An analysis of the influence of crystalline microstructure on fatigue crack propagation in polyoxymethylene is presented. A series of test specimens containing a variety of diverse microstructures was prepared through...
An analysis of the influence of crystalline microstructure on fatigue crack propagation in polyoxymethylene is presented. A series of test specimens containing a variety of diverse microstructures was prepared through controlled thermal treatments of plaques from four different lots of polyoxymethylene. Extensive characterization of the crystalline microstructure was carried out in order to permit a direct comparison between the fatigue behaviour and crystalline microstructure. The degree of crystallinity and tie molecule density were both found to have a significant affect on fatigue crack propagation rate while average spherulite size did not appear to influence fatigue behaviour. Additionally, the fatigue fracture surfaces of many of the test specimens were examined. Three distinct surface topographies were observed and found to correlate with different stages of crack growth. In the region near the end of fatigue crack propagation, closely spaced surface markings that resemble fatigue striations were observed.
The solubility behavior of poly(enaminonitrile) (PEAN) solutions and blends has been investigated by using light scattering. PEANs are soluble in a series of polyether solvents (glymes), and those solutions show cloud...
The solubility behavior of poly(enaminonitrile) (PEAN) solutions and blends has been investigated by using light scattering. PEANs are soluble in a series of polyether solvents (glymes), and those solutions show cloud points as the temperature is raised. The same behavior was observed from miscible blends of PEAN with poly(ethylene oxide). Cloud points were determined by laser light scattering measurements.
The extrusion of blown film polyethylene is a complex process characterized by a large number of interdependent process variables. In order to derive the set of process conditions necessary for a desired film solid st...
详细信息
The extrusion of blown film polyethylene is a complex process characterized by a large number of interdependent process variables. In order to derive the set of process conditions necessary for a desired film solid state property, the processor normally utilizes a laborious trial‐and‐error method. In this work, a technique is described to establish more directly the set of extruder settings for producing film with an optimum value of a given property. Biaxial toughness was optimized in the present work, but the technique is applicable to any quantifiable film property.
In this paper theories of swelling that have been applied to coal are modified to account for hydrogen bonding. The results of various swelling measurements are analyzed and suggest some important conclusions. First, ...
详细信息
This is the first of three papers that deal with coal solubility and swelling. An association model has been applied to coal, and this predicts that the mixing of coal with certain solvents will be determined by a bal...
详细信息
In this paper we propose a model for coal swelling based on a process called disinterspersion. This allows a calculation of the “molecular weight” or number of aromatic “clusters” between cross-link points under t...
详细信息
The synthesis of a thermotropic copolyester based on 4‐hydroxyacetophenone azine ( 1 ) and a 50 : 50 (mole ratio) mixture of sebacoyl/dodecanedioyl dichlorides was investigated in chloroform via a low‐temperature so...
The synthesis of a thermotropic copolyester based on 4‐hydroxyacetophenone azine ( 1 ) and a 50 : 50 (mole ratio) mixture of sebacoyl/dodecanedioyl dichlorides was investigated in chloroform via a low‐temperature solution route. polymers with an inherent viscosity η inh between 0,27–1,56 dL · g −1 were characterised by 1 H NMR, IR, thermal analyses, gel permeation chromatography and static light scattering techniques: Enantiotropic polymers exhibit a large mesophase range (≈100°C) and the values of both crystal‐nematic and nematic‐isotropic transitions are molecular‐weight dependent. Intrinsic viscosity was determined to relate to molecular weight by [η]/(dL · g −1 ) = 9,6 · 10 −4 M̄ in chloroform at 25°C, and the persistence length was calculated to be of the order of 27 Å.
Measurements of the complex permittivity were used to assess the amorphous phase miscibility in blends of poly(butylene terephthalate) (PBT) and several poly(ester-ether) (PEE) segmented block copolymers. In addition,...
详细信息
An investigation of the influence of crystalline morphology on fatigue crack propagation (FCP) resistance in a slightly branched polyethylene is presented. Various thermal histories have been utilized to generate samp...
详细信息
An investigation of the influence of crystalline morphology on fatigue crack propagation (FCP) resistance in a slightly branched polyethylene is presented. Various thermal histories have been utilized to generate samples with different crystalline microstructures and the samples were characterized thoroughly using standard methods. Estimation of tie molecule densities was obtained from measurements of brittle fracture stress. Differences in FCP behaviour for the quenched and annealed samples were shown to be dictated by a competing effect between the degree of crystallinity and tie molecule density. Further, larger spherulite size and distribution appeared to have a deleterious effect on fatigue properties. In general, crystalline microstructure is shown to have a significant influence on fatigue crack propagation behaviour.
暂无评论