Manunya Okhawilai

Preparation of Thai silk fibroin/gelatin electrospun fiber mats for controlled release applications

This work studied the effect of preparation conditions for electrospun fiber mats of Thai silk fibroin/type B gelatin (SF/GB) for controlled release applications. The increasing in applied voltage resulted in decreased average fiber size and narrow fiber size distribution. An increasing in silk fibroin content in blended solution resulted in larger size of the obtained electrospun fibers. Smooth fibers could be produced from SF/GB blended solution at weight blending ratios of 10/90, 20/80, 30/70, 40/60 and 50/50. The results on in vitro biodegradation test showed that SF/GB 10/90 electrospun fiber mat was rapidly degraded in collagenase solution due to direct biodegradation of gelatin by collagenase. From in vitro controlled release of two active agents (azo-casein and methylene blue) from SF/GB blended fiber mats, it was suggested that methylene blue could be adsorbed on the blended fiber mats, possibly due to attractive interaction of the positively charged molecules of methylene blue and negatively charged SF/GB fiber mats. In contrast, the same charge of blended fiber mats and azo-casein would result in the repulsive force, resulting in continuous diffusion of azo-casein from blended fiber mats within 72 h. The results indicated that SF/GB electrospun fiber mats had a high potential to be applied in controlled release applications.

Effects of Graphene and Graphite on Properties of Highly Filled Polybenzoxazine Bipolar Plate for Proton Exchange Membrane Fuel Cell: A Comparative Study

Highly filled graphite and graphene polybenzoxazine (PBA) composites as bipolar plate materials for polymer electrolyte membrane fuel cell (PEMFC) are developed in this work. For graphite-filled PBA, the maximum graphite loading in the PBA composite was observed to be as high as 80 wt% which is significantly higher than that of graphene-filled PBA, i.e., 65 wt%. Mechanical properties, i.e., flexural modulus and flexural strength of both types of composites at their maximum contents, were much greater than the requirements of Department of Energy targets for bipolar plate materials. Electrical conductivity of the highly filled PBA composites was 255 S/cm for graphite composite and 357 S/cm for graphene composite. Furthermore, the graphite-filled PBA composite provides a thermal conductivity value up to 10.2 W/mK. Interestingly, thermal conductivity value of the PBA composite having 75.5 wt% of graphite in combination with 7.5 wt% of graphene loadings was found to be as high as 14.5 W/mK. The obtained properties of the graphite- and graphene-filled PBA composites exhibit various characteristics suitable for PEMFC applications.