Drawing and orientation-relaxation behaviour of monodisperse linear and 3-arm star polystyrenes

Han, Hye-Jin; Duckett, R. A.; McLeish, Tom; Ward, N. J.; Johnson, A. F.

doi:10.1016/s0032-3861(96)00657-x

Cited by 7 publications

(4 citation statements)

References 17 publications

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“…It was not possible to generate visible stable crazes in the lowest molar mass PS, sample A ( M w = 68 000 g/mol), without fracture during the creep time. A number of authors have reported difficulties in growing crazes in monodisperse polymers of molar mass close to 2 M e , , where the entanglement molar mass M e = 18 000 g/mol for PS . For sample A we give instead approximate values for the lower bound for the stress at no craze formation and upper bound for the stress at which unstable craze propagation leads to fracture.…”

Section: Resultsmentioning

confidence: 99%

“…In branched chains with a single branch point, the molar mass associated with chain retraction is the span molar mass M s . 16 Where M s is only a small number of entanglement lengths there may be differences between τ R for a branched chain of M s compared with a linear chain of length M ) M s since the branch point effectively pins the center of mass of the branched chain. However, when the equivalent linear chain is long, the random nature of the fluctuations along the tube effectively pins its midpoint in the same way as a branch point.…”

Section: Branched Polymersmentioning

confidence: 99%

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Roles of Chain Length, Chain Architecture, and Time in the Initiation of Visible Crazes in Polystyrene

Focatiis

Buckley

2008

Macromolecules

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Visible craze initiation stress has been measured for a wide range of linear and branched monodisperse polystyrenes (PS) soaked in diethylene glycol. Results show that, for a given time under stress, craze initiation in linear PS is disentanglement-dominated below a critical molar mass and chain scission-dominated above it. Branched monodisperse PS behaves similarly, with the relevant molar mass in this case being the span molar mass. Disentanglement craze initiation stress is found to vary linearly with log molar mass and log time. These observations can be explained in terms of Eyring-type stress acceleration of the process of chain retraction, required to achieve the entanglement loss necessary for creation of craze fibril surfaces. A single effective activation volume of 1.8 nm3 accounts for the dependence of crazing stress on molar mass, time, and temperature under uniaxial tensile stress, both as observed in the present data and in a previous study of rate/temperature dependence.

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Section: Resultsmentioning

confidence: 99%

Section: Branched Polymersmentioning

confidence: 99%

Roles of Chain Length, Chain Architecture, and Time in the Initiation of Visible Crazes in Polystyrene

Focatiis

Buckley

2008

Macromolecules

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“…The experimental time scale relative to τ R is vitally important in the chain retraction process as discovered in the orientation relaxation of monodisperse linear and star polystyrenes . Although the chain retraction process on time scale τ R modifies the average chain tension, τ R does not appear in the final results because by our assumptions τ R ≈ τ exp , where τ exp is the experimental time scale ruled by k -1, and self-adjusts in the active zone to permit the necessary partial retraction of the chains.…”

Section: Disentanglement Effectmentioning

confidence: 88%

“…It remains for one to explain the persisting quantitative discrepancies between those data and the theory as it stands. One appealing suggestion 14 is to attribute them to curvilinear motion of the centers-of-mass of the entangled chains in the active zone. This conjecture could be verified experimentally by suppressing such motion by molecular architecture.…”

Section: Discussionmentioning

confidence: 99%

Experimental and Theoretical Studies of the Molecular Motions in Polymer Crazing. 1. Tube Model

Han¹,

McLeish²,

Duckett³

et al. 1998

Macromolecules

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A theoretical model has been developed to calculate the craze surface energy for monodisperse linear polymers based on the "tube model" of polymer melts. This model, which is a refinement of models previously proposed, assumes that the essential molecular processes of chain scission and disentanglement occur in the "active zone"sa region of thickness greater than or equal to the chain radius of gyration, situated at the interface between craze and bulk polymer. At high temperatures, greater than a critical temperature, T > Ttr, craze growth occurs by stress-assisted chain disentanglement; below a second critical temperature, Tcr, craze growth occurs by chain scission. Between these critical temperatures, which are molecular weight and strain-rate dependent, craze growth involves both scission and disentanglement. New experimental data on craze growth in monodisperse, linear polystyrene over a range of temperatures at two strain rates are presented, which are well described by the new theory. The theory describes all features of the data with only one fitting parameter, including small peaks observed in the crazing strain/temperature graphs in the mixed-mode region. Similar features have been reported recently in craze data from poly(methyl methacrylate) without explanation.

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Composition and rheology of polyamide-6 obtained by using bi- and tri-functional coupling agents

2012

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Drawing and orientation-relaxation behaviour of monodisperse linear and 3-arm star polystyrenes

Cited by 7 publications

References 17 publications

Roles of Chain Length, Chain Architecture, and Time in the Initiation of Visible Crazes in Polystyrene

Roles of Chain Length, Chain Architecture, and Time in the Initiation of Visible Crazes in Polystyrene

Experimental and Theoretical Studies of the Molecular Motions in Polymer Crazing. 1. Tube Model

Composition and rheology of polyamide-6 obtained by using bi- and tri-functional coupling agents

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