Rubber Elasticity

1982 ◽  
Vol 55 (4) ◽  
pp. 1123-1136 ◽  
Author(s):  
J. E. Mark
Keyword(s):  
Network Structure ◽  
Glassy State ◽  
Crystalline Polymer ◽  
Spatial Arrangement ◽  
High Viscosity ◽  
Rubber Elasticity ◽  
Polymer Chains ◽  
Chain Extension ◽  
Chain Molecule ◽  
High Degree

Abstract Rubber elasticity may be operationally defined as very large deformability with essentially complete recoverability. In order for a material to exhibit this type of elasticity, three molecular conditions must be met: (1) the material must consist of polymeric chains, (2) the chains must be joined into a network structure, and (3) the chains must have a high degree of flexibility. The first requirement arises from the fact that the molecules in a rubber or elastomeric material must be able to alter their arrangements and extensions in space dramatically in response to an imposed stress, and only a long-chain molecule has the required very large number of spatial arrangements of very different extensions. This versatility is illustrated in Figure 1, which depicts a random spatial arrangement of a relatively short polymer chain. In this random arrangement, the chain extension (as measured by the end-to-end separation) is quite small. For even such a short chain, the extension could be increased approximately fourfold by simple rotations about skeletal bonds, without any need for distortions of bond angles or bond lengths. The second characteristic cited is required in order to obtain the elastomeric recoverability. It is obtained by joining together or “crosslinking” pairs of segments, approximately one out of a hundred, thereby preventing the extended polymer chains from irreversibly sliding by one another. The resulting network structure is illustrated in Figure 2, in which the crosslinks are represented by dots. These crosslinks may be either chemical bonds [as would occur in sulfur-vulcanized natural rubber' or physical aggregates (for example the small crystallites in a partially crystalline polymer or the glassy domains in a multiphase block copolymer). The last characteristic specifies that the different spatial arrangements be accessible, i.e., changes in these arrangements should not be hindered by constraints as might result from inherent rigidity of the chains, extensive chain crystallization, or the very high viscosity characteristic of the glassy state.

Chemical Stress Relaxation of NR Networks Prepared in the Swollen State

1986 ◽  
Vol 59 (4) ◽  
pp. 541-550 ◽  
Author(s):  
Kyung-Do Suh ◽  
Hidetoshi Oikawa ◽  
Kenkichi Murakami
Keyword(s):  
Stress Relaxation ◽  
Network Structure ◽  
Three Dimensional ◽  
Polymer Chains ◽  
Chemical Stress ◽  
Network Chain ◽  
Crosslinking Process ◽  
Dimensional Network ◽  
Chemical Relaxation ◽  
The Difference

Abstract From the experimental results of the present investigation, it is apparent that two kinds of networks which have a different three-dimensional network structure give quite different behavior of chemical stress relaxation, even if both networks have the same network chain density. The difference in three-dimensional network structure for the two kinds of rubber arises from the degree of entanglement, which changes with the concentration of the polymer chains prior to the crosslinking process. The direct cause of chemical relaxation is due to the scission of network chains by degradation, whereas the total relaxation is caused by the change of geometrical conformation of network chains. This then casts doubt on the basic concept of chemorheology which is represented by Equation 2.

scholarly journals Room-temperature autonomous self-healing glassy polymers with hyperbranched structure

2020 ◽  
Vol 117 (21) ◽  
pp. 11299-11305 ◽  
Author(s):  
Hao Wang ◽  
Hanchao Liu ◽  
Zhenxing Cao ◽  
Weihang Li ◽  
Xin Huang ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Room Temperature ◽  
Glassy State ◽  
Glassy Polymers ◽  
Self Healing ◽  
External Branch ◽  
Healing Efficiency ◽  
High Degree ◽  
External Stimuli ◽  
Hyperbranched Structure

Glassy polymers are extremely difficult to self-heal below their glass transition temperature (Tg) due to the frozen molecules. Here, we fabricate a series of randomly hyperbranched polymers (RHP) with high density of multiple hydrogen bonds, which showTgup to 49 °C and storage modulus up to 2.7 GPa. We reveal that the hyperbranched structure not only allows the external branch units and terminals of the molecules to have a high degree of mobility in the glassy state, but also leads to the coexistence of “free” and associated complementary moieties of hydrogen bonds. The free complementary moieties can exchange with the associated hydrogen bonds, enabling network reconfiguration in the glassy polymer. As a result, the RHP shows amazing instantaneous self-healing with recovered tensile strength up to 5.5 MPa within 1 min, and the self-healing efficiency increases with contacting time at room temperature without the intervention of external stimuli.

scholarly journals Phase Structure Recording in a Nematic Side-Chain Liquid-Crystalline Polymer

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 356 ◽  
Author(s):  
Ivan Budagovsky ◽  
Aleksey Kuznetsov ◽  
Sergey Shvetsov ◽  
Mikhail Smayev ◽  
Alexander Zolot’ko ◽  
...  
Keyword(s):  
Liquid Crystalline ◽  
Modulation Depth ◽  
Glassy State ◽  
Continuum Theory ◽  
Crystalline Polymer ◽  
Optical Nonlinearity ◽  
Side Chain ◽  
Phenyl Benzoate ◽  
Chain Polymer ◽  
Methylene Groups

Dye-doped nematic side-chain liquid-crystalline polymers possess extraordinary large optical nonlinearity and ability to store the induced orientational deformations in a glassy state, which makes them a very promising material for photonic applications. In this study, the phase structures were generated and recorded in the bulk of a 50-μm layer of a nematic liquid-crystalline side-chain polymer, containing polyacrylate backbone, spacer having five methylene groups, and phenyl benzoate mesogenic fragment. The polymer was doped with KD-1 azodye. The director field deformations induced by the light beam close to the TEM01 mode were studied for different geometries of light–polymer interaction. The phase modulation depth of 2π was obtained for the 18-μm spacing between intensity peaks. The experimental data were analyzed based on the elastic continuum theory of nematics. The possibility to induce and record positive and negative microlenses in the polymer bulk was shown experimentally.

Rubber Elasticity and Gas Elasticity

1939 ◽  
Vol 12 (2) ◽  
pp. 124-129
Author(s):  
H. Mark
Keyword(s):  
Polyvinyl Alcohol ◽  
Room Temperature ◽  
Absolute Temperature ◽  
Rubber Elasticity ◽  
Chain Molecules ◽  
Internal Mobility ◽  
Higher Temperature ◽  
Coefficient Of Elasticity ◽  
Polyacrylic Ester ◽  
High Degree

Abstract All substances which are composed of long mobile chains show one peculiar property, highly reversible elasticity. Even though the range of temperature of this property may be notably variable (in the case of polyvinyl alcohol and rubber at about room temperature, in the case of polystyrene, sulfur, or Thiokol only at a higher temperature) still it is to be noted that for rubber-like elasticity the presence of long flexible chains is an indispensable factor. Thus, typical rubber elasticity occurs in polyvinyl alcohol (Vinarol), polybutadiene (Buna), polymethyl-butadiene (methyl rubber), polyacrylic ester and also in its mixed polymerisate with vinyl chloride. This type of elasticity occurs also in sinew fibrin and muscle fibrin, in polychlorobutadiene (Neoprene, Sovprene), in polyethylene sulfide (Thiokol, Baerite), polyphosphornitrile chloride and finally in vulcanized oils (factice) and also in elastic sulfur. In the cases so far examined (natural rubber, Buna, methyl rubber), it has been found that the coefficient of elasticity increases proportionally to the absolute temperature, and that during the stretching heat is evolved. This behavior is contrary to that of normal elastic materials, steel, quartz, glass, etc. It is striking that the substances which have this property of highly reversible (rubber-like) stretching are widely different chemically. This tempts one to ascribe that property to the similarity of their construction. For example, all the substances mentioned consist of long chain-molecules, which display a high degree of internal mobility. The number of members in these chains varies from 102 to 104 and their mobility is due to the kind of linkage between the members, mostly simple C—C bonds.

Flow induced polymer chain extension and its relation to fibrous crystallization

1975 ◽  
Vol 278 (1276) ◽  
pp. 29-66 ◽  
Keyword(s):  
Flow Field ◽  
Velocity Gradient ◽  
Longitudinal Velocity ◽  
Chain Extension ◽  
Hydrodynamic Conditions ◽  
Concentration Effects ◽  
Chain Molecules ◽  
High Degree ◽  
Theoretical Considerations ◽  
Long Chain

This work examines the effect that appreciable molecular extension has on the crystallization of long chain molecules. Elementary theoretical considerations presented indicate that to achieve high molecular extensions in solution a longitudinal velocity gradient of strain rate about 103s-1 is required. A method of generating such a velocity gradient, involving flow between opposed jets, is reported and the nature of this flow pattern is examined and quantitatively analysed. The behaviour of polyethylene-xylene solutions in the flow field is presented, notably birefringence observations and measurements indicate that a high degree of molecular alinement can be achieved in specific localized areas of the flow field; also concentration effects are observed which are discussed in terms of entanglement concepts. The effect chain alinement has on crystallization is examined in detail, in particular the ‘shish kebab ’ morphology of the crystals so produced is examined in relation to the hydrodynamic conditions in which they were grown.

Evidence of re-entrant behavior in laponite-PEO systems

2005 ◽  
Vol 899 ◽  
Author(s):  
Hossein Baghdadi ◽  
Surita R. Bhatia ◽  
Elizabeth E. C. Jensen ◽  
Nalini Easwar
Keyword(s):  
Molecular Weight ◽  
Viscosity Solution ◽  
High Viscosity ◽  
Polymer Chains ◽  
Low Viscosity ◽  
End Distance ◽  
Depletion Force ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene ◽  
Electrostatic Repulsions

AbstractRheology and dynamic light scattering capture re-entrant behavior of laponite-polymer systems. Neat laponite under basics conditions and concentrations of 2wt% or greater forms a viscoelastic soft glass due to electrostatic repulsions. We show that that addition of low molecular weight poly(ethylene oxide) (PEO) melts the glass due to a depletion force. The depletion force speeds up dynamics in the system resulting in a low viscosity solution. A re-entrant viscoelastic solid is formed with the addition of high molecular weight PEO due to the polymer chains bridging between laponite particles. As expected the transition from a low to high viscosity solution scales with the polymer mean square end-to-end distance and gap between laponite particles.

Binding to semiflexible polymers: a novel method to control the structures of small numbers of building blocks

Soft Matter ◽  
2014 ◽  
Vol 10 (38) ◽  
pp. 7661-7668 ◽  
Author(s):  
Dong Zhang ◽  
Linxi Zhang
Keyword(s):  
Elastic Medium ◽  
Building Blocks ◽  
Spatial Arrangement ◽  
Relative Orientation ◽  
Polymer Chains ◽  
Semiflexible Polymers ◽  
Spherical Building ◽  
Local Organization ◽  
Semiflexible Polymer ◽  
Novel Method

Semiflexible polymer chains can serve as an effective soft elastic medium to control the structures of small numbers of building blocks through three different aspects: local organization of two neighbor particles, spatial arrangement of small numbers of building blocks, and the relative orientation of neighboring non-spherical building blocks.

A Novel Mechanism of Electrorheological Effect in Polymer Blends

1999 ◽  
Vol 13 (14n16) ◽  
pp. 1983-1989 ◽  
Author(s):  
H. Kito ◽  
K. Tajiri ◽  
H. Orihara ◽  
Y. Ishibashi ◽  
M. Doi ◽  
...  
Keyword(s):  
Liquid Crystalline Polymer ◽  
Liquid Crystalline ◽  
Crystalline Polymer ◽  
High Viscosity ◽  
Thin Layers ◽  
The Other ◽  
Parallel Plates ◽  
Low Viscosity ◽  
Electrorheological Effect ◽  
Er Fluid

We present a novel mechanism of an electrorheological (ER) effect found in a polymer blend of a liquid crystalline polymer (LCP) with high viscosity and a polydimethylsiloxane (DMS) with low viscosity. In this type of ER fluid thin layers of DMS are formed between the parallel plates of a viscometer and so the blends separated by them can slide on each other, resulting in the decrease of the apparent viscosity. Under an electric field, on the other hand, the area of the layers decreases and thus the ER effect appears.

Residential Location and Electoral Cohesion: The Pattern of Urban Political Conflict

1973 ◽  
Vol 67 (3) ◽  
pp. 914-923 ◽  
Author(s):  
Timothy A. Almy
Keyword(s):  
Spatial Distribution ◽  
Social Class ◽  
Spatial Arrangement ◽  
Political Conflict ◽  
Class Groups ◽  
Political Conflicts ◽  
Community Data ◽  
Residential Distribution ◽  
High Degree ◽  
American Cities

This study examines the assertions of urban scholars that the spatial arrangement of urban populations is important in determining the amount of conflict displayed within American cities. The article analyzes the spatial distribution of class groups within 18 cities and the degree of voting solidarity and conflict displayed within segregated and integrated sections of each community. Data were gathered from precinct voting returns for several local referenda in each city to test the following hypotheses: (1) The residential distribution of social-class groups will significantly influence the degree of electoral cohesion these groups display; (2) The spatial distribution of class groups will significantly influence the amount of electoral disagreement between class groups. The study found that communities that displayed segregated class groups had a high degree of class electoral solidarity. Within cities that manifested spatially integrated class groups, however, the electoral cohesion of each class was low. A social-class group located in an area of a city possessing wide class dissimilarity was not likely to vote in agreement with other groups of the same class located elsewhere in the city. The findings of this article suggest that location may be one of the sources of urban political conflicts.

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