I. What is an internal mixer?

1. Internal mixers are crucial equipment for rubber plastication and mixing, with their working principles and structure revealed in detail.

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  • An internal mixer is a machine that uses a pair of rotors with specific shapes that rotate relatively to each other. Under adjustable temperature and pressure in a closed environment, it intermittently performs plastication and mixing of polymer materials. It mainly consists of a mixing chamber, rotors, rotor sealing device, feeding and pressing device, discharging device, transmission device, and base.
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  • Working principle: When the internal mixer operates, the two rotors rotate relatively, clamping the material from the feed port and bringing it into the roll gap. The material is squeezed and sheared by the rotors, and after passing through the roll gap, it hits the tip of the lower plug and is divided into two parts. These parts then flow back to the upper part of the roll gap along the gaps between the front and rear chamber walls and the rotors. During the rotation around the rotors, the material is subjected to shearing and friction everywhere, causing the temperature of the rubber to rise sharply, reducing its viscosity, and increasing the wettability of the rubber on the surface of the compounding agent, allowing the rubber and compounding agent to fully contact. The compounding agent lumps pass through the gap between the rotors, the gap between the rotors and the upper and lower plugs, and the gap in the inner wall of the mixing chamber along with the rubber, being sheared and broken down, and surrounded by the stretched and deformed rubber, remaining in a stable broken state. At the same time, the protrusions on the rotor cause the rubber to move axially along the rotor, playing a mixing role and ensuring that the compounding agent is evenly mixed in the rubber.

2. A closed-type rubber mixing machine, also known as an internal mixer, plays a key role in rubber processing.

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  • Since the emergence of the truly meaningful Banbury internal mixer in 1916, the power of the internal mixer has gradually been recognized. It exhibits a series of superior characteristics compared to open mills in the rubber mixing process, such as large mixing capacity, short time, high production efficiency; better overcoming dust flying, reducing the loss of compounding agents, improving product quality and working environment; safe and convenient operation, reducing labor intensity; and facilitating mechanical and automated operation. Therefore, the internal mixer remains a typical and important equipment in plastication and mixing, and continues to develop and improve.