Plastination Research Articles

The effect of a recombinant elastin-mimetic coating of an ePTFE prosthesis on acute thrombogenicity in a baboon arteriovenous shunt

A recombinant elastin-mimetic triblock protein polymer with an inverse transition temperature (∼20 °C) was used to impregnate small-diameter (4 mm i.d.) expanded polytetrafluoroethylene (ePTFE) vascular grafts. Scanning electron microscopy confirmed that initial elastin impregnation of the graft followed by further multilayer coating with elastin films filled in the fibril and node structure of the luminal surface of the ePTFE graft and was macroscopically smooth. Elastin protein polymer impregnation reduced the advancing contact angle of the luminal surface to 43°, which was comparable to the advancing contact angle of 47° for a cast elastin film. Attenuated total reflection infrared spectroscopy and Coomassie blue staining revealed little discernable change in the protein surface film after 24 h of shear at 500 s −1 and 37 °C. Excellent short-term blood-contacting properties as determined by minimal fibrin and platelet deposition were demonstrated using a baboon extracorporeal femoral arteriovenous shunt model. The results of this study demonstrate the applicability of an elastin-mimetic triblock protein polymer as a non-thrombogenic coating or as a component of a tissue-engineered composite.

Mechanical and thermal properties of epoxypolymethyl methacrylate blends synthesizedin supercritical carbon dioxide

AbstractA series of epoxy/polymethyl methacrylate (E/PMMA) blends was synthesized through impregnation polymerization of methyl methacrylate at concentrations ranging (0–1.5 phr) into diglycidyl ether of bisphenol‐A (0.1 mol) in presence of 2,2‐azobisisobutyronitrile (2 × 10−2 mol) at 3000 psi, (60–90 ± 1)°C for 3 h in supercritical carbon dioxide, followed by curing of treated epoxy with triethylene tetramine (10 phr) at (40 ± 1)°C. The progress of all such impregnation polymerization reactions was monitored rheoviscometrically. Formation of E/PMMA blends was ascertained through of PMMA mass uptake (%) into epoxy, UV–vis and FTIR spectra, and TEM. With PMMA mass uptake (%), compression strength and resistance against wear of E/PMMA blends were increased with simultaneous decrease in their Rockwell hardness (R scale), charpy impact, and tensile strength, respectively. All E/PMMA blends have shown nonuniform photoelastic behavior at applied load ranging 4–20 kgf and significant stability against thermooxidation with Tg/Tm and char yield (%) ranging 0.53–0.59, 29.31–31.66, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1303–1310, 2007

Synthesis of controlled release device with supercritical CO 2 and co-solvent

Supercritical carbon dioxide (scCO 2) has found use as a replacement for organic solvents in the creation of controlled release drug devices. This study uses supercritical carbon dioxide with ethanol as a co-solvent. Ethanol increases the solubility of β-estradiol in scCO 2 for impregnation into the glassy polymer polyvinylpyrrolidone (PVPP), leading to more efficient polymer impregnation. Experimental conditions cover a range of temperatures from 40 °C to 50 °C and pressures up to 2500 psi. The effect of polymer swelling time on the sorption process also is studied. A dual mode sorption model describes the sorption of drug into the glassy polymer. The determined sorption parameters allow analysis of polymer conformation and suggest optimum impregnation conditions.

A study on improving mechanical properties of porous HA tissue engineering scaffolds by hot isostatic pressing

Various interconnected porous hydroxyapatite (HA) ceramic scaffolds are universally used to induct the tissue growth for bone repair and replacement, and serve to support the adhesion, transfer, proliferation and differentiation of cells. Impregnation of polyurethane sponges with a ceramic slurry is adopted to produce highly porous HA ceramic scaffolds with a 3D interconnected structure. However, high porosity always accompanies a decrease in the strength of the HA ceramic scaffolds. Therefore, it is significant to improve the strength of the HA ceramic scaffolds with highly interconnected porosity so that they are more suitable in clinical applications. In this work, highly porous HA ceramic scaffolds are first produced by the polymer impregnation approach, and subsequently further sintered by hot isostatic pressing (HIP). The phase composition, macro- and micro-porous structure, sintering and mechanical properties of the porous HA scaffolds are investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), nanoindentation analysis and compressive test. The experimental results show that the nanohardness and compressive strength of HIP-sintered porous HA ceramics are higher than those of commonly sintered HA scaffolds. The HIP technique can effectively improve the sintering property and densification of porous HA ceramic scaffolds, so inducing an increase in the compression strength.

Composite Damping Ceramic Coatings by Polymer Impregnation

The interest in the use of thermal barrier ceramic coatings as damping treatments has recently arisen since they were shown to provide sufficient additional damping. Ceramic coatings can be applied mainly by either Air Plasma Spraying (APS) or Electron Beam - Physical Vapour Deposition (EBPVD). APS was used to deposit the specimens studied here. Previous research has shown that it is possible to enhance their damping effectiveness by tailoring the deposition parameters. This paper presents further work aimed at improving their damping effectiveness significantly by introducing a second material in the ceramic coating; thus creating a composite system. This paper covers the experimental findings of impregnating a ceramic damping coating with a number of commercially available polymeric materials. The most promising case of a type of Polyurethane provided over 40% improvement and was selected for further tests at various temperatures, ranging from -40 to 150 􀁱C. Furthermore, the damping and stiffness of ceramic coatings present amplitude-dependent behaviour which was also taken into consideration when evaluating the composite system. Finally, the paper concludes with a discussion of these promising findings as well as planned research into understanding the physical mechanisms dissipating energy in this composite material.

Effect of Reactive Filler Addition for Matrix of SiC Fiber/SiC Composite

Polymer impregnation pyrolysis method (PIP method) has some advantages to fabricate SiC fiber /SiC composite with large or complex form. However polymer derived SiC contains some amount of excess carbon and porosity. In particular the excess carbon is easy to be oxidized in air at high temperature. Therefore reliability of the composite is not sufficient for long term use, because the oxidized matrix makes strong bonding between the fiber and the matrix. In this study, TiO2 as a reactive filler was added into polymer to consume the excess carbon by chemical reaction. Polycarbosilane (PCS) was used as a precursor polymer to synthesize a SiC matrix. It was confirmed that TiO2 was formed TiC on reaction with PCS over 1673 K by preliminary study. SiC fiber, Hi-Nicalon®, was used as reinforcement. Al2O3 powder was coated on surface of SiC fiber as interface layer of fiber/matrix. TiO2 added PCS/hexane solution was compounded with the fiber tow by filament winding. SiC fiber/SiC composite was synthesized at 1673 K for 3.6 ks in Ar. The composite was densified by reinfiltration of TiO2 added PCS solution and pyrolysis at 1673 K. Though densification behavior of the composite with TiO2 is slower than composite without TiO2, it was suggested that composition of synthesized SiC is close to stoichiometric one by apparent density. Fracture behavior of the composite indicated that addition of TiO2 was increase bonding strength between fiber and matrix. Bending strength of composite was increased after oxidation test at 1473 K for 360 ks in air atmosphere.

New processing methods to produce silicon carbide and beryllium oxide inert matrix and enhanced thermal conductivity oxide fuels

For inert matrix fuels, SiC and BeO represent two possible matrix phase compounds that exhibit very high thermal conductivity, high melting points, low neutron absorption, and reasonably high radiation stability. BeO is chemically compatible with UO2, PuO2 and Zircaloy to very high temperatures, but SiC reacts with all three at somewhat lower temperatures. We have developed the Polymer Impregnation and Pyrolysis or PIP method, making use of a commercial SiC polymeric precursor, to consolidate both particulate fuels like ‘TRISO’ microsphere fuels, and to impregnate UO2 fuels with pure stoichiometric SiC to improve their thermal conductivity. This method was employed to fabricate Enhanced Conductivity Oxide fuels, or ECO fuels with 5–10vol.% of the high conductivity phase, and with 50vol.% for TRISO dispersion fuels. For ECO fuels, a new ‘slug/bisque’ method of fabricating the UO2 fuel granules was necessary to produce sintered fuel with open pore structures, allowing almost complete impregnation of the continuous SiC phase. The advantages of the PIP process are that it is a non-damaging consolidation process for particulates (TRU, UC or TRISO microspheres), forms a continuous, pure β-SiC phase at temperatures as low as 1573K, and allows the maximum in fissile atom density. However, several PIP impregnation cycles and high crystallization temperatures are necessary to obtain high thermal conductivity SiC. For producing IMF fuels using the PIP process, the fissile PuC and/or TRU actinides can be added in small concentrations along with SiC ‘filler particles’ and consolidated with the SiC precursor for either open or closed fuel cycles. For BeO, a second approach was developed for ECO fuels that involves a ‘co-sintering’ route to produce high density fuels with a continuous BeO phase of 5–10vol.%. Special granulation and mixing techniques were developed, but only one normal sintering cycle is required. For BeO matrix IMF fuels, PuO2 granules and TRU actinides or YSZ granules containing actinides could be simply dry-mixed with BeO powder and co-sintered to produce a dispersed fuel form. Alternatively, the BeO could be granulated, and the PuO2 and/or TRU oxides would fill the interstices forming a continuous minor phase that could be recycled in closed fuel cycles. Some advantages and disadvantages of these matrices are discussed.

2729 一方向SiC/SiC複合材料の組織による引張特性への影響(S28-1 セラミックスおよびセラミックス系複合材料(1),S28 セラミックスおよびセラミックス系複合材料)

The influence of each constituent of SiC/SiC composite, i.e. fiber, interface and matrix, on the fracture mechanism and mechanical properties were experimentally studied. As main factors in manufacturing, the carbon thickness of interface, and the kind of precursor polymer of the matrix, the blending rate of filler particle, and the number of densification processing were interested. As a basic structure of various reinforcing structures, systematic evaluation was carried out for the bundle composites which were composed of a fiber bundle densified with a matrix. The specimens were prepared by chemical vapor infiltration to form an interfacial carbon layer on Tyranno-ZMI fiber and polymer impregnation and pyrolysis to form a matrix in the fiber bundle. The specimens were evaluated by tensile test, fiber push-out test and electron microscopy etc.

Polymer swelling and impregnation using supercritical CO 2: A model-component study towards producing controlled-release drugs

We present a model-component-based study of polymer impregnation using supercritical carbon dioxide (SCCO 2) towards producing controlled-release drugs. Polymethylmethacrylate (PMMA) and naphthalene were used as the model components. Impregnation and swelling experiments were performed at 35–40–45 °C and 80–150 bar conditions. Effects of temperature and pressure were studied in a view-cell. Swelling experiments with pure SCCO 2 resulted in 9–25% volume expansion. Volume expansion was directly related to pressure but inversely related to temperature. Compared to swelling experiments, impregnated samples swelled two- to four-fold more at the same conditions. Impregnation loads were found between 103.7 and 289 mg naphthalene per gram of PMMA. Visual observation of the experiments enabled qualitative inspection of the diffusion front. The presence of naphthalene accelerated the diffusion-front propagation. Time histories of the expanding samples during impregnation were also presented.

Fabrication of polymeric scaffolds with a controlled distribution of pores

The design of tissue engineering scaffolds must take into account many factors including successful vascularisation and the growth of cells. Research has looked at refining scaffold architecture to promote more directed growth of tissues through well-defined anisotropy in the pore structure. In many cases it is also desirable to incorporate therapeutic ingredients, such as growth factors, into the scaffold so that their release occurs as the scaffold degrades. Therefore, scaffold fabrication techniques must be found to precisely control, not only the overall porosity of scaffolds, but also the pore size, shape and spatial distribution. This work describes the use of a regularly shaped porogen, sugar spheres, to manufacture polymeric scaffolds. Results show that pre-assembling the spheres created scaffolds with a constant porosity of 60%, but with varying pores sizes from 200-800 microm, leading to a variation in the surface area and likely degradation rate of the scaffolds. Employing different polymer impregnation techniques tailored the number of pores present with a diameter of less than 100 microm to suit different functions, and altering the packing structure of the sugar spheres created scaffolds with novel layered porosity. Replacing sugar spheres with sugar strands formed scaffolds with pores aligned in one direction.

Processing, Microstructures and Mechanical Properties of Laminated Composites of the Si-Ti-C-O Fabric / Ceramic Filler / Polytitanocarbosilane System with Pseudoductility by Polymer Impregnation and Pyrolysis (PIP) Method

Processing, Microstructures and Mechanical Properties of Laminated Composites of the Si-Ti-C-O Fabric / Ceramic Filler / Polytitanocarbosilane System with Pseudoductility by Polymer Impregnation and Pyrolysis (PIP) Method

Property enhancements via matrix microstructure modification of carbon–carbon composites prepared by CVI processing

Carbon-carbon (CC) composites have received considerable interest for aerospace applications due to their superior strength retention at high temperatures and high heats of ablation etc. [1]. In the manufacturing of CC composites, carbon fiber preforms can be categorized dependent upon their final applications, e.g. UD, 2-D, 3-D and n-D etc. [2, 3]. Among them, even though they are high labor-dependent, carbon fiber rodnetwork n-D preforms have been used for thick (larger than 100 mm thickness) and high performance CC composites, especially for aerospace applications. In general, rod-network n-D CC composites are employing three routes for densification (1) chemical vapor infiltration (CVI) of hydrocarbon gases (2) liquid process with impregnation and pyrolysis of high carbon yield polymers or pitches (liquid process) (3) combination of CVI and liquid process [4]. In CVI process, under suitable conditions, pyrolytic carbon (PC) matrix has a preferred crystalline orientation which results in considerable anisotropy. In pyrolytic graphite (PG) which is more anisotropic than PC, for instance, the thermal expansion in the thickness direction (c direction in graphite structure) is approximately 20 times that in the plane of deposition (ab plane) [5]. Similarly, mechanical properties measured parallel to the ab plane are considerably higher than those measured perpendicular to it. Even though the degree of anisotropy is lower than that of PG, PC anisotropy creates considerable thermal stresses during CC processing, which lead to delaminations between PC matrix and the carbon fiber rods and micro-cracks in PC matrix itself. These delamination defects may be eliminated or at least greatly reduced by the modification of PC microstructure resulting in increase of CC composites performance [6, 7]. High-strength PAN-based carbon fiber (ACELAN TZ-307, Korea) with 12 K manufactured by Taekwang Industries Co., (Korea) was used in the present study. The fiber has tensile strength of 3800 MPa, tensile modulus 260 GPa, elongation 1.3%, and density of 1800 kg/m3 [8]. Polyvinyl alcohol (PVA 110, Kuraray, Japan) was used as a binder for carbon fiber rods preparation. Carbon fiber rods with 1.0 mm diameter were prepared using a typical pultrusion process. Three-D orthogonal rod-network preforms (W 150 × D150 × H200 mm) having 59% fiber volume percent

Comparison of Tensile Fracture Behavior between Si-Ti-C-O Fiber Bundle (Yarn), Woven Fabric of Yarn and Laminated Composite of the Si-Ti-C-O Fabric / Mullite Filler / Polytitanocarbosilane System

A polytitanocarbosilane (20-30 mass%)-xylene solution was infiltrated into a porous laminated composite with 35-40 vol% Si-Ti-C-O fabric of 11 diameter fiber and 15-25 vol% mullite filler, and decomposed at 1000°C in an Ar atmosphere. This polymer impregnation and pyrolysis method was repeated 8 times to produce the composites of 76-82 % theoretical density. The yarn (662-765 filament / yarn), fabric and composite provided the following average strengths : 1240 MPa for the yarn; 768 MPa for the fabric; 117 MPa for the composite. The fracture probability of the yarn, fabric and composite was well fitted by the normal distribution function. The tensile strength of the composite was interpreted by the product of the effective fiber content, the Young's modulus of the fiber and elongation of the composite.

Erosion–corrosion behaviour of high-velocity oxy-fuel Ni–Cr–Mo–Si–B coatings under high-velocity seawater jet impingement

In this paper, erosion–corrosion characteristics of self-fluxing Ni–Cr–Mo–Si–B coatings deposited onto carbon steel (BS970 EN8) and stainless steel (UNS S31603) substrates using a commercial high-velocity oxy-fuel (HVOF) thermal spray process are reported. The coatings were studied in as-sprayed, vacuum-sealed (by polymer impregnation) and vacuum furnace fused conditions. In addition, comparisons of the HVOF coatings were made with an uncoated wrought stainless steel (UNS S31603). The erosion–corrosion characteristics were assessed under the influence of a high-velocity single-phase artificial seawater jet (without added solids), impinging perpendicularly onto the coating surface at 72 ms −1 flow velocity. Anodic polarisation tests were performed at both 18 and 50 °C to assess the in situ corrosion performance. Using static seawater results as a reference, the effects of the impinging flow on both the electrochemical response and the damage mechanisms are discussed in this paper. The application of cathodic protection (CP) reduced the extent of deterioration. The study showed the effect of sealing by polymer impregnation did not significantly alter the erosion–corrosion behaviour of the sprayed coating. However, there was an improvement in erosion–corrosion durability afforded by the post-fusion process. The mechanisms by which the improved performance of fused coatings is achieved are discussed.

Influence of soaking and polymerization conditions on the properties of polymer concrete

An experimental investigation was conducted to study the effect of soaking time and polymerization temperature on the mechanical and physical properties of polymer-impregnated concrete. Soaking time was controlled in 4, 8, 12, 16, 20 and 24 h, polymerization temperature was set at 70, 80 and 90 °C for 0.5, 1, 2, 4, 6, 12 and 24 h in impregnation process, respectively. Cylindrical concrete specimens with water/cement ratios of 0.45 and 0.65 were impregnated with methyl methacrylate (MMA) and benzoyl peroxide (BPO) mixtures. The polymer loading increases as immersion time increases until 12 h. Based on compressive strength and surface absorption, optimum polymerization temperature is 70 °C for Mix A (high cement content) and 80 °C for Mix B (low cement content). Polymer impregnation not only increases concrete strength and resistivity but also greatly decreases surface absorption comparing with normal concrete. SEM and MIP observations indicate that the micro-pores and meso-pores of PIC specimens are filled with PMMA and the total pore volume and maximum pore size are reduced significantly.

Polymer impregnation vs. surface coating for targeted manipulation of biocompatibility and mechanical properties of xenogenic decellularized heart valves

Polymer impregnation vs. surface coating for targeted manipulation of biocompatibility and mechanical properties of xenogenic decellularized heart valves

Effect of thick SiC interphase layers on microstructure, mechanical and thermal properties of reaction-bonded SiC/SiC composites

Two types of thick (∼3 μm) SiC interphase layers with new concept between fiber and matrix were prepared; the porous SiC interphase by polymer impregnation and pyrolysis (PIP) treatment, and the two-ply interphase consisting of carbon and β-SiC by chemical vapor deposition (CVD) treatment. The SiC/SiC composites with these new interphase layers were fabricated by reaction bonding (RB) process. The effect of these interphase layers on microstructure, mechanical and thermal properties of SiC/SiC composites was investigated. The densities of SiC/SiC composites in this study attained to relative densities of 92%. The microstructural observation revealed that the two-ply interphase by CVD treatment prevented the fibers from reacting with the melting Si during RB process. This effect leads to the fiber pull-out phenomenon in the specimen with the two-ply interphase, and therefore this specimen exhibited non-catastrophic failure behavior and high bending strength. The thermal conductivities of specimens in this study were much higher than those of the composites by conventional process. The relative density and thermal conductivity of SiC/SiC composites in this study are high enough to attain the assumed design criteria for fusion reactors.

Silver nanoparticles and polymeric medical devices: a new approach to prevention of infection?

Implantable devices are major risk factors for hospital-acquired infection. Biomaterials coated with silver oxide or silver alloy have all been used in attempts to reduce infection, in most cases with controversial or disappointing clinical results. We have developed a completely new approach using supercritical carbon dioxide to impregnate silicone with nanoparticulate silver metal. This study aimed to evaluate the impregnated polymer for antimicrobial activity. After impregnation the nature of the impregnation was determined by transmission electron microscopy. Two series of polymer discs were then tested, one washed in deionized water and the other unwashed. In each series, half of the discs were coated with a plasma protein conditioning film. The serial plate transfer test was used as a screen for persisting activity. Bacterial adherence to the polymers and the rate of kill, and effect on planktonic bacteria were measured by chemiluminescence and viable counts. Release rates of silver ions from the polymers in the presence and absence of plasma was measured using inductively coupled plasma mass spectrometry (ICP-MS). Tests for antimicrobial activity under various conditions showed mixed results, explained by the modes and rates of release of silver ions. While washing removed much of the initial activity there was continued release of silver ions. Unexpectedly, this was not blocked by conditioning film. The methodology allows for the first time silver impregnation (as opposed to coating) of medical polymers and promises to lead to an antimicrobial biomaterial whose activity is not restricted by increasing antibiotic resistance.

Mechanical and thermal properties of poplar wood polyacrylonitrile composites

AbstractWood polyacrylonitrile composite (WPC) from poplar wood was synthesized. The synthetic process was carried out through benzoyl peroxide (0.05 mol l−1) catalyzed impregnation polymerization of acrylonitrile (6.075 mol l−1) into poplar wood in benzene medium at 70 ± 1 °C. Modification of the properties of WPC over untreated wood was evaluated in terms of compression, impact strength and simultaneous differential thermogravimetry‐thermogravimetric‐differential thermal analysis (DTG‐TG‐DTA) in air. Compression, impact strength and resistance of wood against thermo‐oxidation were improved with impregnation of polyacrylonitrile. Impregnation of polyacrylonitrile into poplar wood was ascertained through UV‐vis spectroscopy and scanning electron microscopy. Copyright © 2004 Society of Chemical Industry

Long fibre reinforced ceramics with active fillers and a modified intra-matrix bond based on the LPI process

Silicon-based preceramic polymers are attractive candidates for the manufacture of high temperature and corrosion resistant ceramics, particularly in regard to the formation of a ceramic matrix in long fibre reinforced ceramic matrix composites (CMCs). The manufacture of CMCs constitutes of the infiltration of fibre preforms followed by a subsequent crosslinking and pyrolysis of the Si-precursor, yielding an amorphous ceramic matrix. However, due to the inherent shrinkage of ceramic precursors, a high number of polymer impregnation and pyrolysis (PIP) cycles is required to obtain dense composites. Nevertheless, their microstructure is characterized by large interbundle pores which show a negative impact on the mechanical properties. In order to improve the performance of the long fibre reinforced CMCs as well as to accelerate the manufacturing process, a novel approach was investigated. Thereby, micro-sized powders of Al and Ti are used as active fillers. The powders were strewed between the fabric plies and infiltrated by the resin transfer moulding (RTM) technique. Since reactions with the polymer matrix are associated with a volume increase during pyrolysis, a more dense ceramic matrix is obtained. The processing of the CMCs employs the commercial polysilazanes CERASET SN and VL20 as preceramic precursors. The reinforcement constitutes of Tyranno SA fibres. To densify the composites, up to five PIP cycles were performed. CMC samples were aged in air to evaluate the impact of oxidation on microstructure and mechanical properties. Microstructural characterization was conducted using both optical and electron microscopy. The conversion of the filler particles was analysed by means of EDX and XRD.