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 = [(CH 3 ) 2 SiO] 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 D 4 –D 12 began to decrease. PDMS network variation is verified by free volume size corresponding to τ 3 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.