Shear fracture of polystyrene melts and solutions

Chen, Y.-L.; Larson, Ronald G.; Patel, Sanjay

doi:10.1007/bf00366951

Cited by 38 publications

(19 citation statements)

References 23 publications

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“…[34] The resulting non-linearities showed a dependency on both the molecular weight and topology. [29] For strain amplitudes above a critical value g 0,c , the stress time signal exhibited an amplitude decay that indicates slip, as shown in Figure 5 and in qualitative agreement with Chen et al [28] and Hatzikiriakos and Dealy. [22] As an example, the relative intensities of the second and third harmonic for LCB2, as measured with the ARES and the RPA2000, are depicted in Figure 6.…”

Section: Investigation Of Laos Flow Via Ft Rheologysupporting

confidence: 74%

“…Examples are the evaluation of the slip arising from LAOS flow on monodisperse polystyrene melts, [26] concentrated solutions of high-molecular weight polystyrenes, [27] and PS solutions and melts. [28] In most cases, the above publications state that the appearance of different types of LAOS signals is attributed to the flow properties and to material constitutive instabilities. [26][27][28] To the best of our knowledge, only a few publications have explored and analysed the slip phenomena being developed in both flow types (sliding plate and capillary flow) [22,23] for the same material.…”

Section: Full Papermentioning

confidence: 99%

“…[28] In most cases, the above publications state that the appearance of different types of LAOS signals is attributed to the flow properties and to material constitutive instabilities. [26][27][28] To the best of our knowledge, only a few publications have explored and analysed the slip phenomena being developed in both flow types (sliding plate and capillary flow) [22,23] for the same material. Particularly relevant in terms of capillary flows, is that slip is reduced or hindered by increasing the pressure, thus attenuating or suppressing extrudate distortions.…”

Section: Full Papermentioning

confidence: 99%

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Experimental Correlation between Mechanical Non‐Linearity in LAOS Flow and Capillary Flow Instabilities for Linear and Branched Commercial Polyethylenes

Filipe

Vittorias

Wilhelm

2008

Macro Materials & Eng

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An experimental correlation between the non‐linear behaviour of commercial polyethylene melts in LAOS flow, and the pressure fluctuations associated with melt flow instabilities developed in capillary rheometry are presented. Polyethylene melts with enhanced non‐linear behaviour under LAOS conditions present larger pressure fluctuations during capillary extrusion, and consequently, larger surface distortions on the extrudate. The combination of both methods can be a tool to predict the development of melt flow instabilities in the extrusion process of polyethylene melts, and can elucidate their correlation with material structural properties ($\overline M _{\rm w}$, MWD and topology).

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Section: Investigation Of Laos Flow Via Ft Rheologysupporting

confidence: 74%

Section: Full Papermentioning

confidence: 99%

Section: Full Papermentioning

confidence: 99%

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Experimental Correlation between Mechanical Non‐Linearity in LAOS Flow and Capillary Flow Instabilities for Linear and Branched Commercial Polyethylenes

Filipe

Vittorias

Wilhelm

2008

Macro Materials & Eng

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“…We suggest that this temperature and unloading rate regime falls between solid like-fracture and liquidlike thinning and snapping. Previous studies on shearing Newtonian liquids have shown that solid-like fracture phenomena occur when shear rates exceed a critical value that, for both polymer and simple sugar fluids, is a function of temperature or viscosity (31,32).…”

Section: Adhesion and Detachment Of Viscous Surfaces (T > T G )mentioning

confidence: 99%

Adhesion and detachment mechanisms of sugar surfaces from the solid (glassy) to liquid (viscous) states

Zhao

Zeng

Tian

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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The viscosity of some sugars varies continuously by Ϸ10 orders of magnitude over a temperature range of 50°C. Sugars are therefore ideal model materials for studying the failure mechanism of materials as they change from the solid to the liquid state. We have used a surface forces apparatus coupled to interference and optical microscopy imaging to study the way two sugar surfaces adhere and detach from adhesive contact. The sugar-coated layers on mica displayed significant loading-unloading hysteresis, and the adhesive strength and failure mechanism during a ''loading-unloading cycle'' depended on the loading rate, contact time, and unloading rate. The failure of two glassy sugar surfaces was manifested by the nucleation of many sharp microcracks at the external boundary that rapidly propagate along the original contact interface. At the other extreme, when the material is a liquid, ''failure'' occurs through the nucleation and inward growth of large rounded ripples, characteristic of a Saffman-Taylor fingering instability. In the transition from glassy to viscous failure, sharp crack tips and smooth rounded fingers coexist during the crack propagation. In addition, whereas the detachment geometry of two glassy surfaces was characterized by a peeling-like mechanism along a plane, the fingers associated with the ''snapping'' of a liquid neck extended in all directions. These findings provide insights into the adhesion and failure mechanisms of materials at the micro/nanoscales and are also relevant to the action of interparticle forces between sugar particles, such as those used in inhalation drug delivery.adhesive failure ͉ fingering instability ͉ crack propagation ͉ contact dynamics E veryday experiences tell that solids fracture and liquids flow.However, for many materials there is no clear boundary between the solid and liquid states (1). Also, a material can behave like either a solid or a liquid depending on the time scale of the observation. A typical material that does this is pitch, which, if hit rapidly with a hammer, shatters like a brittle solid, but can flow like a liquid over periods of years (2). Here, we report on a study of the adhesion and detachment mechanisms of a common sugar, glucose, as it transits from the solid (glassy) to the liquid (viscous) state.The classic Hertz and Johnson-Kendall-Roberts (JKR) theories (3, 4) describe the adhesion and contact mechanics of solids. These theories have been found to hold well for molecularly smooth and nonhysteretic surfaces both at macroscopic and microscopic length scales. However, the adhesion mechanics of viscoelastic materials and sticky fluids are not so well understood (5-9). The adhesion or fracture energy of viscoelastic, such as some polymer, materials can be four orders of magnitude greater than the thermodynamic value, which has been attributed to such energy-dissipating processes as molecular interdiffusion or entanglements across the contact junction and macroscopic viscous/plastic deformations (10-12). In addition, detaching viscoelasti...

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“…This time scale is much shorter than that necessary to heal any macroscopic void formation (several hours). 17 Neutron reflectivity measurements were performed at the NG-7 reflectometer at the National Institute of Standards and Technology Center for Neutron Research. The neutron wavelength, λ, was 4.768 Å with ∆λ/λ ) 0.025.…”

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confidence: 99%

Enhanced Polymer Segment Exchange Kinetics Due to an Applied Shear Field

et al. 1999

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Introduction. Fundamental knowledge about the behavior of polymer melts near solid surfaces is important to many technologies such as electronics packaging, adhesion, coatings, and polymer processing. When polymers are placed under flow, surface effects can be critical in widely used polymer processing methods such as die extrusion and injection molding. Changes in the extrusion die material can suppress or induce instabilities that lead to unsatisfactory products. 1 These results show that the short-ranged interactions between the polymer and the substrate (coupled with the general viscoelastic properties of polymers) have macroscopic impacts. These processing instabilities have been correlated with "wall slip" at the polymer/solid interface where the apparent fluid velocity near the solid surface is no longer zero. Much work has been performed to determine the important physical parameters for wall slip and to understand the underlying mechanisms of the behavior of polymers at solid boundaries with the goal of better designing processing routes. [2][3][4][5][6][7][8][9][10][11][12] However, the effect of flow on the microscopic behavior of polymer chains directly at a solid surface is not well understood. Few experimental data are available for the behavior of polymer melt chains at the solid interface because of the inherent difficulty of distinguishing between surfacebound chains and the melt matrix. [13][14][15] In this communication, neutron reflectometry was used to study the effect of a shear deformation on the adsorption/desorption kinetics of an entangled polymer melt at an attractive solid substrate. The high spatial resolution of neutron reflectivity, O (Å), provides information directly at the polymer/solid interface. A labeled (deuterated) polymer layer was formed at the surface of a silicon wafer and was welded with a hydrogenated polymer matrix. The fraction of deuterated polymer segments at the silicon surface was monitored with different annealing times with no applied shear and with varying shear rates after a set annealing time. Increases in the shear rate resulted in an increased rate of desorption of the surface-bound polymer chains (or adsorption of the matrix polymers). To the best of our knowledge, this shear-induced adsorption/desorption of an entangled polymer melt at an attractive solid surface was directly observed for the first time. These results provide important experimental evidence of molecular mechanisms which should be incorporated into future models of flow effects on polymer dynamics at surfaces.

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Shear fracture of polystyrene melts and solutions

Cited by 38 publications

References 23 publications

Experimental Correlation between Mechanical Non‐Linearity in LAOS Flow and Capillary Flow Instabilities for Linear and Branched Commercial Polyethylenes

Experimental Correlation between Mechanical Non‐Linearity in LAOS Flow and Capillary Flow Instabilities for Linear and Branched Commercial Polyethylenes

Adhesion and detachment mechanisms of sugar surfaces from the solid (glassy) to liquid (viscous) states

Enhanced Polymer Segment Exchange Kinetics Due to an Applied Shear Field

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