Waterborne polystyrene-polybutadiene nanoparticles by miniemulsion polymerization

RONCO, LUDMILA I.; MINARI, ROQUE J.; VEGA, JORGE R.; MEIRA, GREGORIO R.; GUGLIOTTA, LUIS M.

Pisa

Congreso; European polymer congress 2013; 2013

European polymer federation

Miniemulsion (ME) polymerization represents an alternative to formulate waterborne nanocompasites on the basis of a synergetic combination of different polymeric materials [1]. In this work, the ME polymerization of styrene (St) in the presence of 5% wbop (weight based on organic phase) of polybutadiene (PB) is investigated, with the aim of synthesizing waterborne polystyrene (PS)-PB nanocomposites, with the potential application as reinforced materials. PS-PB latexes of 20-50% solids content were synthetized using as initiators potassium persulfate (KPS) or benzoyl peroxide (BPO). After 2 hr of reaction, the final conversions observed with KPS (90-95%) were higher than those obtained with BPO (85-89%). On the other hand, BPO promoted droplets nucleation and grafting of PS onto the PB chain due to BPO produced radicals (inside the droplets) which exhibited limited water solubility. Particle morphology was also affected by the employed initiator. With KPS most of the particles were homogeneous, i.e. formed by secondary nucleation; while some of the particles presented a 3-phase internal morphology, with a PS shell, an intermediate PB-enriched phase, and a partially polymerized PS core (Figure 1.a). In the experiments with BPO, larger occluded rubber particles were observed, with multiple PS occlusions (Figure 1.b), as the ?salami? like particle morphologies observed in the synthesis of high impact PS, but at a nanometric scale.