Controlled stress, oscillatory rheometry of a petroleum pitch

Turpin, M.; Cheung, T.; Rand, B.

doi:10.1016/0008-6223(94)90186-4

Cited by 19 publications

(13 citation statements)

References 8 publications

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“…The relevance of such approaches to pitch and mesophase pitch have been discussed by Rand [1], Turpin et al [4], Sato et al [21], Khandare et al [22] and Py et al [26]. The values of T-T g at which the flow curves were measured are shown in Figure 9 (b) and it is evident that with increasing mesophase content the ranges of measurement are increasingly distant from the relevant T g .…”

Section: Temperature Dependencementioning

confidence: 85%

“…At low temperatures isotropic pitch is a glassy material, the glass transition temperature increasing with heat treatment temperature as the average molecular mass increases. Viscoelastic behaviour is observed at temperatures close to the glass transition temperature [4], but at higher temperatures the behaviour is approximately Newtonian, although there have been observations of a yield stress and plastic viscosity (Bingham type behaviour) in some cases.…”

Section: Introductionmentioning

confidence: 99%

“…Pitches are complex viscoelastic materials [1] [4]. At low temperatures isotropic pitch is a glassy material, the glass transition temperature increasing with heat treatment temperature as the average molecular mass increases.…”

Section: Introductionmentioning

confidence: 99%

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Low shear rheological behaviour of two-phase mesophase pitch

Ramjee

Rand

Focke

2015

Carbon

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Section: Temperature Dependencementioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

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Low shear rheological behaviour of two-phase mesophase pitch

Ramjee

Rand

Focke

2015

Carbon

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“…The total extra stress tensor t t for liquid crystalline materials is given by the sum of symmetric viscoelastic stress tensor t s , antisymmetric stress tensor t a and Ericksen stress tensor t Er (Refs. 17 and 18) t t~ts zt a zt Er (22) The symmetric viscoelastic stress tensor t s is expressed as the sum of a symmetric viscous stress contribution t v and an elastic stress contribution t e as 6,18 t s~tv zt e (23) and obtained using the dissipation expansion (2). The stress contribution t v found is given by…”

Section: Landau-de Gennes Mesoscopic Theorymentioning

confidence: 99%

Multiscale theory and simulation for carbon fibre precursors based on carbonaceous mesophases

Grecov¹,

Lima²,

Rey³

2006

Plastics, Rubber and Composites

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An integrated multiscale computational materials modelling toolbox developed to predict product and processing properties of carbonaceous mesophases is presented and used to simulate linear and non-linear rheology, processing flow induced textural transformation and carbon fibre textures. The spatial resolution of the predictions spans from the nanoscale to the microscale. The nanoscale processes that lead to defect nucleation are linked to process induced structuring. Modelling the linear rheology reveals the role of polydomain textures on the elasticity modulus and can be used to predict domain sizes from simple small amplitude oscillatory flows. Geometric modelling provides insights on fibre texture and elucidates the role of surface anchoring on the fibre structure. The shown ability of the integrated model to predict product structure, flow processing and rheology in a linked sequence demonstrates the utility of computational material science as an efficient and economical innovation tool.

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“…The characterization of isotropic and mesophase pitches using this technique has recently received some attention. [24][25][26][27][28][29][30] The main features of the experimental measurements in textured carbonaceous mesophase are summarized in Figure 3, which shows schematics of the master curves for the frequency dependence of the storage G' and loss G" linear viscoelastic moduli using the Williams-Landel-Ferry (WLF) superposition. 11,[25][26][27] Figure 4 shows an schematic of a 2D view of a textured carbonaceous mesophases displaying the polydomain state; 7 H is the average domain size within which a more or less uniform n is found.…”

Section: Introductionmentioning

confidence: 99%

Linear viscoelasticity of textured carbonaceous mesophases

Lima¹,

Rey²

2006

J. Braz. Chem. Soc.

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Fibras de carbono de alto desempenho podem ser produzidas a partir de piche de petróleo anisotrópico usando o processo de extrusão-fiação. O piche mesomórfico é um cristal líquido discótico nemático termotrópico, que possui ordem na orientação das moléculas. Cristais líquidos são materiais que possuem textura, anisotropia e visco-elasticidade. Um fenômeno importante que é encontrado em cristais líquidos é a interação entre a textura devido à orientação das moléculas e o comportamento reológico, no qual a textura ocorre devido à presença de defeitos na orientação das moléculas. O processo de extrusão-fiação usado na fabricação de fibras de carbono a partir de precursores nemáticos usa uma cascata de escoamentos que incluem fluxo capilar convergente e extensional, os quais promovem a formação de uma variedade de estruturas, incluindo radial, concêntrica, randômica e bipolar, que darão propriedades especificas para as fibras de carbono resultantes. Portanto, a compreensão fenomenológica da interação entre a textura e a reologia do precursor nemático é necessária para o controle do processo e para a otimização do produto. Neste artigo, a interação entre a reologia e a textura de cristais líquidos discóticos nemáticos será enfocada e um modelo anisotrópico será desenvolvido para descrever o regime linear visco-elástico de piches mesofásico com textura. O modelo é capaz de prever todas as características observadas experimentalmente, incluindo a dependência dos módulos de armazenamento e de perda com a freqüência de oscilação e a sua dependência com a temperatura, assim como promover uma melhor compreensão do papel dos defeitos e da anisotropia no comportamento visco-elástico do piche anisotrópico.High performance carbon fibers can be produced from anisotropic petroleum pitch using the fiber spinning process. The mesophase pitch is a thermotropic discotic nematic liquid crystal possessing orientational order. Liquid crystals are textured, anisotropic, viscoleastic materials. An important phenomenon of liquid crystals is the interaction between orientational textures and rheology, where the texture is due to the presence of orientational defects. The fiber spinning process used in the carbon fiber manufacture from nematic precursors uses a cascade of processing flows that involves capillary, convergent, and extensional flows, which promotes the formation of a variety of textures that will give specific properties to the resultant carbon fiber. Hence a fundamental understanding of the impact of textures on rheology is needed for eventual process control and product optimization. In this paper we study the interaction of rheology and texture and develop a model of anisotropic linear viscoelasticity of textured mesophases. The model is able to predict all the features observed experimentally, including the frequency dependency of the loss and storage modulus and their temperature sensitivity, and provides a better understanding of the role of defects and anisotropy on pitch viscoelasticity.

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Controlled stress, oscillatory rheometry of a petroleum pitch

Cited by 19 publications

References 8 publications

Low shear rheological behaviour of two-phase mesophase pitch

Low shear rheological behaviour of two-phase mesophase pitch

Multiscale theory and simulation for carbon fibre precursors based on carbonaceous mesophases

Linear viscoelasticity of textured carbonaceous mesophases

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