Effect of particle size distribution on thermo-mechanical properties of NiO filled LDPE composites

The effect of nickel oxide (micro) addition on thermo-physical and mechanical properties of low density polyethylene (LDPE) has been studied. The samples have been prepared by the melt mixing process. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) of the samples have been performed for micro-structural characterization and surface morphology, respectively. The XRD result confirms that the crystallinity of LDPE is affected by NiO addition, whereas the agglomeration of nickel oxide can be seen in the SEM photographs of LDPE samples having higher NiO loading. The thermal stability of the samples has been checked from DSC and TGA analyses under nitrogen atmosphere. The thermal stability of LDPE improves with the addition of a small amount of NiO particles. However, the peak melting temperature of LDPE/NiO composites decreases due to the dispersion of nickel oxide in the LDPE matrix. Again, the thermal conductivity of LDPE/NiO composites measured by a KD2 prothermal analyser increases approximately two times for 40wt.% of NiO loaded LDPE composites. This increase in the thermal conductivity of LDPE may be explained on the basis of a model based on particle size distribution. The coefficient of linear thermal expansion (CTE) of the samples has been measured by a thermo-mechanical analyser as a function of temperature. The experimental value of CTE is well explained by taking the inter-phase volume and interaction between the filler particles and matrix into account. The mechanical properties of LDPE/NiO composites show an improvement with NiO addition and are explained in the light of various models and correlations.