mats was 130 °C for 1 h which could provide a high insolubilization with water capacity of 93.22 ± 2.23%.

Abstract: Organic polymer composites are relatively simple to process and are therefore used in thermoelectric materials. The organic polymers are used as an adhesive agent between thermoelectric material grains. Thermoelectric effects of poly (vinyl alcohol) (PVA) composited with sodium cobalt oxide (Na_xCoO₂) were studied in this work. PVA is a low cost and an excellent biocompatibility polymer. High electrical conductivity, high Seebeck coefficient and low thermal conductivity are required in thermoelectric materials. As PVA is an insulating material, the PVA in between Na_xCoO₂ grain boundaries has an effect on the low electrical conductivity of Na_xCoO₂ composite. This results in a decrease in thermoelectric efficiency. However, PVA has been utilized to increase the Seebeck coefficient and also enhance thermoelectric efficiency. In order to improve the electrical conductivity of Na_xCoO₂ composite, PVA removal was produced by furnace heating at 500̊ C to eliminate PVA from Na_xCoO₂/PVA sample. The general thermoelectric parameters including the Seebeck coefficient, electrical conductivity and power factor of Na_xCoO₂/PVA and PVA removal sample were compared. X-ray diffraction patterns (XRD) and scanning electron microscope (SEM) images were used to identify the phase identification and morphology study, respectively. The results showed that the PVA removal sample had higher electrical conductivity than the Na_xCoO₂/PVA sample. However, Na_xCoO₂/PVA sample had higher thermoelectric performance than the PVA removal sample because the Na_xCoO₂/PVA sample showed higher Seebeck coefficient and power factor.

Abstract: This work focused on the preparation of poly (vinyl alcohol) (PVA)/ layered double hydroxide (LDH) and LDHSA nanocomposites by casting method. The morphology and interlayer spacing of the composites were characterized. The mechanical properties and the photochemical stability of the film of PVA, PVA/LDH and PVA/LDHSA have been studied and compared with PVA/MMT nanocomposites reported in previously. The results indicated that the thermal stability and dynamic mechanical properties of the PVA matrix in the PVA/LDH films and PVA/MMT films was enhanced. PVA/LDH films and PVA/OMMT films were shown stable photochemically more than those of pure PVA.