The mechanical and adhesive properties of electrically and thermally conductive polymeric composites based on high density polyethylene filled with nickel powder

• The percolation concentration of the filler within the HDPE matrix is 8 vol.%.
• The electrical conductivity of the composite increased in 22 orders.
• The thermal conductivity of the composite increased four times.

Electrically and thermally conductive composites made using high density polyethylene (HDPE) matrix blended with a special grade of branch-structured nickel particles were studied. Composites with high filler content were highly electrically and thermally conductive. The electrical conductivity of composites reached a value of 8.3 × 103 S m−1 when filled with 30 vol.% of the filler, and the thermal conductivity obtained using this filler content was found to be 1.99 W m−1 K−1. The percolation concentration of the filler within the HDPE matrix, which was determined from electrical conductivity measurements, was determined to be 8 vol.%.Young’s modulus of composites significantly increased from 606 MPa to 1057 MPa when composites were filled with 20 vol.% of the filler. Further increasing the filler content caused no further increase in Young’s modulus, probably due to high aggregation of the filler. The stress at break of the composites behaved nonlinearly; the low filler content suppressed necking, resulting in a decrease in stress at break, whereas higher filler content (higher than 10 vol.%) led to reinforcement of the composites and therefore increased the stress at break.The presence of nickel particles throughout the HDPE matrix increased the hydrophilicity of the composites. The contact angle of water on the neat HDPE decreased from 93° to 80° as the nickel content of the matrix was increased to 13 vol.% of nickel. Further increases in the filler content did not alter the contact angle. Similarly, the strength of the adhesive joint formed by the composite and aluminum foil increased from a value of 16 N m−1 for the neat HDPE to 27 N m−1 when the HDPE matrix was filled with 13 vol.% of the filler.

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