Assignment2: Writing an introduction

SYNTHESIS OF POLYBUTADIENE-SILICA NANOPARTICLES VIA DIFFERENTIAL MICROEMULSION POLYMERIZATION

by

Thanyaporn Tancharernrat

Stage 1:   Polymer nanocomposites have drawn a great deal of interest in recent years because these materials possess high potential to achieve great property improvement by adding a small amount of nanofillers in the polymer matrices. The combination of nanoscale inorganic species (filler) with organic polymers has highly efficiency for future applications. These materials are widely used in automotive, aerospace, construction, and electronic industries because they provide improved mechanical (e.g., stiffness, strength), electrical, thermal and physical properties over pure polymers (Chen & Feng, 2009). One of the most common inorganic systems is nanosilica that has many functional properties and effective reinforcement. It was widely used in colloidal products, paints, catalysis, chromatographic separation, rubber and plastic reinforcement due to silica is chemically inert and optically transparent (Zhang et al., 2004; Sun et al., 2005).

Stage 2:   Many previous studies have reported on improved properties of polymer filled with nanosilica. According to Zhong et al. (2014), silica-supported 2-mercaptobenzimidazole (SiO₂-s-MB) had high antioxidative efficiency and low color contamination, migration and volatility could be used as an environmentally friendly rubber antioxidant to improve thermal oxidative stability of styrene butadiene rubber (SBR) composite. Guan et al. (2011) reported the hydrogenated nitrile butadiene rubber (HNBR) composites filled with fumed silica was prepared to improve their ablation performance and thermal stability. According to Kongsinlark et al. (2012), polyisoprene (PIP)–SiO₂ nanoparticles produced with a size of 20–60 nm and have been used as an effective nano-filler in natural rubber (NR) latex. The NR filled with PIP-SiO₂ clearly presented an improvement in the storage modulus, tensile strength, modulus at 300% strain and anti-aging properties. In addition, Chuayjuljit et al. (2010) reported that hybrid nanoparticles of polystyrene (PS)-silica were prepared by grafting polymerization and the resulting particles were used as a filler in the NR latex resulting in improved tensile strength, modulus at 300% strain and flammability of NR at low PS-silica loading of 3-9 parts per hundred rubber (phr).

Stage 3:   However, the difficulties as an access to well dispersed silica in rubber matrix are due to  the large quantity of hydroxyl groups on the surface of the nanosilica and the high surface energy and porality, resulting in inferior compatibility and less stability between the rubber matrix and nanosilica; thus severe agglomeration and weak rubber-filler interaction occured (Kim et al., 2010). The great advantage provided by nanosilica can only be achieved if the particles are finely dispersed in the polymer matrix. Encapsulation is regarded as being of major importance since it offers interesting potential applications in different fields. Thus, encapsulation of nanosilica with polymer can improve the compatibility of nanosilica in the rubber matrix resulting in an improvement of filler dispersion and performance of the rubber composite.

Stage 4&5:  In this research work, new approach of the differential microemulsion polymerization method is applied to polybutadiene (PB)-silica. To obtain the core-shell morphology, the composite nanoparticle is designed to have core nanosilica and shell polybutadiene. These composites are desired not only to obtain much smaller diameter (smaller than 50 nm) but also to exhibit a narrow size distribution and thus resulting in reduced nanosilica aggregation at a low level of surfactant. The influence of silica loading, surfactant concentration, monomer to water ratio and initiator concentration on monomer conversion, grafting efficiency, silica encapsulation efficiency and particle size was also investigated. Thus, this novel PB-SiO₂ nanocomposite can be used as a nanoreinforcing filler and thermal and ozone stabilizer for NR composites.