Electrophoretic deposition of silicon-substituted hydroxyapatite/poly(ε-caprolactone) composite coatings

Silicon-substituted hydroxyapatite/poly(ε-caprolactone) composite coatings were prepared on titanium substrate by electrophoretic deposition in n-butanol and chloroform mixture. The effect of the concentration of poly(ε-caprolactone) in suspension on the morphology and the microstructure of coatings were investigated, furthermore, the thermal behavior and in vitro bioactivity were also investigated. The results show that the coarse and accidented silicon-substituted hydroxyapatite/poly(ε-caprolactone) composite coatings were obtained by electrophoretic deposition when the concentration of poly(ε-caprolactone) in suspension was 6–16 g/l. The adsorption of poly(ε-caprolactone) on the surface of Si–HA particles hinders the electrophoretic deposition of Si–HA. The shear-testing experiments indicated that the addition of poly(ε-caprolactone) in suspension is in favor of improving the bonding strength of the coatings. After immersion in simulated body fluid for 8 days, silicon-substituted hydroxyapatite/poly(ε-caprolactone) composite coatings have the ability to induce the bone-like apatite formation.     

Effect of the content of hydroxyapatite nanoparticles on the properties and bioactivity of poly(l-lactide) – Hybrid membranes

Poly(l-lactide)/hydroxyapatite, PLLA/HA, composite membranes for bone regeneration with different concentrations of nanoparticles have been prepared and their physicochemical properties and bioactivity have been determined. Hydroxyapatite nanoparticles act as nucleating agent of the poly(l-lactide) crystals, as detected by DSC, and as reinforcing filler, as proven by the monotonous increase of the elastic modulus of the microporous membranes with increasing nano-filler content. The bioactivity, which regards to the use of these materials in bone regeneration, was tested by immersing the samples in a simulated body fluid, SBF. A faster deposition of a biomimetic apatite layer was observed as increases the content of hydroxyapatite nanoparticles, thus membranes with a 15% (w/w) of hydroxyapatite particles (relative to PLLA weight) present a homogeneous layer of hydroxyapatite on the surface of their pores after 7 days of immersion in SBF. An especial emphasis has been made on the influence of a plasma treatment on the bioactivity of the membranes. With this aim, the membranes were submitted to a plasma treatment previously to their immersion in a simulated body fluid. It has been observed that the surface of a PLLA membrane after 21 days of immersion in SBF is still not completely covered by hydroxyapatite whereas the same sample treated with plasma show a smooth layer of biomimetic hydroxyapatite. The increase of bioactivity achieved with this treatment was less important in high hydroxyapatite content composites.     

Corrosion resistance of Zn–Al layered double hydroxide/poly(lactic acid) composite coating on magnesium alloy AZ31

A Zn–Al layered double hydroxide (ZnAl-LDH) coating consisted of uniform hexagonal nano-plates was firstly synthesized by co-precipitation and hydrothermal treatment on the AZ31 alloy, and then a poly(lactic acid) (PLA) coating was sealed on the top layer of the ZnAl-LDH coating using vacuum freeze-drying. The characteristics of the ZnAl-LDH/PLA composite coatings were investigated by means of XRD, SEM, FTIR and EDS. The corrosion resistance of the coatings was assessed by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed that the ZnAl-LDH coating contained a compact inner layer and a porous outer layer, and the PLA coating with a strong adhesion to the porous outer layer can prolong the service life of the ZnAl-LDH coating. The excellent corrosion resistance of this composite coating can be attributable to its barrier function, ion-exchange and self-healing ability.     

Optimization of mixed silanes agent solution and curing process for composite γ-glycidoxypropyl trimethoxysilane (γ-GPS)/bis-1.2-(triethoxysilyl)ethane (BTSE) silane film on Q235 steel surface

In this investigation, the mixed γ-GPS/BTSE silane solution for preparing well adhered composite γ-GPS/BTSE silane film on Q235 carbon steel surface has been successfully optimized by orthogonal test, and the curing process parameters of temperature and time have also been optimized. The results indicate that the optimized hydrolysis parameters for mixed silanes agent solution are as follows: V_ethanol/V_water 3 : 1, V_γ-GPS/V_BTSE 2 : 3, V_silanes 6 vol.%, pH 4.0 and hydrolysis time 72 h. In addition, the optimized curing condition for composite γ-GPS/BTSE silane film is 120 °C and 30 min. After immersion in the optimized mixed γ-GPS/BTSE silanes agent solution and curing under the optimized condition, the prepared composite γ-GPS/BTSE silane film on Q235 steel surface can have an adhesion strength of 24.52 MPa to underlying steel substrate.     

The effect of titanium dioxide nano-filler on the conductivity,morphology and thermal stability of poly(methyl methacrylate)—poly(styrene-<Emphasis Type="Italic">co</Emphasis>-acrylonitrile) based composite solid polymer electrolytes

The composite solid polymer electrolyte (CSPE) samples, comprising of poly(methylmethacrylate) (PMMA)/poly(styrene-co-acrylonitrile) (SAN)/ethylene carbonate (EC)/propylene carbonate (PC)/lithium trifluoromethanesulfonate (LiCF₃SO₃)/anatase-TiO₂ as nano-filler (0, 5, 6, 7, 8 and 9 wt% for samples T0, T1, T2, T3, T4 and T5 respectively) were prepared by solution casting technique. Fourier transform infrared (FT-IR) spectral studies indicate the interaction of PMMA and plasticizers (EC, PC) with Lithium ion and nano-filler TiO₂ in samples. From AC impedance studies ionic conductivity, dielectric constant increase with increase in the concentration of nano-filler TiO₂ up to 9 wt%. The sample T5 shows lowest activation energy (E_a) of 0.14 eV, very short relaxation time (τ) of 1.49?×?10^?7 s and exhibits maximum ionic conductivity of 1.05?×?10^?4 S cm^?1 at room temperature. The conductivity-temperature dependence studies showed that the conductivity of all samples depict Arrhenius behaviour suggesting ion-hopping mechanism. Dielectric studies reveal ion conducting nature of CSPE samples. Thermogravimetric analysis indicate the thermal stability of CSPE sample T5 up to 333 °C with maximum degradation at 388 °C. DSC studies reveal absence of glass transition temperature (T_g) of atactic component of PMMA in CSPE sample T5 indicating amorphous nature. X-ray diffraction patterns shows shift in the position of peaks confirming the complex formation of the PMMA-SAN-EC-PC-LiCF₃SO₃-TiO₂ system. SEM analysis indicates that the presence of lithium salt and filler TiO₂ on polymer host does not lead to heterogenous polymer blend thus retaining its amorphous nature.     

Effect of poly(acrylic acid) on the preparation of thick silica films by electrophoretic sol–gel deposition of re-dispersed silica particles

Thick silica films were prepared by the electrophoretic sol–gel deposition technique in the presence of poly(acrylic acid) (PAA) using monodispersed silica particles; the particles were prepared by the sol–gel method, pre-heat treated and then re-dispersed in the mixture of H2O and ethanol. The weight of deposited silica films was maximized when 0.2 mass % of PAA against the whole amount of sol was added. The particles constructing the thick silica films were packed densely when the amount of added PAA was less than 0.2 mass%. The weight of the film increased with decrease in the content of H2O in the sol when a fixed amount of PAA was added. After the heat treatment of deposited films at 800 °C, crack-free silica films of about 30 m thickness were prepared. © 1998 Chapman & Hall     

Injectable bioactive glass/biodegradable polymer composite for bone and cartilage reconstruction: Concept and experimental outcome with thermoplastic composites of poly(ε-caprolactone-co-D,L-lactide) and bioactive glass S53P4

Injectable composites (Glepron) of particulate bioactive glass S53P4 (BAG) and Poly(epsilon-caprolactone-co-D,L-lactide) as thermoplastic carrier matrix were investigated as bone fillers in cancellous and cartilagineous subchondral bone defects in rabbits. Composites were injected as viscous liquid or mouldable paste. The glass granules of the composites resulted in good osteoconductivity and bone bonding that occurred initially at the interface between the glass and the host bone. The bone bioactivity index (BBI) indicating bone contacts between BAG and bone, as well as the bone coverage index (BCI) indicating bone ongrowth, correlated with the amount of glass in the composites. The indices were highest with 70 wt % of BAG, granule size 90-315 microm and did not improve by the addition of sucrose as in situ porosity creating agent in the composite or by using smaller (<45 microm) glass granules. The percentage of new bone ingrowth into the composite with 70 wt % of BAG was 6-8% at 23 weeks. At the articular surface cartilage regeneration with chondroblasts and mature chondrocytes was often evident. The composites were osteoconductive and easy to handle with short setting time. They were biocompatible with low foreign body cellular reaction. Results indicate a suitable working concept as a filler bone substitute for subchondral cancellous bone defects.