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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 25 (1992), S. 6419-6424 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 29 (1992), S. 571-578 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary As-polymerized poly(L-lactide), (PLLA), has a much higher impact strength than after compression moulding. Several routes have been explored to further increase the impact strength of nascent PLLA. First results on the preparation of composites with carbon fibres, the copolymerization with trimethylene carbonate and ε-caprolactone, the block copolymerization with rubbers and the plasticization with ethyl acetate indicate possibilities to prepare much more impact resistant as-polymerized PLLA materials.
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  • 3
    ISSN: 1435-1536
    Keywords: Porousmaterials ; foams ; biodegradablepolyurethanes ; meniscusreconstruction ; freeze-drying ; saltleaching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Porous biodegradable poly(urethanes) for reconstructing menisci have been prepared using two different combinations of techniques: freeze-drying/salt-leaching and in-situ polymerization/salt-leaching. Using these methods, homogenous porous materials with a controllable and reproducible morphology can be prepared. The materials were made of three different poly(urethanes): a methylenediphenyldiisocyanate-based polyurethane, a lysine diisocyanate-based poly(urethane), and a poly(ɛ-caprolactone)-based poly(urethane). The compressive stress-strain behavior of the Estane foams was determined. Foams made by the freeze-drying/salt-leaching technique implanted in dogs showed healing and good ingrowth of fibrocartilaginous tissue.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1435-1536
    Keywords: Porousmaterials ; biodegradablefoams ; meniscusreconstruction ; macroporesize ; interconnectedpores ; porevolume
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Several series of porous, biodegradable PU/PLLA foams were used for meniscus reconstruction in dogs. PLLA-fiber reinforced PU/PLLA composites, PU/PLLA, and PU foams were implanted in severe meniscus lesions. The healing process was initiated as a result of blood vessels′ and other cells′ ingrowth into these porous materials. To accomplish good ingrowth of fibrocartilaginous tissue, the materials should have interconnected macropores of 200–300μn with a high total pore volume. PLLA fibers were used to reinforce the materials, but seem to retard the degradation process and the ingrowth of fibrocartilaginous tissue.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 26 (1991), S. 71-77 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Two new lactone polymerization catalysts, tin(II)-bis(2,4-pentanedionato-O,O') (Zn(Acac)2) and zinc-bis(2,2-dimethyl-3,5-heptanedionato-O,O') (Zn(DMH)2), together with tin(II)-2-ethylhexanoate (Sn(Oct)2), were used to study the effect of the catalyst in the L-lactide polymerization on the nascent polymer structure. Using Zn(DMH)2 an ultra high crystalline polymer was obtained with a ΔHm of 100 J.g-1. Independent of the catalyst and the crystallinity the structure of the crystalline polymer was a pure α-structure as revealed by WAXS-measurements. SAXS-measurements showed a long period for both the Sn(Oct)2 and the Zn(DMH)2 polymer of about 33 nm., the latter revealing a more complex highly regular structure with up to fourth-order reflections. SEM micrographs showed a fibrillar like structure for the Zn(DMH)2 polymer.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 5 (1994), S. 575-581 
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: High molecular weight as-polymerized poly(I-lactide) (PLLA) has been successfully used for fracture fixation and orbital floor reconstruction in animals and humans. As this PLLA takes more than 3 years to resorb, a method was developed to obtain insight into the final cellular degradation process of the PLLA by means of short-lasting animal experiments. Pre-degraded PLLA particles (〈 500 μm) were implanted subcutaneously in the backs of 14 rats. Two different methods of sterilization (regular steamsterilization and gamma-irradiation) and implantation vehicles (gelatin capsules and hydroxypropyl-methylcellulose (HPMC)) were used to examine the biological behaviour of the pre-degraded PLLA. Two rats were sacrificed at 48 h, 3 days and 1, 2, 4, 8, 16 weeks following the operation. The tissues were examined using light microscopy and transmission electron microscopy. Gel permeation chromatography (GPC) and differential scanning calorimetry (DSC) were used to characterize the PLLA material. GPC measurements of the pre-degraded PLLA revealed a M n of 5500. Upon hydrolysation the crystallinity of the PLLA increased by about 60% and the heat of fusion was 86 J g-1. Deterioration of the mechanical and physical properties due to the two sterilization methods was negligible. No differences in cellular response were observed between the densely packed PLLA particles (gelatin capsules) and the particles scattered over the tissue (HPMC-gel). The present study enabled an early observation of the late degradation phase of PLLA.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 6 (1995), S. 191-197 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: In this study, reinforced poly(L-lactic acid) (PLLA) fibers made by a dry-spinning/hot-drawing process were evaluated for use as a suture. The initial tensile strength of the PLLA fibers was lower than the initial tensile strength of the commercially available sutures: PDS, VicrylTM, silk, and Ethilon™. However, after 12 weeks immersion in a phosphate saline buffer at 37°C, PDS sutures have lower tensile strength than PLLA sutures and the tensile strength of Vicryl™ was unmeasurable because of fragmentation. Initially, PLLA fibers distinegrated into fibrils during degradation triggering an inflammatory response comparable to degradable multifilament sutures. However, the intensity of the inflammatory response against the PLLA fibers decreased and after 80 weeks implantation in the muscle layer of the abdominal wall of rats it was comparable to the one against Ethilon™. The inflammatory response against Ethilon™, which is considered to be nondegradable, increased in the same period, probably due to the change in shape. In practice, the handling characteristics of PLLA sutures are superior to the monofilament sutures like PDS and EthilonTM and comparable with the multifilament sutures like VicrylTM and silk. The knot security, but this remains to be investigated. It is concluded that dry-spun/hot-drawn (reinforced) PLLA fibers have the potential for use as long-term degradable suture material. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 2 (1991), S. 23-28 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: As-polymerized poly(L-lactide) test rods were sterilized by seven different specially designed computer-operated autoclaving programs. As a control, common hospital sterilization was performed. In all cases, the molecular weight decreased after sterilization. A short time high-temperature sterilization lead to less molecular weight decrease than a low sterilization temperature cycle with a longer sterilization time. Regular hospital sterilization significantly reduced the elongation at break and also resulted in a decrease of 35% in tensile strength. The program causing minimal damage to the material properties was studied in detail. This program, with a steriliztioan period of 60 s and 129°C, was effective for PLLA steriliztation and also looks very promising for sterilization of other thermo- and moisture-labile polymers.
    Additional Material: 1 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1674-1684 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Copolymers of L-lactide with 15 or more mole % D-lactide are amorphous, noncrystallizable hydrolytically degradable materials. These glassy materials are brittle in tension and bending. To make these materials suitable for use as load-bearing devices in biomedical applications, toughness has to be enhanced. This is effectively accomplished by introducing a separate degradable rubber phase in the amorphous matrix. Several approaches have been explored: solution blending and coprecipitation of trimethylene carbonate and ∊-caprolactone rubbers and poly(lactide), preparation of ABA triblock copolymers and blending of ABA block copolymers with the amorphous poly(lactide) matrix. In all cases very tough materials could be prepared. These materials are easily processable by compression molding at relatively low temperatures.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Basel : Wiley-Blackwell
    Die Makromolekulare Chemie, Rapid Communications 9 (1988), S. 589-594 
    ISSN: 0173-2803
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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