Structure Characterization in the Science and Technology of Elastomers

Strate, G. Ver; Lohse, David J.

doi:10.1016/b978-0-08-051667-7.50008-1

Cited by 8 publications

(6 citation statements)

References 496 publications

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“…The networks n3/700/0.10 (Figure a) and n4/1500/0.15 (Figure b) show two glass transitions, one close to the T g of the melt and the other one close to that of the pure network (as illustrated in Figure a for the case of PB700). Notice that the difference between the two T g s of n4/1500/0.15 is of only 5 K. It was concluded that there is phase separation in the cases of n3/700/0.10 and n4/1500/0.15, but possibly not , in the cases of n3/50/0.10 and n2/253/0.10. The results obtained from the mechanical measurements strengthen this conclusion (see the next subsection on Dynamic−Mechanical Measurements).…”

Section: Resultsmentioning

confidence: 98%

“…Because of (a) the central importance of the miscibility in the molecular scale of the unattached chains in the discussion of the networks as model systems for testing the long time dynamics of a chain trapped in a network and (b) the nonconclusive answer given by the T g measurements regarding the phase homogeneity, , another system 11 was prepared . It consisted of mixtures containing about 0.85 mass fractions of a long PB (typically PB900) and 0.15 of a shorter PB (with masses up to 260 000 g/mol).…”

Section: Resultsmentioning

confidence: 99%

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Random Polybutadiene Rubber Networks with Unattached Chains

1998

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The preparation and characterization of randomly cross-linked polybutadiene (PB) networks containing unattached PB chains are presented. These were used as model systems for the experimental study of the dynamics of linear chains trapped in networks, which is the basic model of the reptationin-a-tube model of Doi and Edwards. The preparation consists of the conversion at random of a small fraction of the PB chains' double bonds into epoxide groups and in the subsequent selective use of these as cross-linking centers in the presence of unmodified PB chains; these last remain chemically unattached to the network. The selectivity of the cross-linking reaction was examined by swelling-extraction of networks containing known fractions of relatively short "monodisperse" unattached chains. The polymeric phase composition of the networks with unattached chains (nuc) was tested by glass transition temperature measurements. Dynamic-mechanical measurements were shown to be sensitive to the polymer-phase composition of nuc, as well. The dynamics of the linear PB chains in the melts and in the networks was studied by dynamic-mechanical measurements. The experimental results for the longest relaxation time τ L were compared with the predictions of the reptation-in-a-tube model with and without chain-end effects. Within experimental accuracy, the obtained scaling of τL relative to the chain mass M (up to 9 × 10 5 g/mol) is the same in both media: τL ∼ M x with x ) 3.35 ((0.10 as against x ) (3 from the pure reptationin-a-tube model; correcting for chain-end effects in the form of contour length fluctuation, results in a good description of the experimental data for the τLs of unattached chains. τL for the chains trapped in networks were found to be 1.9-3.2 times longer than the τL of the respective melts. Data on 14 PB prepared by anionic polymerization and covering the range of weight average molar masses 1.0 × 10 4 to 1.5 × 10 6 g/mol are presented. IntroductionRubber networks with unattached chains 1-7 are ideally one-phase, two-component systems; the first component is one macroscopic molecule (the network) and the second consists of linear chains "dissolved" into the network. The materials (with or without phase separation) are also classified in the literature as "semiinterpenetrating networks" (sIPN). 8 Because the short time dynamics (glass and transition regions 1 ) of a rubber network is essentially the same as that of a high polymer melt, 1 the rubber networks containing small concentrations of unattached chains permit one to study the dynamics of almost isolated chains in the rubber plateau and the terminal zones. 1 Therefore, these systems can be used to test the predictions of one-chain theoretical models (specifically the reptation-in-a-tube model 9-12 ) and as references for the study of polymer melts. On the other hand, the same systems are well-fitted for the investigation of the longtime (eventually equilibrium) properties of rubber networks as depending on the degree of cross-linking. The analysis of the con...

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Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Random Polybutadiene Rubber Networks with Unattached Chains

1998

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“…For this reason, ethylene-propylene elastomers have a higher tensile strength than other rubbers (see Figure 24 and Table VIII in Ref. [97]). On the other hand, for adhesive applications, a low plateau modulus is desired, as captured in the well-known Dahlquist criterion [98].…”

Section: Applications Of Linear Polyolefin Rheologymentioning

confidence: 96%

“…This can be a very powerful tool for modeling polymer material performance since the applications where a particular polymer will be useful depend to a large degree on its plateau modulus. For example, the tensile modulus of crosslinked elastomers depends not only on the number of chemical crosslinks (i.e., on the level of curing), but also on the number of entanglements that are trapped by those chemical crosslinks [97]. For this reason, ethylene-propylene elastomers have a higher tensile strength than other rubbers (see Figure 24 and Table VIII in Ref.…”

Section: Applications Of Linear Polyolefin Rheologymentioning

confidence: 97%

The Critical Role of Anionic Polymerization for Advances in the Physics of Polyolefins

Lohse

2015

Anionic Polymerization

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This chapter shows how the great power and versatility of anionic polymerization, which has been described in the rest of this book, has been used to develop an improved understanding of the basic physical principles that underlie the performance of polyolefin materials. When these synthetic tools are employed to polymerize dienes and are then combined with controlled saturation methods, a wide panoply of saturated hydrocarbon polymers can be made. These products can serve as models for commercial polyolefins, which is the most widely used class of synthetic polymers and which continues to develop at a strong pace. The ability to make such models with highly controlled chain architectures, plus the ability to label the molecules for use in techniques such as NMR and neutron scattering, has provided polymer physicists with means to understand polyolefin physics at a deep level. This has been used to determine the size of polyolefin chains (both in dilute solution and in melt state), the ways that polyolefins mix, how their rheology depends on the chemical structure of the chains, and how long branches control their performance. This chapter covers not only the scientific results of this research, but also how these can be applied in the development of novel, useful polyolefin products.

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“…A brief explanation of silicon and silicone nomenclature is given in the Supporting Information. Figure and Table provide scaled comparisons between the chemical structures and physical properties, respectively, of PDMS and its closest carbon-based analogue, poly(isobutylene) (PIB). − A cursory glance at both of these polymer structures reveals marked differences. First, the Si–O bonds (1.63 Å) and Si–C bonds (1.90 Å) are much longer than the C–C bonds in PIB (1.53 Å).…”

Section: Introductionmentioning

confidence: 99%

The Art of Silicones: Bringing Siloxane Chemistry to the Undergraduate Curriculum

et al. 2017

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Siloxane polymers and silicone materials are major components in most people’s daily lives and are important in a wide variety of applications. However, despite their undeniable importance, they are often overlooked in the traditional undergraduate education, as they do not fall neatly into the traditional categories of organic or inorganic chemistry. Even in advanced polymer courses, they are often overlooked despite their value in describing many important polymer concepts. Herein we present three simple experiments to introduce siloxane polymers to the undergraduate education aimed at first-year, upper-level, and non-science-major students. This is prefaced with a brief overview of the history and chemistry of siloxanes and their value as teaching tools in the laboratory and classroom settings.

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Structure Characterization in the Science and Technology of Elastomers

Cited by 8 publications

References 496 publications

Random Polybutadiene Rubber Networks with Unattached Chains

Random Polybutadiene Rubber Networks with Unattached Chains

The Critical Role of Anionic Polymerization for Advances in the Physics of Polyolefins

The Art of Silicones: Bringing Siloxane Chemistry to the Undergraduate Curriculum

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