Expanded polystyrene waste valorization as a hydrophobic coating II: packaging application

The application of the expanded polystyrene (EPS) waste to the functional material is still a challenge. The hydrophobic property of polystyrene has a potential to create a superhydrophobic surface. Here, we use expanded polystyrene waste to coat surfaces in two different ways—spray coating and dip coating—to produce superhydrophobic surfaces for food packaging. The ZnO was employed to make the surface rougher. However, the combination of ZnO and EPS waste produces only a hydrophobic surface. For spray coating and dip coating, the maximum water contact angle is 119° and 125° respectively. The scanning electron microscope (SEM) picture reveals many holes that increase the surface's roughness. The hydrophobic surface significantly cuts down on cleaning time. According to the food packaging parameter test mandated by the Indonesian Food and Drug Administration (BPOM) (BPOM regulation No. 20, 2019), the coating complies with heavy metals and ethanol stimulant migration testing requirements for food packaging. However, the migration condition in acetic acid stimulant surpasses the maximum standard. The total migration in 3% acetic acid stimulant (40°C for 10 days) is 22.95 mg/dm² while the maximum value is 10 mg/dm².