By Clare Edwards, Updated March 24, 2022
Opaque plastics are materials that block all light, rendering them completely non‑transparent. Some polymers naturally exhibit this property due to their molecular structure, while others are rendered opaque through dyes or surface treatments.
Plastics—synthetic or semi‑synthetic polymers—are fabricated from petroleum derivatives or, increasingly, renewable feedstocks. They can be molded, extruded, or fabricated into fibers and films, and are employed in coatings, paints, and varnishes. In contrast to translucent plastics, which allow partial light transmission, and transparent plastics, which transmit all light, opaque plastics prevent light passage entirely.
Common opaque polymers include PEEK™ (Polyether Ether Ketone), a high‑strength, high‑temperature material that replaces metal components in aerospace and medical devices; Polyphenylene Sulfide (PPS), a heat‑resistant plastic used in automotive and electrical applications; and Polypropylene (PP), a versatile polymer employed across household and medical sectors.
Casein plastic—one of the earliest opaque polymers—was derived from milk protein and used in jewelry and button manufacturing. The material can be recreated at home by reacting milk with vinegar, demonstrating its accessible chemistry.
