Effect of aluminum hydroxide (ATH) content on free volumes and water barrier property of silicone rubber

In this paper, the free volumes and water barrier property of silicone rubber with different weight ratios of aluminum hydroxide (ATH) were studied by positron annihilation lifetime spectroscopy (PALS) and electrochemical impedance spectroscopy (EIS). PALS data indicate that the o-Ps intensity (I3) decreased linearly as a function of the ATH content in silicone rubber. It was found that o-Ps are mainly formed and annihilated in the silicone rubber matrix, polydimethylsiloxane (PDMS), and are not formed in the ATH particles. The value of I3 can thus serve as a PDMS composition characteristic in silicone rubber. When the content of ATH is more than 45.3 wt.% (I3 ∼ 9.34%), the ATH particles percolate in the bulk of silicone rubber, resulting the failure of sample’s water barrier property.