Comparison of optical properties and mechanical/electrical degradation of some low density polyethylene-and polypropylene-based polymer blends

Abstract

In this study, the optical properties as well as mechanical and electrical degradation of low-density polyethylene (LDPE)/polypropylene fiber (PP fiber) (10–50% PP fiber), polypropylene (PP)/PP fiber (10–50% PP fiber), and LDPE/diamond (0.1–3% diamond) blends, which are prepared by hot pressing method, with changing thicknesses ranging from 30 to 225 µm, are compared. The spectra, in the wavelength range 200–2500 nm, are examined. Based on optical absorption spectra obtained, Tauc graphs are plotted. Determined values of the direct optical energy gap (Edopt), the indirect optical energy gap (Eiopt), the width of the band (ΔE), and ultraviolet transmittance (TUV) are listed. The direct Edopt and indirect Eiopt values for organic blends are in the range of 3.10–3.17 eV and 1.52–2.99 eV; for inorganic blends they are 1.80–4.13 eV and 1.55–4.7 eV respectively. The electrical strength (e) and the mechanical tension (σ) have been investigated, and graphs (the dependence of the electrical life time log τe on e) are given. The experimental results are analyzed from the viewpoint of the validity of the thermofluctuation theory. LDPE and LDPE/0.5% diamond composite parameters consecutively changed: σ from 68 to 82 MPa, e from 60·106 to 85·106 V/m, mechanical lifetime τσ from 10 to 1.5·105 sec, electrical lifetime τe from 2· 103 to 2·105 sec, and structure-sensitive parameters γ and χ — from 1.48 to 1.18 (J)MPa/mole and from 0.97 to 0.70 (J)Vm−1/mole respectively. The values of mechanical and electrical durability were observed to increase by 20 and 41%, respectively, for LDPE/0.5% diamond composite.