The dielectric constant (Ɛr =Ɛ'r – jƐ”r) and loss tangent (tan δ = Ɛ"/Ɛ') of different thicknesses of 70 % thermoplastic natural rubber - 30% magnetite (fe304) composite / Wan Nurfatin Kamilia Wan Mohd Rusdin

A thermoplastic natural rubber (TPNR) was prepared by melt-blending of
polypropylene (PP) and natural rubber (NR) in percentage weight ratio of 70:30
using an internal mixer. Samples of TPNR filled with same proportion of
magnetite powders were similarly prepared at a fixed TPNR (70% of the total
weight). The pure TPNR and different thickness of TPNR filled magnetite was
prepared by using hot press process. The dielectric constant and tangent loss of
sample with different thicknesses were studied. The thermogravimetric analysis
(TGA) was used to check the homogeneity of the filler dispersion in the matrix of
TPNR and vector network analysis used to study the dielectric constant and loss
tangent. In thermogravimetric analysis, the sample was confirmed homogenous
according to TGA result. The dielectric constant, E' and loss tangent, E"/E' were
studied by using vector analysis in frequency range 8GHz-12GHz. The values of
E' and E"/E' of the composites are almost comparable to each other in the
measured frequency region. For dielectric constant, the 2mm thickness TPNR
filled with magnetite has the highest reading which is 2.077019064 followed by
the TPNR filled magnetite 5mm is 1.498707921 and the pure TPNR is
1.371611802 in the frequency range 8GHz-12GHz. For loss tangent, TPNR filled
magnetite 2mm thickness has the lowest reading which is -0.033864351 followed
by the TPNR filled magnetite 5mm is -0.020930693 and the pure TPNR is 0.017549753
in the frequency range 8GHz-12GHz. The incorporation of pure
TPNR and the different thickness of TPNR filled magnetite has resulted
differences in dielectric constant, loss tangent and microwave properties of the
composites. These composites can be developed as an electromagnetic wave
absorber.