On the Distribution of Fragment Sizes in the Fragmentation of Polymer Chains

Hathorn, Bryan C.; Sumpter, Bobby G.; Noid, D. W.

doi:10.1002/1521-3919(20010701)10:6<587::aid-mats587>3.0.co;2-p

Cited by 9 publications

(8 citation statements)

References 1 publication

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“…Most theoretical investigations of polymer degradation have focused so far on determining the rate of change of average molecular weight [5,6,7,8,9,10,11,12,13,14]. The main assumptions of the theory are that each link in a long chain molecule has equal strength and equal accessibility, that they are broken at random, and that the probability of rupture is proportional to the number of links present.…”

Section: Introductionmentioning

confidence: 99%

Thermal Degradation of Adsorbed Bottle-Brush Macromolecules: A Molecular Dynamics Simulation

et al. 2011

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The scission kinetics of bottle-brush molecules in solution and on an adhesive substrate is modeled by means of Molecular Dynamics simulation with Langevin thermostat. Our macromolecules comprise a long flexible polymer backbone with L segments, consisting of breakable bonds, along with two side chains of length N , tethered to each segment of the backbone. In agreement with recent experiments and theoretical predictions, we find that bond cleavage is significantly enhanced on a strongly attractive substrate even though the chemical nature of the bonds remains thereby unchanged.We find that the mean bond life time τ decreases upon adsorption by more than an order of magnitude even for brush molecules with comparatively short side chains N = 1 ÷ 4. The distribution of scission probability along the bonds of the backbone is found to be rather sensitive regarding the interplay between length and grafting density of side chains. The life time τ declines with growing contour length L as τ ∝ L −0.17 , and with side chain length as τ ∝ N −0.53 . The probability distribution of fragment lengths at different times agrees well with experimental observations. The variation of the mean length L(t) of the fragments with elapsed time confirms the notion of the thermal degradation process as a first order reaction.

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Section: Introductionmentioning

confidence: 99%

Thermal Degradation of Adsorbed Bottle-Brush Macromolecules: A Molecular Dynamics Simulation

et al. 2011

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“…However, up to our notion, the question of how does the corresponding kernel follows from the single polymer chain's dynamics was hardly considered. The only example known to us is contained in [3] which however deals with a model whose relation to the standard polymer dynamics ones is not quite evident.…”

mentioning

confidence: 99%

Thermally activated breakdown in a simple polymer model

Fugmann

Sokolov

2010

Phys. Rev. E

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We consider the thermally activated fragmentation of a homopolymer chain. In our simple model the dynamics of the intact chain is a Rouse one until a bond breaks and bond breakdown is considered as a first passage problem over a barrier to an absorbing boundary. Using the framework of the Wilemski-Fixman approximation we calculate activation times of individual bonds for free and grafted chains. We show that these times crucially depend on the length of the chain and the location of the bond yielding a minimum at the free chain ends. Theoretical findings are qualitatively confirmed by Brownian dynamics simulations.

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“…A special case of equation 15 that has been used frequently in polymer degradation [68] is the power law,…”

Section: E Submodelsmentioning

confidence: 99%

“…Using a model based on transition state theory (TST), it has been suggested [68] that 2 / 3 = α corresponding to a semicircular distribution. We will use this as a nominal value in following sections.…”

Section: E Submodelsmentioning

confidence: 99%

Experimental and Numerical Characterization of Polymer Nanocomposites for Solid Rocket Motor Internal Insulation

Koo¹,

Ezekoye²

2009

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. (From -To) 1 J u n e . 2 0 0 6 -3 0 S e p t . 2 0 0 9 REPORT DATE (DD-MM-YYYY) 30-09-2009 REPORT TYPE Final Report DATES COVERED TITLE AND SUBTITLEExperimental and Numerical Characterization of Polymer Nanocomposites for Solid Rocket PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBERThe University of Texas at Austin, Dept. of Mechanical Engineering, 1 University Station, C2200, Austin, TX 78712-0292 SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S)Dr. Charles Y-C Lee AFOSR AFOSR/NL 875 N. Randolph St., Ste. 325 SPONSOR/MONITOR'S REPORTArlington, VA 22203 NUMBER(S) DISTRIBUTION / AVAILABILITY STATEMENTApproved for public release; distribution unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT Research objective is to develop a modeling framework for simulating the insulative behavior of thermoplastic polyurethane elastomer nanocomposites (TPUNs) for solid rocket motors (SRMs). This research combines numerical modeling and experimental characterization of TPUNs for SRM insulation. Two families of TPUNs based on nanoclay, carbon nanofiber (CNF), and multiwall carbon nanotubes (MWNT) were developed. TGA experiments were conducted on Kevlar-EPDM, TPU, TPUN-clay, TPUN-CNF, and TPUN-MWNT in both air and nitrogen at low heating rates. Kinetics was calculated using isoconversion technique. High heating rate TGA was conducted on selective TPUNs. Flammability tests indicated TPUN-clay has the toughest char, followed by TPUN-MWNT, then TPUN-CNF. We connected the population balance framework to atomistic calculations to determine what aspects of the atomistic simulations would likely affect the meso-scale evolution. We focused on understanding the role that the scission kernel has on the overall degradation process and also on the role of the stoichiometry parameter has on the overall degradation kinetics. We began using the atomistic simulation code RXN MD to compute scission kinetics parameters. We recognized that the critical issue in characterizing a particular materials ablation rate could be captured by investigating the steady state ablation proc...

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On the Distribution of Fragment Sizes in the Fragmentation of Polymer Chains

Cited by 9 publications

References 1 publication

Thermal Degradation of Adsorbed Bottle-Brush Macromolecules: A Molecular Dynamics Simulation

Thermal Degradation of Adsorbed Bottle-Brush Macromolecules: A Molecular Dynamics Simulation

Thermally activated breakdown in a simple polymer model

Experimental and Numerical Characterization of Polymer Nanocomposites for Solid Rocket Motor Internal Insulation

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