Polystyrene and Related Polymers

Parkinson, W.W.; Keyser, Ronald M.

doi:10.1016/b978-0-12-219802-1.50012-5

Cited by 17 publications

(8 citation statements)

References 44 publications

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“…Before answering this question, let us review the reported data first. The G(x) values were found to be within a range of 0.03 to 0.05 [15,24,25], when polystyrene was subjected to 1.25 MeV (average) '%oy-rays (0.2 eV/nm), 275 MeV Ne" (370 eV/nm), and 180 MeV Ar8+ (2260 eV/nm) as summarized in Table 11 In most experiments, G(x) values were derived from the molecular weight distributions determined by gel permeation chromatography (GPC) [ 15,261 or viscosity measurements [24] after dissolving irradiated polymers in a solvent. This requires polymers to be still soluble after irradiation.…”

Section: Discussionmentioning

confidence: 99%

Hardness Enhancement and Crosslinking Mechanisms in Polystyrene Irradiated with High Energy Ion-Beams

Lee

Rao²,

Mansur

1997

MSF

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In the past, radiation effects studies on polymers were mostly aimed at understanding polymerization mechanisms in radiation curing and synthesis, and radiation induced degradation mechanisms. However, little effort has been expended to improve mechanical properties of polymers, because radiation sources such as e-beams, y -rays, and ultraviolet light, which have been used frequently, produce either small improvement due to crosslinking or more often cause degradation due to scission. In recent work at ORNL, surface hardness values several times larger than that of steel were produced by employing high energy ion-beams (HEIB) in the range of several hundred keV to MeV. Studies show that high linear energy transfer (LET) is important for crosslinking. At low LET conditions, induced active free radicals along the track are so sparsely dispersed that little interaction occurs among radicals. Input energy tends to localize at an intra-molecular chain segment, leading to chain scission. On the other hand, at high LET condition, massive ionization induces a high concentration of free radicals over many neighboring molecular chains facilitating crosslinking.Detailed crosslinking mechanisms are studied by analyzing hardness variations in response to irradiation parameters such as ion species, energy, and fluence. Effective crosslinking radii at hardness saturation are derived based on experimental data for 350 keV € I + and 1 MeV Ai-+ irradiation of polystyrene. ABSTRACTIn the past, radiation effects studies on polymers were mostly aimed at understanding polymerization mechanisms in radiation curing and synthesis, and radiation induced degradation mechanisms. However, little effort has been expended to improve mechanical properties of polymers, because radiation sources such as e-beams, y -rays, and ultraviolet light, which have been used frequently, produce either small improvements due to crosslinking or more often cause degradation due to scission. In recent work at ORNL, surface hardness values several times larger than that of steel were produced by employing high energy ion-beams (HEIB) in the range of several hundred keV to MeV. Studies show that high linear energy transfer (LET) is important for crosslinking. At low LET conditions, induced active fiee radicals along the track are so sparsely dispersed that little interaction occurs among radicals. Input energy tends to localize at an intra-molecular chain segment, leading to chain scission. On the other hand, at high LET condition, massive ionization induces a high concentration of free radicals over many neighboring molecular chains facilitating crosslinking. Detailed crosslinking mechanisms are studied by analyzing hardness variations in response to irradiation parameters such as ion species, energy, and fluence. Effective crosslinking radii at hardness saturation are derived based on experimental data for 3 50 keV H' and 1 MeV A r ' irradiation of polystyrene. INTRODUCTIONOrganic polymers are inherently soft due to the lack of chemical bonds between ...

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Section: Discussionmentioning

confidence: 99%

Hardness Enhancement and Crosslinking Mechanisms in Polystyrene Irradiated with High Energy Ion-Beams

Lee

Rao²,

Mansur

1997

MSF

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“… Schematic of radiation‐induced cross‐linking for PS and P4MS and scission for P α MS. (a) For PS (R = H) and P4MS (R = CH 3 ), radiation can remove the α ‐H to form a radical (indicated by *); (b) Two of these radicals can recombine to form a cross‐link between chains; (c) For P α MS, radiation exposure can lead to chain scission (with homolytic cleavage and the formation of a radical on each segment); (d) These radicals can recombine or form cross‐links; or as in (e) ‘hop’ to the next α‐ C in the chain and lead to a depolymerization reaction; (f) (Adapted from ref. 62, 63). …”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulations of Ar⁺–Organic Polymer Interactions

Végh¹,

Graves²

2009

Plasma Processes & Polymers

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MD simulations of ion–organic styrene‐containing polymer interactions are reviewed and compared to experiment. We report results for argon ion bombardment of PS, PαMS and P4MS. All three polymers exhibit the formation of a similar, highly cross‐linking, dehydrogenated near‐surface damaged layer at steady state, but small changes in the structure of the polymer (P4MS and PαMS are isomers) can lead to drastic changes in the initial transient sputtering of the material. We correlate this behavior to differences in radiation chemistry (P4MS and PS are cross‐linking while PaMS is a chain scission polymer), and examine how the behavior in MD may relate to larger‐scale experimental results, such as roughness formation.

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“…The polymer used in this study was polybutadiene (PBD, MW: 2-3×10 6 , containing 98% cis), supplied by Aldrich. Two copolymers of styrene and butadiene were used, styrene-butadienestyrene block copolymer, containing 75% butadiene, with a molecular weight of 5-10×10 5 , supplied by Shell as Kraton D 1102 and herein referred to as SBS, and K-resin, supplied by Phillips Petroleum as KR01, containing about 75% styrene with a molecular weight of 5-10×10 5 .…”

Section: Methodsmentioning

confidence: 99%

“…Infrared spectra of the cross-linked samples were obtained in order to ascertain the role of oxygen in the process. Upon irradiation in the presence of air, peroxide, hydroxide and carbonyl groups are found in the polymers [6], [7] . A similar reaction may occur when PBD is heated in air.…”

Section: The Effect Of Oxygen On Cross-linkingmentioning

confidence: 99%

Thermal decomposition of cross-linked polybutadiene and its copolymers

Jiang¹,

Levchik²,

Levchik³

et al. 1999

Polymer Degradation and Stability

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Polybutadiene and two copolymers containing butadiene and styrene have been cross-linked by thermal processes, by the use of initiators in solution, and by intimately mixing an initiator with the polymer and then heating this blend. The most efficient cross-linking process is the use of an intimate blend of the initiator and polymer. Most cross-linking processes lower the onset temperature of degradation, presumably because chain scission reactions occur simultaneously with cross-linking, while also increasing the fraction of non-volatile residue which is produced. It is believed that the density of cross-links is responsible for the increased yield of non-volatile residue.

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Polystyrene and Related Polymers

Cited by 17 publications

References 44 publications

Hardness Enhancement and Crosslinking Mechanisms in Polystyrene Irradiated with High Energy Ion-Beams

Hardness Enhancement and Crosslinking Mechanisms in Polystyrene Irradiated with High Energy Ion-Beams

Molecular Dynamics Simulations of Ar⁺–Organic Polymer Interactions

Thermal decomposition of cross-linked polybutadiene and its copolymers

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Polystyrene and Related Polymers

Cited by 17 publications

References 44 publications

Hardness Enhancement and Crosslinking Mechanisms in Polystyrene Irradiated with High Energy Ion-Beams

Hardness Enhancement and Crosslinking Mechanisms in Polystyrene Irradiated with High Energy Ion-Beams

Molecular Dynamics Simulations of Ar+–Organic Polymer Interactions

Thermal decomposition of cross-linked polybutadiene and its copolymers

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Molecular Dynamics Simulations of Ar⁺–Organic Polymer Interactions