Processability of EPR in an Internal Mixer (II)–Morphological Changes of Carbon Black Agglomerates During Mixing

Shiga, Shujiro; Furuta, Motonobu

doi:10.5254/0035-9475-58.1.1

Cited by 70 publications

(28 citation statements)

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“…It was assumed that the only mechanism that took place in this device was the erosion process. Shiga and Furuta (1985) obtained similar observations. They found that large carbon black agglomerates remained in the rubber compound even after a long mixing time (10 min).…”

Section: Results From the Experiments Carried Out In The Internal Mixersupporting

confidence: 64%

A Chemical Model for the Dispersion of Fillers in a Polymeric Matrix

Lozano¹,

Lafleur²,

Grmela³

2002

Can J Chem Eng

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1135I n the polymer industry, particulate fillers are often used to improve material properties and to reduce cost. The interest in developing such composites is therefore to widen the range of applications of the polymer. The quality of filler dispersion affects the properties of the finished product. Large agglomerates tend to form a flaw, which causes failure. The size reduction of particles depends upon the nature of the fillers (i.e size, shape, structure, cohesivity, etc.) as the intensity and duration of the applied hydrodynamic stress. Understanding the mechanism of agglomerate dispersion can be useful in improving mixing equipment.There are mainly two mechanisms by which the agglomerate size reduction occurs. Parker et al. (1972) proposed the occurrence of two distinct breakage mechanisms in turbulent conditions (agitation): large scale splitting into a few fragments (breakup process); and fine particle detachment on the periphery of the agglomerates (erosion process). Kao and Mason (1975) and Powell and Mason (1982), by systematic visualization in a well-defined flow field generated by a four-roll apparatus, observed only the erosion mechanism of the flocs model (cohesionless clusters of spherical particles). In that work, the erosion rate did not depend on the magnitude of the applied shear rate; the size reduction rather depended upon total deformation. Quigley (1977), also using a four-roller apparatus, observed that the internal structure of cohesive agglomerates (ferric hydroxide) suspended in water-sucrose affected the rupture mechanism. Agglomerates with greater initial sphericity were observed to undergo only micro-particle erosion at its extremities, without splitting. Agglomerates that were not as irregular underwent gross splitting and the resultant fragments continuously lost fine particle through erosion. Rwei et al. (1990) and (1992), by shearing carbon black agglomerates in simple shear flow (cone and plate rheometer) within low viscosity polymers (PDMS) and high viscosity polymeric melts (PS and PE), confirmed the same mechanisms of rupture and erosion. These authors pointed out that rupture characteristically starts at a shear stress higher than that for erosion. Either in erosion or in the rupture process, shear stresses developed in the polymer must exceed some critical value higher than the interparticle agglomerate forces.The work differs from others (e.g. Pandya, 1982Pandya, , 1981 regarding the agglomeration, breakup and erosion as an infinite series of chemical reactions or, alternatively, as an evolution of the size of one particle subjected to mean-field type interactions with others. The latter framework provides a new method of solving numerically the balance equation.Most dispersion models of cohesive agglomerates found in the literature focus on the prediction of size of a single agglomerate by an erosion mechanism process or the prediction of a homogeneous size of a population of agglomerates undergoing the break-up process. In fact, size distribution affects strongly phys...

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Section: Results From the Experiments Carried Out In The Internal Mixersupporting

confidence: 64%

A Chemical Model for the Dispersion of Fillers in a Polymeric Matrix

Lozano¹,

Lafleur²,

Grmela³

2002

Can J Chem Eng

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“…Park and Jana40 proposed in their study on epoxy nanocomposites that clay exfoliation starts at the surface layers of the tactoids and continues towards the center until all layers are exfoliated. Their proposed process is analog to the erosion process as described in the onion model used for the explanation of the dispersion process of carbon black in a polymer matrix 28, 41. As visible in Figure 10(d,e), the morphology after CP 2 seems to remain unchanged that could explain the plateau of the online conductance in this period [Fig.…”

Section: Resultsmentioning

confidence: 91%

Nanoclay exfoliation in rubber compounds characterized by online measurements of electrical conductance

Ali

Ilisch

et al. 2009

J of Applied Polymer Sci

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A new method based on the online measured electrical conductance is presented for the characterization of the kinetics of dispersion of organoclay in a polar rubber matrix during melt mixing. The charge carriers available in the clay galleries become released as a result of the dispersion processes; thus, the conductance of the nanocomposites is altering during mixing. A coupled conductance/temperature sensor installed inside the mixing chamber enables the online measurement of the electrical conductance during mixing. The online measured conductance shows a characteristic chart correlating to the nanoclay dispersion process. To clarify the structural background of the conductance curve the kinetics of macro-and microdispersion of nanoclay have been investigated with the use of optical microscopy, small-angle X-ray diffraction (SAXS), and atomic force microscopy (AFM), as well as bound rubber measurements. A close correlation was found between the online conductance chart and the development of the clay dispersion. In the first mixing step, breakdown of agglomerates, diffusion of polymer chains into the galleries of the clay, wetting, and intercalation processes take place simultaneously. As a result, a significant increase of conductance is observed during this period. Subsequently, the intercalated structures undergo the exfoliation process, which causes a further but moderate increase of the electrical conductance.

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“…Among different types of conductive additives, carbon black is the most widely used for rubber matrix as it is less expensive, easily processed and also offers good reinforcement to the rubber matrix [12][13][14]. The electrical conductivity of rubber composites is largely influenced by the type and amount of carbon black in addition to its degree of dispersion within the rubber matrix and filler-matrix interfacial effects [15][16][17][18]. Carbon black of smaller particle size and high structure imparts higher conductivity to the polymer matrix [19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Analysis of electrical and dynamic mechanical response of conductive elastomeric composites subjected to cyclic deformations and temperature

2017

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Effects of different mechanical deformations such as cyclic bending and compressive flexing and temperature on electrical and dynamic mechanical properties of elastomeric composites have been investigated. Conductive elastomeric composites were prepared by incorporating different carbon blacks in an insulating polychloroprene (CR) rubber matrix. The filler loading was varied between 10 and 110 phr (parts per hundred rubber) i/r/o different carbon blacks to assess the percolation threshold of different composites. Due to the spatial arrangement of conductive filler particles at certain critical concentration, some conducting networks are formed leading to abrupt increase in conductivity of polymer composites. This critical concentration is known as percolation threshold. The increase in conductivity well below and above percolation threshold is relatively less compared to that around percolation. The variation of electrical conductivity and dynamic mechanical modulus due to bending and compressive flexing are found to be similar, that is, both characteristics show a drop in magnitude with increase in number of flex cycles. The conductivity of system changes when composites are subjected to changes in temperature. This is mainly due to the destruction of existing conducting networks as well as formation of some new conducting networks. The net change depends on the degree of formation or destruction of networks. It is interesting to see that conductivity does not follow the same path during heating–cooling cycles thereby causing electrical hysteresis. POLYM. COMPOS., 39:3912–3923, 2018. © 2017 Society of Plastics Engineers

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Processability of EPR in an Internal Mixer (II)–Morphological Changes of Carbon Black Agglomerates During Mixing

Cited by 70 publications

References 0 publications

A Chemical Model for the Dispersion of Fillers in a Polymeric Matrix

A Chemical Model for the Dispersion of Fillers in a Polymeric Matrix

Nanoclay exfoliation in rubber compounds characterized by online measurements of electrical conductance

Analysis of electrical and dynamic mechanical response of conductive elastomeric composites subjected to cyclic deformations and temperature

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