Novel sintering behavior of polystyrene nano-latex particles in filming process

Filming process of polystyrene nano-latex (NPS) particles was studied by a combination of various methods. For a constant annealing time of 1 h, the AFM images showed that the deformation and sintering temperatures for NPS particles were ca. 90°C and 100°C respectively. In spin-lattice relaxation measurements of solid state NMR, it is found that T_1L, T_1S and I_1I/I₀ increased significantly after annealing at 90°C and above. DSC results showed that there was an exothermic peak near T_g after annealing for 1 h at the selected temperatures below 95°C; otherwise, the exothermic peak disappeared after annealing at 100°C or above. The apparent density of NPS increased suddenly in the temperature range. The results implied that the macromolecules in NPS particles are in a confined state with higher conformational energy and less cohensional interactions which are the drive force for the sintering at a lower temperature compared with the multichain PS particles and the bulk polymer.