Transparent and flame-retardant hybrid protective coating with high surface hardness, yet foldability

With the rapid development of flexible OLED display technology, Poly(ethylene terephthalate) (PET) has also received extensive attention as a protective film. However, it is still a challenge to endow PET with abrasion resistance and flame retardancy while maintaining transparency and flexibility. Here, we developed an epoxy-amine curing hybrid coating based on phosphorus-containing organic amine (DPNP) and ladderlike epoxy-oligosiloxane (AEOS). The ratio of DPNP and AEOS was changed to study the effect of phosphorus and silicon content on the performance of hybrid coatings. All the coatings were transparent. The PET/AE-DP3 sample achieved the limiting oxygen index of 28 % and exhibited self-extinguishing in vertical burning test. In microscale combustion calorimeter (MCC) test, the minimum peak heat release rate was 236.4 W/g with a reduction of 29.5 %, compared with pure PET. In addition, the AE-DP3 coating could withstand the abrasion of copper mesh and cheese cotton with a pencil hardness of 8H, and showed good foldability with a bending diameter of 5 mm. At the same time, the coating exhibited satisfactory adhesion without plasma treatment and good UV resistance. These results indicated the hybrid coating overcome the inherited weakness of PET film such as poor scratch-resistance and flammability, promoting the wider application of PET.