Forming performance and biodegradability of woodfibre–Biopol™ composites

A Taguchi approach to experimental design has been used to analyse the hotpressing and vee-bending of woodfibre–Biopol™ composites. Analysis of the hotpressing process clearly shows that platen temperature is the parameter with the most influence on tensile performance of the composite sheet produced. In bending (a common manufacturing situation), geometric conformance is maximised when forming time is 60 s, forming rate is 250 mm/min and forming radius/thickness ratio is 2 for the composite sheets studied in this paper. A study of the influence of fibre volume fraction on the biodegradability of these sheets show that these composites are highly biodegradable, often degrading at a rate greater than that of pure Biopol™. The results also suggest that a woodfibre mass fraction of ∼15% maximises the degradation of the woodfibre–Biopol™ composites.     

Characterization of the Novel Ophthalmic Drug Carrier Sophisen in Two of Its Derivatives: 3A Ofteno™ and Modusik-A Ofteno™

Sophisen, a new ophthalmic drug carrier, was characterized using physicochemical and morphological criteria. Diclofenac belongs to a nonsteroidal anti-inflammatory molecule group and its ophthalmic use avoids side effects produced by steroid drugs. Cyclosporine-A is a cyclic peptide used as an immunosuppressive when administrated systemically. Its application in ophthalmology has been reported, but it is a very poor soluble drug. Diclofenac sodium and Cyclosporine-A were mixed with Sophisen to render two new ophthalmic solutions that were named 3A Ofteno? and Modusik-A Ofteno?, respectively. Based on transmission electron microscopy and dynamic light scattering studies, we concluded that Sophisen is a polydisperse solution with a molecular weight of 413 ± 122 kDa, whereas 3A Ofteno? and Modusik-A Ofteno? are monodisperse solutions with molecular weights of 169 ± 44 and 153 ± 10, respectively. Sophisen was shown to be a good carrier for diclofenac sodium as evaluated by passive diffusion through the cornea. A comparative study suggests that diclofenac applied as eye drops was better tolerated when associated with Sophisen. In addition, Modusik-A Ofteno?, a new aqueous solution of Cyclosporine-A, improved tear production in patients with moderate or severe dry eye condition.     

Hydrostatically extruded HAPEX™

Hydroxyapatite reinforced high density polyethylene composite (HAPEX) has been developed for bone substitution. To improve its mechanical properties, HAPEX was hydrostatically extruded at different extrusion ratios after compression moulding. Substantial increases in the tensile and flexural properties of both unfilled polyethylene and HAPEX were achieved. It was evident that the higher the extrusion ratio, the stiffer and the stronger the extruded rods. The ductility of HAPEX was also significantly enhanced by hydrostatic extrusion. Hydrostatically extruded HAPEX possesses mechanical properties that are within the bounds for human cortical bone, which indicates its potential for load-bearing skeletal implant applications.     

Structural properties and Mössbauer spectroscopy of Finemet™ doped with Ge

Structural and magnetic properties of amorphous and crystalline alloys Fe_73.5Cu₁Nb₃B₉Si_13?xGe_{x=1;5;10;13.5} were studied by means of energy dispersive X-rays (SEM + EDX), X-ray diffraction (XRD), differential scanning calorimetry (DSC), Mössbauer spectroscopy (MS), as-quenched (a-q) and after annealing (a). EDX show agreement between the nominal and the measured atomic contents for all alloys. DSC provided three phase transition temperatures of the materials, MS spectra reveal amorphous structure of as-quenched alloys and a mixture of amorphous and crystalline structures of annealed alloys. The XRD spectra of annealed alloys allow us to resolve three crystalline phases of Fe.     

Nextel™ 610 alumina fibre reinforced aluminium: influence of matrix and process on flow stress

Continuous alumina fibre reinforced aluminium matrix composites are produced using two different liquid metal infiltration methods, namely direct squeeze casting and gas pressure infiltration. Net-shape fibre performs for longitudinal parallel tensile bars are prepared by winding the Nextel™ 610 alumina fibre (3M, St Paul, MN) into graphite moulds. High purity aluminium, two binary (Al–6% Zn and Al–1% Mg) and one ternary (Al–6% Zn–0.5% Mg) aluminium alloys are used as matrix materials. The composite is tested in uniaxial tension–compression, using unload–reload loops to monitor the evolution of Young's modulus. A linear dependence between Young's modulus and strain is observed; this is attributed, by deduction, to intrinsic elastic non-linearity of the alumina fibre. This conclusion is then used to compare on the basis of the in situ matrix flow curve the influence of matrix composition and infiltration process on the composite stress–strain behaviour.     

Multiobjective optimization and analysis of copper–titanium diboride electrode in EDM of monel 400™ alloy

Electrical discharge machining (EDM) is one of the most accepted machining processes in the precision manufacturing industry. In EDM process, finding an alternative tool material is the demand in modern manufacturing industry. Therefore, an attempt had been made to fabricate copper–titanium diboride powder metallurgy electrode to test in EDM on monel 400? material. The experiments are planned using center composite second-order rotatable design and the model is developed by response surface methodology. The machining characteristics have analyzed using the developed model. In this study, four input parameters such as titanium diboride percentage, pulse current, pulse on time, and flushing pressure are selected to evaluate the material removal rate (MRR) and tool wear rate (TWR). The adequacy of the developed regression model has tested through analysis of variance test. The desirability-based multiobjective optimization is used to find the optimal process parameter which has given maximum MRR and minimum TWR. The optimum process parameters obtained were titanium diboride of 16%, pulse current of 6 A, flushing pressure of 1 Mpa, and pulse on time of 35?µs. The validity of the response surface model is further verified by conducting confirmation experiments.     

Fatigue testing of thermoformed bidirectional LDF™-composites

Specimens made of Long Discontinuous Fiber (LDF) composite material were elongated to different states of deformation by thermoforming. Tension-tension-fatigue tests were performed using waisted bidirectional specimens cut out of the thermoformed parts. These resulted in similar shapes of the Wöhler-curves fairly independently of the deformation state of the LDF-material. In addition, the static strength values were not very much influenced by the elongation of the specimens. The specimens were nondestructively inspected by ultrasonics and thermography.     

Interfacial stability,oxidation response and mechanical properties of a Nicalon™ Fibre reinforced chemical bonded ceramic matrix composite

A slurry of monoaluminum phosphate with fine Al₂O₃ powder was infiltrated into eight harness satin fabric of Nicalon fibres. The infiltrated fabrics were laid up in 16 plies and then cured in an autoclave. Due to the chemical reaction between alumina and monoaluminum phosphate, aluminum phosphate was produced. Carbon coated and uncoated fibres were used to manufacture these composites to produce weak and strong interfaces between matrix and fibres. Two different processing routes were used during manufacturing, which resulted in different amounts of porosity content in the final composites. Thermogravimetric analysis carried out at 850°C for 6000 min in air showed negligible weight change, indicating stable fibres in the composites. Four-point bend flexure tests were conducted at room temperature, 700 and 850°C. Strong interface composites completely failed at high temperatures due to fibre fracture, but a shear dominated delamination-type interface failure was observed for the weak interface composites. Strong interface composites exhibited better flexure strengths than the weak interface composites under all conditions of processing and orientations. However, the weak interface composites absorbed significantly larger amounts of energy before failure compared to the strong interface composites. Little influence of porosity content was seen on flexure properties both at room and elevated temperatures. High temperature failure behaviour is explained using classical lamination theory.     

Tension-Compression Fatigue of a Nextel™720/alumina Composite at 1200 °C in Air and in Steam

Tension-compression fatigue behavior of an oxide-oxide ceramic-matrix composite was investigated at 1200 °C in air and in steam. The composite is comprised of an alumina matrix reinforced with Nextel?720 alumina-mullite fibers woven in an eight harness satin weave (8HSW). The composite has no interface between the fiber and matrix, and relies on the porous matrix for flaw tolerance. Tension-compression fatigue behavior was studied for cyclical stresses ranging from 60 to 120 MPa at a frequency of 1.0 Hz. The R ratio (minimum stress to maximum stress) was ?1.0. Fatigue run-out was defined as 10⁵ cycles and was achieved at 80 MPa in air and at 70 MPa in steam. Steam reduced cyclic lives by an order of magnitude. Specimens that achieved fatigue run-out were subjected to tensile tests to failure to characterize the retained tensile properties. Specimens subjected to prior cyclic loading in air retained 100 % of their tensile strength. The steam environment severely degraded tensile properties. Tension-compression cyclic loading was considerably more damaging than tension-tension cyclic loading. Composite microstructure, as well as damage and failure mechanisms were investigated.     

Cyclic and sustained loading behaviors of oxide/oxide Nextel™720/alumina composite with double edge sharp notch

This study investigated an oxide/oxide CMC consisting of Nextel?720 (meta-stable mullite) fibers in alumina matrix, N720/A, with 0°/90° fiber orientation having double edge sharp notch under sustained and cyclic loading conditions at 1200 °C in laboratory air environment. Monotonic tensile tests at 1200 °C were also conducted. Fracture surfaces were examined to analyze failure and damage mechanisms. Comparisons with counterparts from unnotched geometry showed N720/A is mildly sensitive to the sharp notch under monotonic tensile, creep and fatigue loading conditions. The ultimate tensile strength of the composite was reduced by about 15% in the presence of the sharp notch. The rupture strength of the sharp notched geometry was reduced by about 15% of unnotched geometry for a given rupture time. The fatigue strength was reduced by about 20% of unnotched geometry for a given number of cycles to failure. Deformation under cyclic loading condition had contributions both from fatigue and creep. Damage mechanisms were identical under cyclic and sustained loading conditions.     

Pre-clinical studies to validate the MITCH PCR™ Cup: a flexible and anatomically shaped acetabular component with novel bearing characteristics

A previous clinical study was undertaken to evaluate the safety and efficacy of an anatomically shaped, flexible acetabular cup. Clinical results achieved were satisfactory, although some deficiencies in the model were identified. Design changes to the original model have been implemented to improve both initial stability and long term biological fixation. This was achieved through modifications made to both the anchoring mechanism and by the application of an appropriate backing surface layer promoting bone on-growth. In addition, changes to the articulation couple have also been introduced to improve implant durability and bearing performance, utilising a carbon fibre reinforced polyetheretherketone—alumina couple. Simulated loading, in both models, was performed using Finite Element Analysis. Mechanical and tribological tests were also performed to ensure the robustness of the new optimised design. Bio-compatibility of the articulation couple was demonstrated using an animal model. Implantation of the device has been extensively tested and re-validated in vitro to achieve a favourable polar contact between cup and femoral head and establish a reproducible operative technique. This preliminary work is undertaken prior to commencing a post market surveillance study of the CE marked implant.     

Dielectric properties of Lanxide™ Al2O3/Al composites

The dielectric properties of unreinforced Lanxide Al₂O₃/Al composites have been investigated over a wide range of temperatures and frequencies. These composites were formed by the directed oxidation of suitably doped aluminium-based alloy melts, with no filler or reinforcing material in the reaction path. As-grown composite materials were good electrical conductors in all directions owing to the presence of an interconnected metallic constituent. As the metallic phases were partially removed (in favour of porosity) by continuing the oxidation reaction to completion, the composites remained electrically conducting parallel to, and became insulating transverse to, the original growth direction of the composite. This anisotropy apparently was caused by different connectivity of the metal phase between the two directions. Thermal treatments at 1600°C in argon resulted in volatilization of the residual metal in the composite, thus further increasing the porosity. As the metal content was decreased, the composites changed from conducting to insulating along the growth direction. When the metallic phase was removed completely, the porous alumina ceramic maintained anisotropic dielectric properties, due to c-axis alignment of the alumina (corundum) phase along the growth direction. The dielectric constants were 8.0 and 6.4, respectively, parallel and perpendicular to the c-axis aligned directions of the porous alumina ceramic. A dielectric relaxation phenomenon was observed in some samples of both as-grown and thermally treated material, and was attributed to an unidentified impurity effect.     

Evaluating 3D bone tissue engineered constructs with different seeding densities using the alamarBlue™ assay and the effect on in vivo bone formation

Bone tissue engineering using patient derived cells seeded onto porous scaffolds has gained much attention in recent years. Evaluating the viability of these 3D constructs is an essential step in optimizing the process. The alamarBlue (aB) assay was evaluated for its potential to follow in vitro cell proliferation on architecturally standardized hydroxyapatite scaffolds. The impact of the aB assayed and seeding density on subsequent in vivo bone formation was investigated. Twelve scaffolds were seeded with various densities from 250 to 2.5×10⁶ cells/scaffold and assay by aB at 5 time points during the 7-day culture period. Twelve additional scaffolds were seeded with 2.5×10⁵ cells/scaffold. Two control and 2 aB treated scaffolds were subcutaneously implanted into each of 6 nude mice for 6 weeks. Four observers ranked bone formation using a pair wise comparison of histological sections form each mouse. The aB assay successfully followed cell proliferation, however, the diffusion kinetics of the 3D constructs must be considered. The influence of in vitro aB treatment on subsequent in vivo bone formation cannot be ruled out but was not shown to be significant in the current study. The aB assay appears to be quite promising for evaluating a maximum or end-point viability of 3D tissue engineered constructs. Finally, higher seeding densities resulted in more observed bone formation.     

Evaluating the performance of the ORTEC® Detective™ for emergency urine bioassay

The performance of the ORTEC(?) Detective? as a field deployable tool for emergency urine bioassay of (137)Cs, (60)Co, (192)Ir, (169)Yb and (75)Se was evaluated against ANSI N13.30. The tested activity levels represent 10 % RL (reference level) and 1 % RL defined by [Li C., Vlahovich S., Dai X., Richardson R. B., Daka J. N. and Kramer G. H. Requirements for radiation emergency urine bioassay techniques for the public and first responders. Health Phys (in press, 99(5), 702-707 (2010)]. The tests were conducted for both single radionuclide and mixed radionuclides at two geometries, one conventional geometry (CG) and one improved geometry (IG) which improved the MDAs (minimum detectable amounts) by a factor of 1.6-2.7. The most challenging radionuclide was (169)Yb. The measurement of the mixture radionuclides for (169)Yb at the CG did not satisfy the ANSI N13.30 requirements even at 10 % RL. At 1 % RL, (169)Yb and (192)Ir were not detectable at either geometry, while the measurement of (60)Co in the mixed radionuclides satisfied the ANSI N13.30 requirements only at the IG.     

Development and comparative evaluation of in vitro,in vivo properties of novel controlled release compositions of paroxetine hydrochloride hemihydrate as against Geomatrix™ platform technology

The objective of this study is to develop, in vitro and in vivo evaluation of novel approaches for controlled release of paroxetine hydrochloride hemihydrate (PHH) in comparison to patented formulation PAXIL CR^® tablets of GlaxoSmithKline (Geomatrix? technology). In one of the approaches, hydrophilic core matrix tablets containing 85% of the dose were prepared and further coated with methacrylic acid copolymer to delay the release. An immediate release coating of 15% was given as top coat. The tablets were further optionally coated using ethyl cellulose. In the second approach, hydrophobic matrix core tablets containing metharylic acid copolymer were prepared. In the third approach, PHH was granulated with enteric polymer and further hydrophobic matrix core tablets were prepared. The effect of polymer concentration, level of enteric coating on drug release was evaluated by in vitro dissolution study by varying dissolution apparatus and the rotation speeds. It was found that increase in concentration of high viscosity hydroxypropylmethylcellulose (HPMC) resulted in reduction of the release rate. The drug release was observed to be dependent on the level of enteric coating and ethyl cellulose coating, being slower at increased coating. The release mechanism of PHH followed zero-order shifting to dissolution dependent by the increase of HPMC content. The formulation was stable without change in drug release rate. In vivo study in human volunteers confirmed the similarity between test and innovator formulations. In conclusion, HPMC-based matrix tablets, which were further coated using methacrylic acid copolymer, were found to be suitable for the formulation of single layer-controlled release PHH.