Effect of C₈mimPF₆ on miniemulsion polymerization for application in new latex coating products

Abstract

C8mimPF6, as a type of room temperature ionic liquid (RTIL) with non-volatility and a low melting point, may replace conventional coalescing agents in latex coatings, thus preventing volatile organic compound (VOC) emissions caused by coalescing agents. In this study, systematic investigations on the effect of various factors including initiator type, initiator concentration, temperature and C8mimPF6 concentration on the conversion of latex and droplet/particle size of a miniemulsion during polymerization have been conducted. The presence of C8mimPF6 has shown to have a marked effect on the reaction rate. Such an effect strongly depends on the type of initiator being used. For polymerization initiated by 2,2-azobis (isobutyronitrile) (AIBN), C8mimPF6 had a promoting effect on the reaction rate at low concentrations, but this effect might be reversed upon certain C8mimPF6 concentrations, e.g. 10 wt%. While initiated by H2O2/Vc, this promoting effect faded even at low C8mimPF6 concentrations. The different limiting factors, which determine the reaction rate with different types of initiator, may contribute to the results. For reactions initiated by hydrophobic AIBN, the reaction was dominated by kinetics. The presence of C8mimPF6 may cause an enhanced chain propagation rate and reduced chain termination rate, which may further contribute to the increase in reaction rate at lower concentrations of C8mimPF6. With hydrophilic H2O2/Vc, the resistance for the transfer of radicals into a droplet/particle might be increased significantly with increasing C8mimPF6 concentration due to a tighter interfacial structure at lower concentrations of C8mimPF6. Thus, such transfer of radicals may become a limiting step whilst the presence of C8mimPF6 increases the transfer resistance on radicals resulting in a decrease in reaction rate. The reaction temperature, which is related to the decomposition temperature of the initiator being used, was another factor affecting the conversion of latex and the size of latex particles. A higher temperature e.g. 50 °C promotes the coalescence of droplets/particles, and hence produces larger latex particles. In the presence of C8mimPF6, the reaction temperature could be significantly reduced to as low as 40 °C, which prevents phase separation. The final particle size depends on the nucleation mechanism as well as the coalescence of droplets/particles during polymerization.

Synthesis and Characterization of PolyHIPE-Gellan Gum Material with Tunable Macroporosity for Tissue Engineering Applications

“…As the temperature increases, the viscosity of the gel and continuous phase decreases, allowing water droplets to merge, resulting in larger pores until AIBN efficiently initiates and decomposes at 70 °C. A study conducted by Hu et al showed that AIBN begins decomposition once the system temperature reaches 40 °C and above . In addition, elevated temperatures can accelerate the degradation and viscosity reduction of Span 80 which may weaken the interfacial film formed by Span 80 around the water droplets, leading to droplet coalescence or fusion.…”

“…A study conducted by Hu et al showed that AIBN begins decomposition once the system temperature reaches 40 °C and above. 31 In addition, elevated temperatures can accelerate the degradation and viscosity reduction of Span 80 which may weaken the interfacial film formed by Span 80 around the water droplets, leading to droplet coalescence or fusion. Therefore, the transition from HIPEs to polyHIPEs also facilitated a further increase in voids.…”

A perspective on liquid salts for energy and materials

“…24 The thermal diffusivity of various molten carbonate electrolytes has also been determined as a function of temperature using a novel laser ash system. 25 High temperature 35 Cl NMR has been utilised to probe changes in local structure on dissolving the model compound CeCl 3 in LiCl. 26 Coordination can also be probed by techniques such as EXAFS, and molecular dynamic simulations provide highly complementary information to such experimental measurements on coordination chemistry of dissolved lanthanides or actinides.…”

“…There are many applications of ionic liquids and molten salts that may come to fruition in the near future. For ionic liquids, examples include use in paints to reduce volatile organic compounds 35 and as a solvent in 3D ink jet printing. 36 Molten salt electrochemistry also nds many important applications such as electrorening of Neodymium, which is so important in wind turbine magnets, and in molten LiF electrolytes.…”

Characterization of Absorption Performance for Gaseous Acetone with Ionic Liquid Solutions

“…However, due to the low solubility of ILs in DGBE, a third component is needed to adjust solubility and uniformity of the absorbents. The addition of oils allows for keeping the DGBE‐ILs system from stratification . Taking both absorption ability and security into account, absorbents composed by DGBE, ILs, and paraffin oil may be suitable for the removal of VOCs such as acetone.…”