FRACTURE BEHAVIOR OF A POLYPROPYLENE INJECTION MOLDING WITH MELD LINE

RUEDA FEDERICO; FRONTINI PATRICIA; QUINTANA MARÍA CAMILA

Encuentro; 34 encuentro del grupo español de fractura; 2017

Weld lines in polymeric injection molded parts occur wherever two or more melt fronts meet. They cause reduced mechanical properties and visual defects due to poor intermolecular entanglement, molecular orientation induced by the fountain flow, and the stress concentration effect of surface V-notch. Although the effect of weld line on the strength of injection moldings can be easily evaluated in specimens in which two flow fronts collide head-on at its center in the final stage of the filling phase, the effect on the fracture behavior in practical injection moldings is not determinate straightforward in all cases. This is the case of meld lines, a type of weld line, that appears when two emerging parallel melt flow fronts enter in contact. The bonding region will be affected by the flow behavior because polymer continues to flow after the flow fronts contact each other, that means that pressure and temperature continue to vary until the end of filling.In this work fracture behavior of meld lines is investigated under a SENT configuration . Meld-lines were generated by injection molding polypropylene into plates using a two-gate mold. The effect of the induced residual stresses by different process conditions on fracture behavior is established.