Preparation and characterization of Santa Barbara Amorphous-15 particles functionalized with mercaptopropyl groups and of their composites with poly(lactic acid)

Santa Barbara Amorphous-15 (SBA-15) particles functionalized with mercaptopropyl groups (named as SBASH) have been prepared by a synthetic one-pot approach, and then have been incorporated into poly(lactic acid) (PLA), comparing their characteristics with those shown by composites attained with neat SBA-15 (PLASBA). The silica including the mercaptopropyl groups exhibits a certain loss of regularity because of its functionalization, although displays a better interaction with PLA than the pristine SBA-15 particles in the resulting materials. These composites (PLASBASH and PLASBA) also show a thermal stability slightly higher than neat PLA. An important nucleation effect of SBASH silica in the crystallization of PLA has been deduced from cooling experiments as well as from the cold crystallization in heating runs and from the degree of crystallinity reached. Small Angle X-ray Scattering (SAXS) profiles show that the PLA long spacings are rather similar for the different composites and the neat PLA. Thus, crystal size is rather similar in all samples. Microhardness values show an evident effect of reinforcement in all the composites compared with that shown by neat PLA. Nevertheless, the increase in rigidity is smaller in the biobased PLASBASH composites, those containing the modified silica, than in the PLASBA materials with the pristine SBA-15 particles.