Melting mechanisms of single-component polymers in co-rotating twin-screw kneading blocks through visual and microscopic analysis

Visual and microscopy analysis was performed on solid carcasses collected from the split-barrel Twin-Screw Mixing Element Evaluator (TSMEE) (1) to study melting phenomena and mechanisms of single-component polymers in twin-screw kneading blocks. The results were interpreted in terms of dissipative phenomena such as interparticle frictional heat generation, irreversible deformation and break of the particulate solids and viscous energy dissipation of the resulting melt or melt solid mixtures. Simple estimates of the thermal energy generated by each of the above phenomena were carried out for a number of polymer systems of different particulate size and solid and melt properties. The contributions of each dissipative phenomenon on the healing of Polypropylene (PP) powder or pellets, LDPE and PET were experimentally evaluated. To better understand the effect of the particulate size distribution on the melting of PP powders, batch melting experiments woe conducted with a regular Brabender batch mixer at the Polymer Processing Institute and with the glass end plate fitted apparatus of Dr. Chi-Kai Shih at his DuPont Laboratories.