In-situ modified cellulose nanocrystals as water droplet stabilizer in polystyrene beads targeted for water expanded foam

Synthesis of polystyrene beads containing well-dispersed water microdroplets via surfactant free Pickering emulsion polymerization in water-in-oil emulsion followed by suspension method. The water microdroplets with a diameter of 8-15 mu m were stabilized using in situ modified cellulose nanocrystals (CNCs). The morphological investigation revealed that the water droplets were surrounded by a dense layer of the modified CNCs. The thermogravimetric analysis confirmed two types of water inside the beads; free water and bound water with release temperatures of 102 and 118 degrees C, respectively. The bound water was responsible for higher water preservation ability and therefore long shelf-life of the beads, which over 75% of the initial entrapped water was kept 7 months after synthesis. The beads can be expanded at an optimum temperature of 130 degrees C due to water vapour pressure developed inside the beads. The best max expansion ratio of around 15 was found for the beads included 5.45 wt% of water. During the expansion process, the CNCs were located in the cell wall to reinforce it from rupturing. Eventually, we report a new type of water expanded polystyrene beads synthesized by the use of CNCs, named CNCWEPS, with good expandability and extended shelf-life.