Effects of accelerator type on stress relaxation behavior and network structure of aged natural rubber/chloroprene rubber vulcanizates

2016 ◽  
Vol 49 (5) ◽  
pp. 381-396 ◽  
Author(s):  
Farzad A Nobari Azar ◽  
Murat Şen
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Network Structure ◽  
Structural Changes ◽  
Relaxation Behavior ◽  
Stress Relaxation Behavior ◽  
Rubber Blends ◽  
Chloroprene Rubber ◽  
Weather Changes ◽  
Behavior Network

Natural rubber/chloroprene rubber (NR/CR) blends are among the commonly used rubber blends in industry and continuously are exposed to severe weather changes. To investigate the effects of accelerator type on the network structure and stress relaxation of unaged and aged NR/CE vulcanizates, tetramethyl thiuram disulfide, 2-mercaptobenzothiazole, and diphenyl guanidine accelerators have been chosen to represent fast, moderate, and slow accelerator groups, respectively. Three batches have been prepared with exactly the same components and mixing conditions differing only in accelerator type. Temperatures scanning stress relaxation and pulse nuclear magnetic resonance techniques have been used to reveal the structural changes of differently accelerated rubber blends before and after weathering. Nonoxidative thermal decomposition analyses have been carried out using a thermogravimetric analyzer. Results indicate that there is a strong interdependence between accelerator type and stress relaxation behavior, network structure, cross-linking density, and aging behavior of the blends. Accelerator type also affects decomposition energy of the blends.

Stress-relaxation behavior of natural rubber/polystyrene and natural rubber/polystyrene/natural rubber-graft-polystyrene blends

2008 ◽  
Vol 108 (2) ◽  
pp. 904-913 ◽  
Author(s):  
R. Asaletha ◽  
P. Bindu ◽  
Indose Aravind ◽  
A. P. Meera ◽  
S. V. Valsaraj ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Relaxation Behavior ◽  
Stress Relaxation Behavior

The Stress Relaxation of Sulfur Vulcanizates of Natural Rubber

1957 ◽  
Vol 30 (1) ◽  
pp. 42-53
Author(s):  
J. P. Berry
Keyword(s):  
Experimental Study ◽  
Stress Relaxation ◽  
Natural Rubber ◽  
Oxygen Pressure ◽  
Relaxation Behavior ◽  
Two Stage ◽  
Stress Relaxation Behavior ◽  
Stage Process ◽  
Force Time ◽  
Effect Of Oxygen

Abstract An experimental study is reported of the stress relaxation behavior of sulfur vulcanizates of natural rubber maintained at constant extension. Of particular interest is the effect of oxygen pressure on the shape of the force-time curves, and the relaxation proceeding in absence of oxygen. The results are interpreted according to a two-stage process: (1) oxidation at the crosslinks and (2) scission of oxidized crosslinks.

Stress Relaxation of a Twaron®/Natural Rubber Composite

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
N. V. David ◽  
X.-L. Gao ◽  
J. Q. Zheng
Keyword(s):  
Stress Relaxation ◽  
Natural Rubber ◽  
Rheological Model ◽  
Maxwell Model ◽  
Relaxation Behavior ◽  
Stress Relaxation Behavior ◽  
Generalized Maxwell Model ◽  
Rubber Composite ◽  
Long Time ◽  
Different Levels

The stress relaxation behavior of a Twaron CT709® fabric/natural rubber composite under a uniaxial constant strain is studied using three viscoelasticity models with different levels of complexity and a newly developed para-rheological model. The three viscoelasticity models employed are a one-term generalized Maxwell model (comprising one Maxwell element and an additional spring in parallel), a two-term generalized Maxwell model (including two Maxwell elements and an additional spring in parallel), and a four-parameter Burgers model. The values of the parameters involved in each model are extracted from the experimental data obtained in this study. The stress relaxation tests reveal that the stress starts to decay exponentially for a short duration and then continues to decrease linearly with time. It is found that the initial relaxation response of the composite is predicted fairly well by all of the four models, while the long-time stress relaxation behavior is more accurately predicted by the para-rheological model. The accuracy of each model in describing the stress relaxation behavior of the composite is quantitatively compared.

scholarly journals Rheometer Evidences for the Co-Curing Effect of a Bismaleimide in Conjunction with the Accelerated Sulfur on Natural Rubber/Chloroprene Rubber Blends

Polymers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1510
Author(s):  
Marek Pöschl ◽  
Shibulal Gopi Sathi ◽  
Radek Stoček ◽  
Ondřej Kratina
Keyword(s):  
Mechanical Properties ◽  
Natural Rubber ◽  
Tensile Properties ◽  
Crosslinking Agent ◽  
Alder Reaction ◽  
Diels Alder ◽  
Ene Reactions ◽  
Rubber Blends ◽  
Diels Alder Reaction ◽  
Chloroprene Rubber

The rheometer curing curves of neat natural rubber (NR) and neat chloroprene rubber (CR) with maleide F (MF) exhibit considerable crosslinking torque at 180 °C. This indicates that MF can crosslink both these rubbers via Alder-ene reactions. Based on this knowledge, MF has been introduced as a co-crosslinking agent for a 50/50 blend of NR and CR in conjunction with accelerated sulfur. The delta (Δ) torque obtained from the curing curves of a blend with the addition of 1 phr MF was around 62% higher than those without MF. As the content of MF increased to 3 phr, the Δ torque was further raised to 236%. Moreover, the mechanical properties, particularly the tensile strength of the blend with the addition of 1 phr MF in conjunction with the accelerated sulfur, was around 201% higher than the blend without MF. The overall tensile properties of the blends cured with MF were almost retained even after ageing the samples at 70 °C for 72 h. This significant improvement in the curing torque and the tensile properties of the blends indicates that MF can co-crosslink between NR and CR via the Diels–Alder reaction.

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