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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 4 (1993), S. 97-101 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: This study evaluated the biocompatibility of an unfilled, fluoride-releasing acrylic resin by subcutaneous implantation in guinea pigs. The experimental fluoride resin was compared to a nonfluoride, dental pit and fissure sealant (DELTON) of similar composition. Thirty-four male albino guinea pigs received four Teflon® tubes each, implanted in the dorsal area. The tubes were open at both ends, three contained the experimental fluoride resin and one held the nonfluoride resin. The tubes and surrounding tissue were excised in 1-2 cm blocks, by necropsy, at 14 and 84 days. Histological evaluation showed that inflammatory response was none-to-slight at 14 days for 95% of the fluoride and 100% of the nonfluoride specimens. Five percent of the fluoride specimens produced a moderate tissue response. At 84 days, inflammatory response was none-to-slight for 82.5% of the fluoride and 61.5% of the commercial nonfluoride specimens, while 17.5% of the fluoride and 38.5% of the nonfluoride specimens produced moderate tissue responses. Chi-squared analysis and Fisher's Exact test revealed no statistically significant difference (p ≤ 0.05) in tissue response between the two resins at either 14 or 84 days. Hence it is concluded that the experimental, fluoride-releasing resin produces a very mild subcutaneous tissue response and that its biocompatibility is comparable to that of a widely used nonfluoride dental resin. It can, therefore, be considered as having a high potential for biological safety as a dental restorative resin or adhesive, or for other biomedical applications. © 1993 John Wiley & Sons, Inc.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 2 (1959), S. 181-185 
    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
    Notes: Differential spectra have been obtained of a number of irradiated polyamides and monomeric amides. These spectra indicate that both free radical and molecular products are produced as primary products. The transient colored products (which are believed to be free radicals) and molecular products appear to be in the amine portion of the molecvle for the most part. The approximate G yield for radical production in nylon 66 is 5.8, and the approximate molar extinction coefficient of the free radical at 355 mμ is 690.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 8 (1964), S. 2465-2478 
    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
    Notes: The relation between polymer and fiber structure and fiber properties is discussed. The specific effects of intermolecular forces, chain stiffness, monomer unit regularity, crystallinity, crosslinking, orientation, molecular weight, and chemical composition on the important fiber properties of melting point, modulus, elasticity, or recovery from strain, tensile strength, moisture adsorption, and dyeability are discussed in some detail. An example is given to illustrate the role of today's sophisticated engineering in further controlling and modifying fiber properties.
    Additional Material: 10 Ill.
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  • 4
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A simple kinetic model for the formation of a nucleotide homopolymer is presented and evaluated. It consists of an initial dinucleotide formation followed by growth through further monomer addition and a competitive phosphorolysis. The molecular weight distribution is narrow up to the first 10-30% conversion and broadens on approach to equilibrium. From the equilibrium amounts of phosphate liberated, the final average molecular weight, and the time pattern of the synthesis, it is possible to obtain estimates of the rate constants. Turning to copolymers, the analysis of experimental data on sequence frequencies in an AU polymer in terms of addition probabilities indicates the existence of a penultimate effect, and a consistent set of four such probability parameters is derived. Finally, we consider a set of rate equations for binary copolymer formation suggested by these results. Their solution will permit a calculation of sequence distributions by utilizing kinetic experimental results exclusively.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 44 (1960), S. 107-116 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The molecular weight distributions of vinyl polymers grafted by irradiation have been deduced theoretically. The derivations are rigorous for cases where chain transfer is not important or in all cases where the radiation dose is high (〉1 Mrad). In the absence of chain transfer, the width of the distribution depends mainly on conversion of monomer to grafted polymer and on the ratio of the rate constant for propagation to that for termination (kp/2kt). As this ratio gets smaller, the molecular weight distribution becomes broader. For relatively small values of kp/2kt (e.g., 0.5 or less), the width of the distribution increases markedly with increasing conversion. In such cases, the occurrence of chain transfer tends to make the distribution narrower. For a monomer grafted to a substrate where kp/2kt = 0.9 (for example), the ratio of weight to number average molecular weight is ca. 2. In general, monomers which have lower rates of propagation should form grafted polymers with broader molecular weight distributions.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 17 (1973), S. 2039-2051 
    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
    Notes: In the history of the automobile, organic fibers have dominated the tire reinforcement field, starting with cotton and progressing through a series of man-made fibers, each finding its place on the basis of its special attributes and overall performance. In general, these fibers were engineered for textile applications, but were subsequently adapted by special processing to make them as suitable for tires as possible. However, each has had limitations which have kept it from certain segments of the market. Moreover, the performance demands on tires have become progressively more stringent, and new tire designs have evolved, so that new tire reinforcement materials are needed. While glass and steel wire are contributing some of the desired properties, they also have their limitations. On the other hand, the potential for creating new, more favorable property balances from organic fibers is far from exhausted. This paper will discuss the main tire yarn property criteria and the polymer and fiber structural factors which control them. Then, the properties and performance of an entirely new fiber, specifically engineered chemically and physically for tire reinforcement, will be described. Fiber properties discussed will include tensile strength, modulus, dimensional stability, fatigue resistance, adhesion, and thermal stability.
    Additional Material: 8 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 19 (1975), S. 1373-1379 
    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
    Notes: An apparatus is devised for measuring the real and imaginary components of the piezoelectric strain constant d = d′ - id″ for polymer films with a d.c. bias field. Electric fieldinduced piezoelectricity is observed for films of several types of polymer. The ratio of the piezoelectric constant to the d.c. bias field gives (∊ + κ)/G where ∊ is the dielectric constant, κ is the electrostriction constant, and G is the elastic constant. The temperature dependence of the field-induced piezoelectricity gives, therefore, combined information of dielectric and elastic properties of polymers. After heating to about 95°C followed by cooling to room temperature, maintaining a constant d.c. basis on a poly(vinyl chloride) film, piezoelectricity is observed at null d.c. field, which suggests the introduction of a residual polarization in the films.
    Additional Material: 5 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 39 (1990), S. 2067-2081 
    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
    Notes: Attempts to spin high-molecular-weight liquid crystalline polyarylates frequently lead to decreases in strength rather than increases as a result of draw resonance in spinning and formation of thick-thin yarns. This phenomenon is attributed to the onset of highly non-Newtonian elongational flow behavior for these polymers. However, the use of small spinneret capillaries, (≤ 6 mils diameter) maintained at temperatures below the melting point of the polymer but above the freezing point, and selection of copolymers which have relatively low heats of fusion (≤ 10 J/g) can eliminate draw resonance and produce relatively high-strength fibers (up to about 14 dN/tex) without heat strengthening. With critical selection of polymer composition (i.e., copolymers containing phenylhydroquinoneterephthalate as the major component and 1,4 hydroxybenzoic acid plus, optionally, a small amount of another monomer as minor components), spinning of high-molecular-weight polymers can be effected above the melting point of the polymers without draw resonance. Tensile strengths as high as 18 dN/tex (as-spun) have been obtained in this way. A mechanism for these effects is proposed.
    Additional Material: 8 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 46 (1960), S. 151-162 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The changes in relative viscosity which occur when nylon 66 is irradiated with 2 m.e.v. electrons under an oxygen-free atmosphere under various conditions have been observed. A mechanism is proposed which reconciles all of these observations, and on the basis of this postulated mechanism yields of chain breaks and crosslinks are calculated. The effect of the presence of a small concentration of a vinyl monomer (acrylic acid) in the polymer during irradiation on degradation and crosslinking is also considered. The rate of penetration of oxygen into irradiated polyamides has been measured. There is a marked reduction in penetration rate which results from the presence of free radicals in the fiber and the irreversible reaction which results. The data are treated by an approximate diffusion equation and estimates of true diffusion coefficients are given. The effect of filament diameter on the extent of degradation which occurs when fibers of nylon 66 are irradiated and then exposed to air has been investigated. The marked dependence of degradation on fiber thickness is related qualitatively to the data on rate of oxygen penetration.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Biomaterials 6 (1995), S. 117-123 
    ISSN: 1045-4861
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The main function of the intervertebral disc is to transmit and attenuate compressive and torsional forces, and stabilize the intervertebral joint. Unfortunately, the disc may be displaced or damaged due to trauma or disease causing the nucleus to herniate and protrude into the vertebral canal or intervertebral foramen. Pressure on the spinal nerve may cause pain or paralysis in the area of its distribution. At present, the surgical procedures used to alleviate this condition include disc excision, and/or spinal fusion. A more desirable situation would involve removing the nucleus pulposus and part or all of the annulus fibrosis and implanting a suitable biofunctional equivalent. Such a prostheis should attenuate stresses and prevent abnormal stress at adjacent intervertebral joints. Maintenance of normal disc height would prevent impingement of the posterior facet joints and facet joint syndrome. In a previous companion paper (J. Applied Biomat. 5:125-132; 1994), the mechanical behavior of disc prostheses manufactured from fiber reinforced, elastomeric thermoset resins were examined. In order to develop devices which were more practical from a manufacturing standpoint and extremely reproducible, the fiber reinforced thermoset resins were replaced by multi-durometer thermoplastic elastomeric materials. In the present paper, the mechanical properties of thermoplastic multicomponent desings have been investigated. © 1995 John Wiley & Sons, Inc.
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