Performance analysis of solid‐state shear milling of plastic particles

Abstract The paper presents an analysis of plastic particles flow and breakage in a solid‐state shear mill (S3M). This mill resembles the traditional stone mill used for flour milling. Particle flow and their breakage are modeled as being the result of the work done on the surface of the particles as they are compressed, sheared, and cut between the rotating disc and the stationary normally loaded disc. The resulting equations give the fractions milled, x w,d , and size reduction S r in terms of the applied load f , the number of passes, n p , through the mill, and the disc rotational speed, N . The model equations were fitted against a wide range of S3M data of plastic particles, plastic particles with grinding additives, and mixed waste plastic particles. A single parameter function ( fn p / N ) Φ was found to control size reduction, with the exponent Φ distinguishing the effects of the feed nature and composition. Highlights Solid state shear milling provides intense 3D scissor size reduction. In the S3M the particles follow a long spiral path. Simple particle milling model based on work done on the particles surfaces. The model combines load f , number of passes n p and rotational speed N . A single dimensionless number was found to control size reduction