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  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 9 (1971), S. 801-814 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of temperature and strain rate on the compressive yield behavior of polystyrene is compared with the effect of the same variables on crazing in tension. The results support the conclusion of other, more extensive work, which shows that crazing involves the same types of molecular processes as those which occur during deformation under compression and shear. An improved method of measuring compressive stress-strain curves is then described, and the compressive yield stress is also compared with an extrapolated tensile yield stress. The difference between the two is in line with concepts which assume a dependence of yield stress on the state of hydrostatic tension (or compression). It can be adequately described by the Mohr-Coulomb yield criterion. Application of this criterion also enables a theoretical stress strain curve in tension to be derived from other results in compression. Comparison of the tensile stress-strain curve so obtained with those which can be directly measured with other plastics, supports the hypothesis that crazing is favored by a marked decline in engineering stress during tensile elongation (plastic instability).
    Additional Material: 7 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 34 (1987), S. 2507-2516 
    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 interactions and partitioning of diethyl phthalate and low molecular weight polyethylene-glycols in blends of ethylcellulose/hydroxypropyl methylcellulose have been studied. Both plasticizers were shown to diffuse in both phases according to the overall volume composition. The plasticizers interacted preferentially with one polymer component of the blend as predicted from studies of the individual polymers. Diethyl phthalate, a preferential plasticizer for ethylcellulose, demonstrated increased partitioning in the ethylcellulose-rich phase only at 80/20 w/w ethylcellulose/hydroxypropyl methylcellulose compositions. Polyethylene glycols, PEG200 and PEG400, preferential plasticizers for hydroxypropyl methylcellulose, showed increased partitioning in the hydroxypropyl-methycellulose-rich phase also in blends containing 80% w/w ethylcellulose. The general effect of the mechanism and kinetics of the phase separation of the blend on the plasticizer partitioning has also been discussed.
    Additional Material: 7 Ill.
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  • 3
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Replamineform porous implants (4 mm × 4 mm diameter) were placed into full-thickness cartilage and bone defects of the weight-bearing surface of the lateral femoral condyles of adult male white rabbits. These were analyzed at 1 day, 1 week, 6 weeks, 3 months, and 6 months for (1) ingrowth of tissue within the implants and (2) restoration of the articular surface overlying them. Appropriate unfilled, but similar, control defects were also studied.Mineralized bone was seen within the substance of both the TiO2 and hydroxyapatite implants at 1 week; this extremely rapid response was present in every specimen studied and was not seen with αAl2O3 or control animals. With the passage of time, maturation of this bone ingrowth occurred so that by 3 months, they were all incorportated into the surrounding bone.Only the hydroxyapatite implants showed consistent regenerative healing of hyaline articular cartilage from the margins of the defects with the passage of time; this occurred whenever the subchondral bone adjacent to the defect proliferated in a “creeping” fashion over the articular aspect of the implant, and the undamaged cartilage then followed it. Fibrocartilage, and not hyaline cartilage, formed the articular surface over the TiO2 and αAl2O3 implants and in the controls.
    Additional Material: 3 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 34 (1959), S. 271-285 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polymerization of a monomer in the presence of a preformed polymer with suitable structural features gives rise to block or graft copolymers, which, in favorable circumstances, may be isolated as well-characterized materials. For preparing block copolymers a primary polymer with amine endgroups can be used as a macromolecular transfer agent. Graft copolymers may be prepared by using a primary polymer with terminal double bonds which copolymerize with the second monomer. We have studied the kinetics of block and graft copolymerization based on these methods with particular references to the systems in which the second monomer is acrylonitrile. All transfer agents reduce the rate of heterogeneous polymerization of acrylonitrile since the reduction in molecular weight leads to a diminution in the mean degree of occlusion of the propagating radicals and a consequent increase in the effective termination coefficient. We have found the effect of macromolecular transfer agents on the rate to be greater than that of simple amines. This behavior is attributed to the fact that the radicals produced by transfer are attached to primary polymer chains which are present in solution; as propagation proceeds the growing radicals remain in solution until a comparatively late stage in their growth on account of the solubilizing action of the primary polymer chains. The termination coefficient for these radicals is therefore relatively high and the rate of polymerization correspondingly low. The solubilization of polymer radicals in graft polymerization is less marked than in block copolymerization; this is shown to be consistant with the mechanism of solubilization suggested.
    Additional Material: 5 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 47 (1960), S. 149-156 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Large time-dependent changes in solution viscosity and turbidity have been found on adding nonsolvents to solutions of block, random, and homopolymers containing polyacrylonitrile in N,N-dimethylformamide. These changes have been related to the reversible aggregation of polyacrylonitrile molecules in solution. The effects of polymer concentration, molecular weight, structure and composition have been investigated and a possible mechanism of aggregation suggested.
    Additional Material: 2 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 54 (1962), S. 143-145 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurde gefunden, daß eine Zugabe von monofunktionellen Säurechloriden bei der Grenzflächenpolymerisation von bifunktionellen organischen Säurechloriden mit Diaminen einen kleineren Einfluß auf den Polymerisationsgrad ausübt, als die Theorie vorhersagt.Es zeigte sich, daß dieses Ergebnis auf Molekülverzweigung zurückzuführen ist.
    Notes: The addition of monofunctional acid chlorides in the interfacial polycondensation of bifunctional organic acid chlorides and diamines is less effective in reducing the degree of polymerization than expected from the theory. This result is attributed to branching.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Letters 7 (1969), S. 157-160 
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Letters 1 (1963), S. 171-176 
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Letters 2 (1964), S. 793-797 
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 10 (1972), S. 2545-2564 
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Styrene has been copolymerized at low conversion with minor quantities of p-divinyl-benzene (p-DVB) in (10-15%) solution in toluene and cyclohexane. Under these conditions the molecular weight of the polystyrene formed in the absence of p-DVB was controlled by chain transfer, and the copolymerization coefficients of the styrene and the p-DVB agreed with previous work. Polymer molecular weights were studied as a function of conversion. At very low conversions the number-average (2.2 × 105) and the weight-average (4.4 × 105) molecular weights were unaffected by substituting some of the styrene by p-DVB, but as the reaction continued M̄n increased slowly and M̄w much faster. On the other hand, even at the lowest conversions the intrinsic viscosity was drastically reduced by the introduction of p-DVB, and the radius of gyration, as measured by light scattering, fell. Infrared studies on the polymer show that the concentration of pendent double bonds in low-conversion copolymers is about half of the doubly substituted phenyl groups. It is concluded that the first polymer chains formed are extensively cyclized with the formation of a relatively large number of small rings.
    Additional Material: 13 Ill.
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