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  • 1
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 15 (1975), S. 869-872 
    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: A series of tests was conducted to measure the failure strengths of notched polymethylmethacrylate tensile specimens in air and n-propanol. Tests were conducted on specimens which had been subjected to creep stresses of various magnitudes and for different times. The resulting data indicate that two opposing factors contribute to the fracture strength in n-propanol. The presence of fluid during crack propagation increases the nominal fracture failure stress. Diffusion of the fluid into the polymer produces crazing resulting in the provision of a preferential crack path and consequent lowering of the fracture strength. The former mechanism dominates at small pre-stresses or at short creep times, resulting in an increase in strength in n-propanol over that in air. However, the latter mechanism is dominant at higher creep stresses and longer creep times with a resulting decrease in strength in n-propanol compared to that in air.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 14 (1974), S. 831-839 
    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: The effects of an isopropanol environment on the deformation characteristics of copoly (acrylonitrile-butadiene-styrene) (ABS) and poly (vinyl chloride) (PVC) have been investigated. Creep tests were performed in tension and torsion both in air and in isopropanol. It was noted that accelerated rates of creep were encountered during the tensile tests in isopropanol as compared with air but no differences were noted during the torsion tests. An explanation is proposed that the greatly increased creep strains encountered in tension result from diffusion of the fluid into the polymer. The rate of diffusion is controlled by changes in the free volume which occur on application of uniaxial tensile stresses. The existence of the fluid molecules in the polymer matrix reduce its local creep resistance and produce swelling, both of which are manifested as increased creep strains. The fact that no effects were noted during torsion tests (where the free volume remains constant) or when an unstressed specimen was immersed in the fluid indicates that no significant absorption occurs at the equilibrium (unstressed) free volume.
    Additional Material: 14 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 18 (1984), S. 255-269 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The activation of the rabbit complement system by each of three different synthetic materials is reported. Samples of each type of material were subjected to one of two different priming procedures. One priming procedure was intended to remove the air nuclei from the surface roughness of the materials; the other procedure was just the normal one. It was found that the removal of the air nuclei during priming reduced the complement activation by each of the two materials of lower surface tension, but not by a statistically significant amount for the material of highest surface tension, cellophane. For the denucleated samples of the three materials, the amount of complement activation was found to correlate with the critical surface tension of the materials; if the samples of the materials were normally primed, there was no correlation of the amount of complement activation with the critical surface tension of the material.
    Additional Material: 3 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 25 (1991), S. 199-211 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Biomaterials activate the complement system which is important since C3a promotes platelet aggregation and release, and C5a activates neutrophils that may augment coagulation. Tiny air nuclei (microbubbles) are found in the surface roughness of biomaterials on exposure to a liquid, therefore two interfaces exist: (a) a blood/biomaterial, and (b) a blood/air interface. Experiments were carried out that documented that air bubbles activate complement and augment in vitro platelet aggregation in human plasma. The air nuclei were removed from the surface of silicone rubber by a technique termed denucleation to determine if complement activation and platelet aggregation could be reduced. We observed a significant reduction in C3a and C5a in the plasma samples incubated with denucleated silicone rubber as compared to the control samples (p 〈 0.001, ANOVA). The plasma incubated with the denucleated silicone caused reduced platelet aggregation as compared to the plasma incubated with the control silicone when added to a platelet suspension (p 〈 0.001, ANOVA). Surface chemical analysis by x-ray photoelectron spectroscopy (XPS) showed no change in the silicone rubber surface after the denucleation procedure.
    Additional Material: 7 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 9 (1975), S. 127-142 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A thermodynamic approach to the problem of platelet adsorption out of a suspension on to a smooth and homogeneous solid surface is developed. The interfacial tension values required may be estimated from contact angle data by means of an equation of state relation. According to the thermodynamic approach the functional dependence of platelet adsorption on surface tension of the solid differs according to whether the surface tension of the platelets is smaller or larger than the surface tension of the liquid in which they are suspended. The implications of this thermodynamic approach in situations where plasma proteins are present and the biomaterials surfaces may be heterogeneous and rough are discussed. Previous analyses using the critical surface tension of wetting and other surface-related parameters are compared with the thermodynamic analysis given here.
    Additional Material: 4 Ill.
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