Dielectric Behaviour of Maleic Anhydride Grafted Polypropylene (MA-g-PP) Modified Sisal Fibre Reinforced PP Composites

Sisal fiber reinforced polypropylene composites having different weight percent sisal fiber with and without Maleic anhydride grafted polypropylene (MAgPP) have been developed by melt mixing method. Dielectric properties such as ε′, tanδ, and a.c. conductivity of sisal fibers reinforced polypropylene composites with and without MAgPP have been determined. Dielectric constant, tan δ, and a.c. conductivity increases with increase in temperature at different frequencies. 10 wt% sisal fiber addition to PP gave two tanδ peaks. First peak appears at 90°C, which is similar to 5 wt% sisal fiber PP composite. Another peak appears at 105°C, which is due to the sisal fiber. MAgPP addition to sisal-PP composite suppresses the first 90°C peak. There is a peak that appears at 123°C, 126°C, 135°C, and 140°C in 1 phr (parts per hundred) MAgPP added sisal-PP composite. On adding 2 phr maleic anhydride grafted polypropylene (MagPP) to 5wt% sisal-PP composite the peak appears at 125°C, 128°C, 132°C, and 135°C. Peak is shifted to higher temperature side due to the improved bonding between the sisal fiber and PP matrix. The relaxation time values calculated at 70°C for sisal fiber/PP composites with and without MAgPP show that addition of sisal fiber decreases the relaxation time due to shortening of PP chains. Addition of low concentration of coupling agent increased the relaxation time and further increase of MAgPP concentration decreased the relaxation time value, increase is due to increased bonding between sisal fiber and polypropylene chains. Better bonding between fiber and polypropylene would have created hindrance in the movement of the dipoles, which would have increased the relaxation tim