Phase separation effects in processing of glass‐bead‐ and glass‐fiber‐filled thermoplastics by injection molding

Abstract

Abstract Dumbbell specimens, tubular specimens, spirals, and rectangular boxes were used to study phase separation effects occurring in injection molding of glass‐bead‐ and glass‐fiber‐filled thermoplastics. The weight specific separation effects were more pronounced with beads than with fibers, and they increase with increasing bead diameter. The weight distribution is further influenced by mold geometry, filler concentration, matrix material, and processing conditions. If the use of fillers, which promote inhomogeneity, is unavoidable, it is possible to improve the distribution of the rigid phase by a favorable choice of injection speed and melt temperature. Analysis which was made with dumbbell specimens and spirals showed no significant measurable size specific separation effects. With the theories available at present a qualitative interpretation of the origin of the observed separation phenomena is feasible.