ISSN:0032-3888    

DOI:10.1002/pen.760270502

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractA procedure is described for the simultaneous prediction of the binodal and spinodal curves of polymer mixtures at various pressures using a form of the equation‐of‐state theory of Flory and co‐workers. The results of the calculation are compared with experimental results for the effect of pressure on the cloud points of both oligomer mixtures showing upper critical behavior and polymer mixtures showing lower critical behavior. The procedure successfully predicts the sign of the effect and its magnitude within the experimental and theoretical uncertainties for the systems st

ISSN:0032-3888    

DOI:10.1002/pen.760270503

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractA cell theory for the prediction of the surface tension of simple liquids is adapted to polymer liquids. The combinatory, free volume and potential energy zero terms of the partition function are all modified to account for the preservation of connectivity when a surface is created. Theory and experiment are in good agreement without an adjustable surface parameter.

ISSN:0032-3888    

DOI:10.1002/pen.760270504

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractInformation on the interfacial region in incompatible polymer mixtures can be gathered using various techniques including electron microscopy, thermal transition analysis, and more sophisticated methods such as nonradiative energy transfer (NRET). Selected examples are reported here to illustrate the exciting potentialities offered by diblock copolymer emulsifiers in controlling interfacial adhesion and devising high performance polymer blends.

ISSN:0032-3888    

DOI:10.1002/pen.760270505

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractThe formation of dispersed phase in blends of incompatible polymers during melt extrusion with a co‐rotating twin screw extruder was studied, using nylon and polyester as the matrix and ethylene‐propylene rubbers as the dispersed phase. A master curve is obtained, i.e.,Gηmα/γ = 4p±0.84, whereGis the shear rate, γ the particle diameter, η the interfacial tension, ηmthe matrix viscosity, ηdthe dispersed‐drop viscosity, andp= ηd/ηm. The plus (+) sign applies forp>1, and the minus (−) sign forp<1. Thus, the dispersed‐drop size is directly proportional to the interfacial tension and the ±0.84 power of viscosity ratio. The dispersed drops are the smaller, when the interfacial tension is the lower and the viscosity ratio is the closer to unity. The interfacial tension is largely controlled by the polarities of the two phases, and can be varied over several orders of magnitude by using app

ISSN:0032-3888    

DOI:10.1002/pen.760270506

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractA hypothesis for critical conditions for a transition from a two‐phase system to a homogeneous state during simple shear flow is advanced. It is predicted that at sufficiently high shear stress a homogeneous state is the stable steady state structur

ISSN:0032-3888    

DOI:10.1002/pen.760270507

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractAn advanced hypothesis derived in Part I (this issue) is tested with selected model blends. Blends of copolymers of styrene and acrylonitrile (SAN) and poly(methylmethacrylate), (PMMA) were studied because they are both amorphous, thermally stable, have large density differences, are easy to cut (in an ultramicrotome) and because comprehensive studies have been reported In the literature on this system. The melt viscosity of the blends were studied using a Rheometrics Mechanical Spectrometer and an Instron capillary rheometer. Light scattering measurements were performed during flow in order to measure the critical transition stress. The phase structure of quenched samples was studied by transmission electron microscopy on ultramicrotome cuts. It was shown that an Interpenetrating co‐continuous structure develops when flow is stopped, if a homogeneous phase Is formed during flow. Melt fracture limits the applicability of this approach to nearly compatible blend

ISSN:0032-3888    

DOI:10.1002/pen.760270508

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractTen commercial linear low‐density polyethylenes (LLDPE) were characterized by solution viscosity, size exclusion chromatography, SEC, and13C nuclear magnetic resonance. The resins were copolymers of ethylene with butene, hexene, or octene. They were prepared in gas phase (with narrow or very broad molecular weight distribution), or in solution. The macromolecules were found to be linear. For all but the very broad molecular weight distribution resins the average comonomer sequence length was found to be 1; in the other case diad formation was observed. The weight average molecular weights calculated from SEC, and intrinsic viscosities agreed quite well. Mechanical degradation of LLDPE was observed during the solution viscosity measurement

ISSN:0032-3888    

DOI:10.1002/pen.760270509

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractThe steady state and dynamic shear behavior of eleven commercial linear low density polyethylenes (LLDPE) and one low density polyethylene (LDPE) resin were measured in capillary and parallel plate geometries atT= 150 to 230°C. The extrudate swell and the Bagley correction were determined. A large pressure effect on capillary flow of narrow molecular weight distribution LLDPE was observed and a new corrective procedure was proposed. After the correction the steady state viscosity was found to be equal to the dynamic (not complex) viscosity: η(\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}) = η'(ω =\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}). A newly proposed four parameter relation between η and the deformation rate was found to provide a simple means for computation of the zero shear viscosity, ηo, and the primary relaxation time. Both these parameters showed a high degree of correlation. The expected relation: ηo∝︁Mw3.4was observed for low molecular weight samples with low polydispersity. The LLDPE activation energy of flow,Eσ=29.9 ± 1.8 kJ/mole, wa

ISSN:0032-3888    

DOI:10.1002/pen.760270510

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractThe uniaxial extensional flow at 150°C of 11 linear low density polyethylenes (LLDPE) and one low density polyethylene was measured in a Rheometrics Extensional Rheometer. The presence of silicone oil did not affect the results. However, large effects of the molding time were observed. For specimens molded for 14 min, strain hardening was not observed for any gas‐phase polymerized LLDPE. As the molding time was increased to 40 min, the strain hardening was quite apparent, the elongational viscosity nearly doubled, the equilibrium plateau vanished, and the maximum strain at break Increased by about 20 percent. Explanation for the molding time effects can be found in the concept of low entanglement density in the virgin gas‐phase resins. The entanglement increases with time at temperatures above the melting point. The specimens molded for longer time show strain harde

ISSN:0032-3888    

DOI:10.1002/pen.760270511

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY