Structural characteristics of HDPE/CaCO3 polymer composites probed by positron annihilation

Abstract

The results of positron lifetime measurements as a function of volume fraction QV of CaCO, particles on the high density polyethylene/CaCO, (HDPE/CaCO,) polymer composites with and without addition of a coupling agent are presented. It is observed that, first, positronium (Ps) is formed and annihilates in the free-volume hole of HDPE and the free-volume concentration decreases with increasing @"; second, the positron lifetime T~ and its intensity I, are strongly affected by the structure of the interface layer between CaCO, particle and HDPE matrix. An interesting correlation between positron parameters and the tensile strength of the composites is found.

Comparison between the effects of alcohols and diols on polymethyl‐methacrylate and polyacrylamide with positron annihilation lifetime and electric conductivity measurements

“…A composite model for positron annihilation was proposed to account for the observed changes in the relative intensities with increasing amount of filler. Wang et al 3 measured the positron lifetime as a function of volume fraction of CaCO 3 particles on HDPE-CaCO 3 polymer composites with and without addition of a coupling agent. They found that the positron lifetime ( 2 ) and its intensity (I 2 ) are strongly affected by the structure of the interface layer between the CaCO 3 particle and HDPE matrix.…”

Light-cured dimethacrylate dental restorative composites under a prism of annihilating positrons

“…[14][15][16][17][18][19][20][21] Under such analysis (arranged as constraint-free decomposition [14][15][16][17][18][19][20] or partially-constrained decomposition fixing the shortest τ 1 lifetime 14,15,21 ), the 3 rd component with a long-lived lifetime τ 3 is ascribed to o-Ps annihilation in free-volume holes (voids), the 2 nd component with an intermediate lifetime τ 2 is due to free positron annihilation in interfacial free volumes or other defect states mainly in a solid phase, and the 1 st component with the shortest lifetime τ 1 is attributed to p-Ps self-annihilation conjugated with reduced e + annihilation from defect-free bulk state. [4][5][6] The lifetime-fixing fitting is preferred to overcome inadequacy in the resolving of the shortest component due to mixing different annihilation events (especially, when I 1 intensity occurs to be substantially greater than I 3 ).…”

“…This task can be solved due to multicomponent fitting of PAL spectra with 3 or 4 negative exponentials under unconstrained (free fitting components) or constrained (most often for some fixed fitting parameters, such as shortest positron lifetime maintained close to 0.125 ns) [14][15][16] decomposition procedures, and normalized component intensities (I = 3.4): (2) Positron annihilation lifetime spectra treatment algorithms…”

“…In case of stronger input from Ps decaying in the x3-term decomposed PAL spectrum (as for many nanocomposites 5,9,[14][15][16][17][18][19][20][21] ), the e + -trapping can be defined in terms of a simple trapping model assuming 2 additive inputs arise from trapped e + and decayed o-Ps states. 22 This model with 2 additive e + -trapping defects with κ d1 and κ d2 annihilation rates defined as …”

“…[24][25][26] Within a x4-fitting route assuming fixed τ 1 value, the 4 th component was ascribed to o-Ps annihilation in the main part of the polymer matrix, while the 3 rd was explained as arising from o-Ps annihilation in the filler-matrix interphase. With re- [16][17][18][19] Recently, some current authors have shown that x4-fitting assuming fixed shortest lifetime (τ 1 = 0.125 ns) was also favorable for dimethacrylate DRC subjected to long-term aging, which were initially characterized by x3-decomposed best-fitted PAL spectra. 20,27 The origin of the additional component in o-Ps decaying in these polymer/filler DRC was not clarified unambiguously, while a version on stress-inducing destruction through growing inner and surface cracks seems quite plausible.…”