Electron beam irradiation of low-density polyethylene filled with metal hydroxides for wire and cable applications

The effects of electron beam irradiation for crosslinking of polymers used for wire and cable insulations are still being researched. In this research, the influence of electron beam irradiation on the different blends of low-density polyethylene (LDPE) filled with aluminum trihydrate and magnesium hydroxide (ATH, MH) were studied. It was revealed by melt flow index, tensile strength, and elongation at break tests that addition of MH to LDPE increases the adhesion forces inside polymer matrices more efficient than similar ATH/LDPE compounds. Field emission scanning electron microscopy test showed that MH is platy in structure and more homogenous mixed than ATH with LDPE. The results on thermogravimetric analysis and limiting oxygen index tests revealed that the thermal stability and incombustibility properties of MH blends are more efficient than similar ATH blends. Meanwhile, it was observed by smoke density test that MH blends produce the lowest smoke density compared with virgin LDPE and similar ATH blends. It was also observed that increasing irradiation by electron beam had impressive affections on the density, gel content, and mechanical properties for all the polymeric samples in this study

Dielectrical, optical, and structural characterization of TiO2/PVA nanocomposite films for dielectric applications

In this study, titanium dioxide/poly(vinyl) alcohol (TiO2/PVA) nanocomposite thin films were prepared by a simple spin-coating method for dielectric applications. Structural, morphological, optical, and dielectric properties of samples were analyzed by XRD, SEM, AFM, UV-VIS, and dielectric measurements. The effect of TiO2 nanoparticles on these properties was investigated. It was found that TiO2 nanoparticles lead to increase the crystallinity of nanocomposites. As TiO2 content in the composite structure increases, while average transmittance values decrease, reflectance values increase. The dielectric parameters such as real and imaginary part of complex permittivity which are related to the stored energy and the dissipation (or loss) of energy were significantly affected by the presence of TiO2 nanoparticles. In addition, alternating current (A.C.) conductivity increased with increasing applied frequency. The A.C. conductivity also confirmed that all the samples exhibited the insulator behavior and obeyed the universal power law

Influence of branching density on the cross-linkability of ethylene-octene copolymers

Ethylene-octene copolymers (EOCs) with two different octene contents (20 and 35 wt%) and the same melt flow index (3 g per 10 min) were cross-linked using various levels (0.3, 0.5 and 0.7 wt%) of dicumyl peroxide at different temperatures. Cross-linking and degradation were analyzed by rubber process analyzer (RPA) within a temperature range of 150-200 °C. The highest s′ max (maximum elastic torque) and the lowest tan(delta) were found for EOC-20 with low-octene content at all cross-linking temperatures. Lower peroxide efficiency was observed in the case of the high-octene copolymer. Increased degradation was observed with increasing cross-linking temperature. High-octene EOC was found to be more vulnerable to degradation. According to dynamic mechanical analysis, the storage modulus (M′) and the glass transition temperature (T g) obtained from the tan(delta) peaks were found to decrease with increasing octene content. The differential scanning calorimetry (DSC) results show that the octene content has an inverse effect on the crystallinity (X) and melting point (T m) - due to the reduction in the average number of consecutive ethylene units. Creep testing at 150 °C confirmed the cross-linkability results obtained by RPA and the gel content analyses. Increased β-scission due to high numbers of tertiary carbon atoms present in the chain has resulted in the poorer cross-linking and inferior properties of high-octene EOC. © 2013 The Society of Polymer Science, Japan (SPSJ) All rights reserved