ALBERT

Notes: Summary It has been experimentally observed that one-inch thick soil-cement slab (fine-grained soil), upon drying from the top face, first deforms with a concave surface at the top and gradually assumes an opposite curvature with convex surface at the top. The latter shape contradicts the classical analysis ofPickett. A theory whereby the doming can be predicted is proposed in this paper. Moisture migration in the drying slab is determined by the unsaturated capillary flow theory, modified to account for the fact that soil-cement will exhibit hysterisis in the relation between pressure head (capillary tension) and its moisture content. By postulating that moisture tension (stress) results in deformation or shrinkage, a relation between shrinkage and moisture tension is obtained from experimental data. The results seem to violate an intuitive feeling that the exposed top face should shrink more than the sealed bottom face. The creep compliance of soil-cement specimens is determined for a range of humidities from 55–100%. Finite difference techniques have been employed to compute the relaxation modulus from creep compliance which are related throughBoltzmann integral. To include the dependence of the modulus upon a variable humidity field, constitutive law is modified on the basis of time-humidity equivalence hypothesis. Imposing on the theoretical shrinkage distribution, computations for stresses and deflections are made from two points of view: 1. Using the simplifying assumption that the relaxation modulusG(t) does not vary with humidity and 2. allowing for the humidity variation in the transient problem and using a generalG(t, H). The solution from the first point of view is obtained by equivalent shrinkage concept and from the latter by finite element method. The computed deflections not only predict doming but also show good agreement with the observed values. It should be noted that the current theory predicts deflections opposite to those predicted by conventional analysis when the moisture movement is assumed to be governed by diffusion law and shrinkage to be proportional to moisture loss.

Notes: Summary The equations for determining die swell of molten polymers are discussed. The critical conditions for melt fracture and die swell results are combined in order to explain the flow behavior at the onset of instability. It is shown that the factor $$\bar M_z \bar M_{z + 1} /\bar M_w^2 $$ is the most important parameter in die swell and melt fracture studies.

Notes: Résumé Les premiers essais réalisés sur la planche à peindre nous ont permis de chiffrer l'ordre de grandeur des efforts d'application et de mettre en évidence l'importance pour une peinture donnée, du rapport de l'effort normal sur l'effort tangentiel. Cette technique simple peut permettre un contrôle rapide, en cours de fabrication, de la brossabilité d'une peinture. Toutefois la mise au point d'un applicateur automatique éliminant sur les résultats la dispersion due au peintre semble indispensable si l'on veut lier la brossabilité aux caractéristiques rhéologiques d'une peinture.

Notes: Summary In order to investigate the short time response of solid polymers, a high resolution laser interferometer has been employed to observe the detailed structure of stress waves produced by the impact of polymeric plates. From the observed stress waves the loading and unloading stress-strain paths followed by the material can be determined. For the polymer, polymethyl methacrylate, over the stress range from 0–60 kbar such observations have disclosed a stress-strain behavior which exhibits large strain nonlinearities and significant rate-dependence. For stress levels below ≈7 kbar and above ≈40 kbar, rate-effects are of secondary importance and the observed wave profiles may be modeled using a nonlinear elastic description of the material behavior. However, at about 7 kbar, a transition is observed in the dynamic stress-strain behavior which is characterized by greater stress relaxation and significant hysteresis upon unloading. This transition, which we attribute to a yield phenomenon, requires a rate-dependent description of the material behavior to be used in the stress range of approximately 7–40 kbar.

Notes: Summary A simple and reliable relative method to derive the molecular weight distribution of linear polymers is proposed. It is shown that both the zero-shear viscosity,η 0, and the intrinsic viscosity, [η], have a logarithmic dependence on the weight average molecular weight, $$\bar M_w $$ , and the polydispersity, $$Q = \bar M_w /\bar M_n $$ . The coefficients of these relationships can be determined by applying a multiple regression analysis to a series of samples for which $$\bar M_w $$ andQ are known. By making use of the two established relationships, the determination of $$\bar M_w $$ andQ for a given polymer sample reduces to the experimental measurement of itsη 0 and [η]. An analysis has been performed to estimate to what extent experimental errors onη 0 and [η] affect the calculated molecular weight distribution. It has been found that only the experimental error on [η] contributes heavily to the final error on the polydispersity.

Notes: Summary High shear capillary viscometry at 37.8°C (100°F) of concentrated solutions of a series of polyalkylmethacrylate viscosity index improvers in a petroleum lubricating oil is reported. Viscosity average molecular weights of the four polymers varied from 355 000–1650 000 and solution concentrations varied from 2–20 wt.-%. An approximating function based on the error function was computerfit to the complete flow curves by correlating the distribution of apparent viscosity with the product ( $$\dot \gamma $$ τ), the rate of viscous energy dissipation. This gave an estimate of the secondNewtonian viscosity (η ∞ ) and two parameters of the approximating function. The fourth quantity required to completely define the flow curve is the low shear or firstNewtonian viscosity (η 0 ). Representation of the original data was within 2%, by this technique. The parameters of the flow function — the energy level at the inflection point and the slope of the transformed flow function — were found to vary in a regular manner with both molecular weight of the polymer and polymer concentration, expressed as relative viscosity (η rel). The limiting asymptotes of the approximating function —η 0 andη ∞ — could not be treated according to the conventionalHuggins equation, but they were fit adequately by theMartin equation: log(η sp/C)=log[η]+K[η]C. The intrinsic viscosities thus determined for both low shear ([η M ]0) and high shear ([η M ]0) demonstrate aMark-Houwink relationship, i.e., [η M ]0=5.668×10−5 M v 0.660 and [η M ]∞=2.574×10−5 M v 0.0669 so that ([η M ]∞≈[η M ]0/2) over the range studied. The relationship of these results to other reports of high shear viscometry of polymer solutions is discussed.

Notes: Summary A literature survey and an experimental study are presented on the short term strength variation of G.R.P. specimens subjected to the combined effect of loading and different environmental conditions. Findings are as follows: a) Residual longitudinal strength was found to decrease above a preloading level of about 25–35% of the corresponding reference strength — on exposure to hot (80 °C) water, even after an environmental-loading history (E.L.H.) stage of 48 h. b) No reduction in residual longitudinal strength (R.L.S.) was observed on exposure to cold water (22 °C) and to a dry-hot environment (80 °C). Conclusions are as follows: a) Early reduction of the residual strength is conditional on a combination of temperature and humidity, whereas each factor alone does not cause any deterioration, even under high preloading. b) Humidity is the main factor in the onset of internal failure in the glass-fiber phase, the effect being probably due to reduction of the surface energy of the glass by water adsorbed on its surface, accompanied by drastic reduction of its strength (Griffiths theory). Temperature has an indirect effect, accelerating the diffusion process and reducing the time scale for failure initiation.

Notes: Summary One of the main problems in Rheology is the determination of the yield condition for which no satisfactory form seems to exist. If a start is made with the stress tensor field, one soon runs into a number of difficulties. It is therefore better to deal with the geometry of the field. The change from elastic to plastic deformation can be interpreted as a mapping of one space into another, and the yield as an asymptotic sub-space. If the elastic strain field ise ij , whose invariants areJ 1,J 2,J 3, then an asymptotic behaviour may be represented by the existence of a functional relationf(J 1, J2,J 3) = 0, between theJ's, which are independent of one another in the normal part of the field. This does not fix the nature of the functionf, for which we can invoke the additional geometric condition that yielding can result from infinite contraction or expansion of a macro-element. Thus theJacobian of the mapping must take on the singular values zero or infinite. These concepts give rise to the yield condition in the strain tensor field in the form 8J 3 − 4J 2 + 2J 1 → 1. If generalized measure of strain is used, which is necessary for creep problems, this takes the formn 3 J 3 −n 2 J 2 +nJ 1 → 1.n being a real constant, which is equal to 2 for theAlmansi measure. These conditions do not depend on either the isotropicity or homogeneity of the field, and hence should be used for all types of yield conditions.

Notes: Summary The time-dependent behavior of the viscosity of bentonite-water suspensions was studied experimentally inCouette flow for various transitions between constant shear rates. It was found that, in general, the characteristic times become longer as the final shear rate becomes smaller and, for the same final shear rate, as the differences in shear rates become smaller. The characteristic time increases with increasing temperature and decreasing concentration. A discussion of the kinetics of the time dependence is given.

Notes: Summary For viscometric, axial, annular flow, the second normal stress differenceN 2 is related to the difference in normal thrust across the annular space,ΔT rr . Past attempts using this method have yielded values ofN 2 for polymer solutions which are different in magnitudeand opposite in sign from those obtained in other experiments. This inconsistency is attributed to errors resulting from the use of pressure holes in the measurement ofΔT rr , and is supported by a second-order fluid analysis. The present work focuses on the measurement of the effect of pressure hole errors on the determination ofN 2 with aqueous polymer solutions. In the measurement ofΔT rr , simultaneous use is made of both pressure holes and miniature pressure transducers to measure and account for pressure hole errors. Results indicate that hole errors are sufficiently large to reverse the sign of the computedN 2. This technique is therefore suggested as a preferred method for determiningN 2, especially at high shear rates.

Notes: Summary This paper deals with the measurement of the second normal stress difference in a viscoelastic flow in an open semi-circular inclined channel; associated theory is also given. The theory shows that simple correlations exist for the second normal stress difference, the shear stress, and the profile (or the deflection) of the free surface of the flow. It leads to a method for deducing the second normal stress from the measured surface profile. A treatment of surface tension, whose effect has been ignored in previous analyses is given as an integral part of the formulation. Samples of polyisobutylene/cetane and some aqueous solutions of different concentrations were used for measurements using two tubes of different materials and sizes tilted at different angles. The N.B.S. No. 1 nonlinear sample was also tested. Agreements between results for different tube sizes and angles indicate the consistency of the theory and measurements. The results presented here show that the ratio of the second to the first normal stress differences is negative and the functional form of the second normal stress difference is close to a square law in shear stress in the range investigated. Relatively speaking, we find the ratio |N 2 /N 1| to be greater for more dilute solutions. A summary of available data onN 2 is given for polyisobutylene, and reasonable consistency between various investigators is demonstrated for this material. Besides, a correlation ofN 2 for various polymer solutions is also shown.

Notes: Summary The total momentum-energy tensor describing the interaction of a polarizable and magnetizable continuum with an electromagnetic field is constructed on the basis ofLorentz invariance. The equations of balance of energy and momentum are deduced and applied to the study of the magnetooptical, electrooptical and photoelastic behavior of an elastic polarizable and magnetizable isotropic continuum. This model exhibits theCotton-Mouton andKerr effects but thePockels andFaraday rotations don't appear.

Notes: Summary A model to describe bond rupture and fracture in polymeric fibers is described. An experimentally determined distribution in stresses is incorporated with absolute reaction rate theory in the model to predict bond rupture. Model predictions are compared with experimentally determined fracture and free radical concentrations for various loadings. The experimental parameters in the model are discussed and their “best fit” values given. In general, these values are found to compare quite satisfactorily with accepted values from theory or other tests in the literature.

Notes: Summary Apparatus for the measurement of extensional viscosity of polymer solutions is described. The range of extensional strain rates is 100–800 sec−1. Two converging liquid jets of high velocity impinge on a central low-velocity jet, causing the liquid in the central jet to be rapidly stretched. The force causing extension of this jet is measured from the change in reaction on the central capillary nozzle, whilst the initial and final velocities are obtained by jet thrust and photographic methods respectively. The Instron system provides accurately-controlled liquid flowrates and continuous recording of the various forces involved. Tests are reported on polyacrylamide solutions of concentration 0.10% and 0.07%, and on poly (ethylene oxide) solutions of concentration 0.10%. The extensional viscosity of the more concentrated polyacrylamide solution is over 30 poise at an extensional strain rate of 600 sec−1, exceeding the shear viscosity by a factor of 400 (the “Trouton” ratio). For the poly (ethylene oxide) solution, theTrouton ratio reaches 1400 at an extensional strain rate of only 200 sec−1. The results are shown to be consistent with orifice jet thrust data for similar solutions at higher strain rates. The axial stress rises rapidly with increasing extensional strain rate, but there is no evidence of an abrupt increase of stress in the range of strain rates between 102 and 104 sec−1. The triple jet method is of value in giving data for intermediate extensional strain rates and being dependent on fewer assumptions than the orifice jet thrust experiment.

Notes: Summary A unique shear stress-shear rate relationship exists for laminar flow of any time independent substance in a tube, whereas this is not the case for turbulent flow. In order to obtain a unique relationship for turbulent flow, a new approach based on the elementary theoretical interpretation of experimental data is adopted in the present paper. In particular, wall shear stress is found to be a unique function of a new turbulent pseudo shear rate term. In this relationship therè are two parameters which characterize a given substance — the limiting viscosity at high shear rateµ m and a factorα m which takes into account modification of turbulent structure by the non-Newtonian properties. Both of these parameters must be determined experimentally. Methods of predicting pressure gradients and of scaling up are outlined. In applying the approach to suspensions in which the solid phase has a density greater than that of the liquid medium, it may be important to determine the increment in shear stress equivalent to the energy required to maintain the solid particles in suspension. The validity of this approach is confirmed by data for the flow of a variety of substances including kaolin suspensions and Carbopol solutions in tubes ranging in diameter from 1.5 to 20 mm.

Notes: Abstract This paper describes the work carried out to investigate the pore pressures occurring in secondary consolidation. A theoretical approach and an experimental technique was developed in order to conduct the study. By considering compression to occur only due to water leaving the soil it was possible to derive an expression for the dissipation of pore pressure in the secondary phase. By further simplified assumptions which are based on experimental observations, the above general solution was reduced to a simple formula which predicted the observed behaviour of pore water pressures during secondary consolidation.

Notes: Zusammenfassung Es wurde die Abhängigkeit der Haftfestigkeit im System Polymer-Faser von der Geschwindigkeit der Belastung untersucht. Die Versuche wurden mit Metalldraht von 150µm Durchmesser, alkalifreien Glasfasern von 12 und 200µm Durchmesser und wärmehärtenden Polymeren: Epoxidharz, Polyesterharz, siliziumorganischen und Butvar-Phenolharzen durchgeführt. Der Großteil der Messungen erfolgte bei Zimmertemperatur, bei Butvar-Phenol-Polymeren auch bei Temperaturen oberhalb und unterhalb der Zimmertemperatur. Es wurde gefunden, daß die Haftfestigkeit aller untersuchten Systeme eine lineare Funktion des Logarithmus der Belastungsgeschwindigkeit darstellt. Während sich der absolute Wert der Haftfestigkeitτ merklich beim Übergang von System zu System ändert, hängt die Empfindlichkeit vonτ gegenüber der Belastungsgeschwindigkeit wenig von der Natur der Unterlage und des Adhäsivs sowie vom Härtungsregime des Polymers ab. Aus den erhaltenen Daten wurde mittels desBailey-Kriteriums und der Lebensdauerformel vonShurkov die Aktivierungsenergie des adhäsiven Zerstörungsprozesses bestimmt. Es erwies sich, daß die Aktivierungsenergien der adhäsiven und der kohäsiven Zerstörung ähnlich sind.

Notes: Summary Three types of coordinate systems for the analysis of relaxation data are examined. When the data can be described by a single relaxation time, the graphs are straight lines. The slopes and intercepts of these lines can be used to evaluate the parameters which characterize the process, such as relaxation time. The advantages and disadvantages of displaying data with each of these types of coordinate systems are known and can be applied here. When more than one relaxation time is present, the graphs are curves. Nevertheless, the limiting slopes and intercepts can still be used to estimate the relaxation parameters. In this case various average relaxation times, 〈τ〉 p , are obtained, $$\left\langle \tau \right\rangle _p = {{\sum\limits_{i = 1}^m {\Delta _i } \tau _i^p } \mathord{\left/ {\vphantom {{\sum\limits_{i = 1}^m {\Delta _i } \tau _i^p } {\sum\limits_{i = 1}^m {\Delta _i } }}} \right. \kern-\nulldelimiterspace} {\sum\limits_{i = 1}^m {\Delta _i } }}$$ wherem is the number of relaxation processes,τ i andΔ i are the time and magnitude of thei-th process andp is any integer between −3 and +4. These averages are useful both as a means of characterizing the distribution of relaxation times and determining other parameters describing the relaxation process. The application of these graphical methods is illustrated in two specific areas: the frequency dependence of the shear modulus and ultrasonic longitudinal wave propagation. For these two examples the expressions for the intercepts and limiting slopes are evaluated. With these expressions the graphs of experimental data can be used to estimate the relevant parameters. A section discussing the special case of a system with two relaxation times is also included. This section illustrates how intuitive generalization from a case with one relaxation time can be misleading.

Notes: Summary An analytical comparison is made of a stress-activated nonlinear model (E) and a linear spectral model (M) for visco-elastic bodies in relaxation, creep, relaxation-creep recovery, constant strain-rate extension and periodic strain. A special reason for this is an observed “invariance” in relaxation (eq. [1]). Significant parameters are the frequency functionH for (M) and the rate constantα for (E).H should be roughly constant in relaxation and in still rougher approximation also in creep recovery, whileα should be inversely proportional to the stress and in additionα (creep-recovery)/α (relaxation) ≈ 22. For strain extension both models predict similar results but none takes the plastic creep of large rate in consideration. Regarding periodic strain model (M) gives a conventional behaviour, while model (E) predicts significant time dependent frequency effects. Possible physical mechanisms for explanation of the results obtained are discussed.

Notes: Summary The theory of the elastic moduli of composite materials in which an inversion of the phases can occur is reviewed. The morphology of the system and the packing fraction of the dispersed phase are important in determining the moduli. The applicability of the theoretical equations is illustrated for four systems of block polymers and polyblends. In three of the systems, phase inversion occurs. Agreement between theory and experiment is good, and where the morphology of the composites is known, the moduliagree with the values expected for that morphology.

Notes: Summary Dynamic mechanical properties of cured epoxy resins filled with small mica flake were investigated. A secondary absorption peak was observed for filled specimens around 80 °C, while unfilled specimen showed only a primary absorption peak around 140 °C. Modulus of filled specimens at high temperature rubbery region showed extraordinary high value. As an explanation to this behavior, it was proposed that the tensile stress applied to specimen was converted to shear stress in a thin resinous layer sandwiched by two mica flakes.

Notes: Summary The processing of polyimides gives rise to a number of rheological problems that cannot be solved using normal flow measurements. In particular, the effect of molecular structure on curing, flow and molecular weight leads to different ultimate properties depending on the thermal history. One technique that has been used to study these systems is the Torsional Braid Analysis (TBA). It is shown that with the TBA one obtains time-temperature relationship for cyclization of the prepolymer; curing and post cure parameters needed for processing. Thermal stability can also be determined. In addition, it is possible to relate the glass temperature of the cured system to the molecular weight of the prepolymer.

Notes: Summary The many uses of leather have largely relied on the range of mechanical properties which it can provide, according to the raw material employed in its manufacture and the manufacturing processes themselves. The contrasting behaviour of a stiff sole leather and of a fine gloving leather exemplify this point. The last twenty years have seen intensive investigation of many mechanical properties of leather and the design of test methods now accepted internationally. At ambient temperatures and humidities most types of leather show mainly elastic behaviour, although delayed elastic effects may give the semblance of plasticity. The stress relaxation-time relation for constant linear strain shows the stress decaying linearly with log (time). The stress decay becomes discontinuous after sufficient time. The stress-strain relation for extension of leather strips is often markedly non-linear even at low strains (〈2%). Two dimensional extension of leather has been analysed using an instrument allowing independent extension in two perpendicular directions. To a first approximation each stress component is linearly related to the two elastic strain components in the perpendicular directions. As with other materials of biological origin, the mechanical behaviour of leather varies from place to place in the skin, not only over its area, but also through its thickness. The extent of variation is briefly discussed and related to the underlying fibre structure. Leather which has been strained and then subjected to either heat alone or heat and moisture, shows much more extensive plasticity than occurs at lower temperatures. This behaviour has been used to enable leather to be given appropriate shapes, as in the heat setting of upper leathers. Quantitative studies of heat setting are reported and the influence of such variables as temperature, moisture content of the applied air stream, the air stream velocity and the duration of treatment are discussed. The plastic deformation obtained in this way is contrasted with “run” in gloving leather.

Notes: Summary The relation of chain rigidity of thermally stable polypyromellitimide (PI) with the orientation of molecules in the stretched films was looked for in the temperature dependence of the dynamic mechanical properties and also in the thermal shrinkage of the film. In the temperature dependence of the dynamic loss modulus of the commercial PI film, du Pont, Kapton H, a broad peak was found around 300°C at 0.1 ~ 0.2 Hz. This peak was magnified by stretching the film by 40%, and disappeared after heating up to 500°C. Thermal shrinkage of the stretched film was measured by thermomechanical analysis (TMA) at a uniform heating rate, and a significant shrinkage was found over the range 100 to 400°C for the stretched films. When stretched, the rigid polymer chains are extended and frozen in a metastable state. The extended chains recoil back to the more stable state when heated in TMA and also in dynamic measurements.

Notes: Summary Measurements of the elasticity or viscoelasticity of various materials by the vibrating-reed method at very low frequencies require the use of long and heavy samples. The effect of gravity on these samples has been considered theoretically, and new equations for the storage and loss moduli have been derived. Vibrating-reed measurements were carried out with several kinds of materials at frequencies ranging from about 1–20 Hz. The experimental results indicate that the above equations are satisfactory in practice.

Notes: Summary In this investigation, the repeated chemical stress relaxation measurements were carried out to observe the relaxation behaviors at large deformation. It was found that the repeated chemical stress relaxation curves were affected by both temperature measured and extension ratio of rubber. It was suggested from the results obtained that temperature and mechanical stimulus have a similar effect on the stress relaxation curves. Thus we propose the followingArrhenius type eq. [1] for high extension ratios. $${{f(t)} \mathord{\left/ {\vphantom {{f(t)} {f(0)}}} \right. \kern-\nulldelimiterspace} {f(0)}} = \exp (A \cdot e^{\frac{{E_f }}{\alpha }} \cdot t).[1]$$ Where,α is the extension ratio, andA, andE f are the constants determined experimentally. On the other hand, from eq. [1] and usualArrhenius equation, the universal eq. [2] for the extension ratio and the temperature in large deformation was derived as follows, $$\begin{gathered} \ln \{ (\ln f(0)/f(t))/t\} - E/R(1/T_0 - 1/T) \hfill \\ = \ln A - E_f /\alpha [2] \hfill \\ \end{gathered} $$ where,T 0 is adequate temperature. The curves obtained for different temperatures and extensions were very well consistent with those by eq. [2] in large deformation.

Notes: Summary Both stress relaxation behaviour and time-to-breakt b as a function of stressσ were studied in identical time and temperature intervals using poly(2-hydroxyethyl-methacrylate) gels in the swollen state, prepared both in the homogeneous and in the heterogeneous form. Homogeneous samples were prepared by means of crosslinking polymerization (concentration of ethylene dimethacrylate as a crosslinking agentc=0.21 and 0.65×10−4mol cm−3) in the presence of ethylene glycol (v 0=0.6−0.3); heterogeneous samples with various degrees of porosity were prepared in the presence of water (v 0=0.8−0.2). Irrespective ofv 0, an agreement was found between the temperature shift factors, loga T , obtained from the viscoelastic and ultimate measurements for the systems prepared with a higher concentration of the crosslinking agent; for the lightly crosslinked systems thea T values from the viscoelastic data were less sensitive to temperature. The temperature dependence of loga T was not the same at temperaturesT〉30°C and additional horizontal-vertical shifts had to be used; this effect is very similar to that observed previously for the other polymethacrylates byFerry and coworkers. In the water preswollen systems the isochronous breaking stress vs.v 0 curves exhibit a maximum which disappears with time. The moduliE(t) of the same systems decrease approximately withv 0 -1 irrespective of the degree of preswelling. The effect of crosslinking and preswelling on the shape of the superimposed logE(t) vs. logt/a T and logt b /a T vs. logσ curves was ascribed to the different role of viscoelastic mechanism in the relaxation and in the ultimate process and to different topological features of the networks prepared.

Notes: Summary Temperature dependent properties of some segmented copolyurethanes were compared with those of soft- and hard-segment polyurethanes. To understand the chemical nature of associated phase more explicitly, far-infrared spectral behaviors were precisely analyzed. Mid-infrared frequency shift of NH-stretching vibration of associated carbonamide group was taken as a measure of the strength of hydrogen bond. Dynamic viscoelastic response as well as flow property estimated from viscoelastic shift factor were compared with the infrared spectral behaviors. A strong intersegmental carbonamide association was found through a preferential “solvation” of —(CH2)6NHCOO— group in the soft segment derived from poly-butyleneglycoladipate (PBA) and hexamethylene diisocyanate (HMDI), to the same group in the hard segment derived from butanediol (BD) and HMDI, yielding a thermoplastic copolyurethane, (PBA + BD) —HMDI, with high activation energy of segmental flow. While, a unique aromatic association was observed in copolyurethane derived from diphenylmethane diisocyanate (MDI). A weakening of hydrogen bond in hard segment by aromatic cohesion of soft segment was observed from mid-infrared measurements, which gave a typical thermoelastic copolyurethane with moderate activation energy of flow. The same effect of weakening of hydrogen bond was observed by the replacement of polyester soft segment by less polar polyether, which gave also thermoelasticity. Polyurethanes derived from toluene diisocyanate (TDI) and xylylene diisocyanate (XDI) did not show the aromatic association of MDI type. The mid-infrared stretching vibration and farinfrared out-of-plane deformation vibration of associated NH-group were found to correlate with hydrogen bond- andvan der Waals-crystals having been assigned from (200) and (002) interferences, respectively, in X-ray scattering measurements byKilian et al.

Notes: Summary An approximate solution to the flow past an impulsively started infinite plate in an elastico-viscous fluid is derived for the velocity and shearing stress. It is observed that the velocity increases with increasing the elastic parameterk and the shearing stress decreases with increasingk.

Notes: Summary The rheological behaviour of alginate gels with a high D-mannuronate content has been investigated at strains of less than 0.1 and under stresses of 1000–3000 dyne cm−2. Under these conditions linear viscoelastic behaviour was observed. The effects of varying pH, calcium ion and alginate concentrations were examined in gels which had been aged for 25 h. At pH 6.0 the reciprocal of the ten second compliance was directly proportional to the alginate concentration. The compliance of the gels exhibited a pronounced dependence on pH being larger at pH 6.0 than at lower pHs. Syneresis was greater for acid gels than those formed at neutral pH and increased with decreasing polysaccharide concentration. In general an enhanced calcium ion concentration resulted in a decrease in the compliance of the gels. The results are discussed in terms of polymer network theory.

Notes: Summary The shear creep behavior of polymethylmethacrylate, PMMA, samples has been studied in the neighborhood of and above their glass temperatures. One of the materials studied was “ideally” atactic with equal numbers of random isotactic and syndiotactic placements, while the other was a commercial or “conventional” PMMA which was about 76% syndiotactic. The glass temperatures,T g , were found to be 106 and 117 °C respectively. Evacuation above the glass temperature for several weeks was necessary before reproducible creep compliance,J (t), curves could be obtained. It is believed that absorbed water plasticized the polar materials and its removal led to the shifting of theJ (t) curves to longer times. For both materials apparently successful temperature reduction was found to be possible within the temperature range of our investigations, i.e. up to 200 °C. Retardation spectra were calculated from the reduced curves and are compared. The temperature dependences, as described by the time scale shift factors,a T , were similar when allowance is made for the different glass temperature. Botha T curves could not be fitted to theWilliams, Landel, andFerry, WLF, free volume expression. These are the first examples of such a deviation for amorphous high polymers. It is proposed that the primary softening dispersion has two distinctly different groups of viscoelastic mechanisms contributing to it. On this basis the primary dispersion was decomposed into the two contributions. Both of the resulting temperature dependences were satisfactorily fitted to the WLF equation. Differences in the retardation spectra are noted. The glassy compliance of the commercial PMMA appears to be about twice that of the atactic PMMA.

Notes: Summary Sodium carboxymethylcellulose (CMC) is a valuable and widely used component of food systems. The rheological properties of a series of CMC solutions and gels have been determined under both steady and imposed sinusoidal shear conditions, over a wide range of shear rates and frequencies, using theWeissenberg Rheogoniometer. Depending upon the CMC type, degree of substitution, and method of solution preparation, the rheological behavior ranged from viscolastic solutions to unctuous gels. If certain polyvalent cations, e.g., Al3+, are present, rigid elastic gels may be formed. These results are interpreted in terms of fringe micelles, arising from crystalline residues in the CMC. Gels which show unctuous behavior may be described in terms of a modifiedBingham Body model. Where appropriate, the experimental results are quantitatively analyzed in terms of the parameters of this model. The application of these findings to the use of CMC in food systems is discussed.

Notes: Résumé Dans cette étude, on apporte quelques éléments, permettant de mieux comprendre le mode de propagation des fissures de fatigue dans un matériau agrégataire. Le début de fissuration n'a pas pu être défini avec précision. On constate seulement qu'il apparaît à 80% de la durée de vie des éprouvettes.

Notes: Summary Flow patterns of disperse systems such as TiO2-water and ZnO-water suspensions were investigated over a wide shearing range both in laminar and in turbulent regions. The results indicated in fig. 11 a were decided as the laminar and the turbulent flow patterns respectively.f-Re relations were also investigated for the systems which possessed varying non-Newtonian parametern. f-Re diagram was revealed to be affected by varyingn values both in laminar and in turbulent regions similarly as shown in fig. 11 b.

Notes: Résumé Les valeurs du facteur de viscositév pour les ellipsoïdes allongés et aplatis ont été calculées pour des allongementsp, respectivement 1/p, compris entre 2 et 600 et jusqu'à des valeurs du paramètreα = G/D = 500. Des relations permettant de déterminerp en fonction de la viscosité intrinsèque à gradient nul, la constante de diffusion de rotationD en fonction de la forme de la courbe de viscosité non-newtonienne, et un critère de rigidité des ellipsoïdes ont été établis. Ces résultats sont appliqués au poly-L-glutamate de benzyle et permettent de penser que ce produit, en configuration hélicoïdale subit des transconformations à certaines masses critiques; par ailleurs, toujours rigide dans le metacrésol, il est déformable dans le dichlorétane.

Notes: Summary The amylose molecule is extended by the insertion of iodine in quantities up to a ratio of one molecule per turn of the helix. Ordinary cornstarch and its amylopectin fraction do not respond in the same manner. As the iodine content was increased the intrinsic viscosity [η] rose from 0.55 to 1.45 dl/g, then remained constant. In this same range theHuggins' interaction parameterk′ for the dependence of reduced viscosity [η sp/C] on iodine concentration rose from 0.31 to 5.65 and continued to increase. Reduction ofd[η]/dT by complexing from −0.36 × 10−2 to −0.23 × 10−2 dl/g/deg provided an independent measure of the flexibility of the molecule and revealed that iodine stiffens the helix in some manner. The dipolar interaction between iodine and the helix restricts conformational changes and increases the average extension. As more iodine molecules enter the helical chain the average distribution of molecular segments relative to the center of mass of the molecule spreads outward.

Notes: Summary The compressibility and expansion coefficient of polyethylene were measured under the pressure up to 5000 kg/cm2 and the temperature up to 250°C by dilatometry. The used polyethylene was an extended-chain type crystallized under high pressure. The value of compressibility coefficient of this sample coincided well with the theoretical value of pure crystalline polyethylene. The experimental volume was applied to theClausius-Clapeyrons equation and enthalpy of fusion of polyethylene up to the pressure of 5000 kg/cm2, and consequently entropy of fusion were evaluated. It was found out that the entropy decreased with pressure. The results seem to suggest that some structure change occurred under high pressure in the amorphous state of polyethylene.

Notes: Summary Applying the method of continuous variation of concentration of precipitating components the precipitation bodies (PB) (as a plot of logarithm of concentration of the cationic components against anionic one) are used for description and discussion of experimental results of Hg2Cl2, Hg2Br2 and Hg2J2 systems. The precipitation inside of PB is characterized by a region of crystal aggregates and a colloidal region.

Notes: Summary A new statistical theory leads to a simple relation [eq. 3] between the crystallinity and the branching ratio e for polyethylene (PE) cold drawn to the natural draw ratio. Three assumptions are made: 1) The branches all are incorporated in the amorphous phase, 2) they are distributed randomly along the chain and 3) the sample tends to obtain the highest possible crystallinity during the stretching process. Ifm is the mean number of monomers in chain direction within one paracrystal, then this optimum can never be attained, ifmε during the whole process of necking is larger than 1. Now the theory gives no answer and the experiments give a crystallinity of ∼ 0.55 for all observed cases. Formε 〈 1, where the optimal crystallinity is established the volume occupied by the direct backfolds is about two third of the volume of the amorphous phase. Comparison with the crystallinity obtained from other methods proves that the superstructure consists of paracrystalline lamellae and not of clusters of lamellae imbedded into a amorphous matrix.

Notes: Zusammenfassung An einem Niederdruck-Polyäthylen (HDPE) wurden die Aufladeströme, die stationäre Gleichstromleitfähigkeit sowie die Entladeströme im Feldstärkenbereich bis zu 2,8 × 105 V/cm gemessen. Einige elektrische Meßgrößen wurden in Abhängigkeit von der Zeit und der Temperatur an 36, 60 und 115 μm dicken Proben untersucht. Durch ein modifiziertesPoole-Frenkel-Modell, das auf der thermischen Befreiung von Elektronen aus ionisierbaren Zentren beruht, kann die Feld- und Temperaturabhängigkeit der stationären elektrischen Leitfähigkeit quantitativ beschrieben werden. In diesem Modell wird die Überlappung benachbarter Coulombpotentiale berücksichtigt, wobei der Potentialverlauf zwischen drei benachbarten Poole-Frenkel-Zentren betrachtet wird. Die gute Übereinstimmung der berechneten und experimentellen Ergebnisse stützt die Annahme, daß der Ladungstransport nach Befreiung von Elektronen aus energetisch tiefliegenden Zentren durch Sprünge über intermolekulare Schwellen in Form eines thermisch aktivierten Prozesses erfolgt.

Notes: Zusammenfassung In PMMA ist der Übergang von der langsamen, unterkritischen Bruchausbreitung zur schnellen, überkritischen Bruchausbreitung mit einer Änderung in der Bruchflächenstruktur und einem Geschwindigkeitssprung verbunden. Die Bruchgeschwindigkeiten wurden mit zwei verschiedenen Methoden gemessen; die registrierten Endgeschwindigkeiten des langsamen Bruchausbreitungsbereiches liegen zwischen 6 und 21 cm/s, der Geschwindigkeitssprung beträgt etwa 3 Zehnerpotenzen. Dieses Bruchverhalten wird nachWilliams auf einen isotherm/adiabatischen Effekt zurückgeführt. Mit Hilfe einer vonWeichert,Schönert angegebenen Berechnung des Isothermenfeldes einer bewegten Wärmequelle kann dieser Effekt konkreter gefaßt und die Endgeschwindigkeit im langsamen Bruchausbreitungsbereich eingegrenzt werden.

Notes: Zusammenfassung Mit Hilfe der Ergebnisse der Röntgenweitwinkel-und Röntgenkleinwinkeluntersuchungen ist es möglich, aus Breitlinienkernresonanzmessungen an uniaxial orientierten Proben und Infrarotmessungen an Einkristallen und isotropen Proben detaillierte Rückschlüsse auf den Bewegungszustand der Moleküle in den verschiedenen Modifikationen des n-Tritriacontans (n-C33H68) zu ziehen. In allen Modifikationen treten neben der Rotation der CH3-Endgruppen um die C-C-Bindung Bewegungen der Kettenmoleküle um ihre Längsachse auf. Unterschiede ergeben sich durch die Art der Rotationsbewegung, durch zusätzliche Translationen in Kettenrichtung und durch Defekte, die entlang der Kette diffundieren und zu einer Abweichung von der gestreckten Kettenkonformation führen. Am Ende der Phase A kommen bei gestreckter Kettenkonformation als mögliche Bewegungstypen Oszillationen der Kettenebenen um ihre Gleichgewichtslage (mittlere Oszillationsamplitude 25°) oder Rotationssprünge eines Teils der Moleküle mit Sprungweiten von ca. 90° in Betracht. Die mögliche Bevorzugung des 2. Mechanismus wird durch die Beobachtungen an polaren Derivaten der n-Alkane nahegelegt, wo ähnliche Abnahmen des 2. Momentes der Kernresonanzspektren auftreten. Für diese Verbindungen ist aus dielektrischen Messungen bekannt, daß sprunghafte Bewegungsprozesse aktiviert sind. Die Phase B ist durch Rotationssprünge aller Moleküle mit Sprungweiten von 180° gekennzeichnet. Die Sprünge erfolgen kooperativ, so daß die Nahordnung in lateraler Richtung erhalten bleibt. In der Phase C treten zusätzlich zu den 180°-Sprüngen Translationsbewegungen gestreckter Ketten in Kettenrichtung auf. Durch die Translationskomponente ist die Nahordnung in lateraler Richtung auch bei nichtkooperativem Bewegungsablauf gewahrt. Die Rotationssprünge mit und ohne Translationskomponente, die in den Phasen B und C nacheinander einsetzen, treten möglicherweise gleichzeitig auf, wenn keine Phasenübergänge vorliegen, die den Übergängen A-B und B-C entsprechen. Insbesondere scheinen beide Mechanismen zum a-Prozeß im Polyäthylen beizutragen, für den man eine ähnliche Abhängigkeit im Verlauf des 2. Momentes beobachtet wie beim n-C33H68 bis zum Endes der Modifikation C. Der sprunghafte Charakter der Rotationskomponente geht in der Phase D zugunsten einer kontinuierlichen Rotationsbewegung weitgehend verloren. Jedoch deutet das Fehlen der hexagonalen Symmetrie darauf hin, daß sich die Kettenebenen nicht gleichförmig um die Moleküllängsachse drehen, wie es im Rotator-Modell vorausgesetzt wird. Als zusätzlicher Bewegungstyp tritt die Diffusion von innermolekularen Defekten entlang der Kette auf.

Notes: Summary The grain boundary relaxation phenomena, which have been found in the mechanical relaxation of the cast films of a series ofgraft copolymers ofpoly(methyl acrylate) with styrene, are examined again, in order to understand its relaxation mechanism, by using some particular series of heterogeneous systems of two components having different interaction between the two phases and, subsequently, different grain boundary structure; i. e., two series of poly(vinyl acetate) filled with two types of carbon blacks having relatively high and low surface activities, respectively, a series ofmechanical mixtures ofpoly(vinyl acetate) with polystyrene, and a series of styrene-isoprene-styrene tri-block copolymers. The grain boundary relaxation phenomena are again detected for the series of the tri-block copolymers but definitely not for the series of the mechanical mixtures, suggesting that the grain boundary relaxation phenomena must arise not from the heterogeneous structures themselves but from characteristic arrangements of molecular chains at the boundary of the two phases. That is, there must be a considerably strong interaction between the two phases, and there exists an intermediate phase in which the polymer segments of soft component are rigidified while the other polymer segments of hard component are softened. In other words, there must be a cooperative motions of chain segments of the two components to produce a mechanical relaxation under a certain environmental condition, such as temperature and time scale of observation.

Notes: Zusammenfassung Das Molekulargewicht verschiedener Gelatinepraparate (Knochen- und Hautgelatine; pI = 4,9 bzw. 8,1) wurde durch Sedimentation in der analytischen Ultrazentrifuge nach der Methode vonArchibald und der Sedimentationsgleichgewichtsmethode in verschiedenen Pufferlösungen und bei unterschiedlicher Temperatur bestimmt. Für die Gelatine wurde jeweils in verdünnten Salzlösungen bei 40°C, in konzentrierten KSCN-Lösungen bei 25°C und in 6 m Guanidinhydrochloridlösung bei 40°C das gleiche Molekulargewicht gefunden. Die Gelatine lag bei diesen Versuchsbedingungen molekulardispers vor. Die Gelatine wurde durch Ausfällen und durch Lösungsmittel-Gradienten-Chromatographie fraktioniert. Von den Fraktionen wurden die Viskositätszahlen [η]40, die SedimentationskonstantenS 40,w 0 und die MolekulargewichteM w mit Hilfe der Ultrazentrifuge bestimmt. Für die Molekulargewichtsabhängigkeit der Viskositätszahlen und der Sedimentationskonstanten der untersuchten Fraktionen gelten die Beziehungen: $$\begin{gathered} [\eta ]_{40} = 7,75 \cdot 10^{ - 2} ml/g M_w^{0,51} \hfill \\ s_{40,w}^{0,w} = 0,61 Svedberg M_w^{0,17} . \hfill \\ \end{gathered} $$ Die für Gelatine in der Literatur publizierten unterschiedlichen [η]-M w -Beziehungen werden auf den unterschiedlichen Verzweigungs- und Vernetzungsgrad der Präparate zurückgeführt. Der kleine Exponent ders-M-Beziehung wird u. E. von der Durchspülbarkeit der untersuchten Gelatinemoleküle verursacht. Bei der Gelchromatographie läßt sich die Molekulargewichtsabhängigkeit des Elutionsvolumens der untersuchten Gelatinefraktionen und von verschiedenen Proteinen durch die gleiche Eichkurve darstellen. Zur Erklärung dieses Befundes wird gezeigt, daß die gelchromatographische Trennung beider Molekülarten nicht nach dem hydrodynamischen Volumen [η] ·M, sondern mit großer Wahrscheinlichkeit bei den knäuelförmigen Gelatinemolekülen nach dem Trägheitsradius $$(\overline {r^2 } )^{1/2} $$ und bei den ellipsoidförmigen Proteinmolekülen nach der großen Halbachse erfolgt. Die Molekulargewichtsverteilung der Gelatine wurde durch Lösungsmittel-Gradienten-Chromatographie und durch Gelchromatographie bestimmt. Die erhaltenen Verteilungskurven stimmen gut überein. Die Lösung der untersuchten Knochengelatine enthält bei 40°C keine Aggregate, sondern Einzelmoleküle im Molekulargewichtsbereich 4 · 103 bis 10 · 106.

Notes: Zusammenfassung Die rheologischen Eigenschaften verdünnter Lösungen von Hochpolymeren mit Molmassen zwischen 106 und 107 g sowie Konzentrationen um und erheblich unter einem Massenprozent werden durch eine ausgeprägt schergeschwindigkeitsabhängige Viskosität (Fließkurve) sowie durch ein elastisches Relaxationsverhalten beschrieben. Während die Fließkurve heute wegen der wesentlich verbesserten Meßtechnik in der Regel im gesamten interessierenden Beanspruchungsbereich zu ermitteln ist, bereitet die Bestimmung der Relaxationszeit, die eine charakteristische Größe für das elastische Verhalten ist, bei den genannten viskoelastischen Flüssigkeiten Schwierigkeiten. Es bieten sich drei, Methoden an, die in diesem Zusammenhang diskutiert werden: Die stationäre Strömung, für die das Kugel-Kugel-Rheometer als Anwendungsbeispiel angeführt wird. Das gleichzeitige Auftreten der entgegengesetzt gerichteten Terme der Elastizität und der Trägheit stellt für die obengenannte Flüssigkeit an die Meßtechnik hohe, z. T. nicht erfüllbare Anforderungen. Ähnliche Schwierigkeiten bereitet die instationäre Strömung, für die der Anlaufvorgang der Couette-Strömung hier näher beschrieben wird. Die größten Erfolgsaussichten verspricht das Heranziehen der bekanntermaßen bei viskoelastischen Flüssigkeiten gegenüberNewtonschen Flüssigkeiten veränderten Grenzschichtphänomene : In der turbulenten Rohrströmung kommt es zu einer Widerstandsabsenkung. Die Widerstandscharakteristik zeigt bei geeigneter Darstellung als Gerade eine deutlich andere Steigung als dieNewtonschen Flüssigkeiten. Die Steigung der Gerade ist materialabhängig. Der Schnittpunkt mit derPrandtl-Gerade fürNewtonsche Flüssigkeiten ist material-spezifisch dem Durchmesser proportional. Darüber läßt sich die Relaxationszeit to bis auf eine universelle Größe x gewinnen. Ein hier beschriebenes Doppelkapillarrheometer gestattet sowohl die Ermittlung der Fließkurve als auch — über Turbulenzmessungen — die Bestimmung von κ ·t 0.

Notes: Zusammenfassung Betrachtet werden n-Paraffin-Lamellen, in denen die Kettenmoleküle mit Konformationsfehlem behaftet sein können. Die Gleichgewichtszustände dieser Lamellen werden mit Hilfe derBragg-Williams-Näherung berechnet. Die ideale Gesamtheit (ohne Wechselwirkung der Ketten untereinander) ist identisch mit einerSchottky-Gesamtheit, wenn die maximal mögliche Anzahl von Defekten pro Kette und die Anzahl der einem Einzeldefekt längs der Kette zur Verfügung stehenden Plätze übereinstimmen. In der kooperativen Gesamtheit (mit Wechselwirkung zwischen nächsten Nachbarn) kann das Vorschmelzen von einer gewissen Kettenlänge an mit einer diskontinuierlichen Umwandlung verbunden sein. Die Umwandlung tritt jedoch nur dann auf, wenn sich die Defekte zu energetisch günstigen Arrangements zusammenfinden. In bezug auf das einphasige Vorschmelzen sind drei Klassen von Lamellen zu unterscheiden: 1. Lamellen aus kurzen Ketten: das Vorschmelzen verläuft kontinuierlich; 2. Lamellen aus Ketten mittlerer Länge: das Vorschmelzen kann von einer Umwandlung erster Ordnung unterbrochen sein; 3. Lamellen aus langen Ketten: eine Umwandlung erster Ordnung ist möglich, jedoch ohne Defekt-Vorschmelzen.

Notes: Summary In a previous paper the structure of extended native collagen was discussed. It was and still remains an open question if these kinks, are already established in the unstretched sample or are only formed under stress. If so, their production is explained in this paper by a heterogeneous expansion of the protofibrils similar as in elastomers. All 135 Å one meets “amorphous” non helical regions where the polypeptide-chains are more disordered as in the paracrystalline triple helical domains. In synthetic elastomers these parts of a molecule are called “soft segments”. If this expansion solely takes place in the “amorphous” ranges and if these zones are 20 Å long, then the earlier published (observed) data of the kink model quantitatively can be explained by expanding the protofibrils 11% in the “amorphous” ranges. An example is given, where the density of the “amorphous” region does not change during stretching. The expansion by 11% takes place because the polypeptide chains within the triple helices are straightenend. They run more or less parallel to the screw lines of the triple helix through this zone. The long period only increases by 0.3%. If the density of the “amorphous” regions diminishes more than a few percent, an appreciable increase of the long period would happen. This contradicts the experiments. The mean density does not change in the “amorphous” regions during stretching. Most of the macroscopic elongation takes place outside of the fibrils with the 670Å periodicity. Only about 1/7 of it is elastic and is produced by the restoring force of network peptides aligned in between adjacent octafibrils and bundles of them. The important role of these “intermicellar” molecules and similarities with the affine transformation in synthetic high polymers is discussed. The model of staggered collagen molecules ofSchmitt (1956) which explains the 670 Å-period in quite another way cannot explain an elastomeric production of tilted paracrystalline triple helical regions under strain.

Notes: Summary The degree of aggregation of some commercial polyoxyethylene sorbitan fatty acid esters (Tweens) and sorbitan fatty acid esters (Spans) in cyclohexane, carbon tetrachloride and chloroform has been investigated by light-scattering, vapour pressure osmometry and sedimentation velocity techniques. Light-scattering results were corrected for the contribution of fluorescence to the scattered light, which was appreciable at excitation wavelengths of 436 nm. Mean aggregation numbers of 26 and 12 monomers were determined for sorbitan monooleate (Span 80) in cyclohexane and carbon tetrachloride respectively. No significant aggregation of this compound was observed in chloroform. Other detergents studied showed only limited aggregation, if any, in these solvents. Correlation of the aggregation numbers of Span 80 with the solubility parameters, δ, of the solvents (including results from a previous investigation) indicated that the degree of aggregation approached a minimum value when the δ values of the solute and solvent were matched.

Notes: Summary The influence of surface viscosity on the rate of thinning and on the critical thickness of rupture of foam films has been studied. It is shown that this effect depends strongly on the length-scale of the flow. Therefore it is possible to neglect it when calculating the rate of thinning, but to assume for the wave motion, caused by the thermic fluctuations, that the surface viscosity is infinitely great. The expression for the critical thickness, obtained in this way, agrees relatively well with the experimental results. A possible explanation of the dependence of critical thickness on surfactant concentration is suggested.