Multilayer Coextrusion of Polymer Composites to Develop Organic Capacitors

Abstract

Multilayer coextrusion is applied to produce at ape containing layers of alternating electrical properties to demonstrate the potential for using coextrusion to manufacture capacitors. To obtain the desired properties, we develop two filled polymer systems, one for conductive layers and one for dielectric layers. We describe numerical models used to help determine the material and processing parameters that impact processing and layer stability. These models help quantify the critical ratios of densities and viscosities of the two layers to maintain stable layers, as well as the effect of increasing the flow rate of one of the two materials. The conducting polymer is based on polystyrene filled with ab lend of low-meltingpoint eutectic metal and nickel particulate filler, as described by Mrozek et al. (2010). The appropriate concentrations of fillers are determined by balancing measured conductivity with processability in at win screw extruder. Based on results of the numerical models and estimates of the viscosity of emulsions and suspensions, ad ielectric layer composed of polystyrene filled with barium titanate is formulated. Despite the fact that the density of the dielectric filler is less than the metallic filler of the conductive phase, as well as rheological measurements that later showed that the dielectric formulation is not an ideal match to the viscosity of the conductive material, the two materials can be successfully coextruded if the flow rates of the two materials are not identical. Am easurable capacitance of the layered structure is obtained. 1I ntroductionMultilayer coextrusion combines multiple polymers into a layered structure to produce composite properties that are not found in asingle polymer. Coextrusion processes have been in use for over 40 years, and multilayered film structures have found commercial application in the area of food and beverage packaging for their barrier properties and as protective coatings (Wagner, 2010). The multilayer coextrusione quipment used here is based on work by Zhao and Macosko (2002). The equipment combines the polymer flows from two single screw extruders into an initial layered structure that then passes through aseries of dies to multiply the number of layers. The first die splits the flow vertically; the two components are stacked and recombined to effectively double the number of layers. As the number of layers is increased in the same die cross-sectional area, the individual layer thickness decreases. This method has successfully been implemented by companies like 3M and Dow to produce multilayered structures of * 20 m ma nd 110 nm, respectively (3M 2005(3M , Dow 2007). In our equipment the initial layered structure consists of 8layers. As aresult, the number of multiplication sections, n, will result in 2 n+3 layers in a1mmtape.

Design, Processing, and Challenges of Multicomponent Polymer Composites for Improved Electromagnetic Interference Shielding Properties: A Review

“…Cast film coextrusion or forced assembly multilayer coextrusion (FAMCO) has drawn much attention lately due to the performance of multilayer polymer films: notably their outstanding barrier, dielectric, and optical properties. [113][114][115][116] Sluijter (1962) and Tollar (1966) independently developed a layer-multiplying coextrusion system that uses two or three extruders to feed material into a feedblock, followed by one or more multipliers. [117] In each multiplier die, the layered polymers are split, compressed and expanded, and then recombined one on top of the other, which doubles the number of layers.…”

“…[118] However, when this constraint is overcome, the process allows the versatile development of multilayered materials, with micro-or even nanolayers, that are tailored to the need of the consumer, from multilayered sheets and films for packaging applications [119] to capacitors and CPCs. [115] 6. Multicomponent Composites with Different Structure Designs…”