摘要:

AbstractThe effects of rubber content, particle size and interparticle spacing on the fracture behaviour of toughened polymers over a range of strain rates and temperatures are discussed with particular reference to high‐impact polystyrene and rubber‐toughened nylons. It is concluded that the limiting factor in determining fracture resistance is a kinetic one: the rate at which the matrix polymer can respond to stress by forming oriented fibrils. Fibrillation can occur either by multiple crazing, in which case the preferred particle diameter D is about 1 μm; or as a result of cavitation within the rubber particles followed by shear yielding, which requires smaller inter‐particle spacings. An extension of the Argon‐Salama model for crazing is proposed to explain the interparticle spacing effect. Morphology is less critical in controlling fracture at low strain rates or higher temp

ISSN:0258-0322    

DOI:10.1002/masy.19900380102

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractMiscibility can particularly easily be “tailored” with blends P (AxB1‐x)/P (AyB1‐y) of random copolymers and with blends P (Ax‐b‐B1‐x)/P (Ay‐b‐B1‐y) of diblock copolymers, where the blend components differ only in composition. The former class of blends is discussed in some generality, the latter only in one special example, where the components are a homopolymer (x=0) and a symmetric copolymer (y=0.5). Phase diagrams and phase mor

ISSN:0258-0322    

DOI:10.1002/masy.19900380103

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractExperimental and theoretical results of the investigation of the laws governing the lamination process in polymer‐polymer systems in the transient region between binodal and spinodal have been systematized. The causes of the viscosity decrease in the phase separation region have been explained. An assumption has been made that the laws observed result from differences in the conditions of segregation of macromolecules of polymers forming a mixture and segments of the same molecules in interphase laye

ISSN:0258-0322    

DOI:10.1002/masy.19900380104

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractA simplified model for the formation of steady state structure of discrete domains in polymer blends is established for simple shear flow. It is assumed that the domain size distribution, which results from an equilibrium between breakup processes and coalescence processes, may be divided in small and stable spherical domains and large and unstable ellipsoidal domains. Based on simplified rate balances and an expression for domain deformation rate the volume fraction of large domains and the large and small semiaxes of the ellipsoids are expressed as functions of volume fraction and shear rate/shear stress. The ability of the model to simulate actual behaviour is tested against quantitative data for polystyrene/poly(methyl methacrylate) blends. It is concluded that the Taylor type behaviour is approached at low volume fraction and low shear stress. The aspect ratio, P, shows a maximum in a plot against shear stress with volume fraction as discrete variable. For certain concentrations P seems to approach infinity thus forming infinitely long fibers.

ISSN:0258-0322    

DOI:10.1002/masy.19900380105

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractMixtures of poly(ethylene oxide)/atactic poly(methyl methacrylate) (PEO/At‐PMMA) blends and poly(ethylene oxide)/poly(ethylene‐co‐vinylacetate) (PEO/EVAc‐1) blends were prepared by casting from a common solvent and were found miscible. The applications of the Solubility Parameter Theory, Patterson Theory and the Equation of State Theory of Flory are reported. The miscibility predictions obtained are discussed and compared to experimental miscibility e

ISSN:0258-0322    

DOI:10.1002/masy.19900380106

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe main part of this report deals with the thermodynamic fundamentals of one‐ and multi‐phase polymer blends and the presently reached state of a theoretical prediction is estimated. Potentialities and limits of the thermodynamic theories are discussed. Furthermore, a theoretical conception, basing on interfacial tensions between polymers and successfully used for the theoretical description of polymer alloys, is considered. The second topic of this report is the development of highly impact resistant thermoplastics and thermoplastic elastomers. In connection with it, the technological parameters necessary for the realization of multi‐phase polymer blends by mechanical mixing in the melt, are discussed. The experimental methods for the determination of the distribution are presented. The practical importance of multi‐phase blends is substantiated, the role of the interfacial energies revealed and discussed. In the third part the possibilities of the increase of compatibility are given forth and in further part demonstrated by e

ISSN:0258-0322    

DOI:10.1002/masy.19900380107

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractInterpenetrating polymer networks are combinations of two crosslinked polymers. Often, they exhibit dual phase continuity, meaning that both phases extend continuously throughout the sample. Recent research on IPNs has shown that both nucleation and spinodal decomposition mechanisms are important in the kinetics of phase separation.If the polymers are almost miscible, a microheterogeneous morphology will develop. Under these conditions, the glass transition of the IPN may be very broad, extending the range between the glass transition of the two homopolymers. Such materials are useful for sound and vibration damping. The loss and storage modulus, and tan δ behavior of polymers and IPNs in the glass transition region were evaluated on a quantitative basis, in order to characterize their damping behavior better. Corrections for background in dynamic mechanical spectroscopy studies will be discussed. The storage modulus of polystyrene at 25°C was selected as a standard. The development of a group contribution analysis of the integral area under the linear loss modulus‐temperature curves, the loss area, LA, is reviewed, and applied to a number of acrylic, styrenic, and vinyl statistical copolymers and IPNs. Each moiety in a polymer is shown to contribute to LA on a simple, additive basis.New research emphasizes the role of morphology and phase continuity in determining LA. The system cross‐poly(vinyl methyl ether)‐inter‐cross‐polystyrene was selected, because its phase diagram in the blend state is well known, and it has become both a model and interesting system to investigate. Midrange IPN compositions exist as two phases at room temperature, as illustrated by dynamic mechanical s

ISSN:0258-0322    

DOI:10.1002/masy.19900380108

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThermal ageing of PC/PBT blends and alloys has been studied with dynamic mechanical, calorimetric, and tensile dilatometry tests during creep. The substantial embrittlement occuring in PC/PBT during ageing is tentatively explained in terms of an unusually high densification of the amorphous phase. The phase boundaries have been found to increase in strength during ageing, improving the load bearing properties of the material.

ISSN:0258-0322    

DOI:10.1002/masy.19900380109

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe impact behavior of nylon 6‐ rubber blends is studied by varying the rubber concentration (0–26 vol. %), rubber particle size (0.1 ‐ 2.0 μm) and rubber properties.The brittle to tough transition shifts to lower temperatures by increasing the rubber concentration, decreasing the particle size and by lowering the modulus of the elastomer. With very small particle sizes, however, the transition temperature increases again.The toughness of the blends above their transition temperature increases with the rubber concentration, but the particle size has only some effect. Very small particle sizes decrease the impact behavior.The postulated deformation mechanism is cavitation of the rubber followed by shear deformation of the

ISSN:0258-0322    

DOI:10.1002/masy.19900380110

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY

摘要:

AbstractThe grafting of various vinyl monomers on polyethylene and on ethylene‐propylene copolymers has been initiated by mechanoradicals in an internal mixer. This is possible if the polymer has been slightly cross‐linked by γ‐radiation before processing or is dynamically cross‐linked by peroxides during processing. Some properties such as adhesion to metals or impact resistance of blends containing the modified polymers are

ISSN:0258-0322    

DOI:10.1002/masy.19900380111

出版商:Hüthig&Wepf Verlag    

年代:1990

数据来源: WILEY