Mechanical and electrical properties of Bijoypur white clay polypropylene composites

Abstract

l")ta~lic polypropylene (iPPJ with Bijoyp'" white elay (BWC) as filler (il'l'-BWC) were fabri~alcd by a double- molding tecbnique. Thc compo,ile, wcrc cxamined by asscssing ,urfacc morphology, mcchanical properties, thermal properlics, direct currenl (DC) and alternaling current (AC) electrical properlies. Scanning eleclron mi~rographs show thaI thc surtace of lhe iPP sample is ,moolh and the surfaces of compo,il~, become slightly rough and pale c"lo" Thc impro,'~menl of some mechanical propel1ie; of lhc BWe filled iPP-BWe compositGs sllch as Young',1 modulus and microhardness were "h,erved whereas the e1ongatioll at hreak and tensile strellglh were decrea..ed with the increa,e oj" BWC. '1he thermal behavior ofiPP-BWC composites wa, analyzed by TGA and DT A. It is ,een tliat the melting lemperature (1"m)does llot show any noticeable change bllt the degradation temperature (T oj increases with thc increase of filler. Analysis of TCiA ,how; that the neat if'l' sample is seen to be thennally stable up to 416°C whereas the 30 wl% BWC-Ioaded sample shows the maximum thennal stability at ahout 450 "C. The current -voltage relationship ofthc composites were studied in the vollage rangc from II to 120 V al ,Iiflerent temperature,. It is observed that ~lLrr~nt"voltage curve' Ihow ohmtc behavior in thc lower voltage region. Thc DC conductivily ill~rcascs with illcrca,ing filler content and lempcmture. The acti,alion cncrgy of all lhe s~mples has high~r value in high temperature region than those at low tempcmture regioll , '1he dielectri~ ~onstant measured over a freyueocy range of 1000 117-1 MHz alld ill thc temperat\lre range 01'299-373 K showed dependcnce on ti"cquency, temperalure and conccntration of IJWC in the ~ompositcs. It is obsel"\'ed thaI dielcelric constant decrca,es with freqllency_ The AC condllctivity increases with frequency and temperature, A ,ignificant change of dielectri~ constant is shown ill the composites with the increase of filler loading. The activation energy ealcillated from the plot, bctween AC conductivity and lempcrature ,how, that it is low at low temperature r~gioll and high at higher temperature region.