TECHNOLOGY | THERMALLY CONDUCTIVE COMPOUNDS
made of neat polymer and the other containing AvanThermal 440 50PE MB) in the same quantity of water at the same initial temperature, a difference of 5°C can be measured within five minutes,” says Elvira Villaro Ábalos from Avanzare’s R & D depart- ment. “While the neat specimen just increases by 1°C, the reinforced one increases by 7°C.”
Figure 6: Wear rate of graphite-polystyrene compounds measured using ball-on-three-plate method at constant rotational speed (500rpm) and force (30N) against steel ball Source: Imerys Graphite & Carbon
not only to thermal and electrical conductivity, but also to lubrication and wear resistance, gas and moisture barrier performance.
Heat dissipation
Right: This infrared camera image shows the difference in temperature of compounds with and without Avanzare’s graphene nanoplatelet additives
“High thermal conductivity additives are of particu- lar interest in self-lubrication applications, where they contribute to frictional heat dissipation,” says Ellett. “Compared to standard graphites, the high aspect ratio Timrex C-Therm will provide superior thermal conductivity at lower loading (typically half the loading is needed to reach the same perfor- mance), lower friction coefficient, and lower wear rate. This makes C-Therm an additive of choice for high-end self-lubrication compounds, where it outperforms low purity, low crystallinity secondary graphite scrap and even high purity and high crystallinity natural and synthetic graphites.” Avanzare Innovación Tecnologica has launched three new AvanThermal masterbatches to enhance thermal conductivity of plastics and elastomers using graphene nanoplatelets in PE, PA or EVA carrier resins. “These masterbatches multiply the thermal conductivity of the base polymer by three or four times with low impact in processability,” the company says. Due to an extremely high aspect ratio, greater than 10,000, graphene nanoplatelets allow the creation of a highly effective thermally conductive network in the polymer matrix. Thermal conductivi- ties of the masterbatch products range from 13.5 W/m·K (AvanThermal 440 50PE MB) through 15.2W/m·K (AvanThermal 440 50PA6 MB) to 16.5W/m·K (AvanThermal 440 50EVA MB). “As a visual example, if we introduce two injected samples previously heated to 70°C (one
48 COMPOUNDING WORLD | August 2021
Building concepts Thermally conductive materials are not only of interest in the electronics sector. Spanish research organisation Aimplas is currently involved in two projects covering applications in the construction sector. The Habitatge 2020 project covers ad- vanced construction materials that can reduce the temperatures of buildings and urban centres and includes development of PE pipes with enhanced thermal conductivity for use in solar collectors. According to Aimplas, the first validation tests of the polymer prototypes showed yields of 50% were achieved. “This is a very interesting value since solar collectors manufactured with copper pipes obtain performance values of 50-60%,” says Arsenio Navarro, a researcher covering Construc- tion and Renewable Energies at Aimplas. “We designed a small-scale solar collector ), which we monitored during part of June.
(0.52m2
We have proved that it is possible to build a solar collector made entirely of plastic materials, including highly conductive polymers [polyester resins as well as PE]. This opens the door to new improvements in this type of product, as well as new ideas in active façades, heat sinks, heat
www.compoundingworld.com
IMAGE: AVANZARE
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