Supranee Kaewpirom

Preparation and properties of pineapple leaf fiber reinforced poly(lactic acid) green composites

Green composites from Pattawia pineapple leaf fiber (PALF) and poly(lactic acid) (PLA) were prepared. The mechanical method was chosen to extract PALF from fresh leaves due to this method gave high yield of fiber, short extraction time, and environmental friendly. Tensile and thermal properties, together with morphology of the fibers were disclosed. The fibers were conducted into a specified length of 1–3 mm and blended with PLA, using a twin screw extruder, with the PALF content of 10–50 wt%. Tensile testing, morphology investigation and thermogravimetric analysis were applied. Preliminary results showed that tensile modulus of the composites depended on PALF content. The tensile modulus and elongation at break of the composite containing 40 % PALF was about 48 %, and 111 % increase, respectively, compared with that of PLA. With addition of maleic anhydride coupling agent, such the composite showed the tensile modulus of 5.1 GPa, which was 34 % higher than that of the non-coupling agent composite, and about 104 % higher than that of PLA. Although the elongation at break of the composite containing 40 % PALF was found to dramatically increase by 111 %, the introduction of maleic anhydride in such the composite caused only 57 % increase in the elongation at break compared with that of PLA. Finally, a pilot product of square boxes was produced successfully from the proposed composite, by conventional injection molding process.

A numerical model for ultrasonic measurements of swelling and mechanical properties of a swollen PVA hydrogel

This paper presents a numerical model for the evaluation of mechanical properties of a relatively thin hydrogel. The model utilizes a system identification method to evaluate the acoustical parameters from ultrasonic measurement data. The model involves the calculation of the forward model based on an ultrasonic wave propagation incorporating diffraction effect. Ultrasonic measurements of a hydrogel are also performed in a reflection mode. A Nonlinear Least Square (NLS) algorithm is employed to minimize difference between the results from the model and the experimental data. The acoustical parameters associated with the model are effectively modified to achieve the minimum error. As a result, the parameters of PVA hydrogels namely thickness, density, an ultrasonic attenuation coefficient and dispersion velocity are effectively determined. In order to validate the model, the conventional density measurements of hydrogels were also performed.

Effect of Poly(vinyl alcohol)/Chitosan Ratio on Electrospun-Nanofiber Morphologies

Series of poly (vinyl alcohol)/chitosan (PVA/CS) electrospun nanofibers with different weight ratio of PVA and CS were fabricated by electrospinning method. The surface morphology, diameter, and structure of electrospun nanofibers were investigated by scanning electron microscopy (SEM). As a result of PVA and CS composition measurements, the electrospun nanofibers morphologies were mainly affected by weight ratio of the polymer solution. When increasing the chitosan content in the blend solution, the electrospun nanofibers could hardly form. This result indicates that the electrospun nanofiber formation is enhanced by chitosan content.

Effect of ZnO Concentration on the Diameter of Electrospun Fibers from Poly(Vinyl Alcohol) Composited with ZnO Nanoparticles

Recently, the composited nanofiber attraction has been growing from researchers across the world due to its exciting opportunities for use in biomedical applications. In this study, we fabricated electrospun fibers from poly (vinyl alcohol) (PVA) composited with Zinc Oxide (ZnO) nanoparticle for potential use in biomedical applications. From the experimental results, there was not any chemical bonding between the ZnO nanoparticles and the PVA molecules. The effect of concentration of ZnO nanoparticles in PVA solution on the diameter of electrospun fibers was found that the diameter of electrospun fibers increased with raising the concentration of suspended ZnO nanoparticles in solution. This is probably because the effect of nanoparticles on the diameter of electrospun fibers was through their effect on the viscosity of solution. In addition, we found that the diameter of electrospun fibers depended on the solution and processing parameters.

Highly-transparent multi-layered spin-coated silk fibroin film

In this study, the silk fibroin films with different numbers of layers were fabricated by the spin-coating method and their optical transmittances were observed. The process to synthesise the silk fibroin solution was explained – starting from the silk cocoon until the silk-fibroin solution, approximately 7.5% concentration wt/vol, was obtained. The solution was spin-coated onto clean glass substrates to fabricate samples. Totally 10 samples with different numbers of layers, from 1 to 5 layers, were obtained. All samples can be separated into two groups: those left dried at room temperature after spin-coating and those heated at 60°C. They were then measured for their transmittance over the visible-to-near-infrared region. All samples exhibited the high transmittance where the values were at 95% and 98%, for the samples at room temperature and those at 60°C, respectively. This was believed to be due to the heating effect that caused the silk fibroin to arrange itself after being heated, hence the higher transmittance. These high transmittances were maintained regardless of the number of layers and length of heating time. Results from this study could be used to fabricate a silk fibroin film with high optical transmittance and adjustable other properties.

A system identification model for ultrasonic characterization of a swollen PVA hydrogel

In this paper, the development of an ultrasonic characterization method for Poly-Vinyl Alcohol (PVA) hydrogel incorporating diffraction effects is purposed. The Lommel integral, diffraction correction procedure, is applied to the model. Nonlinear least square algorithm, iterative computation in forward model, is employed to minimize the error of the predicted parameters efficiently. To validate the model, the ultrasonic signal is measured in the reflection mode experiment. The system consists of PVA hydrogel as a testing sample immersed in water tank and 10 MHz unfocused piston transducer. Before the transducer is utilized to generate the ultrasonic beam, the alignment between sample and transducer must proceed to get the maximum spectrum of the ultrasonic incident beam. The properties of PVA hydrogel in the experimental results are shown in density, dispersion and thickness in micron scale. Finally, the purposed model has potential to estimate other parameters such as the scatterer size in future work.