摘要:

AbstractAn experimental and theoretical study of two‐phase flow of molten polymers has been carried out. The theoretical analyses apply the theory of nonlinear viscoelastic fluids to consider stress and velocity profiles and interface shape in stratified flow between parallel plates and in a tube. The second normal stress difference is predicted to influence interface shape. Experimental studies have been made of stratified two‐phase flow of a low viscosity but elastic low‐density polyethylene and a high‐viscosity polystyrene in a capillary rheometer. In the stratified flow experiment, velocity fields and interface shape in the reservoir approaching capillary die and the emerging extrudate were investigated, the former being observed through visual experiments. The emerging extrudates possessed convex polystyrene surfaces at the interface. A strong tendency toward the collection of bubbles near the capillary entry was found. We have made an experimental study of the extrusion of disperse mixtures of polystyrene and different polyolefins. The morphology of the disperse two‐phase emerging extrudates has been inv

ISSN:0021-8995    

DOI:10.1002/app.1972.070160601

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe γ‐ray‐induced copolymerization of vinylphosphonic dichloride (VPDC) with methyl methacrylate (MMA) and styrene (St) was studied at 25°C (liquid phase) and −78°C (Solid phase). The reaction mechanisms are discussed. The reactivity ratios for the copolymerization of the VPDC–MMA system were determined as follows:\documentclass{article}\pagestyle{empty}\begin{document}$\begin{array}{l} 25^\circ {\rm C}:\quad r_1 = 0.084,\quad r_2 = 6.6 \\ - 78^\circ {\rm C}:\quad r_1 = 0.081,\quad r_2 = 2.1 \\ \end{array}$\end{document}The difference between the reactivity between the liquid‐phase (25°C) and solid‐phase (−78°C) copolymerization is mainly attributable to ther2value. The behavior of the liquid‐phase copolymerization of the VPDC–St system was anomalous, ther1value being negative in the range from 0 to 80 mole‐% of VPDC monomer. In the solid‐phase (−78°C) copolymerization for the VPDC–St system, the reactivity ratiosr1andr2were 0.097 and 1.6, respectively. The rate of copolymerization (Rp) at 25°C, for both the VPDC–MMA and VPDC–St systems, passes a maximum point at a certain monomer concentration, suggesting that the composition of copolymer is considerably affected byRp. This phenomenon was interpreted by the assumption that an energy transfer reaction from VPDC monomer to the o

ISSN:0021-8995    

DOI:10.1002/app.1972.070160602

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

年代:1972

数据来源: WILEY

摘要:

AbstractMixtures of styrene andn‐butyl acrylate of various compositions were grafted onto cellulose and cellulose triacetate fibers preirradiated with γ‐rays at 0°C in air. Monomer reactivity ratios of the grafted copolymers were found to be different from those of the nongrafted copolymers or those of AIBN‐initiated copolymers. The active species initiating the graft copolymerization were trapped radicals for cellulose and peroxides for cellulose triacetate. Kinetic investigations of the graft copolymerization of styrene onto preirradiated cellulose triacetate fibers were also carried out, and it was found that the kinetic scheme for radical polymerization is also applicable to graft copolymerization in a heterogeneous

ISSN:0021-8995    

DOI:10.1002/app.1972.070160603

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

年代:1972

数据来源: WILEY

摘要:

AbstractAcrylic fibers containing methyl acrylate copolymer have been thermally treated in the temperature range 473°–573°K in an inert, oxygen‐free environment. The optical properties and an x‐ray diffraction orientation parameter have been studied in these fibers, with special attention to correlation with the essential chemical reactions and to the behavior of polymer chain orientation. Densification of the fibers, illustrated by specific gravity and refractive index changes during the thermal treatment, is interpreted as a more efficient packing of the polymer chains in addition to the development of more highly refractive and dense chemical species. An extrapolated value of refractive index of 1.70 for 100% nitrile polymerization supports the presence of naphthyridine structures. Birefringence changes from −0.003 to +0.27 imply a high degree of retention of the preferred orientation of polymer chains, despite the severe change in the chemical identity of the chains. The contrary behavior of the orientation parameter from the 100 arc of the x‐ray diffraction of polyacrylonitrile as the thermal treatment proceeds indicates that the residual polyacrylonitrile sequences have reduced

ISSN:0021-8995    

DOI:10.1002/app.1972.070160604

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

年代:1972

数据来源: WILEY

摘要:

AbstractOptical, mechanical, and thermal data on cold‐ and hot‐drawn as well as crazed films of bisphenol A polycarbonate suggest that three separate processes occur during deformation. These processes are a volume change, a preferential orientation of the molecules along the deformation axis, and a configurational change within the molecules (ordering). An attempt is made to correlate these processes with the various types of experimental data. It is suggested that the ordering process is activated by surface, bulk, or external stresses, which are dependent upon molecular weight, processing history, and sample geome

ISSN:0021-8995    

DOI:10.1002/app.1972.070160605

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe molecular bond rupture rate during ozone attack of torsionally loaded rubber was determined from electron paramagnetic resonance (EPR) measurements. The rupture rate was successfully correlated by a Griffith‐type energy balance to the strain‐energy release rate in the samples. These observations substantiate the results from a similar study on tensile loading previously reported. In both cases there is a one‐to‐one correspondence between the rate of bond rupture (or crack growth) and the rate of energy release from the strain field and external work. A fracture energy, γn, of approximately 5×10−12(±20%) ergs per free radical formed during the cracking was experimentall

ISSN:0021-8995    

DOI:10.1002/app.1972.070160606

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

年代:1972

数据来源: WILEY

摘要:

AbstractA seven‐step systems engineering approach is described and applied to the integral‐skin foam system. Through the use of a hybrid computer simulation of a dynamic mathematical model, the two process variables with the greatest lever on the skin‐forming process are determined. These data are then utilized to develop a new foam concept which makes it possible to control skin thickness and core foam density independ

ISSN:0021-8995    

DOI:10.1002/app.1972.070160607

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

年代:1972

数据来源: WILEY

摘要:

AbstractViscoelastic properties of polymer fluids are single‐valued functions of shear stress or shear rate only at high total applied shear. These parameters may vary with applied shear under milder shear histories. The mean total shear in capillary extrusion is shown to be a function of orifice geometry. Apparent flow curves can be measured at various total shear values by changing the length/radius ratio of the capillary. The true shear stress and true shear rate at the orifice wall correspond to infinite total shear conditions. The true flow curve and elastic parameters like die swell are not measured at equivalent total shear unless the capillary is extremely lon

ISSN:0021-8995    

DOI:10.1002/app.1972.070160608

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe shear storage modulus has been determined for 0.05, 0.10, and 0.22 g/cc polystyrene bead foams and for the full density polymer at frequencies from 0.005 to 0.5 Hz at temperatures from −5° to 84°C. These data are superposed to form master curves of log modulus versus log temperature‐reduced frequency, using shift factors calculated by the Arrhenius equation. A plot of log modulus versus log density is linear for the three density foams; however, the modulus value for the solid polymer does not follow this relatio

ISSN:0021-8995    

DOI:10.1002/app.1972.070160609

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe extent and rate of reaction between cotton yarn before and after slack mercerization and slack mercerization followed by stretching and formaldehyde, in the presence of various amounts of sulfuric acid (5–60% by weight) were studied. Beyond a concentration of 45% sulfuric acid, the reaction takes place very rapidly, and an explanation is put forward in terms of the extent of swelling of the fiber in sulfuric acid solutions. The reaction was also studied in the presence of glycerin, when the combined formaldehyde value is shown to decrease with an increasing concentration of glyceri

ISSN:0021-8995    

DOI:10.1002/app.1972.070160610

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

年代:1972

数据来源: WILEY