Effect of Strain-Induced Crystallization on the Elastomeric Properties of Cis-1,4-Polybutadiene Networks

1978 ◽  
Vol 51 (2) ◽  
pp. 285-296 ◽  
Author(s):  
T-K. Su ◽  
J. E. Mark
Keyword(s):  
Polymer Network ◽  
Polymer Networks ◽  
Experimental Studies ◽  
Anomalous Behavior ◽  
Critical Examination ◽  
Complete Suppression ◽  
Stress Strain ◽  
Strain Induced Crystallization ◽  
Alternative Suggestion ◽  
Induced Crystallization

Abstract Polymer networks, when studied at very high elongations, frequency show anomalous stress-strain isotherms in that they exhibit values of the modulus or “reduced force” [ƒ*] which increase markedly with increasing elongation. Such isotherms depart appreciably from the form predicted by the molecular theories of rubberlike elasticity and from the Mooney—Rivlin representation adopted from phenomenological arguments as well. For this reason, the interpretation of the increase in [ƒ*] at high elongations has been of great interest for a considerable period of time. For several decades now, this behavior has generally been attributed to the limited extensibility of the network chains. Critical examination of various published results pertinent to this question, in conjunction with more definitive experimental studies reported recently, however, support the alternative suggestion that such atypical isotherms are due to strain-induced crystallization. One experiment particularly relevant to this issue is the study of the stress-strain isotherms of a polymer network as a function of temperature. Such experiments have been carried out on natural rubber, but the relatively poor thermal stability of this polymer and the extent to which its melting point is increased by elongation make it essentially impossible to study the high elongation stress-strain relationships for this polymer at a temperature sufficiently high to ensure complete suppression of strain-induced crystallinity. Similar experiments carried out on networks of a more suitable polymer, polyisobutylene, gave stress-strain isotherms showing the upturn in the reduced force at low temperature, but not at higher temperatures, thus strongly implicating strain-induced crystallization as the origin of this anomalous behavior. These experiments, however, suffered somewhat from the one shortcoming that the increase in temperature required to suppress the upturn in [ƒ*] also decreased the maximum extensibility of the network to below the elongation at which the upturn occurred at the lower temperatures.

Influence of Crosslink Characteristics Induced by Aromatic-Based Antioxidants on the Swelling and Stress-Strain Behavior of Natural Rubber Vulcanizates

2003 ◽  
Vol 76 (2) ◽  
pp. 334-347 ◽  
Author(s):  
Tarek M. Madkour ◽  
Rasha A. Azzam
Keyword(s):  
Natural Rubber ◽  
Crosslinking Agent ◽  
Oxidative Degradation ◽  
Thermal Oxidative Degradation ◽  
Stress Strain ◽  
Strain Behavior ◽  
Strain Induced Crystallization ◽  
Elastomeric Chains ◽  
Natural Rubber Vulcanizates ◽  
Induced Crystallization

Abstract Stress-strain measurements were performed on dry and swollen natural rubber vulcanizates prepared using both sulfur as the crosslinking agent and aromatic-based bound antioxidants acting as a second crosslinking agent. The aromatic-based antioxidants were synthesized and analyzed spectroscopically in order to relate the final behavior of the vulcanizates to the nature of the crosslink characteristics. The anomalous upturn in the modulus values of these networks in response to the imposed stress was shown to persist in the dry as well as the swollen state. Since the swollen elastomeric chains cannot undergo a strain-induced crystallization, the abnormal upturns in the modulus values in an absence of a filler were explained on the basis of the limited extensibility of the short chains of networks prepared using two different crosslinking agents in line with earlier modeling predictions. Remarkably, the swelling experiments revealed the increase in the crosslink density of the networks in the early stages of the thermal oxidative degradation procedure indicating a post-cure of the chemically bound antioxidants to the elastomeric chains, which incidentally corresponds to a maximum in the modulus values of the networks. The rheological and other mechanical properties such as the hardness were shown not to have been affected as a result of the incorporation of the chemically bound antioxidants.

DEPENDENCE OF THE ONSET OF STRAIN-INDUCED CRYSTALLIZATION OF NATURAL RUBBER AND ITS SYNTHETIC ANALOGUE ON CROSSLINK AND ENTANGLEMENT BY USING SYNCHROTRON X-RAY

2017 ◽  
Vol 90 (4) ◽  
pp. 728-742 ◽  
Author(s):  
Watcharin Sainumsai ◽  
Shigeyuki Toki ◽  
Sureerut Amnuaypornsri ◽  
Adun Nimpaiboon ◽  
Jitladda Sakdapipanich ◽  
...  
Keyword(s):  
Natural Rubber ◽  
Crosslink Density ◽  
Inhomogeneous Material ◽  
Synthetic Analogue ◽  
Stress Strain ◽  
X Ray ◽  
Stress Strain Relation ◽  
Strain Induced Crystallization ◽  
Induced Crystallization ◽  
Flow Induced Crystallization

ABSTRACT Strain-induced crystallization (SIC) and stress–strain relations of varied crosslink structures and varied crosslink densities of vulcanized natural rubber (NR), vulcanized synthetic polyisoprene rubber (IR), and un-vulcanized natural rubber are compared using a synchrotron X-ray. The onset strain of SIC does not depend on crosslink density and crosslink structures. Un-vulcanized NR shows a smaller onset strain of SIC than that of vulcanized NR. Therefore, entanglements in NR are pivot points to induce SIC, just as entanglements in semi-crystalline plastics induce flow-induced crystallization (FIC). During deformation, complicated phenomena occur simultaneously such as cavitation, crosslink breakdown, SIC with temperature upturn, and limited extensibility of chains between crosslinks, because rubber is a significantly inhomogeneous material. It is still difficult to evaluate the contribution of SIC to stress-upturn of the stress–strain relation of rubber.

scholarly journals Monte Carlo Study of Rubber Elasticity on the Basis of Finsler Geometry Modeling

Symmetry ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1124 ◽  
Author(s):  
Hiroshi Koibuchi ◽  
Chrystelle Bernard ◽  
Jean-Marc Chenal ◽  
Gildas Diguet ◽  
Gael Sebald ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Finsler Geometry ◽  
Standard Technique ◽  
Rubber Elasticity ◽  
Large Strains ◽  
Surface Model ◽  
Stress Strain ◽  
Geometry Model ◽  
Strain Induced Crystallization ◽  
Induced Crystallization

Configurations of the polymer state in rubbers, such as so-called isotropic (random) and anisotropic (almost aligned) states, are symmetric/asymmetric under space rotations. In this paper, we present numerical data obtained by Monte Carlo simulations of a model for rubber formulations to compare these predictions with the reported experimental stress–strain curves. The model is defined by extending the two-dimensional surface model of Helfrich–Polyakov based on the Finsler geometry description. In the Finsler geometry model, the directional degree of freedom σ → of the polymers and the polymer position r are assumed to be the dynamical variables, and these two variables play an important role in the modeling of rubber elasticity. We find that the simulated stresses τ sim are in good agreement with the reported experimental stresses τ exp for large strains of up to 1200 % . It should be emphasized that the stress–strain curves are directly calculated from the Finsler geometry model Hamiltonian and its partition function, and this technique is in sharp contrast to the standard technique in which affine deformation is assumed. It is also shown that the obtained results are qualitatively consistent with the experimental data as influenced by strain-induced crystallization and the presence of fillers, though the real strain-induced crystallization is a time-dependent phenomenon in general.

Effects of plasticizers on the strain-induced crystallization and mechanical properties of natural rubber and synthetic polyisoprene

RSC Advances ◽  
2015 ◽  
Vol 5 (15) ◽  
pp. 11317-11324 ◽  
Author(s):  
Yueqing Ren ◽  
Suhe Zhao ◽  
Qian Yao ◽  
Qianqian Li ◽  
Xingying Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Natural Rubber ◽  
Stress Strain ◽  
Strain Induced Crystallization ◽  
Induced Crystallization

Effects of different type of plasticizers on the strain-induced crystallization and stress–strain curves of crystallizable rubber.

Entanglements and Networks to Strain-Induced Crystallization and Stress–Strain Relations in Natural Rubber and Synthetic Polyisoprene at Various Temperatures

2013 ◽  
Vol 46 (13) ◽  
pp. 5238-5248 ◽  
Author(s):  
Shigeyuki Toki ◽  
Justin Che ◽  
Lixia Rong ◽  
Benjamin S. Hsiao ◽  
Sureerut Amnuaypornsri ◽  
...  
Keyword(s):  
Natural Rubber ◽  
Stress Strain ◽  
Strain Induced Crystallization ◽  
Induced Crystallization

The Effects of Cross-Linking and Strain on the Glass Transition Temperature of a Polymer Network

1980 ◽  
Vol 53 (4) ◽  
pp. 982-987 ◽  
Author(s):  
M. A. Sharaf ◽  
J. E. Mark
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Polymer Network ◽  
Thermal Shrinkage ◽  
Cross Linking ◽  
Scanning Calorimetry ◽  
Increase With Increase ◽  
Strain Induced Crystallization ◽  
Induced Crystallization

Abstract The glass transition temperature Tg of an elastomer is of great importance with regard to its utilization since at this temperature and below, the material can no longer exhibit rubberlike behavior. In the present study, networks were prepared from atactic poly(vinyl acetate) and poly(isobutyl methacrylate), both types of networks being inherently non-crystallizable and therefore immune from complications associated with strain-induced crystallization. The values of Tg were obtained by dilatometry, differential scanning Calorimetry, the measurement of viscoelastic losses, and irreversible thermal shrinkage. For both types of networks, Tg was found to increase with increase in degree of crosslinking and with increase in elongation. These results suggest that the most important effect of crosslinking and network elongation is a decrease in the mobility or entropy of the network chains.

Stress-Strain and Stress-Birefringence Studies on Natural Rubber, Isomerized Natural Rubber, and Synthetic Poly(Isoprene)

1974 ◽  
Vol 47 (5) ◽  
pp. 1234-1240 ◽  
Author(s):  
D. P. Mukherjee
Keyword(s):  
Natural Rubber ◽  
Rate Process ◽  
Stress Strain ◽  
Similar Reasoning ◽  
Strain Behavior ◽  
Three Samples ◽  
Strain Induced Crystallization ◽  
High Elongation ◽  
The Difference ◽  
Induced Crystallization

Abstract With respect to stress-birefringence, isomerized natural rubber behaves the same as natural rubber at low elongations, but at high elongation levels the natural rubber sample exhibits higher stress-hysteresis accompanied by higher mechanical loss energy. Therefore, it appears that at low elongation level the viscoelastic rate process governing the stress-strain hysteresis is not sensitive to structural imperfection (within the range of cis-1,4 content studied here), but the crystallization process at higher elongation is strongly dependent on the cis content. This is in agreement with the conclusion made by Scott and co-workers from their dynamic measurements on synthetic poly(isoprene)s. The difference in cis-content between Natsyn and natural rubber and the effect on crystallizability explains the lower hysteresis on the stress-birefringence plot for Natsyn. Similar reasoning explains the stress-birefringence difference between the A.C. rubber and Natsyn. The data, however, shows that Natsyn has the lowest amount of loss energy of the three samples (except at very high input energy >4.5). This difference might be due to effects of physical entanglements or gels which may differ. In addition, the difference in microstructure contributes to the difference in extent of strain-induced crystallization. Since the viscoelastic rate process governing the stress-strain behavior and the strain-induced crystallization are associated with molecular motion, they may not be independent.

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