摘要:

AbstractStreaming or flow‐birefringence is the optical anisotropy induced by laminar flow in liquids. The optical anisotropy can lie described by an optical tensor which is coaxial with the stress tensor in an elastic material In a tension experiment this is obvious. In laminar flow this has been proved by investigating the distribution of the birefringence in three directions of space. The amount of anisotropy, usually described by the degree of birefringence Δn, is proportional to the difference in principal stresses of the mechanical stress tensor in a very large range of variables, therefore giving the possibility of using optical measurements for the determination of mechanical stresses. However, the relationship is valid either for concentrated solutions or for conditions where the solvent and the polymer have essentially the same index of refractionn—a condition usually termed matching solvent. The proportionality constant between the difference in principal stresses and Δn—the stress‐optical coefficient C—is, as also follows from theory, independent of concentration, shear stress temperature, molecular weight and its distribution, only determined by the structure of the monomer unit and itsn.Another quantity in flow birefringence is the so‐called extinction angle which is measured between the direction of the principal optical axis and the direction of flow. A reasonable amount of experimental data has been obtained to show that this angle can be quantitatively correlated with the so‐called “recoverable shear” that is the shear component of the elastic strain tensor in laminar flow. Therefore, the experimental determination of the angle gives a measure of the elastic strain. A survey of the experimental results in the field shows the generalities of this approach in a variety of polymer

ISSN:0449-2994    

DOI:10.1002/polc.5070050103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1964

数据来源: WILEY

摘要:

AbstractThis paper reviews the theoretical and experimental evidence currently available to establish criteria to aid the experimenter who wishes to use streaming birefringence as a tool for studying fluid flow. Instrumental techniques are reviewed, and the possibilities for both qualitative and quantitative flow visualization by streaming birefringence in pure Newtonian liquids, colloidal suspensions and dilute and concentrated polymer solutions are discussed. Methods of reconstruction of the velocity and stress fields from birefringence data are outlined.

ISSN:0449-2994    

DOI:10.1002/polc.5070050104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1964

数据来源: WILEY

摘要:

AbstractAqueous suspensions of Milling Yellow dye have been found to lie useful for engineering flaw studies by employing established birefringent techniques. In the present work, the basic birefringent and rheologic properties of Milling Yellow suspensions wore measured for a range of deformation rates important to the engineering applications. A concentric‐cylinder polariscope was used to measure the amount of birefringence and the angle of extinction for ten Milling Yellow suspensions at 25°C. varying in concentration from 1.25 to 1.46% dye by weight. The optical properties exhibited by these suspensions are similar to those of a number of colloidal suspensions as reported by past investigators. Rheologic data for Milling Yellow suspensions in the same concentration range were measured at 25°C. for deformation rates of 50–10 sec.−1by means of a capillary viscometer. Over the complete range of deformation rates the rheologic data are accurately described with the Powell‐Eyring relationship for pseudo‐plasti

ISSN:0449-2994    

DOI:10.1002/polc.5070050105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1964

数据来源: WILEY

摘要:

Abstract1Equal energy per unit mass (or volume) proved to be a valid scaling criterion for particle size distribution as well as mean particle size for geometrically similar vessels with a volume range of 4 to 1.2Binodal particle size distributions were observed. Although the coarse fraction varied as the −6/5 power of the agitation rate, the tine size was relatively independent of agitation rate.3The system with the greater drop viscosity gave a smaller fine‐fraction and a larger coarse‐fraction than the other system (IB/W).4Both systems approached equilibrium size slowly (many minutes). Equilibrium was approached more rapidly at high agitation rates. Differences were small between different tank sizes at equal energy dissipation rates per unit mass.5The average size of the fine fraction remains about the same through the run (although the amount increases). The size of the coarse fraction decreases with time. More experiments are necessary to elucidate the mechanism behind

ISSN:0449-2994    

DOI:10.1002/polc.5070050106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1964

数据来源: WILEY

摘要:

AbstractThe birefringence exhibited by high polymers can be explained by considering light as an electromagnetic wave propagating through an anisotropic dielectric. The observed dependence of the birefringence on the deformation stale is described by expressing the dielectric tensor as a functional of the strain history. For small strains, the functional can be approximated by an integral so that the birefringence and strain are related by a law of the Boltzmann superposition integral form.

ISSN:0449-2994    

DOI:10.1002/polc.5070050107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1964

数据来源: WILEY

摘要:

AbstractThe above is an exploratory study started in September 1961 with a view to solving the time dependent stress and strain distributions in structural problems through optical model analysis. The present analysis, however, is restricted to monotonically increasing uniaxial loading. Finally, “optical creep parallels mechanical creep” is the basis on which this analysis is bu

ISSN:0449-2994    

DOI:10.1002/polc.5070050108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1964

数据来源: WILEY

摘要:

AbstractThe principles underlying the dynamic birefringence method are outlined, giving particular emphasis to the use of this technique in investigating the molecular mechanism of relaxation in amorphous polymers. Data are presented for amorphous polyacetaldehyde in the frequency range 1‐20 cycles/sec. and temperature range 0 to −25°C. The results are discussed and compared briefly with dielectric data for poly‐acetaldehyde and also with earlier dynamic birefringence data obtained for polymethyl‐

ISSN:0449-2994    

DOI:10.1002/polc.5070050109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1964

数据来源: WILEY

摘要:

AbstractThe temperature dependence of orientation birefringence has been measured for several different polymers, by producing samples with a fixed degree of orientation by mechanical stretching, and varying the temperature. The following three polymers were studied: polystyrene, poly (methyl acrylate), and poly(methyl methacrylate)—the last in both atactic and stereospecific forms. These all have negative orientation birefringence at room temperature. Measurements were carried out in a range of temperatures below the glass transition temperature, except for poly(methyl acrylate) which was crosslinked. The curves obtained for the different polymers showed considerable differences in form; they were reversible in regard to temperature cycling, and showed no appreciable time effects. Polystyrene showed little change in its orientation birefringence with temperature. The other polymers showed appreciable changes with temperature, and an actual change of sign of the birefringence from negative to positive with increasing temperature. The crossover temperature was near the glass transition temperature for the various stereo forms of PMMA, and measurement of this crossover temperature might therefore provide a fairly accurate method for determining the stereo composition of a PMMA sample. However, the crossover temperature is considerably aboveTgin the case of PMA. We believe that these curves reflect thermal motions of the molecular groups with polarizability anisotropy (such as the phenyl and eater side groups) whose orientation gives rise to the birefringence. The small change is the case of polystyrene is undoubtedly a consequence of the rigidity of the phenyl ring and the steric hindrance of its immediate environment. These results may also reflect chain backbone motions, and other effects, in an indirect way. The theory and experimental data for a complete interpretation of these results is not yet available. However, some of the evident consequences of the present findings are discusse

ISSN:0449-2994    

DOI:10.1002/polc.5070050110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1964

数据来源: WILEY

摘要:

AbstractAssuming that the crystalline polymer consists of the crystalline and the non‐crystalline phase, a mechanical model for the crystalline polymer is constructed. We introduced into this model such complicated circumstances as some parts of the crystalline phase will be largely deformed under a stress concentration and other parts not so much. The temperature dependence of complex moduli of the crystalline polymers with various degrees of crystallinity is illustrated by using the model. On the basis of the model, we have derived an equation for calculating the strain‐optical coefficient of the crystalline polymer from those of the crystalline and the non‐crystalline phase. The equation gives a relation among the rheo‐optical quantities, the viscoelastic quantities and the parameters representing the fine structure and the crystallinity of the polymer. It is concluded from this equation that the strain optical coefficients cannot be expressed by such a simple additive relation as usually e

ISSN:0449-2994    

DOI:10.1002/polc.5070050111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1964

数据来源: WILEY

摘要:

AbstractThe complex strain‐optical coefficient, complex stress‐optical coefficient, complex modulus of elasticity and the corresponding loss tangent of phase angles between the stress, strain and birefringence have been measured for several high polymers in the frequency range from 0.001 to 10 cycles/sec. Frequency and temperature dependences of the dynamic optical properties of vulcanized Hevea rubber are very similar to those of the dynamic mechanical properties. On the other hand, the dynamic optical properties of polyethylene and polypropylene show remarkable dispersions in the above frequency range. The dynamic optical behavior of these three materials are very typical and are quite different from each other. The differences have been explained by considering different frequency dependences of three kinds of deformation mechanism, namely, orientation of molecules in amorphous region, deformation of spherulites, and orientation of cryst

ISSN:0449-2994    

DOI:10.1002/polc.5070050112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1964

数据来源: WILEY