ISSN:0032-3888    

DOI:10.1002/pen.760240202

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe theory of multicomponent polymeric systems, termed “polymeric alloys”, composed of block copolymers, homopolymers and solvents is discussed. We first review the microscopic interfacial properties of polymeric mixtures, highlighting the interfacial activity of block copolymers as emulsifying agents in incompatible homopolymer blends. We then turn to some interesting features of the phase diagrams, such as homopolymer‐induced mesophase formation and the existence ofeutecticpoints, similar to those for metallurgical alloys. Finally, we address problems in polymer dynamics and present some recent new theoretical results based on the tube

ISSN:0032-3888    

DOI:10.1002/pen.760240203

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractAn abbreviated review of the current state of knowledge of polymer interfacial phenomena is given. Classical thermodynamics treats the interfacial zone (the interphase) as a “black box” and yields rigorous relationships among interfacial quantities. A recent reformulation of interphase thermodynamics, which eliminates the use of a Gibbs dividing surface, is shown to be an invaluable tool for investigating interfacial properties. Microscopic theories, such as the gradient theory, yield more details about what is in the black box, but the information is only approximate. The gradient theory has been used to: (1) relate the surface tension of a polymer liquid to its isothermal compressibility, (2) develop a quantitative theory of polymer liquid surface tension, and (3) determine the interfacial tension between two immiscible polymer liquids. The gradient theory will be shown to be in harmony with the microscopic theory of Helfand and co‐workers although the latter treats polymer interfaces from a completely different point of

ISSN:0032-3888    

DOI:10.1002/pen.760240204

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractApplications of fluorescence techniques to the study of polymer colloids are reviewed, with emphasis on excimer and exciplex forming probes and fluorescence energy transfer processes. In these experiments non‐aqueous dispersions covalently labelled with naphthalene or anthracene were examined by a variety of techniques in order to elucidate aspects of core morphology with a resolution of about 10Å. The current “concentric sphere” or “core‐shell” model of colloid structure was found to be inconsistent with the results of the luminescence experiments. A new “microphase” model is proposed which overcomes these difficulties. In this model, the core structure is seen to be made up of phase‐separated microdomains of core and

ISSN:0032-3888    

DOI:10.1002/pen.760240205

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe Lower Critical Solution Temperature (LCST) of polyethylene (PE), polypropylene (PP), and ethylene‐propylene block and random copolymers have been measured in heptanes. A thermogram related to the variation of the turbidity of the solution is obtained between 100 and 210°C. The temperature of the onset of the turbidity peak is defined as the LCST of the system. The width and the area of the turbidity peaks are tentatively associated with the polymer polydispersity and the amount of polymer involved in the phase separation. The thermograms of solutions containing both homopolymers show two distinct turbidity peaks situated at a 70°C interval. Correlations of molecular orientations in the concentrated phase, possible in PE systems but not in PP solutions, are at the origin of the lower LCST values for PE solutions. The LCST of copolymers are situated between those of the homopolymers but the dependence of the LCST on the copolymer ethylene content is different for block and random copolymers. Examples of thermograms are also given for mixtures of copolymers with PE and PP. By analysis of their thermograms, some commercial block EP copolymers were also found to contain PK and PP. This method seems well suited for characterizing polymer mixtu

ISSN:0032-3888    

DOI:10.1002/pen.760240206

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractPolymer blends, because of the well‐known immiscibility of polymers, generally show phase separation. Block polymers can be considered as simple models of two‐phase systems. Because unlike segments are connected by covalent bonds, the phase separation is on a smaller scale and takes rather unusual forms. The types of block polymers of commercial importance are described with a consideration of the morphologies which result from particular compositions. Their use as solubilizing agents to increase the compatibility of the corresponding homopolymers is also discus

ISSN:0032-3888    

DOI:10.1002/pen.760240207

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThis note describes the application of infrared spectroscopy to determine the proportion of ester groups of poly(ϵ‐caprolac‐tone) which are involved in specific interactions with the hydroxyl groups of the poly(2‐hydroxypropyl ether of bisphenol A) (Phenoxy, Union Carbide) in a series of miscible blends of the two polymers, Even with a fifteen‐fold excess of hydroxyl groups, only about 50 percent of the ester groups of poly(ϵ‐caprolactone) are hydrogen‐bonded, presumably reflecting steric restrictions to the ester‐hydroxyl interactions. Partially miscible blends of these two polymers may also be prepared by a suitable choice of casting solvent, and infrared spectroscopy may then be used to follow the kinetics of miscibility when the partially miscible

ISSN:0032-3888    

DOI:10.1002/pen.760240208

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractAn attempt was made to melt incorporate ultra high molecular weight polyethylene, UHMWPE, into medium density polyethylene, MDPE. The behavior of the mixtures, containing up to 6 wt percent of UHMWPE, was examined using mechanical and rheological testing. The mechanical test results were found to contain large experimental errors, which makes interpretation very difficult. On the other hand, melt rheology studies, using dynamic and extensional deformations, gave direct insight into the extent and effect of blending. Degradation during the processing was evaluated by size exclusion chromatography. The degree of dispersion of the UHMWPE was examined under the optical microscope.

ISSN:0032-3888    

DOI:10.1002/pen.760240209

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe technique of Thermo Stimulated Creep (TSC) has been applied to the study of anelastic properties of polyethylene, polypropylene, their copolymers and blends. In the temperature range −200 to 100°C, complex TSC peaks were observed in all samples, namely around 0°C, about the same temperature as for the homopolypolymer polypropylene. By applying “fractional stresses”, with a convenient choice or the loading program, these peaks have been experimentally resolved. Two components can be distinguished: 1. The “low temperature” component is characterized by mechanical retardation times following a compensation law. It has been attributed to microbrownian motions of polypropylene sequences liberated at the glass transition of the “true” amorphous regions. 2. The “high temperature” component which is influenced by thermal treatment has been assigned to microbrownian motions of polypropylene sequences liberated at the glass transition of the “constrained” amorphous regions. In block polymers, an additional TSC peak is observed around −50°C: it has been associated with the glass transition of ethylene‐propylene‐rubber (EPR) interphase. The coupling of this interphase with polyethylene and polypropylene phases is insured by diffusion of some ethylene and propylene sequences in‐EPR. At about −140°C, a TSC peak associated with the low temperature component of the glass transition of polyethylene can be disting

ISSN:0032-3888    

DOI:10.1002/pen.760240210

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractA new predictive relation between pressure and temperature changes on the glass‐transition boundary is derived for random solutions. The isobaric version of this relation is integrated to recover a previous theory for the compositional variation of glass‐transition temperatures. The isothermal form of the differential equation gives an equation for the compositional variation of glass‐transition pressures. An enthalpic definition of the transition boundary provides a relation between excess enthalpies of mixing for the glassy and liquid states for the isobaric and isothermal transitions. Similarly, a definition of the boundary in terms of the solution volume provides a relation between excess volumes of mixing for these two states for the isobaric and isothermal transitions. The primary entropic equation for the composition‐dependent isobaric transition gives two hierarchies of approximation, one of which is shown to be preferred for physical reasons. A parallel situation arises for the isothermal tra

ISSN:0032-3888    

DOI:10.1002/pen.760240211

出版商:Society of Plastics Engineers, Inc.    

年代:1984

数据来源: WILEY