Carbon-filled polymer blends mechanical properties

To address the issues of the manufacturing cost and concurrent reduction in mechanical properties when a high fiUer concentration is used, carbon-filled polymer blends containing a triple-continuous structure in 3D space have been pursued recently [24-26]. Shown in Fig. 12.1 is the schematic of the carbon-filled polymer blend with a triple-continuous structure, consisting of a binary polymer blend (i.e.. Phases A and B) and CB or CNT particles. Both polymer phases are continuous in 3D space. The conductive carbon is preferentially located in Hiase A and its concentration is... 

In spite of the substantial progress made with the concept of carbon-filled polymer blends containing a triple-continuous structure, the carbon-filled polymer blends studied so far only contain relatively low carbon concentrations. As a result, their electrical conductivities are still far below the desired values (such as >100 S cm ) for the application of PEM fuel cell bipolar plates. Therefore, it is imperative to investigate (a) whether such a triple-continuous structure can still be injection molded for polymer blends with high carbon concentrations (e.g., >30 vol% carbon) and (b) whether the polymer blends with high carbon concentrations and a triple-continuous structure, if injection moldable, still possess superior electrical conductivity and mechanical properties. Both issues will be the topics of future studies. 

Owing to the different mechanical properties, filler particles can be in most cases differentiated from the polymeric matrix in SFM. Examples include carbon black or silica-filled rubbers, carbon-black-filled polymer blends or salt-loaded block copol5nner micelles. For the latter case, Spatz and co-workers demonstrated... 

Meincke O, Kaempfer D, Weickmann H, Friedrich C, Vathauer M, Warth H (2004). Mechanical properties and electrical conductivity of carbon-nanotube filled polyamide-6 and its blends with acrylonitrile/butadiene/styrene. Polymer 45 739-748. 

Carbon-black-filled rubber compounds are usually produced on Banbury-type mixers, while conductive thermoplastics are preferably produced on twin-screw extruders. Unlike other filled compounds or polymer blends it is essential to adhere very precisely to the carbon-black concentration and the production parameters, since a very delicate balancing act is usually required to stay on the tight-rope of optimum composition and avoid falling into the pits of insufficient conductivity, inadequate mechanical properties or sharply increased viscosity. 

Some studies with filled and unfilled rigid PVC were made in our laboratory to describe the effect of chalk as additional stabilizer. A suspension PVC (K-value 70) with an organotin stabilizer (2 phr) and lubricants (1.8 phr) was used as the experimental material. A part of this compound was filled with a stearic acid coated calcium carbonate (10 phr) as an additional component. The PVC powder and the additives were mixed at a high speed in an intensive mixer. The received dry blends were pelletized by extrusion to get a better dispersion of the additives in the polymer material. Finally, the granulates were processed by injection molding to test specimens for measurements of mechanical properties. 

H. Nabil, H. Ismail, A.R. Azura, Compoimding, mechanical and morphological properties of carbon-black-filled natural mbber/recycled ethylene-propylene-diene-monomer (NR/R-EPDM) blends. Polymer Testing, ISSN 0142-9418 32 (2) (April 2013) 385-393. http //dx.doi.Org/10.1016/j.polymertesting.2012.ll.003. 

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