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...
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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.
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.
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...
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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.
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,...
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Three new bis(l-chloro-2,2-dicyanovinyl) aromatic monomers have been synthesized. Vinylic nucleophilic substitution polymerization with 4,4’-diaminodiphenyl ether led to moderately high molecular weight poly(enaminon...
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Thermogravimetric analysis is typically employed to study degradation and curing processes. The work presented here will show that thermogravimetry (TG) can also be used to probe other types of thermal processes. In p...
Thermogravimetric analysis is typically employed to study degradation and curing processes. The work presented here will show that thermogravimetry (TG) can also be used to probe other types of thermal processes. In particular, TG can be used to determine glass transitions T g in certain polymers. A premise of the technique is that low molecular weight species can be imbibed into a polymer sample. Upon heating, major gas evolution will take place in the glass transition region and such gas evolution can be utilized as an indicator of T g . This technique is particularly beneficial for determining T g values of semicrystalline polymers without major modifications of crystallinity. To demonstrate the concept, studies were carried out in two phases. Phase one looked at well characterized amorphous polymers using several solvents to show that the technique does indeed work. In phase two it was established that glass transitions of semicrystalline polymers could be detected.
Gelation of PVC solutions is generally agreed to result from network formation. The proposed network linkages include crystallites, hydrogen‐bonds, and entanglements brought about by spinodal decomposition. The objec...
There are many methods currently producing high modulus and high strength films and fibers in industry. This publication examines the results of a hot nip drawing process to produce high modulus PP films at a relative...
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There are many methods currently producing high modulus and high strength films and fibers in industry. This publication examines the results of a hot nip drawing process to produce high modulus PP films at a relatively rapid production rate. The effects of both temperature and rate of draw on the drawn material will also be examined.
Fabrication discontinuities in weldments pose a serious engineering problem for structural applications involving cyclic loading. Often, the discovery of fabrication discontinuities through nondestructive inspection c...
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