Method of preparing a transparent polumer material comprising a thermoplastic polycarbonate and mineral nanoparticles

A method of preparing a transparent polymer material, the method comprising the following steps:

• i) mixing mineral nanoparticles selected from the group consisting of nanoparticles of alkaline-earth metal carbonates and alkaline-earth metal sulfates and a composition A including at least one thermoplastic polymer in the molten state selected from the group consisting of polycarbonate (PC), polystyrene (PS) and polymethyl methacrylate (PMMA) in order to obtain a master-batch, the mixture of step i) including at least 25% and at most 75% by weight of said mineral nanoparticles;
• and
• ii) mixing the master-batch obtained in step i) with a composition B comprising a transparent thermoplastic polycarbonate matrix (PCm) in the molten state, to obtain the transparent polymer material including at most 10% by weight of said mineral nanoparticles, wherein said addition of said master batch including said nanoparticles is added in an amount, concentration and manner to said transparent thermoplastic polycarbonate matrix (PCm) such that it results in said transparent thermoplastic polycarbonate matrix having no more than a 25% reduction in light transmission percentage relative to a reference material of a transparent thermoplastic polycarbonate matrix (PCm) having no master batch included, such that there is no significant loss of contrast to an object viewed therethrough
• wherein said polymer material has a light transmission loss at 650 nm, compared with a reference material obtained solely from the thermoplastic polycarbonate matrix (PCm), of at most 25%, and
• wherein said polymer material has a molecular weight loss, compared with a reference material obtained solely from the transparent thermoplastic polycarbonate matrix (PCm), of at most 30%.