Advanced Materials Research Vol. 410

Abstract: In this work, the effect of heat treatment on chemical and crystalline structure of vetiver powder was studied. The vetiver powder was heat treated at 170°C, the temperature below thermal decomposition of hemicellulose, for 2-6 hours. The chemical structure, crystalline structure, and thermal decomposition of untreated and heat-treated vetiver were examined via FTIR spectrometer X-ray diffractometer, and thermogravimetric analyzer, respectively. In addition, the particle size and size distribution, fiber surface, and specific surface area were investigated by particle size analyzer, scanning electron microscope, and BET surface analyzer, repectively. It was founded that some waxes, lignin, and hemicellulose were removed by the thermal treatment. This resulted in smaller particle size of heat-treated vetivers. In addition, moisture content was minimized from 7 to 4 wt% by the treatment. However, removal of those compositions did not influence crystal structure of cellulose and surface functional groups of heat-treated vetiver.

Abstract: The anti-fungal and anti-algal growth performances of wood poly (vinyl chloride) composite (WPVC) and poly (vinyl chloride) (PVC) containing either fungicides or algaecides at various concentrations were quantitatively evaluated using biological standard tests. The commercial fungicides, namely Carbendazim and IPBC in range of 10,000-50,000 ppm, and algaecides, namely Terbutryn and Isoproturon in range of 250-1,500 ppm, were incorporated into PVC and PVC composites with a fixed wood flour content of 100 pph. Disk diffusion test and dry weight technique, using Aspergillus niger as testing fungi, were used for anti-fungal evaluation while inhibition zone test using Chlorella vulgaris as testing algae, were utilized for anti-algal evaluation. The results suggested that IPBC exhibited better anti-fungal efficiency than Carbendazim for both PVC and WPVC composites, especially at the suggested IPBC concentrations of 30,000 ppm or higher. Terbutryn showed better anti-algal efficiency than Isoproturon. The recommended loadings of Terbutryn for complete algae killing were 1,000 and 500 ppm for neat PVC and WPVC composites, respectively. The wood particles added in PVC were found to improve the anti-fungal and anti-algal properties in PVC composites, which could be regarded as “anti-microbial promoter” under the commercial biocides used in this work.

Abstract: Our previous study has illustrated that chitosan could enhance human anterior cruciate ligament cells to exhibit a dramatic effect on increasing the gene expression of transforming growth factor β1, which is a specific gene for wound healing and collagen synthesis. However, most of cells could not adhere and proliferate well on chitosan. In order to overcome this drawback, we introduced polycaprolactone (PCL) into chitosan by the method of blending in this study. It was found that the morphology, viability and gene expression of specific cells on the chitosan/PCL blended materials could be effectively regulated. Therefore, it is possible to combine the advantages of chitosan and PCL to create a new blended material, which could control cellular morphologies specifically, and further to regulate the gene expression and protein production of cells for specific applications.

Abstract: In this work, rice husk silica (RHS), obtained from rice husk waste, was used as a reinforcing filler for preparing PBAT composites. In order to facilitate interfacial adhesion between PBAT matrix and RHS filler, the RHS surface was treated with acrylic acid (AA) at a reaction temperature of 140°C. The RHS to AA weight ratio was fixed while the reaction times were varied between 3-24 h. TGA results and FTIR spectra indicated the appearance of AA molecules on RHS surface. Untreated RHS (U-RHS) and AA treated RHS (AA-RHS) were used to produce PBAT composites. The filler content was 30 wt%. Tensile properties and impact strength of AA-RHS/PBAT composites were higher than those of U-RHS/PBAT composite. As revealed by SEM micrographs, AA-RHS was well dispersed in PBAT matrix and the interfacial adhesion between RHS surface and PBAT matrix was improved.

Abstract: In this study, PLA/sericin films at various contents of sericin were prepared. Thermal properties, in vitro degradability and in vitro cytotoxicity of the films were characterized. The results illustrated that the incorporation of sericin into PLA matrix crucially affected thermal properties and biodegradability of the films and also enhanced human fibroblast cells attachment and proliferation on the film surface.

Abstract: In this study, rice husk fiber (RHF) was used as a reinforcing filler for natural rubber (NR). NR composites were prepared at various RHF contents, i.e., 10, 20, 30, 40 and 50 phr. Sulfur conventional vulcanization was used. Effect of RHF content on cure characteristics, mechanical properties and morphological properties of NR composites were investigated. The results showed that scorch and cure times of RHF/NR composites were not affected by increasing RHF content. Crosslink density, tensile strength, elongation at break and tear strength of NR composites slightly decreased with increasing RHF content whereas M100 and M300 of the composites slightly increased with increasing RHF content.

Abstract: The phenomena of molecular self-assembly have inspired interesting development of novel functional materials. We have been focusing on developing novel polymers with the ability to self-assemble into novel supramolecular structures, which can function as biomaterials for potential drug/gene delivery and tissue engineering applications. The key components in our macromolecular self-assembling structures include the biodegradable and biocompatible microbial biopolyesters, poly (β-hydroxyalkanoates), and the macrocyclic polysaccharides, cyclodextrins. A series of novel block copolymers and interlocked supramolecular architectures were designed and synthesized. They were characterized in terms of their molecular and supramolecular structures, as well as their properties and functions as biomaterials for potential drug and gene delivery, and tissue engineering applications. Amphiphilic block copolymers of different chain architectures composed of poly [(R)-3-hydroxybutyrate] as hydrophobic segments, and poly (ethylene glycol), poly (propylene glycol), or poly (N-isopropylacrylamide) as hydrophilic segments were synthesized. They could self-assemble to form stable micelles, nanopatterning thin films, and thermo-sensitive hydrogels, which were demonstrated to be promising potential biomaterials for controlled and sustained delivery of drugs and tissue engineering scaffolding materials. The self-assembly of block copolymers with cyclodextrins resulted in supramolecular hydrogels and cationic supramolecules, which were used as injectable drug delivery systems, and novel polymeric gene delivery vectors.

Abstract: Electrospinning is a popular technique for constructing nanofibrous tissue engineering scaffolds. Electrospinning is also amenable to the incorporation of drugs or biomolecules in fibers, which can provide local and sustained delivery of biological signals, such as growth factors, for the seeded cells. Drugs can normally be dissolved in polymer solutions for electrospinning, forming nanofibrous drug delivery systems. However, simply blending biomolecules in polymer solutions can result in denaturation of biomolecules and large initial burst release. Therefore, emulsion electrospinning, which can provide protection for biomolecules during electrospinning, is of great interest. In this investigation, biomolecule-containing scaffolds were emulsion electrospun using bovine serum albumin (BSA) as the model protein. Two polymers, poly (lactic-co-glycolic acid) and poly (D,L-lactic acid), were used due to their different degradation characteristics. Nanofibers with core-shell structures were electrospun from water-in-oil emulsions formulated by polymer solution, BSA-containing deionized water and a surfactant. By changing the polymer concentration and water phase volume, the fiber diameter and core-shell structure were varied. With different polymers and different fiber structures, the in vitro BSA release behaviours from fibrous scaffolds were different.

Abstract: Natural fiber based bio-composites are gaining prime importance these days because of their high strength to weight ratio and environmental benefits. An increase in the application spectrum of these materials necessitates cost effective high quality processing in order to meet the stringent design requirements. In the present investigation, fully biodegradable natural fiber (grewia optiva) reinforced poly lactic acid (PLA) composite has been developed. The tensile strength of the composite has been found to increase by 75% of that of the neat polymer. The developed composites have been joined using the adhesive bonding and the microwave joining. The tensile shear strength of the joint has been experimentally evaluated and it has been found that the bond strength of adhesively bonded specimen (4.9% of the parent material strength) is substantially lower as compared to microwave joined specimen (62.85% of the parent material strength). The process of microwave joining has also been simulated using standard Multiphysics software and the results were in close agreement with the experimentally recorded values.

Abstract: Silk fibre has been popularly used for bio-medical engineering and surgically-operational applications because of its biocompatible and bio-resorbable properties for centuries. Using silk fibre as reinforcement for some bio-polymers to enhance the stiffness of scaffolding and bone implant plates has been developed. However, its dynamic mechanical properties with the biodegradable properties have not yet well understood. In this paper, the dynamic mechanical and thermal properties of degraded and non-degraded silk fibre reinforced Polylactic acid (PLA) composites are discussed.