Dielektrične i toplotne osobine kompozita na bazi polietilena niske gustine NaA zeolita

Abstract

U okviru rada na doktorskoj disertaciji sintetisani su uzorci kompozita polietilena niske gustine i NaA zeolita (LDPE/NaA) i analizirane njihove dielektrične i toplotne osobine. Razvijena je metoda za određivanje masenog udela i stepena disperzije zeolita u kompozitu, XRD i FTIR analizom. Izvršena je verifikacija dobijenih vrednosti za masene udele zeolita termogravimetrijskom analizom. Primenom skenirajuće elektronske mikroskopije ustanovljeno je da čestice zeolita u polimernoj matrici imaju kubičan oblik, kao i da su dobro dispergovane. Dielektrična spektroskopija uzoraka LDPE/NaA zeolita izvršena je u opsegu frekvencija od 20 Hz do 30 MHz, na sobnoj temperaturi. Ispitivan je uticaj masenog udela zeolita na realan i imaginaran deo dielektrične propustljivosti. Uočena su dva relaksacion pika na graficima frekvencijske zavisnosti imaginarnog dela dielektrične propustljivosti. Ustanovljeno je da je relaksacioni pik na nižim frekvencijama, koji se sa porastom masenog udela zeolita pomera ka nižim frekvencijama, posledica Maxwell-Wagner-Sillars-ove polarizacije. Drugi uočeni relaksacioni pik posledica je preskakanja slobodnih jona natrijuma sa jednog na drugo slobodno mesto unutar čestica zeolita. Analizom električne provodnosti LDPE/NaA zeolit kompozita ustanovljeno je da ona raste sa porastom masenog udela zeolita. Toplotna difuzivnost ispitivanih uzoraka, pomoću koje je odredjivana toplotna provodnost, analizirana je korišćenjem laserske impulsne metode. Dobijeni rezultati upoređeni su sa rezultatima dobijenim koriscenjem teorijskih modela opisanim u literaturi

In this doctoral dissertation, the samples of low-density polyethylene/NaA zeolite (LDPE/NaA) composites were synthesized and analyses of dielectric and thermal properties were conducted. The method for determination of weight fraction and the dispersion degree of zeolite in the LDPE/NaA zeolite composites by using XRD and FTIR analyses was established. The obtained data for the weight fraction of zeolite was verified by using thermogravimetric analyses. By scanning electron microscopy, it was established that the zeolite particles in the polymer matrix have a cubic shape and that they are well dispersed. Dielectric spectroscopy measurements are performed in the frequency range 20Hz-30MHz, at room temperature. The impact of weight fraction on both the real and the imaginary part of the dielectric constant was investigated. Two relaxation peaks of the imaginary parts of permittivity of LDPE/NaA zeolite composites are detected. It was found that the relaxation peak at lower frequencies, which shifts to lower frequencies with increasing zeolite mass fraction, is due to Maxwell-Wagner-Sillars polarization. The second relaxation peak is due to the hopping of free sodium ions from one free place to another within the zeolite particles. Analysis of the electrical conductivity of LDPE/NaA zeolites showed that it increases with an increase in the weight fraction of zeolite. The thermal diffusivity, by which the thermal conductivity was determined, was investigated using the laser flash method. The obtained results were compared with those obtained by using the theoretical model reported in the literature.