Mechanical Properties of Natural Chitosan/Hydroxyapatite/Magnetite Nanocomposites for Tissue Engineering Applications

Chitosan (CS), hydroxyapatite (HA), and magnetite (Fe3O4) have been broadly employed for bone treatment applications. Having a hybrid biomaterial composed of the aforementioned constituents not only accumulates the useful characteristics of each component, but also provides outstanding composite properties. In the present research, mechanical properties of pure CS, CS/HA, CS/HA/magnetite, and CS/magnetite were evaluated by the measurements of bending strength, elastic modulus, compressive strength and hardness values. Moreover, the morphology of the bending fracture surfaces were characterized using a scanning electron microscope (SEM) and an image analyzer. Studies were also conducted to examine the biological response of the human Mesenchymal Stem Cells (hMSCs) on different composites. We conclude that, although all of these composites possess in-vitro biocompatibility, adding hydroxyapatite and magnetite to the chitosan matrix can noticeably enhance the mechanical properties of the pure chitosan

1,2,4-Triazole and quinoxaline based polyimide reinforced with neat and epoxide-end capped modified SiC nanoparticles: Study thermal, mechanical and photophysical properties

In this paper, properties of nanocomposite films which were prepared from a new polyimide and SiC nanoparticles via two simple methods are reported: (1) SiC nanoparticles were firstly functionalized with epoxide-end groups (mSiC) and then solution blended with poly(triazole-imide) (PTAI) in DMAc. The homogeneous solution was heated in vacuum to give PTAI/mSiC film. (2) A new diamine containing 1,2,4-triazole ring and a commercial dianhydride was reacted in situ in the presence of native SiC nanoparticles to give a homogeneous poly(amic acid) PAA/SiC mixture which was then heated in vacuum under high temperature thermal process to give PTAI/SiC film. The nanocomposite films were tested for different properties including thermal using TGA and DMTA, mechanical and photophysical. The results showed that strong chemical bonding between SiC nanoparticles and the polymer matrix contributed to the enhanced Tg from 300 °C to >350 °C, tensile strength from 108 MPa to 165 MPa and temperature of 5% weight loss (T5%) from 380 °C to 500 °C. The photoluminescence intensity of the nanocomposites increased and the spectra showed blue shift with increasing SiC content

The effect of stabilisers on integrated chemiluminescence in the early stages of polypropylene photo-oxidation

The integrated chemiluminescence obtained by heating photo-oxidised polypropylene films in an inert atmosphere is affected by a number of common stabilisers, particularly free radical scavengers, such as hindered phenols, and hydroperoxide decomposers, such as thiodipropionate esters. These stabilisers must be removed prior to chemiluminescence analysis of the hydroperoxide content in the early stages of photo-oxidation. From an analysis of the effect of stabilisers on the peak in hydroperoxide concentration observed after short times of UV irradiation with wavelengths longer than 300 nm, it was found that only the thiodipropionate ester and a 2-hydroxybenzophenone UV absorber affected the kinetics of hydroperoxide formation and decomposition and increased the induction period as measured by carbonyl index. A hindered triphenyl phosphite produced an immediate increase in integrated chemiluminescence and was a pro-degradant unless a hindered phenol was incorporated to inhibit peroxy radical attack on the stabiliser. A commercial hindered piperidine caused a lowering of the chemiluminescence when the sample was heated for analysis, consistent with a weak radical scavenging and hydroperoxide-decomposing activity of the amine, but did not affect the kinetics of formation and decomposition of hydroperoxides on UV irradiation

Adsorption of heavy metal ions and azo dyes by crosslinked nanochelating resins based on poly(methylmethacrylate-co-maleic anhydride)

Chelating resins are suitable materials for the removal of heavy metals in water treatments. A copolymer, Poly(MMA-co-MA), was synthesized by radical polymerization of maleic anhydride (MA) and methyl methacrylate (MMA), characterized and transformed into multifunctional nanochelating resin beads (80–150 nm) via hydrolysis, grafting and crosslink reactions. The resin beads were characterized by swelling studies, field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR). The main purpose of this work was to determine the adsorption capacity of the prepared resins (swelling ratio ~55%) towards metal ions such as Hg2+, Cd2+, Cu2+ from water at three different pH values (3, 6 and 9). Variations in pH and types of metal ions have not significantly affected the chelation capacity of these resins. The maximum chelation capacity of one of the prepared resin beads (Co-g-AP3) for Hg2+ was 63, 85.8 and 71.14 mg/g at pH 3, 6 and 9, respectively. Approximately 96% of the metal ions could be desorbed from the resin. Adsorption capacity of these resins towards three commercial synthetic azo dyes was also investigated. The maximum adsorption of dye AY42 was 91% for the resin Co-g-AP3 at room temperature. This insures the applicability of the synthesized resins for industrial applications