The scission step in hevea oxidation

Bevilacqua, E. M.; English, E. S.

doi:10.1002/pol.1961.1204915229

Cited by 18 publications

(9 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…That is, on mixing NR latex and CNT dispersion, CNT was transformed to [CNT -]Na + after addition of NaOH solution for adjusting the pH to about 11 [24]. Also, some NR molecular chains might be degraded by thermo-oxidation during drying, which generated ketone groups at NR chain ends [25,26]. Therefore, the [CNT -]Na + can possibly react with NR at the ketone groups to form NR-CNT linkages.…”

Section: Results and Discussion 31 Attenuated Total Reflection Fourmentioning

confidence: 99%

Influence of carbon nanotube and ionic liquid on properties of natural rubber nanocomposites

Krainoi¹,

Kummerloewe²,

Nakaramontri³

et al. 2019

Express Polym. Lett.

View full text Add to dashboard Cite

Some properties of carbon nanotube (CNT) filled natural rubber (NR) composites were improved by adding an ionic liquid (IL), 1-butyl-3-methyl imidazolium bis (trifluoromethylsulphonyl)mide (BMI). In this work, the CNT and IL (CNT-IL) were mixed with NR by latex mixing method. Cure characteristics, thermo-mechanical properties, Payne effect, electrical conductivity and thermal stability were investigated. It was found that IL (BMI) accelerated vulcanization reactions and reduced scorch time. In addition, Fourier Transform Infrared (FTIR) results confirmed the role of IL in NR composites along with the reaction between CNT and NR molecules. The temperature scanning stress relaxation (TSSR) measurement was used to assess thermo-mechanical properties, and a relaxation peak of IL was found due to interactions of cations and anions in IL (BMI). Furthermore, the Payne effect was used to qualitatively analyze the roles of IL and CNT in three-dimensional CNT networks in the NR matrix. It was found that CNT dispersion was finer in the NR/CNT composites with IL. Furthermore, the NR/CNT-IL composite had higher electrical conductivity and lower percolation threshold concentration than the NR/CNT composite.

show abstract

Section: Results and Discussion 31 Attenuated Total Reflection Fourmentioning

confidence: 99%

Influence of carbon nanotube and ionic liquid on properties of natural rubber nanocomposites

Krainoi¹,

Kummerloewe²,

Nakaramontri³

et al. 2019

Express Polym. Lett.

View full text Add to dashboard Cite

show abstract

“…-In polyene elastomers, a second important source of propagation is the addition of radical species onto double bonds. [6][7][8][9] These two reactions are summarized in Scheme 5. In a first approach, they are considered exclusively intermolecular, although it is known that, in other types of elastomer (in particular in IR), they can be also intramolecular.…”

Section: Theoretical Chemical Levelmentioning

confidence: 99%

“…On one hand, chemists tried to provide a concrete basis to the ''standard'' mechanistic scheme by identifying the main oxidation products and checking the validity of their formation paths. [6][7][8][9] On the other hand, physicists analyzed the consequences of oxidation on mechanical behavior and tried to explain them by using the theory of polymer behavior in solution 10,11 or the statistical theory of rubber elasticity. 12 Today, one key question is still unsolved: How to connect these two axes of research?…”

Section: Introductionmentioning

confidence: 99%

“…Chemists highlighted all the complexities of oxidation reactions for unsaturated hydrocarbon polymers, for which propagation occurs as much by hydrogen abstraction, according to the ''standard'' mechanistic scheme, 3,4 as by addition of radical species onto double bonds. [6][7][8][9] However, the numerous attempts for relating the macromolecular changes to the mechanistic scheme led to results that were regarded as convincing, but also in many ways, contradictory.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Chemo-Mechanical Model for Predicting the Lifetime of Epdm Rubbers

Colin

Hassine²,

Nait-Abelaziz

2019

Rubber Chemistry and Technology

View full text Add to dashboard Cite

A chemo-mechanical model has been developed for predicting the long-term mechanical behavior of EPDM rubbers in a harsh thermal oxidative environment. Schematically, this model is composed of two complementary levels: The “chemical level” calculates the degradation kinetics of the macromolecular network that is introduced into the “mechanical level” to deduce the corresponding mechanical behavior in tension. The “chemical level” is derived from a realistic mechanistic scheme composed of 19 elementary reactions describing the thermal oxidation of EPDM chains, their stabilization against oxidation by commercial antioxidants but also by sulfide bridges, and the maturation and reversion of the macromolecular network. The different rate constants and chemical yields have been determined from a heavy thermal aging campaign in air between 70 and 170 °C on four distinct EPDM formulations: additive free gum, unstabilized and stabilized sulfur vulcanized gum, and industrial material. This “chemical level” has been used as an inverse resolution method for simulating accurately the consequences of thermal aging at the molecular (concentration changes in antioxidants, carbonyl products, double bonds, and sulfide bridges), macromolecular (concentration changes in chain scissions and cross-link nodes), and macroscopic scales (weight changes). Finally, it gives access to the concentration changes in elastically active chains from which are deduced the corresponding changes in average molar mass MC between two consecutive cross-link nodes. The “mechanical level” is derived from a modified version of the statistical theory of rubber elasticity, called the phantom network theory. It relates the elastic and fracture properties to MC if considering the macromolecular network perfect, and gives access to the lifetime of the EPDM rubber based on a relevant structural or mechanical end-of-life criterion. A few examples of simulations are given to demonstrate the reliability of the chemo-mechanical model.

show abstract

“…A further assumption (1,4) that oxidation of levulinic acid proceeds through malonic acid with the yield of two moles of acetic acid and one of COz for each mole of levulinic acid is also in conflict with observation. Oxidation of levulinaldehyde (5) and of levulinic acid (6) under mild conditions proceeds quantitatively to 1 mole of acetic acid and 3 of carbon dioxide for each mole of starting material.…”

mentioning

confidence: 99%