ROLE OF COAGENTS IN PEROXIDE VULCANIZATION OF NATURAL RUBBER

2013 ◽  
Vol 86 (3) ◽  
pp. 488-502 ◽  
Author(s):  
Rejitha Rajan ◽  
Siby Varghese ◽  
K. E. George
Keyword(s):  
Natural Rubber ◽  
Hydrogen Abstraction ◽  
Polymer Chains ◽  
Hydrocarbon Chains ◽  
Equilibrium Swelling ◽  
Link Density ◽  
Cross Links ◽  
Cross Link Density ◽  
Curing Agents

ABSTRACT The drawbacks of peroxide vulcanization can largely be overcome by introducing suitable co-curing agents (coagents) in the formulation. The role of various coagents, such as zinc diacrylate (ZDA), trimethylolpropane trimethacrylate (TMPTMA), and triallyl cyanurate (TAC) in the peroxide vulcanization of natural rubber (NR) was studied by Fourier transform infrared spectroscopy. Cross-link density was measured by the equilibrium–swelling technique. Cross-linking mechanism of peroxide in NR was interpreted by comparing the spectra of cured and uncured vulcanizates. The predominance of hydrogen abstraction over the radical addition was established (at 160 °C). Coagent ZDA produces ionic as well as covalent cross-links in the vulcanizate. Ionic cross-links have the ability to slip along the hydrocarbon chains and thus resemble polysulfidic cross-links. Hence, ZDA can be chosen for applications where good mechanical properties are required. Coagent TMPTMA produces covalent cross-links between polymer chains and is suitable for high-modulus applications. TAC, although it bridges through covalent cross-links, is not a suitable coagent for highly unsaturated rubbers like NR.

scholarly journals Devulcanization of ground tire rubber: microwave and thermomechanical approaches

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Dániel Ábel Simon ◽  
Dávid Zoltán Pirityi ◽  
Tamás Bárány
Keyword(s):  
Microwave Treatment ◽  
Chain Scission ◽  
Polymer Chains ◽  
Tire Rubber ◽  
Ground Tire Rubber ◽  
Elongation At Break ◽  
Link Density ◽  
Cross Links ◽  
Cross Link Density ◽  
Internal Mixer

Abstract We devulcanized ground tire rubber (GTR) in a laboratory microwave oven and an internal mixer, measured the soluble content and the cross-link density of the samples, and then used Horikx’s analysis. The results showed that microwave treatment caused severe degradation of the polymer chains, while in the case of thermomechanical devulcanization, the selective scission of covalent cross-links is more common. Four devulcanized ground tire rubber (dGTR) samples were chosen for further study and three groups of samples were produced: dGTR samples containing vulcanizing agents and different amounts of paraffin oil (dGTR-based mixtures), natural rubber-based rubber mixtures with different dGTR contents and reference rubber mixtures with dGTR-based mixtures (increased vulcanizing agent contents). Cure characteristics showed a plasticizer-like effect of dGTR. Tensile and tear strength decreased drastically with increasing dGTR content; however, elongation at break values did not follow such a trend. Mechanical properties improved with increased vulcanizing agent contents. The examined properties of the samples improved even further with the use of thermomechanically devulcanized samples. Horikx’s analysis showed that this is attributable to moderate polymer chain scission.

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.

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.

Uncertainties in the Determination of Cross-Link Density by Equilibrium Swelling Experiments in Natural Rubber

2008 ◽  
Vol 41 (13) ◽  
pp. 4717-4729 ◽  
Author(s):  
J. L. Valentín ◽  
J. Carretero-González ◽  
I. Mora-Barrantes ◽  
W. Chassé ◽  
K. Saalwächter
Keyword(s):  
Natural Rubber ◽  
Cross Link ◽  
Equilibrium Swelling ◽  
Link Density ◽  
Cross Link Density

scholarly journals Magnetic composites based on NR and strontium ferrite

2019 ◽  
Vol 12 (1) ◽  
pp. 63-69
Author(s):  
Ján Kruželák ◽  
Andrea Kvasničáková ◽  
Rastislav Dosoudil ◽  
Ivan Hudec
Keyword(s):  
Carbon Black ◽  
Strontium Ferrite ◽  
Rubber Matrix ◽  
Cross Link ◽  
Magnetic Composites ◽  
Link Density ◽  
Cross Links ◽  
Cross Link Density ◽  
The Cross ◽  
Thermo Physical Properties

Abstract Two types of composites based on natural rubber (NR) and strontium ferrite were tested in this study. Composites of the first type were prepared by incorporation of strontium ferrite in the concentration range ranging from 0 to 100 phr (parts per hundred rubber) into pure NR based rubber matrix, while with those of the second type, strontium ferrite was dosed in the same concentration level into NR based rubber batch with constant amount of carbon black — 25 phr. For rubber matrices cross-linking, a standard sulfur based curing system was used. This work is focused on the effect of magnetic filler content on physico-mechanical, magnetic and thermo-physical properties of composite materials. Subsequently, the cross-link density and the structure of the formed sulfidic cross-links were examined. The results showed that the cross-link density of both types of composites increased with the increasing content of magnetic filler, while the structure of the sulfidic cross-links was almost not influenced by the amount of strontium ferrite. Tensile strength of rubber composites with pure rubber matrix was slightly improved by the incorporation of ferrite, while in case of composites based on a carbon black batch, the incorporation of magnetic filler resulted in the decrease of this characteristic. The presence of magnetic filler in both types of composites leads to a significant increase of the remanent magnetic induction.

Role of Thermo-responsiveness and Poly(ethylene glycol) Diacrylate Cross-link Density on Protein Release from Poly(N-isopropylacrylamide) Hydrogels

2011 ◽  
Vol 22 (1-3) ◽  
pp. 59-75 ◽  
Author(s):  
Pawel W. Drapala ◽  
Eric M. Brey ◽  
William F. Mieler ◽  
David C. Venerus ◽  
Jennifer J. Kang Derwent ◽  
...  
Keyword(s):  
Ethylene Glycol ◽  
Protein Release ◽  
Poly Ethylene Glycol ◽  
Cross Link ◽  
Glycol Diacrylate ◽  
Link Density ◽  
Cross Link Density ◽  
Poly Ethylene

Degradation Behaviour of Thin Polymer Films of Poly(Amide Ester) Hydrogel Using Quartz Crystal Microbalance

2013 ◽  
Vol 812 ◽  
pp. 38-45
Author(s):  
Dzaraini Kamarun ◽  
Ahmat Norizan ◽  
Steffi Krause ◽  
Chris Hunter ◽  
Lilia Milanesi
Keyword(s):  
Quartz Crystal Microbalance ◽  
Polymer Films ◽  
Quartz Crystal ◽  
Base Catalysis ◽  
Degradation Behaviour ◽  
Thin Polymer ◽  
Link Density ◽  
Cross Links ◽  
Cross Link Density

Quartz Crystal Microbalance (QCM) has been typically used as a mass sensor in the study of monolayer and multilayer depositions and dissolution, mass transport in polymer films on electrodes, corrosion processes at electrodes and mass changes caused by protein adsorption at electrodes. Thin films of an aromatic poly (amide ester) hydrogel with hydrolyzable cross links were prepared in-situ on a gold-coated quartz crystal which is the transducing element of a Quartz Crystal Microbalance (QCM). Here we report the synthesis and degradation behavior of an aromatic poly (amide ester) hydrogel with hydrolyzable cross links using QCM. Degradation of the hydrogel films was found to proceed with Δf increment, indicating mass decrease and is in line with the theory proposed by Sauerbrey. Films with a higher cross-link density underwent partial degradation with swelling; and are depicted as a decrease in the Δf values with time. Deviation from the general base catalysis of ester hydrolysis was observed at higher base concentration due to the biphasic environment of the hydrolysis reaction.

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