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  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 601-608 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The glass transition temperatures Tg of several fluorine-containing polymers were determined by use of the differential scanning calorimeter. Values between -3 and 230°C were obtained. In polymers of α-olefins, Tg increases with the fluorine content of the backbone and the length of the n-perfluoroalkyl branch. In styrene polymers Tg also is higher if the backbone contains fluorine but nearly the same Tg's are found for polymers with phenyl and pentafluorophenyl groups. Saturated polymers of perfluoro-α,ω-dienes have lower Tg's than polyperfluoro-α-olefins. The Tg's of chloroperfluoropolymers are higher than those of perfluoropolymers. Polyperfluoropentadiene-1,3 has the lowest Tg of the polymers examined. Polyperfluoropentadiene-1,3 forms by 1,4-addition.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 27 (1993), S. 575-585 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This study investigated strain distribution changes in the proximal femur after implantation of a flexible composite femoral component (carbon composite material, modulus of elasticity = 18.6 GPa), a titanium alloy implant (E = 100 GPa), and a stainless steel implant (E = 200 GPa). Transverse as well as longitudinal strain was measured using bipolar strain gauges at eight locations on the proximal femur under both physiologic axial (1000 N and 2000 N) and physiologic torsional (10 N-m and 20 N-m) loads. Under axial load, longitudinal compressive strain at the calcar region was significantly greater in intact femurs and the carbon composite stem specimens than in the two metal stem specimens. The difference between intact femurs and the carbon composite stem specimens was not significant. Stress shielding in the proximal lateral region of the femur, however, was still apparent even in the carbon composite stem specimens. Without seating of the stem collar on the femoral neck, longitudinal compressive strain was not generated at the calcar region, and transverse tensile strain at this region was increased. With conventional implant design, the stem collar was still necessary even in the flexible composite stem to provide near normal longitudinal compressive strain in the calcar region. Under torsional load, proximal strain in intact femurs was small and the proximal strain levels observed after either carbon composite or titanium alloy stem implantation were greater than strain levels before implantation. It seemed unlikely that torsional stress relief played a significant role in proximal bone loss after total hip arthroplasty. Both longitudinal and transverse strains at the calcar region under torsional load were significantly greater in the carbon composite stem specimens than in both intact femurs and the titanium alloy stem specimens, suggesting that these abnormally high proximal stresses may cause high proximal micromotion of the implant, and even bone fracture. Proximal implant design seems to be of paramount importance with flexible composite femoral components to avoid excessive proximal stress concentration under torsional load and-to provide near normal strain distribution in the proximal femur. © 1993 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 26 (1992), S. 93-102 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Tricalcium phosphate (TCP) is an osteoconductive bioceramic which, when applied to a porous-coated prosthesis, may enhance osseous ingrowth and mechanical stability. TCP plasma-sprayed and unsprayed porous-coated tibial intramedullary rods were bilaterally implanted in seven adult rabbits. All rabbits were killed at 12 weeks. Pull-out tests were performed on 4 rabbits while all were evaluated histologically for osseous response and adverse tissue reaction. TCP-sprayed implants showed significantly greater osseous ingrowth in comparison to unsprayed implants. Neither implant type exhibited adverse tissue reactions. Average pull-out strengths were 69 lb for treated rods and 72 lb for controls (p 〉 0.05); quality of fit for all pull-out specimens except one was deemed poor. We conclude that plasmasprayed TCP enhances osseous ingrowth into porous-coated devices. However, our data further suggest that enhanced ingrowth may not always lead to enhanced fixation.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Copolymers of tetrafluoroethylene and propylene were prepared that contained 30-65 mole-% of the former. Reactivity ratios of tetrafluoroethylene- and propylene-ended radicals are 0.008 and 0.06, respectively, resulting in formation of highly alternating copolymers. The glass temperatures, Tg, were determined using a differential scanning calorimeter. Values ranged from 260 to 275°K. A plot of Tg versus composition has a low maximum centered about the equimolar composition. Copolymers of tetrafluoroethylene and isobutylene were prepared that contained 30-56 mole-% of the former. Reactivity ratios of tetrafluoroethylene- and isobutylene-ended radicals are 0.005 and 0.021, respectively. The glass temperatures of these copolymers range from 257 to 313°K. A higher maximum at the equimolar composition is obtained when Tg is plotted versus composition. Isobutylene-containing copolymers having 45-54 mole-% tetrafluoroethylene are crystalline. Melting temperatures range from 416 to 476°K and have their maximum value at the equimolar composition. It is thought that long sequences of alternating units behave as a third entity in these copolymers, the other two being nonalternating units of the two monomers. Unless inhibited, ionic homopolymerization of isobutylene can be appreciable, sometimes resulting in the polymer having two Tg.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The radiation-induced polymerization of cis- and trans-1,3,3,3-tetrafluoropropene in bulk and with tetrafluoroethylene was studied at pressures between 5000 and 15000 atm and temperatures between 21 and 100°C. At 103 rad/hr the homopolymerization rates range from about 10-4 to 1%/hr. The activation enthalpy and volume are about 8 kcal/mole (33 kJ/mole) and -10 cm3/mole, respectively, for both isomers. The cis isomer polymerizes about twice as rapidly as the trans isomer. The latter freezes in the experimental range of temperature and pressure; the polymerization rate is very low in solid phase. Polymer intrinsic viscosities increase with polymerization pressure and decrease with polymerization temperature; the largest value obtained was 0.23 dl/g. In the copolymerizations all reactivity ratios favor incorporation of tetrafluoroethylene by factors of 6-16. The preference is stronger when the trans isomer is used.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 2 (1947), S. 542-543 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 62 (1962), S. S5 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The extent of branching in polystyrene is attributed to a polymer transfer step occurring during polymerization. In this process a radical abstracts a hydrogen atom from along a chain which then adds monomer at the site of the abstraction. The rate of this process should be decreased if the hydrogen is replaced by deuterium, and consequently deuterated monomers should polymerize to form polymers less branched than those from the nondeuterated monomer. Polymers of α- and β-deuterostyrene were synthesized and thier intrinsic viscosity and molecular weight by light scattering determined. In the case of the α-deuterostyrene, the polymer was also fractionated and measurements were made on the fractions. The data for the deuterated styrenes fit quite closely the same relationships as a normal styrene sample prepared simultaneously and under the same conditions, i.e., 70°C. and without catalyst. The results indicate, therefore, that branching is quite small in polystyrene prepared under such typical conditions. A check of the isotope effect on the transfer process was made utilizing S-deuterobutyl mercaptan. A value of 4.0 was obtained at 60°C. for the relative rate of transfer with butyl mercaptan to that for the deuterated mercaptan.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 17 (1955), S. 141-142 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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