Thermal conductivity, coefficient of linear thermal expansion and mechanical properties of LDPE/Ni composites

Abstract

Thermophysical and mechanical properties of low density polyethylene (LDPE) filled with nickel powder (10 μm) is reported. The composites are characterized by XRD, SEM, DSC and TGA. XRD analysis indicates that Ni affects the crystallinity of LDPE, whereas, scanning electron micrographs reveals formation of Ni clusters/conducting chains especially for high filler concentration. The DSC and TGA data show a marginal decrease in peak melting point and a moderate enhancement in thermal stability, respectively with increasing volume % of Ni in LDPE. Thermal conductivity of the composite increases by ~240 % with addition of 25 volume % of nickel and we confirm that the measured data is in excellent agreement with a percolation based model. Coefficient of thermal expansion (CTE) of LDPE decreases by ~38 % for composite with 25 volume % of Ni. The measured CTE agrees well with the estimates of a recent model which takes into account the interphase volume and interaction between filler particles and polymer. An overall improvement in mechanical properties is also observed for LDPE/Ni composites and the results are explained in the light of existing models.