Advanced Materials Research Vols. 123-125

Abstract: Polyurethane (PU)/starch biocomposites have been prepared with different weight fractions of starch (viz., from 0 to 40 wt %). The fabricated PU/starch composites were characterized by mechanical properties and thermal (DSC and TGA) behaviors. Microcrystalline parameters were calculated using X-ray profile. Water uptake and its effect on mechanical properties have been evaluated.

Abstract: Ce1-xFexO2 (x=0, 0.01, 0.03 and 0.0 5) thin films were grown by pulsed laser deposition technique on Si and LaAlO3 (LAO) substrates. These films were deposited in vacuum and 200 mTorr oxygen partial pressure for both the substrates. These films were characterized by x-ray diffraction XRD and Raman spectroscopy measurements. XRD results reveal that these films are single phase. Raman results show F2g mode at ~466 cm-1 and defect peak at 489 cm-1 for film that deposited on LAO substrates, full width at half maximum (FWHM) is increasing with Fe doping for films deposited on both the substrates.

Abstract: Chitosan nanoparticles (CS NPs) was prepared by mixed with TPP for drug release carrier in this study. Generally, Chitosan is a good and non-toxic biodegradable polysaccharide polymer with low immunogenicity. Tripolyphosphate (TPP) is a polyanion, and can interact with cationic chitosan by electrostatic forces. So Chitosan/TPP nanocomposites were synthesized Berberine, a naturally occurring isoquinoline alkaloid, was shown to have anti-inflammatory and anti-tumour properties in vitro systems. And we have used the transmission electron micro-graphs (TEM) and Dynamic light scattering (DLS) to gain the CS nanoparticles’ size. The action of tripolyphosphoric groups of TPP crosslinked with ammonium groups on chitosan in the nanoparticles and it was identified by FTIR. We also obtained the poison property of berberine mantled by CS NPs to human breast cancer cell.

Abstract: Cellulose, the most widespread biopolymer, is known to occur in a wide variety of living species from the worlds of plants and microbial sources like bacteria. Bacterial cellulose produced by Gluconacetobacter xylinus in the form of long fibers can be acid hydrolyzed under controlled conditions to obtain nanocrystals. Such nanocrystals constitute a generic class of ‘green’ nanomaterial and have attained great importance in the field of polymer nanocomposites attributed to their superior properties. However, conventional sulfuric acid hydrolysis route provides cellulose nanocrystals with inferior mechanical and thermal properties. In this study, a hydrochloric acid (HCl) assisted top down approach has been adopted to synthesize bacterial cellulose nanocrystals, which is found to retain some of the natural properties of native cellulose even in nano-dimensions. The morphological parameters were analyzed using atomic force microscopy which confirmed the formation of nanocrystals. Using these novel nanocrystals, poly vinyl alcohol (PVA) nanocomposite films were prepared and characterized for elucidating their properties. The addition of nanocrystals has significantly improved the thermal stability and mechanical properties of PVA nanocomposites. Results of this study demonstrated that nanocrystals obtained by HCl have several advantages in the fabrication of high performance polymer nanocomposite films for food packaging applications.

Abstract: Methacrylic acid (MAA) was grafted onto sodium alginate (SA) by thermal heating at ambient temperature (70±2OC) using potassium persulphate as an initiator (PPS). SA-g-MAA and pure sodium alginate beads were prepared and were characterized using Scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X-ray diffraction techniques (X-Rd). The resultant products (SA-g-MAA) were used to prepare Glutaraldehyde (GA) crosslinked beads of various formulations by varying, monomer, cross-linker (GA) and drug content (CFHCl) in the graft co-polymer. Preparation conditions of the beads were optimized by considering the percentage entrapment efficiency, swelling capacity and release profiles. Release profile of CFHCl was discussed at 370C in a gastrointestinal atmosphere (pH -7.4 and acidic medium pH-1.2). It was observed that, CFHCl release from the beads increased with increasing MAA content over the entire studied range. As GA and CFHCl content increases, swelling ratio decreases resulting in decrease in the drug release rate. The highest CFHCl release was obtained to be 99% for the beads containing 40% monomer, 0.5mL GA and 10% CFHCl at pH-7.4. It was also observed that the release profiles have effect on pH and hence the graft co-polymeric beads can be used as pH sensitive drug devices.

Abstract: Composites of silk fibre reinforced chain extended polyurethane (CEPU) was synthesized by the reaction of castor oil with different diisocyanates and glutaric acid as chain extender. The effect of incorporation of silk fibre into neat CEPU on the physico- mechanical properties and thermal behaviours (TGA and DMA) has been investigated. The incorporation of silk fibre into CEPUs resulted in an enhancement of tensile strength and Tg. The effects of biological fluids and salt solution on swelling behavior of CEPU biocomposites were reported. Key words: Castor oil, silk fibre, composites, polyurethane, DMA, TGA.

Abstract: Functional scaffolds fabricated from biopolymers are of great importance for tissue engineering. In this paper, by mimicking the combination of two major components in Extracellular Matrix – collagen and polysaccharide respectively, we fabricated gelatin and chitosan hybrid sponge for cartilage tissue engineering. Extending previous results of gelatin/chitosan film showed that all the hybrid coating film (chitosan: gelatin= 4:1; 1:1; 1:4) can support the adhesion of ATDC5 that comparable to Tissue Culture Dish (TCD). More importantly, stem cell line ATDC5 on coating dish of chitosan: gelatin=1:4 showed enhanced differentiation rate than that on other films and TCD. For three dimensional scaffolds, we fabricated hybrid sponge scaffold of chitosan: gelatin=4:1, 2:1, 1:1, 1:2, 1:4 respectively. Morphological characterizations of the sponges showed that this kind of gelatin/chitosan hybrid scaffold is promising for application in cartilage tissue engineering.

Abstract: Lead-free piezoelectric (Bi1/2Na1/2)TiO3 (BNT) films were deposited on 1 mm thick pure titanium(Ti) substrates by a hydrothermal method. Tensile tests were performed to quantitatively assess the adhesion strength between BNT films and Ti substrates. Ti substrates were pretreated by chemical polish and mechanical polish respectively prior to BNT film deposition. In the tensile test, the behavior of BNT film exfoliation was investigated by the replica method. The critical Ti substrate strain inducing BNT film exfoliation was determined by the aid of finite element analysis (FEM). In this study, the results revealed that BNT film exfoliations were caused by the strain of Ti substrate, and the mechanical polish pretreatment improved the adhesion of BNT film to Ti substrate.

Abstract: Advanced atomic force microscopy techniques such as contact resonance force microscopy, noncontact mode phase imaging, and scanning thermal microscopy techniques have been used to characterize material properties in the interphase of fiber reinforced polymer composites. With contact resonance force microscopy, the average interphase thickness was found to be (49 ± 5) nm, (64 ± 12) nm, and (139 ± 21) nm for samples containing lyocell fibers in matrix materials consisting of 100 % polypropylene (PP)/0 % maleated polypropylene (MAPP), 95 % PP/5 % MAPP, and 90 % PP/10 % MAPP, respectively. Clear distinctions in modulus values between the fiber, interphase zone, and matrix are clearly visible in modulus images. A gradient of modulus was observed across the interphase region that ranged between the modulus values of fiber and the polymer matrix. Noncontact mode images showed a clear phase difference between the fiber, interphase, and matrix owing to the difference in material properties between the components. Interphase regions were observed to possess higher thermal conductivity than the matrix polymer due to cross-linking within the interphase.

Abstract: The surfaces of concrete airfield aprons and runways deteriorate for a number of reasons, such as surface scaling due to freeze/thaw, impact loading, hot weather, de-icing fluids, deterioration of joints, jet fuel chemicals and so on. A limited field and laboratory study was performed to investigate the constructability and performance of prospective materials for repair of airfield concrete damaged by exposure to heat and oil. Two prospective coating materials and six prospective inlay materials were field-testes at the Base in USA Kansas, and were evaluated in the laboratory at the University of Florida before and after the field installation. The results of the study indicate that it is feasible to repair these damaged concrete surfaces by placing a suitable inlay material with a minimum depth of 2 inches. Among the prospective inlay materials investigated, two promising materials for this application are a magnesium phosphate concrete (Set-45) and a calcium aluminate concrete (Fondag). Both two concretes set very quickly, and make high early-strength, impermeable patches that bond to clean and dry surfaces. Guidelines for the placement of inlay materials for this purpose are proposed based on the experience from this study.