In situ synthesis of ABS containing hydrophobic silica nanoparticles and their effects on mechanical properties

In this study, in situ synthesis of acrylonitrile-butadiene-styrene rubber particles containing hydrophobic silica nanoparticles (HDTMS-silica) was carried out. Firstly, three of HDTMS-silicas (HDTMS-silica1, HDTMS-silica2, and HDTMS-silica3) were prepared by silanization of SiO2 nanoparticle with hexadecyltrimethoxysilane (HDTMS : SiO2 wt ratios of 1 : 1, 2 : 1, and 3 : 1) in an emulsion system. Then, HDTMS-silica/styrene and acrylonitrile mixture was fed into a polybutadiene latex reactor. Following that, graft copolymerization was carried out using persulfate initiator at temperature of 65 °C for 3.5 h. Thus obtained Acrylonitrile-butadiene-styrene rubber containing HDTMS-silica was melt extruded with styrene-acrylonitrile (SAN) to prepare ABS nanocomposite compound. Mechanical properties of ABS nanocomposite compounds were evaluated. It was found that all of HDTMS : SiO2 wt ratios produced hydrophobic SiO2 nanoparticles exhibiting good dispersibility in toluene test. In fact, 3 : 1 HDTMS : SiO2 showed the complete hydrophobicity modification, judged by the absence of silanol absorption band. However, the optimum mechanical properties were achieved at 2 wt% loading of 2 : 1 HDTMS: SiO2. Below 2 : 1 ratio, the HDTMS ratio was not enough to obtain the fully hydrophobic surface modification. Above 2 : 1 ratio, the excessive HDTMS ratio led to a decrease in SiO2 content judged by Si EDX mapping, causing a gradual decrease in its energy absorption and reinforcement performance. In case of 2 : 1 HDTMS : SiO2, optimum mechanical properties were achievable at 2 wt% HDTMS-SiO2 loading, resulting from the optimum dispersibility of HDTMS-SiO2 nanoparticles. Further increase in HDTMS-SiO2 loading resulted in a reverse effect due to agglomeration problem.