And:

The protective coatings may include a binder material like polymer (occasionally known as a matrix or silicone matrix) and may comprise particles embedded inside the binder. The particles may have high hardness to enhance the durability of these protective coatings.
This week the US Patent & Trademark Office released a patent application from Apple that relates to new protective coatings being added to Apple apparatus in the future that will protect against damage to home structures, transparent members associated with optical part windows and displays, and other device structures.
Better.
Patently Apple: