Crystallization kinetics and melting behavior of PEEK were studied by differential scanning calriometry (DSC) and modulated differential scanning calriometry (MDSC). The isothermal crystallization was performed in DSC between 290 and 320¢XC. The Avrami constants (n1, n2) and the level off time were determined from the Avrami analysis. The n1 values varied from 1.50 to 2.98, and the n2 values were between 0.52 and 1.37. The minimum induction time required for the occurrence of double melting peaks was obtained by increasing the isothermal crystallization time in a interval per minute. It was found that the minimum time was always longer than the level off time, which cannot be used as the delimitation for the occurrence of single or double melting peaks. To study the melting behavior and the mechanisms of double melting peaks, the samples after melting at 400¢XC for 15 min were crystallized isothermally between 200 and 320¢XC for 10 or 60 min, and then they were heated to 380¢XC at 10 or 2 ¢XC/min, respectively. From the MDSC results of crystallization temperatures between 280 and 310¢XC, it is found that two different morphologies and melting-recrystallization phenomenon coexisted. As the isothermal crystallization temperature increased from 280 to 310¢XC, the contribution of melting-recrystallization to the upper melting peak gradually decreased. In the case of 320¢XC, the mechanisms of double melting peaks were dominated by two different morphologies only. Quasi-isotropic composites in the stacking sequence of [0/¡Ó45/90]2s were fabricated by a modified diaphragm forming apparatus. Three different processing conditions were used to prepare AS4/PEEK composites with the same crystallinity but different transcrystallinity. The morphology before and after the long-term tensile-tensile tests was observed by means of scanning electron microscope. The transcrystallinity has no significant effect on the short-term tensile test. This was due to the fibers in the 0¢X plies of [0/¡Ó45/90]2S laminates dominated the failure at high stress for the short-term tensile test. However, as the transcrystallinity increased, the failure cycles for the long-term tensile test became longer. This expressed that the delay of damage initiation in the 90¢X and ¡Ó45¢X plies of [0/¡Ó45/90]2s led to a longer failure cycles in the long-term tensile tests.

In this study, the molecular dynamics simulation method was used to investigate the mechanical properties of non-crystalline PEEK mixed with SiO2 nanoparticle. It is found the SiO2/PEEK nano-composite has higher mechanical properties in comparison with pure PEEK composite. Therefore, we wish to obtain the reason. The radial distribution function was used to explain the conformation of the change of microstructure and mechanical properties. The parametric study of different SiO2 particle size was discussed, such on the effects on the structure of PEEK and the strength of the structure.

In this study, PEEK/SiO2 nanocomposites were fabricated by means of simple compression molding technique. The performances and properties of the resulting PEEK nanocomposites were examined in terms of tensile loading, hardness, dynamic mechanical analysis (DMA), thermal mechanical analysis (TMA), thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results indicated that the modified nanosilica was seen to disperse more uniformly than the unmodified counterparty. The XRD patterns of the modified-silica filled PEEK composites reveal a systematic shift toward higher angles, suggesting the smaller d-spacing of the PEEK crystallites. As for the thermal properties of the resulting PEEK nanocomposites, there is no significant difference for the melting and crystallization temperatures, as well as the degree of crystallization between the modified and unmodified silica filled PEEK nanocomposites. The TMA results show that the coefficient of thermal expansion (CTE) becomes lowered when the content of the nanosilica increases. Furthermore, the CTE of the modified-silica filled PEEK nanocomposites shows the higher CTE values, as compared with those of the unmodified counterparts. In addition, the inclusion of the nanosilica could improve the microhardness and the stiffness of the resulting PEEK nanocomposites with the sacrifice of the elongation, as evident from the tension and DMA testing.

Magnesium alloys have attracted considerable attention owing to its low density of ~1.7 g/cm3. On the other hand, the carbon fiber (CF) reinforced polyether ether ketone (PEEK) polymer composites possess extraordinary specific strength and stiffness along the longitudinal (or fiber) direction. It follows that the combination of Mg/CF/PEEK would offer an alternative in forming a high specific strength and stiffness composite. In the first part of this study, the low density and high performance Mg-based laminated composites were fabricated by means of sandwiching the AZ31 Mg foils with the carbon-fiber/PEEK prepreg through hot pressing. Proper surface treatments of AZ31 sheet using CrO3 base etchants are necessary in order to achieve good interface bonding characteristics. The resulting Mg base laminated composite, with a low density of 1.7 g/cm3, exhibits high modulus of 75 GPa and tensile strength of 932 MPa along the longitudinal direction. The experimentally measured tensile modulus and strength data along both the longitudinal and transverse direction are within 90-100% of the theoretical predictions by rule of mixtures, suggesting that the bonding between layers and the load transfer efficiency are satisfactory. The flexural stress and modulus along the longitudinal direction are 960 MPa and 54.6 GPa, respectively, suggesting a sufficiently high resistance against bending deflection. The peel strengths are about 2.75 and 4.85 N/mm along the longitudinal and transverse directions, respectively, superior to that of the epoxy-resin-adhered and carbon-fiber-reinforced aluminum laminated composites. Polymer nanocomposites have attracted considerable attention during the past decade due to their versatile and extra-ordinary performances. The polymer nanocomposites can be prepared by the well-known sol-gel method. It is well known that PEEK is a good solvent resistant polymer. Hence, it is impossible to fabricate the PEEK nanocomposite by means of sol-gel method. In the second part of this study, the PEEK nanocomposites filled with nano-sized silica or alumina measuring 15-30 nm to 2.5-10 weight percent were fabricated by vacuum hot press molding at 400oC. The resulting nanocomposites with 5-7.5 wt% SiO2 or Al2O3 nanoparticles exhibit the optimum improvement of hardness, elastic modulus, and tensile strength by 20-50%, with the sacrifice of tensile ductility. With no surface modification for the inorganic nanoparticles, the spatial distribution of the nanopartilces appears to be reasonably uniform. There seems no apparent chemical reaction or new phase formation between the nanoparticle and matrix interface. The crystallinity degree and thermal stability of the PEEK resin with the addition of nanopartilces were examined by X-ray diffraction, differential scanning calorimetry, and thermogravity analyzer, and it is found that a slight decrease in crystallinity fraction and a higher degradation temperature would result in as compared with the prestine PEEK.

Die Snake Plate ist ein im Composite Flow Moulding Verfahren (CFM) aus endlosen Kohlenstofffasern und PEEK (CF/P) hergestelltes neues Implantat für die Frakturbehandlung. Besondere Merkmale sind hohe Formbeständigkeit, konvergierende, winkelstabile Schrauben sowie eine völlige Strahlendurchlässigkeit. Integrierte Tantalfäden machen die Platte artefaktfrei radiologisch sichtbar. Ziel dieser in vivo Studie war ein Vergleich des Heilungsverlaufes zwischen der 7-Loch Snake Plate und der bereits klinische verwendeten 7-Loch LCP. Die Tiere wurden in 2 Gruppen (n=6) zufällig aufgeteilt. Eine 0,6mm breite Osteotomie der rechten Schafstibia wurde mit der Snake Plate bzw. der LCP und 6 winkelstabilen Schrauben versorgt. Zur postoperativen Fluoreszenzmarkierung des Kalzifizierungsprozesses erhielten die Tiere in der 5. Woche Xylenol Orange und in der 7. Woche Calcein Grün. Die Makrophagen/Histiozyten- Schichtdicke des Weichteilgewebes wurde computerunterstützt semiquantitativ vermessen. Eine qualitative Beurteilung der Gewebszonen und der Sentinel Lymphknoten folgte. Der Kalzifizierungsprozess in der Osteotomiezone wurde computerunterstützt quantitativ erfasst und qualitativ beurteilt. Die Osseointegration der Schrauben wurde quantifiziert, indem der prozentuale direkte Schrauben-Knochen-Kontakt computerunterstützt berechnet wurde. Die Knochenumbauvorgänge im Bereich des Schrauben-Knochen-Interfaces wurden erfasst, indem die Anzahl der Osteone gezählt und ihre Tiefe in den Bereich der Kortikalis errechnet wurde. Es ergaben sich zwischen den Gruppen hinsichtlich der semiquantitativen Ausmessung der Makrophagen-Histiozyten-Schichtdicke keine Unterschiede. Die zelluläre Zusammensetzung im plattennahen Weichteilgewebe zeigte keine Unterschiede. Abriebpartikel wurden in den Sentinel-Lymphknoten nicht gefunden. Zwischen den Gruppen zeigten sich keine Unterschiede im Ausmaß des kalzifizierten Kallusgewebes im Osteotomiespalt. Die knöcherne Überbrückung der Frakturzone war plattennah weiter fortgeschritten als plattenfern. Die qualitative Beurteilung war unauffällig und in beiden Gruppen ähnlich weit fortgeschritten. In der Beurteilung des Knochenumbauprozesses konnten zwischen den beiden Gruppen keine Unterschiede gefunden werden. Auch im zeitlichen Verlauf der Heilung zeigten sich in beiden Gruppen keine Unterschiede. Die Titan-Schrauben wiesen eine signifikant höhere direkte Knochen-Kontakt Zone auf als die PEEK-Schrauben. Im Allgemeinen zeigt sich das Gewebe sowohl im Kontakt mit den Kohlefaserimplantaten als auch mit den Titanimplantaten reizarm und ohne die bei Entzündungen üblichen zellulären Reaktionen. Die biologischen und mechanischen Bedingungen der beiden Plattenarten müssen offensichtlich ähnlich sein, da die Frakturheilung in beiden Gruppen gut fortgeschritten war. Der geringere direkte Knochenanteil der PEEK-Schraube ist wahrscheinlich materialbedingt. Es ist bekannt, dass Knochenzellen sich direkt auf Titanmaterialien ablagern können, wodurch das Einwachsverhalten in den Knochen begünstigt werden kann. Einen Einfluss der unterschiedlichen Biokompatibilitäten der Implantatmaterialien auf die Knochenumbauprozesse im Bereich des Schrauben-Knochen-Interfaces konnte nicht nachgewiesen werden. Die Verbesserung des Interface zwischen Knochen und Implantat ist immer noch ein ungelöstes Problem. Ziel ist es, eine geeignete Umgebung zu schaffen, durch die das natürliche Potential des Knochens zur Regeneration stimuliert und maximiert werden kann. In weiteren Studien sollte untersucht werden, ob die Biokompatibilität der neu entwickelten PEEK-Schraube durch unterschiedliche Oberflächen-behandlungen, beispielsweise mit Titan, erhöht werden kann und daraus eine bessere Osseointegration erzielt werden könnte. / The Snake Plate, produced out of carbon fibre and PEEK (CF/P) by using the composite flow moulding method (CFM),is a new implant for fracture treatment. The special features are resistance to deformation, converging locking screws and radiolucency. The Radiological visualization free of artefacts is made possible by integrated tantal threads. The goal of this “in vivo study” was to compare the process of recovery using the seven-hole Snake Plate to the actual in clinical use seven-hole LCP. The animals were randomly divided into two groups (n=6). A 0.6 mm wide osteotomy of the right tibia was stabilized with the snake plate for the one and LCPs for the other group. All were fixed with six locking screws. The animals received Xylenol orange in week five and Calcein green in week seven as fluorescent dye in order to mark the postsurgical calcification process. The thickness of the macrophage/histiocyte layer of the soft part tissue was measured in a computer-assisted and semi-quantitative way. It was followed by a qualitative assessment of the different layers of the tissue and of the sentinel lymphatic nodes. The process of calcification in the osteotomy area was also measured computer-assisted and was qualitative assessed. The osseointegration of the screws was quantified by a computer-assisted calculation of the percentage of direct contact between screws and bone. The osteogenetic processes in the interface between screws and bone were measured by counting the osteones and calculating their depth in the area of the corticalis. Neither the semi-quantitative measurements of the macrophage/histiocyte layers nor the cellular composition of the soft part tissues near the plate showed different results for the two groups. No particles of attrition were found in the sentinel lymphatic nodes. The two groups did not show any differences concerning the semi-quantitative measurements of the macrophage/histiocyte layers. There was also no difference regarding the amount of calcified callus in the gap of osteotomy. The osseous bridging of the fracture zone was further advanced near the plate. The qualitative assessment was not unusual and the progress was comparable in both groups. There were no differences between the two groups concerning assessment of the osteogenetic processes. The chronological process of the consolidation did not show any differences between the two groups either. The area of direct bone contact was significantly higher with the titanium screws than with the PEEK-screws. In general the tissue was hardly irritable in contact with the carbon fibre implants as well as with the titanium implants. Neither were there any cellular reactions typical for inflammations. The biological and mechanical conditions of the two types of plates are apparently similar, as the healing of the fracture was advanced in both groups. The low direct bone contact of the PEEK-screws is probably associated with the material. It is well-known that osteocytes can accumulate on titanium, a fact which may favour the growing-in of the material into the bone. An influence of the different biological compatibilities of the materials of the implantations on the osteogenetic processes in the interface between screws and bone could not be proven. The improvement of the interface between bone and implant is still an unsolved problem. The aim is to create a suitable environment for stimulating and maximizing the natural regenerative potential of the bone. Further studies should be carried out in order to find out whether the biological compatibility of the new PEEK-screw can be improved by treating its surface with titanium for example. This might lead to an improvement in osseointegration.

The effect of orientation and crystallinity of certain polymers, polyethylene, polypropylene, polyethylene terephthalate (PET) and poly (ether ether ketone) (PEEK) , upon the extent and nature of plasma oxidation was studied. It was found that increasing the extent of surface ordering lessened susceptibility to plasma oxidation and reduced the subsequent decay of surface treatment. The surface ageing of plasma oxidised PEEK was extensively studied with regards to the transient increase in hydrophilicity that has been observed after plasma modification. The decay and transient increase in hydrophilicity were found to be dependent upon crystallinity and storage temperature. An estimate of the activation energies for processes leading to the increase in contact angle after plasma modification were calculated and found to suggest that these processes were rotational reorganisations at the surface as opposed to migrational reorganisations. The decay of other plasma modified surfaces revealed that plasma oxidised PET and plasma fluorinated PEEK both underwent transitional reorganisations at the surface, however no such change was observed for ammonia plasma treated PEEK. Plasma modification of carbon fibres was investigated with regards to improving composite performance. Microwave plasma treatments were found to be as good as standard commercial treatments. Graphitic carbon was investigated as a model for carbon fibre surfaces, however, the plasma modified surface was found to age more readily and to be too labile for useful comparison.

Long time annealing of semicrystalline PEEK above the glass transition results in the observation of several time dependent phenomena - "physical aging", "secondary crystallization", "multiple melting" of lamellae with different thermal stability etc. Their interrelation - common origin and kinetics of development, is characterized extensively for the first time in this study. The evolution of the crystallinity during the secondary crystallization process was monitored by DSC and density measurements. Crystallinity was characterized according to the standard two-phase model of semicrystalline polymers and analyzed with respect to the failure of the model to adequately describe the physical state of the polymer. A discrepancy was observed between DSC and density crystallinity values and their respective rates of development during the secondary crystallization stage. WAXS reveals that the crystal density is not a physical constant, but depends on the crystallization and/or annealing temperature. Furthermore, the crystalline lamellae densify with time during crystallization and/or annealing. This observation leads to the conclusion that there is no one-to-one correspondence between density and crystallinity and necessitates the application of a revised equation for density crystallinity which accounts for the dynamics of crystal densification. The characteristics of the low temperature endothermic peak in the DSC scan of PEEK (peak maximum, transition enthalpy etc.) were found to evolve with annealing time and temperature during the secondary crystallization process in a way similar to the kinetics of development of the enthalpy relaxation process in amorphous polymeric glasses. This study reports for the first time in the literature the observation of "physical aging" above the glass transition in the case of PEEK (according to the definition of this term given by Struik). An extensive investigation of the "double melting"/"multiple melting" phenomenon, which is observed as a result of isothermal treatment of the polymer above Tg, was performed and several new observations reported. After the end of the primary crystallization process, the semicrystalline polymer is a nonequilibrium system due to the fact that crystallinity is less than unity. The system's continuing approach to equilibrium and its response to mechanical perturbations follow kinetics similar to that of segmental relaxation below the glass transition. / Ph. D.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第20234号 / 医博第4193号 / 新制||医||1019(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 安達 泰治, 教授 横出 正之, 教授 鈴木 茂彦 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

A cheaper access to space is needed in current times and new technologies need to be developed to reduce the cost of space access to increase productivity. This thesis presents a study on carbon fiber reinforced polymer (CFRP) composites which is an enabling technology for cost reduction in space vehicles. A literature review of the behavior of CFRP composite has been conducted and it was found that the currently used IM7/977 carbon fiber reinforced epoxy composites do not microcrack at a lower number of thermal cycles. Nano-composites and Thermoplastic matrix composites have been found as two promising alternatives for cryogenic applications. With the use of nano sized inclusions in currently used epoxy resins, coefficient of thermal expansion can be reduced while increase in strength and fracture toughness can be achieved. Some thermoplastics were found to have non-linear stress-strain relationships with signs of ductility even at 4.2K. Both of these resin systems show promise in reducing microcracking at cryogenic temperatures.

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