摘要:

AbstractThe general principles of thermodynamic equilibrium in binary liquid systems are reviewed briefly, and extended to quasi‐binary mixtures of polydisperse polymers. Molecular models allowing actual phase behaviour to be discussed in terms of molecular parameters are exposed to data on the system polystyrene/polyvinylmethylether. Disparity in size and share between the repeating units must be introduced to obtain reasonable agreement between theory and experiment. The neccessary introduction of the molar‐mass distribution detracts from this agreement which makes clear that other aspects exist that must be taken into account. For example, cross association between repeating units has a marked effect on phase behaviour. Blends are subject to two kinds of thermodynamic aging which lead either to considerable mutual solubility in supposedly immiscible blends, or to metastable equilibria transforming into states of lower Gibbs energy. In both cases physical proerties of the blend will change with t

ISSN:1022-1360    

DOI:10.1002/masy.19940780103

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe mean field, rigid lattice treatment as applied to polymer mixtures has been used to estimate segment‐segment interaction parameters for a wide range of polymers. These parameters incorporate, without distinction, contributions from non‐combinatorial entropy effects, dispersion forces and any specific interactions that operate in the polymer blend. Thus while these parameters can be used to predict successfully the nature of the phases in untested polymer blends, structural effects may also play a role in determining miscibility, and these may have to be assessed individually. Examples of structural effects are described using chlorine‐containing polymers and blends of copolymers with an anhydride ring attached in two different ways to the polymer chain. The extension of binary interaction parameters to the prediction of phase behaviour in complex ternary copolymer blends and the effect on the phase behaviour of changing the component ratios in the blends, is also illust

ISSN:1022-1360    

DOI:10.1002/masy.19940780104

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe importance of including specific monomer structures, local correlations, and “equation of state effects” into the statistical thermodynamics of polymer blends is accomplished by developing and applying the lattice cluster theory. This new theory provides systematic corrections to Flory‐Huggins theory from local correlations and describes polymers as containing structured monomers that extend over several lattice

ISSN:1022-1360    

DOI:10.1002/masy.19940780105

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThis contribution embraces two topics related to phase behavior of polymer blends under equilibrium and nonequilibrium. 1. Polymer blends can undergo different phase changes as liquid‐liquid phase transition and crystallization. Coupling of demixing and crystallization may occur at the kinetic stage. This is illustrated by blends of poly(ϵ‐caprolactone)(PCL) and poly(styrene‐co‐acrylonitrile)(SAN). 2. Extension of studies to blend systems under flow is necessary for the better understanding of structure formation in polymer blends outside equilibrium. Polymer molecules will be oriented and stretched when subjected to flow. This may result in flow‐induced phenomena. Effects of flow on the phase behavior have been studied only for a few blends, as yet. The primary observation was flow‐induced miscibility. Apparent shifts of the phase transition temperatures will be discussed qualitatively in terms of a decoupled

ISSN:1022-1360    

DOI:10.1002/masy.19940780106

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractExperimental data are shown which confirm the existence of increased macromolecules association in a polymer mixture. The increase of association is revealed in the increase of light scattering intensity and the increase of density (local ordering increase). The grown up association degree determines the peculiarities of network formation through cross‐links in the solution of polymer mixtures. Macromolecules associates degrade under mechanical stresses or after addition of slight amounts of substances which are able to interact intensively intermolecularly (solvating) with macromolecules of one of the polymer components in the mixture. Representation of associates formation and degradation in polymer mixture help to explain many experimental data on thermodynamics, structure and properties of polymer mixture

ISSN:1022-1360    

DOI:10.1002/masy.19940780107

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractA new model for impact modification in polymer blends is being presented. The new model is derived from the new non‐equilibrium thermodynamical description of heterogeneous polymer systems and is interpreting crazing fracture energy dissipation and fracture mechanism in a new way: on the basis of dissipative structures in polymer blends and their dynamic

ISSN:1022-1360    

DOI:10.1002/masy.19940780108

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe interaction energy between two polymers determines whether they form a miscible blend or a phase separated one. In the latter, these interactions also determine the nature of the interface between phases which in turn influences stress transfer between the phases in the solid state and morphology generation during formulation. Estimates of polymer‐polymer thermodynamic interactions are used to rationalize the behavior of polycarbonate/ABS materials and a series of polyamides toughened by reactive blending with a functionalized elastome

ISSN:1022-1360    

DOI:10.1002/masy.19940780109

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractA combined study by SAXS and DSC on quenched blends of PVDF and PMMA is presented. Attention is focused on the first stage of the phase separation process during annealing that is shown to be mainly determined by the diffusion of the PVDF molecules from the amorphous blend phase towards the crystals growth front. The experimental monomer diffusion constants at T>Tgare compared with those expected theoretically using the approximation of the fast model process and the WLF equation for the relaxation frequency of the monomer. The nature and composition of the crystal interphase are discussed in terms of the SAXS invariant for the whole system and the calorimetric data derived from the Tgtransitions observed.

ISSN:1022-1360    

DOI:10.1002/masy.19940780110

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractInitial stages of interdiffusion at the interface between two films of poly(methylmethacrylate) (PMMA) and poly(vinyl chloride) (PVC) have been determined by neutron reflectometry. Experiments are performed at temperatures between the glass transition temperatures of the homopolymers. PMMA chains are thus not mobile, but are dissolving in PVC. The growth of the interface width with time follows a power law, which depends on temperature, and the position of the interface moves in the direction of the immobile component. With a PVC film on top, the enrichment of PMMA at the free surface is observed at later times.

ISSN:1022-1360    

DOI:10.1002/masy.19940780111

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe system formed by isotactic polypropylene (iPP) and hydrogenated oligo(cyclopentadiene) (HOCP) is investigated in order to study the influence of the composition and thermal history on the morphology, phase structure, miscibility and thermal and mechanical properties of the blends. A phase diagram presenting both the lower and the upper cloud point curves is proposed. It is shown that these blends assume different morphologies and consequently present diverse thermal and dynamic‐mechanical behaviours depending on quenching processes from one‐phase region or two‐phase region. From the analyses of the results of optical microscopy, WAXS, DSC and DMTA techniques it is found that: blend films, quenched from the melt of one‐phase region to room temperature, contain one amorphous phase and iPP in smectic form; moreover they are transparent and possess a reduced permeability to oxygen and aroma; conversely when the samples are quenched from the melt of two‐amorphous phase region there is the formation of two amorphous phases (the iPP‐rich phase and the HOCP‐rich phase) and at room temperature the iPP crystallizes in the mono

ISSN:1022-1360    

DOI:10.1002/masy.19940780112

出版商:Hüthig&Wepf Verlag    

年代:1994

数据来源: WILEY