VULCANIZATION CHARACTERISTICS OF NATURAL RUBBER COAGULATED BY MICROORGANISMS

2018 ◽  
Vol 91 (1) ◽  
pp. 64-78
Author(s):  
Si-Dong Li ◽  
Jing Chen ◽  
Le-Fan Li ◽  
Zhi-Fen Wang ◽  
Jie-Ping Zhong ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Natural Rubber ◽  
Transverse Relaxation Time ◽  
Cross Link ◽  
Mass Percentage ◽  
Transverse Relaxation ◽  
1H Nuclear Magnetic Resonance ◽  
Link Density ◽  
Cure Time ◽  
Cross Link Density

ABSTRACT The network variations of natural rubber (NR) during the vulcanization process were investigated by 1H chemical shift by liquid-state 1H nuclear magnetic resonance (NMR) spectroscopy. NR latex coagulated by microorganisms (NR-m) was contrasted with NR latex coagulated by acid (NR-a). The influences of the coagulation process on the structures, vulcanization characteristics, and mechanical properties of NR were analyzed. The results show that the cross-link density (XLD) and mass percentage of cross-link network (A(Mc)) can be increased with the increment of the vulcanization time; while the mass percentage of dangling free ends of the hydrocarbon and small molecules (A(T2)), the longitudinal relaxation time (T1), transverse relaxation time (T2), and molecular mass of inter–cross-link chains (Mc) decreased with the prolonging of vulcanization time both NR-m and NR-a. NR-m exhibits shorter scorch times (ts1, ts2) and optimum cure time (t90) and shows higher maximum torque (MH) and minimum torque (ML) than that of NR-a. It is obvious that the higher XLD and A(Mc) and lower A(T2), T1, T2, and Mc values of NR-m result in higher stress, tensile strength, and tear strength of NR compounds.

INVESTIGATION OF THE VULCANIZATION CHARACTERISTICS OF NATURAL RUBBER COAGULATED BY MICROORGANISMS

2017 ◽  
Vol 90 (3) ◽  
pp. 521-535 ◽  
Author(s):  
Si-Dong Li ◽  
Jing Chen ◽  
Le-Fan Li ◽  
Zhi-Fen Wang ◽  
Jie-Ping Zhong ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Transverse Relaxation Time ◽  
Cross Link ◽  
Mass Percentage ◽  
Maximum Torque ◽  
Transverse Relaxation ◽  
Link Density ◽  
Cure Time ◽  
Cross Link Density ◽  
Vulcanization Process

ABSTRACT The network variations of NR during the vulcanization process were investigated by 1H chemical shift by liquid-state 1H-NMR spectroscopy. NR latexes coagulated by microorganisms (NR-m) or acid (NR-a) were contrasted. The influences of coagulation on the structures, vulcanization characteristics, and mechanical properties of NR were analyzed. The results show that the cross-link density (XLD) and mass percentage of cross-link network [A(Mc)] increased with the increment of the vulcanization time, whereas the mass percentage of bangling free ends of the hydrocarbon and small molecules [A(T2)], the longitudinal relaxation time (T1), the transverse relaxation time (T2), and the molecular mass of inter–cross-link chains (Mc) decreased with the prolonging of vulcanization time for both NR-m and NR-a. Although NR-m exhibits shorter scorch times and optimum cure time, it shows higher maximum torque and minimum torque than that of NR-a. It is obvious that the higher XLD and A(Mc), the lower the A(T2), T1, T2, and Mc values of NR-m, resulting in higher stress, tensile strength, and tear strength of NR compounds.

Reclaiming of waste guayule natural rubber vulcanizate—reclaim rubber for green tire applications: An approach for sustainable development

2018 ◽  
Vol 51 (3) ◽  
pp. 193-210 ◽  
Author(s):  
Soumyajit Ghorai ◽  
Dipankar Mondal ◽  
Sawar Dhanania ◽  
Santanu Chattopadhyay ◽  
Madhusudan Roy ◽  
...  
Keyword(s):  
Natural Rubber ◽  
Polymer Chains ◽  
Cross Link ◽  
Scanning Calorimetry ◽  
Infrared Study ◽  
Differential Scanning Calorimetry Study ◽  
Link Density ◽  
Cross Link Density ◽  
Silica Dispersion ◽  
The Fourier Transform

This article illustrates the reclaiming of guayule natural rubber (GNR) vulcanizate by bis[3-(triethoxysilyl)propyl] tetrasulfide (TESPT), and as-grown reclaim rubber facilitates the silica dispersion in GNR product application without adding any coupling agent. This article deals with the performance evaluation of silica-filled revulcanizates with promising application in green tire. The extent of reclaiming was monitored through the measurement of sol content, cross-link density, Mooney viscosity, and degree of reclaiming. The differential scanning calorimetry study was carried out to evaluate the fraction of immobilized polymer chains and its dependence on cross-link density of the vulcanizates. The Fourier transform infrared study and also sulfur analysis independently indicate the attachment of the fragmented TESPT with the polymer chain and cross-link bonds. The study of mechanical properties clearly shows that in revulcanized GNR, the optimum property is achieved when reclaiming time is set for 40 min. The effect of reclaiming time on dynamic mechanical behavior such as storage modulus and loss tangent was studied. The scanning electron microscopy studies show the coherency and homogeneity of silica-filled revulcanize rubber with reclaiming time.

Sulfur-Cured Natural Rubber Elastomer Networks: Correlating Cross-Link Density, Chain Orientation, and Mechanical Response by Combined Techniques

2013 ◽  
Vol 46 (3) ◽  
pp. 889-899 ◽  
Author(s):  
Arnaud Vieyres ◽  
Roberto Pérez-Aparicio ◽  
Pierre-Antoine Albouy ◽  
Olivier Sanseau ◽  
Kay Saalwächter ◽  
...  
Keyword(s):  
Natural Rubber ◽  
Mechanical Response ◽  
Cross Link ◽  
Chain Orientation ◽  
Link Density ◽  
Cross Link Density

REINFORCED MECHANICAL PROPERTIES OF FUNCTIONALIZED SILICA AND EGGSHELL FILLED GUAYULE NATURAL RUBBER COMPOSITES

2019 ◽  
Vol 92 (4) ◽  
pp. 687-708 ◽  
Author(s):  
Xianjie Ren ◽  
Yang Geng ◽  
Alfred B. O. Soboyejo ◽  
Katrina Cornish
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
Energy Consumption ◽  
Natural Rubber ◽  
High Surface ◽  
Particle Diameter ◽  
Cross Link ◽  
Final Particle ◽  
Link Density ◽  
Cross Link Density

ABSTRACT Replacing synthetic fillers, which are commonly used to reinforce rubber, with bio-fillers has potential to improve the sustainability of rubber products. Eggshell (ES) (a powder with a maximum particle diameter of 9.4 μm and a median of 1.1 μm) was added to guayule natural rubber (GNR) composites to partially or fully replace bifunctionally silanized, high surface area, precipitated silica (BSS). The mixing energy consumption, mechanical properties, cross-link density, filler dispersion and final particle size, fracture surface morphology, and dyeability of GNR composites were characterized. ES filler effectively reinforced vulcanized GNR compared with unfilled vulcanized GNR. Energy consumption, modulus at 300% strain (M300), and hardness generally decreased with increasing ES fraction (decreasing BSS), but tensile strength, gel fraction, and elongation at break increased even where cross-link density and M300 were similar. Thus, composite cross-link density was not solely influenced by silane content as the ratio and loading of ES and BSS changed. The production of the composites reduced particle size to submicron size. Even a small amount of ES improved the dispersion of BSS filler particles in the composites and hence the mechanical properties. The contributions of the two fillers to the composite properties are explained. Linear mixed models were built to predict the mechanical properties of a broader range of GNR–ES–BSS composites, and r2 (the quality of the model predictability) was above 0.9 for all models. ES filled GNR, with or without BSS, can be dyed different colors for specific applications. The lower-cost, renewability, dyeability, and excellent performance of ES–GNR composites addresses the need for sustainable rubber products with low carbon footprint.

scholarly journals Effect of the cure time on the Mechanical Properties of Silicone Rubber used as Socket Liners

2022 ◽  
Vol 961 (1) ◽  
pp. 012100
Author(s):  
Ahmed K Hassan ◽  
Zuhair Jabbar Abdul Ameer
Keyword(s):  
Silicone Rubber ◽  
Crosslink Density ◽  
Skin Inflammation ◽  
Moisture Stress ◽  
Curing Time ◽  
Cross Link ◽  
Local Pressure ◽  
Link Density ◽  
Cure Time ◽  
Cross Link Density

Abstract This work is focused on the upper part of the prosthesis which is called a socket, it is in contact connect with the amputated part. The shear force between skin and socket, local pressure, sweating, and bacteria generation, all lead to skin inflammation and a bad smell. Consequently, the prosthesis became uncomfortable for a patient. To address this issue silicone rubber liners is proposed to use because it can absorb moisture, stress distribution, and anti-bacterial. The curing time and temperature are important factors for determining crosslink density, from the results obtained, can be noticed that, the cross-link density can greatly affect the silicone rubber properties, it can have a direct effect on the tensile strength, modulus of elasticity, percentage of elongation as well as the water absorption, and the cure time (15 min.) shoes the best resalt. As a result, using it making the prosthesis more comfortable and acceptable to the patient. In this paper, the effect of cure time on physical properties was studied.

Effect of the cure system on aging resistance of natural rubber compounds

2019 ◽  
Vol 52 (5) ◽  
pp. 397-409 ◽  
Author(s):  
Luciana Ribeiro Honorato ◽  
Regina Celia Reis Nunes ◽  
Jaqueline Guimarães Lima Cosme ◽  
Leila Lea Yuan Visconte ◽  
Augusto Cesar de Carvalho Peres ◽  
...  
Keyword(s):  
Natural Rubber ◽  
Mechanical Performance ◽  
Dynamic Properties ◽  
Lower Number ◽  
Cross Link ◽  
Rubber Compounds ◽  
Before And After ◽  
Link Density ◽  
Cross Links ◽  
Cross Link Density

This work investigates natural rubber (NR) composites vulcanized with different combinations of accelerators in efficient cure systems. The NR compounds were characterized for cross-link density, hardness, tensile strength, and dynamical–mechanical properties, before and after aging. Among the cure systems used, that containing the highest amount of free sulfur presented the best mechanical performance, before and after aging; concerning dynamic properties after the aging, the composition with a lower number of cross-links was the best.

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