The role of fibrillar elements in thermomechanical pulp

To get a better insight of the behaviour of fibre mass in refining, a micro scopic study on the structural morphology of fibre flocs discharged by a TM P process was initiated. It was observed that fibres are discharged in a fo rm of flocs which consist of smaller constituent flocs. The discharged floc s are predominantly of tadpole shape or in strand form, while the constitue nt flocs are principally strand-like. Fibres in the tail of a tadpole flee are aligned in parallel while those in the head are randomly oriented. Sphe rical aggregates are formed with fibre wall fragments and fibrillar element s. Excessive amount of fibrillar elements could reduce screening efficiency by increasing screen rejects, and adversely affect sheet formation. It is believed that both a rolling mode and along fibre length refining could occ ur.