Effect of aluminum hydroxide on low-molecular-weight siloxane distribution and microstructure of high-temperature vulcanized silicone rubber.

ABSTRACT This paper investigates the effect of aluminum hydroxide (ATH) content on the free volume and surface recovery property of polydimethylsiloxane (PDMS)-based silicone rubber containing low-molecular-weight siloxanes. With increasing ratio of ATH up to 43.1 wt %, the concentration of cyclic siloxanes ( D _n = [(CH₃)₂SiO] _n, n = 4-12) in the PDMS matrix increases remarkably, indicative of a spacing effect of ATH particles on the crosslinking of PDMS chains. When more ATH is added, the concentration of D₄-D₁₂ began to decrease. PDMS network variation is verified by free volume size corresponding to τ₃ in positron annihilation lifetime spectroscopy. The o-Ps intensity decreases linearly with ATH content. Data obtained from X-ray photoelectron spectroscopy suggest the surface recovery property is weakened by ATH. This process is dominated by the amount of free volume holes in the sample. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45803. [ABSTRACT FROM AUTHOR]