THE INTERPARTICULATE FRICTION BEHAVIOR OF ACETAL COPOLYMER PELLETS WITH BILOBAL AND TRILOBAL CROSS-SECTIONS

The interparticulate friction coefficient has been measured for a range of pellet cross-sections. This measurement is postulated as representing the integrity of the solid bed in plasticating extrusion, reciprocating-screw injection molding and extrusion blow molding. The value of the interparticulate friction coefficient has been found to be consistently greater for profiled pellet cross-sections such as bilobal and trilobal than for conventional pellets with circular cross-sections. It is postulated that this result means that solids beds formed from pellets with profiled cross-sections are less likely to fracture, or break-up, than are solids beds formed with conventional pellets, during plasticating extrusion, reciprocating-screw injection molding and extrusion blow molding. It is further postulated that this will result in surge inhibition, and allow the manufacturing units to run faster with fewer operational problems. The effects of normal load, pellet geometry, polymer molecular weight and agitation of the bed are also presented. In addition to the measurement of the interparticulate friction coefficients, the manufacturing procedures for profiled pellets are explained.