Positron lifetime studies on the free volume changes during deformation of rubber‐carbon black composites

Jobando, Vincent; Quarles, C.A.

doi:10.1002/pssc.200675851

Cited by 4 publications

(3 citation statements)

References 21 publications

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“…Positron annihilation lifetime spectroscopy is a very useful technique for structural characterization in polymers, especially at the nanoscale, for the aforementioned reasons and, therefore, has been extensively used to investigate CB-filled rubber composites. [48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64] Nonetheless, those studies remained mostly inconclusive due to inconsistencies in the results of different groups and the difficulty in effectively relating the o-Ps data to the viscoelastic properties of the rubber and the networkchain density. For instance, some of the earlier works detected a variation of the o-Ps lifetime as a function of CB concentration, whereas other studies simply reported that the o-Ps lifetime depends only on the type of rubber composite but is independent of the CB loading.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Free volume in carbon‐black‐filled isoprene rubber investigated by positron annihilation lifetime spectroscopy

Chiari

Nippa

Ikeda

et al. 2022

J of Applied Polymer Sci

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The free volume in the amorphous phase of a simple carbon‐black‐filled peroxide cross‐linked isoprene rubber (IR) is investigated by positron annihilation lifetime spectroscopy to clarify the structural changes in the rubber phase by the carbon black (CB) fillers. The ortho‐positronium (o‐Ps) pick‐off annihilation lifetime measured in the rubber without CB is around 2.8 ns and is found to be almost constant even after CB filling. This result indicates that in a portion of the rubber phase the free volume remains similar in size to that in the cross‐linked IR without CB. The o‐Ps intensity drastically decreases from 37% without CB to 15% with a CB loading as high as 80 phr. This decline is revealed to exceed the contribution, which is expected only from the decrease in the fraction of the amorphous phase by CB addition, by a factor of 0.37 at the highest CB loading. The additional reduction is related to the generation of a bound rubber layer surrounding the CB fillers with low molecular‐chain mobility where positronium formation is inhibited. The decrease rate is found to represent the volume of this rigid rubber phase and strongly depend on the formation of the CB network structure.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Free volume in carbon‐black‐filled isoprene rubber investigated by positron annihilation lifetime spectroscopy

Chiari

Nippa

Ikeda

et al. 2022

J of Applied Polymer Sci

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“…Some investigators have given considerable attention to the change of free‐volume in CB filled rubber composites by using PALS during the curing of composites or during deformation while, others prepared a blend of different types of rubber. On our knowledge, such study on an attractive and interesting class (type) of rubber, PDMS, has not been undertaken deeply.…”

Section: Introductionmentioning

confidence: 99%

Correlation of electrical and swelling properties with nano free-volume structure of conductive silicone rubber composites

et al. 2013

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The present study focuses on finding a correlation between the positron annihilation parameters of silicone rubber polydimethylsiloxane (PDMS) composites loaded with different conductive fillers and their swelling and electrical properties. Four types of conductive fillers have been used in this study, i.e., carbon black (CB), graphite (G), copper, and nickel powders. The investigated swelling parameters for PDMS composites such as the maximum degree of swelling Qm%, the penetration rate, P, and consequently the diffusion coefficient, D, decreased with increasing the filler content due to the reduction of the size of free‐volume, which could be observed through a decrease of the probability of ortho‐positronium (o‐Ps) formation I3, that has been measured by the positron annihilation spectroscopy (PALS). Accordingly, a positive correlation has been found of 76.78% and 61.1% between Qm% and the o‐Ps lifetime τ3, representing the size of free‐volume for the CB and G filled composites, respectively. It is worthwhile, mentioning that the CB filled composites exhibit relatively low values of P, D, and Qm% as compared to the G filled composites due to the difference in the physical properties of the filler, particle size, surface area as well as the tendency of the filler particles to make aggregates. On the other hand, the variation of the diffusion coefficient with the relative fractional free‐volume Fr is found in good agreement with the Fujita's free‐volume theory. On the other hand, the electrical conductivity increases with increasing the conductive filler content. Positive temperature coefficient of conductivity (PTCC) behavior is detected, except for the composite containing 20 or 25 phr CB, which showed a metallic behavior. Besides, CB filled PDMS composites exhibit higher electrical conductivity as compared to the composites filled with the other three fillers. The electrical conductivity ln (σ) is positively correlated with the probability of free annihilation of positrons at interfaces I2, thus suggesting an increase in the electron density with the filler content. The activation energy of conduction, Ea, decreases with the increase in the loading of conductive filler. Moreover, it was noticed that Ea varies with the filler type, the values of Ea increase as the particle size of the filler increases. Finally, a correlation between the free‐volume Vf, determined by PALS with the DC electrical conductivity ln(σ) is found to be in accordance with Miyamoto and Shibayma model. POLYM. COMPOS., 34:2105–2115, 2013. © 2013 Society of Plastics Engineers

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Physical Phenomena Related to Free Volumes in Rubber and Blends

Marzocca

Salgueiro

Somoza

2013

Advanced Structured Materials

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Positron lifetime studies on the free volume changes during deformation of rubber‐carbon black composites

Cited by 4 publications

References 21 publications

Free volume in carbon‐black‐filled isoprene rubber investigated by positron annihilation lifetime spectroscopy

Free volume in carbon‐black‐filled isoprene rubber investigated by positron annihilation lifetime spectroscopy

Correlation of electrical and swelling properties with nano free-volume structure of conductive silicone rubber composites

Physical Phenomena Related to Free Volumes in Rubber and Blends

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