The laboratory internal mixer is a small‑scale closed mixing equipment widely used in rubber, plastic, polymer composite and new‑material research laboratories. It is mainly applied for batch mixing, plasticization and homogenization of raw materials under controlled temperature, rotation speed and pressure conditions. Equipped with a closed mixing chamber, two counter‑rotating rotors, temperature control system and pressing ram device, it can provide strong shearing and kneading force for materials. Compared with open mills, its closed structure effectively prevents material splashing and volatile loss, ensuring stable and repeatable experimental data.