Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Relationship between the structure, rheological properties and processability of methacrylic polymers (1976)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 53 (1976), S. 1-18 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Polymethylmethacrylat (PMMA) zählt zu den seit langem bekannten Polymeren und findet wegen seiner besonderen Transparenz und Alterungsbeständigkeit vielfache Anwendung. Trotzdem liegen zum rheologischen Verhalten von PMMA nicht genügend Angaben vor.Aus einem größeren Untersuchungsprogramm zur Bestimmung eines Zusammenhangs zwischen chemischem Aufbau verschiedener Polymethylmethacrylate und deren rheologischem Verhalten wie auch zwischen rheologischem Verhalten und Verarbeitbarkeit wird im vorliegenden ersten Teil speziell über den Einfluß von Molekulargewicht (MG) und Molekulargewichtsverteilung (MGV) auf das rheologische Verhalten berichtet.Aus den Meßergebnissen läßt sich folgern, daß (a)der Exponent a in der Beziehung η = KMa unabhängig von der MGV ist und mit guter Näherung gleich 4 gesetzt werden kann,(b)die Aktivierungsenergie nicht vom MG abhängt und gleich 44,7 kcal/mol gesetz werden kann und(c)die reduzierte Viskosität in Abhängigkeit von der reduzierten Schergeschwindigkeit \documentclass{article}\pagestyle{empty}\begin{document}$\mathop {\gamma _r }\limits^ \cdot $\end{document} im Bereich kleiner Werte von \documentclass{article}\pagestyle{empty}\begin{document}$\mathop {\gamma _r }\limits^ \cdot $\end{document} gut mit der Theorie von Graesslay, für große \documentclass{article}\pagestyle{empty}\begin{document}$\mathop {\gamma _r }\limits^ \cdot $\end{document} mit der Theorie von Bueche beschrieben werden kann.
    Notes: Poly(methyl methacrylate) is one of the oldest synthetic polymers and is widely used because of its intrinsic properties of transparency and ageing resistance. There is, however, relatively little information in literature concerning its rheological behaviour in the molten state.In our laboratory the correlations between the composition of methacrylic polymers and their rheological behaviour on the one hand and between rheological behaviour and processability on the other hand have been studied. This first part gives the results relevant to the influence of molecular weight and its distribution on the rheological behaviour of methacrylic homopolymers.It has been found that (a) the exponent, a, of the η=K·Ma relation is independent of the molecular weight distribution and may be assumed with close approximation as equal to 4, (b) the activation energy of the viscous flow is independent of the molecular weight and may be assumed as equal to 44.7 kcal/mol, (c) the experimental curves of reduced viscosity as a function of the reduced shear rate correspond fairly well with Greasslay's theory at low shear rates and with Bueche's theory at high values.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1976.050530101
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Mineralization and calcium fixation within a porous apatitic ceramic material after implantation in the femur of rabbits (1988)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 22 (1988), S. 445-457 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Cylinders (0.8 cm long, 1.0 cm of diameter and with an axial hole), constituted, after firing, of a ceramic mixture of hydroxylapatite (HA) and β-ricalciumphosphate (β-TCP) in a 10:1 ratio, were implanted into mid-diaphiseal defects of one femur of 20 rabbits and stabilized with intramedullary rods. The implantation sites were checked radiographically every month, and after 3 months (3 animals) and 6 months (17 animals) the rabbits were sacrificed and the implants with the surrounding tissue were embedded in methylmetacrylate, cut to thick sections and analyzed by scanning electron microscopy (SEM). Porosimetric and x-rays diffraction analyses were carried out before and after implantation of the cylinders, and the state of mineralization at the bone-implant interface was determined by EDAX microprobe analysis. Bony callus formation started at 1 month at the osteotomy sites, as judged by radiography, but after 3 months a not-mineralized zone had still been demonstrated between bone and the implants. At 6 months, 13 implants showed themselves firmly fixed in their implantations beds, while 4 implants were only incorporated at their proximal ends. In bone contact zones, an enrichment of Ca2+ was displayed by microanalytical techniques in the outer zone of the implanted samples which may be explained by an apparent additional phase transformation of HA into TCP, thanks to the change of the Ca/P ratio, that takes place in vivo.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820220602
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    The interface of bone microstructure and an innovative coating: An X-ray diffraction study (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 86-91 
    Details
    ISSN: 0021-9304
    Keywords: X-ray diffraction ; ceramic ; external fixation ; coating ; biocompatibility ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The in vivo compatibility and degradation aspects of an innovative coating to be sprayed onto titanium implants were investigated. The surface of fluorinated apatite (fHA), consisting of fluorhydroxyapatite plasma sprayed in a vacuum atmosphere, was treated with carbonate to improve its biological compatibility. fHA coating was compared with titanium implants coated (a) with hydroxyapatite (HA) by the traditional plasma spraying, and (b) with titanium oxide (TiOx). Screw-shaped implants were inserted in the cortical bone of sheep tibiae. X-ray diffraction (XRD) analysis of bone tissue and coatings was carried out at 2, 4, 12 and 36 weeks after surgery. The crystallographic habit of the implant-facing bone, as well as the structural stability of the coating, were evaluated. For each time period and type of ceramic bone apatite lattice at the interface, no significantly different reference apatite lattice and no foreign peak were recorded. Two weeks after implantation, the bone at the interface was strongly unmineralized in all samples; after 4 weeks, poorly mineralized bone microareas decreased. At 12 weeks, the newly formed bone tissue at the interface with both the new coating and HA coating was shown to be fully mineralized; this crystallographic habit was retained at 36 weeks, when particle release from the tested material was lower compared to the controls. The XRD pattern of bone apatite surrounding the coating particles was unmodified. The innovative coating did not alter the mineralization process at the interface. It improved implant osteointegration, mainly due to a limited release of particles. Consequently, clinical performance of external fixation treatment could be improved by modifying the chemical composition of the implant surface. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 86-91, 1998.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    Microhardness of bone at the interface with ceramic-coated metal implants (1995)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 695-699 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We evaluated bone microhardness at the interface with hydroxyapatite-coated stainless-steel pins used in an external fracture fixation system. Pins were transversally inserted into the diaphyses of sheep tibiae and were loaded in for 6 weeks. Uncoated pins were implanted as controls. Microhardness analysis, based on the measure of the resistance of the bone to the penetration of a small diamond pyramid, yielded an accurate and reproducible measure of the mineralization degree and of the orientation of collagen fibers. Bone tissue close to the pin is less hard than bone tissue far from it. Moreover, the presence of hydroxyapatite coating on the pins did not significantly affect bone hardness; actually, the mean hardness at the interface with the pins was 56.9 Vickers degrees, whereas at the interface with the uncoated pins it was 62.2. It can be concluded that, 6 weeks postsurgery, the bone growing into the threadings of a loaded screwed implant reached maturity at a degree lower than that of the host both uncoated and coated implants. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820290604
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...