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41.
Melt spun matrix fibers of toughened polypropylene copolymers modified by high energy electrons 下载免费PDF全文
Binary blends of polypropylene (PP) and ethylene‐octene copolymer (EOC) are prepared by continuous electron‐induced reactive processing at various mass ratios of the blend components and various doses without adding of any grafting agents. The influence of mass ratio and dose is investigated in order to get the optimum processing behavior of toughened PP as well as optimum properties of resulting fibers. It is found that toughened PP with a PP/EOC blend ratio of 97.5–2.5 mass % can be used advantageously as a matrix component for the process of online spinning of glass fiber/toughened PP hybrid yarns. Such hybrid yarns belong to one of the most advanced production methods for the manufacturing of fiber reinforced thermoplastic composites with an increased mechanical performance. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44011. 相似文献
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43.
Hai Hong Le Katrin Reincke Amit Das Klaus‐Werner Stöckelhuber Swen Wiessner Tung Pham Quang Khang Do Xuan Tung Hoang Wolfgang Grellmann Gert Heinrich Hans‐Joachim Radusch 《大分子材料与工程》2016,301(4):414-422
The selective wetting behavior of silica in emulsion styrene butadiene rubber (ESBR)/solution styrene butadiene rubber (SSBR) blends is characterized by the wetting concept, which is further developed for filled blends based on miscible rubbers. It is found that not only the chemical rubber–filler affinity but also the topology of the filler surface significantly influences the selective filler wetting in rubber blends. The nanopore structure of the silica surface has been recognized as the main reason for the difference in the wetting behavior of the branched ESBR molecules and linear SSBR molecules. However, the effect of nanopore structure becomes more significant in the presence of silane. It is discussed that the adsorption of silane on silica surface constricts the nanopore to some extent that hinders effectively the space filling of the nanopores by the branched ESBR molecules but not by the linear SSBR molecules. As a result, in silanized ESBR/SSBR blends the dominant wetting of silica surface by the tightly bonded layer of SSBR molecules causes a low‐energy dissipation in the rubber–filler interphase. That imparts the low rolling resistance to the blends similar to that of a silica‐filled SSBR compound, while the ESBR‐rich matrix warrants the good tensile behavior, i.e., good abrasion and wear resistance of the blends.
44.
C. Oelgardt J. Anderson J.G. Heinrich G.L. Messing 《Journal of the European Ceramic Society》2010,30(3):649-656
We report on how the mechanical properties of sintered ceramics (i.e., a random mixture of equiaxed grains) with the Al2O3–Y2O3–ZrO2 eutectic composition compare with those of rapidly or directionally solidified Al2O3–Y2O3–ZrO2 eutectic melts. Ceramic microcomposites with the Al2O3–Y2O3–ZrO2 eutectic composition were fabricated by sintering in air at 1400–1500 °C, or hot pressing at 1300–1400 °C. Fully dense, three phase composites of Al2O3, Y2O3-stabilized ZrO2 and YAG with grain sizes ranging from 0.4 to 0.8 μm were obtained. The grain size of the three phases was controlled by the size of the initial powders. Annealing at 1500 °C for 96 h resulted in grain sizes of 0.5–1.8 μm. The finest scale microcomposite had a maximum hardness of 19 GPa and a four-point bend strength of 282 MPa. The fracture toughness, as determined by Vickers indentation and indented four-point bending methods, ranged from 2.3 to 4.7 MPa m1/2. Although strengths and fracture toughnesses are lower than some directionally or rapidly solidified eutectic composites, the intergranular fracture patterns in the sintered ceramic suggest that ceramic microcomposites have the potential to be tailored to yield stronger, tougher composites that may be comparable with melt solidified eutectic composites. 相似文献
45.
Polymer crystallization under flow was investigated because final properties of polymers strongly depend on the crystalline structure and morphology formed during processing. In-situ synchrotron WAXS and SAXS were used to investigate the structure formation and morphological developments during quiescent and shear-induced crystallization of iPP with 3 different concentrations (0.01, 0.03 and 0.1 wt%) of β-nucleating agent. Under quiescent conditions, a high β-content was obtained at all those concentrations indicating the high β-nucleating efficiency of the nucleating agent. After application of shear, the β-nucleating ability at small concentration was retained, while at larger concentrations it was strongly retarded. Furthermore, the addition of β-nucleating agent was beneficial for the molecular alignment during processing, the anisotropic particles of β-nucleating agent were much more effective to align the molecular chains in the flow direction compared to isotropic ones. A crystallization scheme for the iPP β-nucleating agent under shear was proposed. 相似文献
46.
The paper presents an alternative constraint-handling technique that converts a nonlinear constrained programming problem
into an unconstrained multi-objective optimisation problem. The technique is derived from the behavioural memory constraint-handling
method, which was originally implemented for single-objective optimisation with genetic algorithms. We compare our presented
technique with two other popular constraint-handling concepts and demonstrate its superiority over them when applied to a
propeller optimisation problem. We conclude that the multi-objective behavioural memory constraint-handling technique conjugated
with the non-dominated sorting genetic algorithm (NSGA-II) is a prudent method to apply to problems with an infeasible initial
design and where constraints have a natural order of satisfaction, which, if not conformed to, would lead to unrealistic designs
that impair the search by GA. 相似文献
47.
48.
Sergiy Antonyuk Stefan Heinrich Jürgen Tomas Niels G. Deen Maureen S. van Buijtenen J. A. M. Kuipers 《Granular Matter》2010,12(1):15-47
The discrete modelling and understanding of the particle dynamics in fluidized bed apparatuses, mixers, mills and others are
based on the knowledge about the physical properties of particles and their mechanical behaviour during slow, fast and repeated
stressing. In this paper model parameters (modulus of elasticity, stiffness, yield pressure, restitution coefficient and strength)
of spherical granules (γ-Al2O3, zeolites 4A and 13X, sodium benzoate) with different mechanical behaviour have been measured by single particle compression
and impact tests. Starting with the elastic compression behaviour of granules as described by Hertz theory, a new contact
model was developed to describe the force-displacement behaviour of elastic-plastic granules. The aim of this work is to understand
the energy absorption during compression (slow stressing velocity of 0.02 mm/s) and impact (the impact velocity of 0.5–4.5 m/s)
of granules. For all examined granules the estimated energy absorption during the impact is found to be far lower than that
during compression. Moreover, the measured restitution coefficient is independent of the impact velocity in the examined range
and independent of the load intensity by compression (i.e. maximum compressive load). In the case of repeated loading with
a constant load amplitude, the granules show cyclic hardening with increasing restitution coefficient up to a certain saturation
in the plastic deformation. A model was proposed to describe the increase of the contact stiffness with the number of cycles.
When the load amplitude is subsequently increased, further plastic deformation takes place and the restitution coefficient
strongly decreases. 相似文献
49.
V. A. Pugsley G. Korn S. Luyckx H. -G. Sockel W. Heinrich M. Wolf H. Feld R. Schulte 《International Journal of Refractory Metals and Hard Materials》2001,19(4-6):311-318
The influence of a corrosive wood-cutting environment on the strength of hardmetals and on their behaviour under static loading conditions has been investigated. Two commercial hardmetals were tested, which differed in hard phase composition. The results show exposure to this environment to have a highly detrimental influence on the strength of both hardmetals investigated, due to localised corrosive attack which results in the formation of stress raisers. The relative loss in strength as a function of corrosion time is the same for both hardmetals. However, the performance of the two grades differ significantly when a static load is applied in this corrosive environment: the strength of the WC-Co grade remains unaffected by the applied load, while the grade containing a mixed carbide phase exhibits stress corrosion cracking which results in a further reduction in strength. 相似文献
50.
The feasibility of performing SI-traceable carbon isotope amount ratio measurements following conversion of carbon into CF4 was studied. A procedure for the direct fluorination of carbon with elemental fluorine was developed, and the conversion step was checked for losses, blank contributions, and the absence of systematic isotope effects. Gas chromatography was used to identify and quantify the gaseous fluorination products and to isolate CF4 from byproducts. After fluorination of graphite carbon, CF4 and perfluoroalkanes with up to six carbon atoms were observed as reaction products. Within an uncertainty of 10%, the graphite carbon was fully recovered in the gaseous carbon fluorides, with the main product being CF4 (80-90%) and C2F6 as the major byproduct. The fluorination and GC procedures were found to introduce an alteration not bigger than 0.03 +/- 0.04/1000 on the isotopic composition of CF4. Carbon blank contributions introduced during the fluorination procedure were below 0.5% relative to a typical sample of 4 mg of carbon. For two of the materials investigated, the carbon isotope ratios measured on a differential mass spectrometer were reproducible within a standard deviation of approximately 0.1/1000 for several individual fluorinations. For these materials, the developed fluorination procedure is a straightforward process, which can be used as a foundation to establish SI-traceable measurements of carbon isotope amount ratios. However, for the third graphite material the formation of byproducts (C2F6-C6F14) was found to induce significant isotopic fractionation. 相似文献