In this work, a poly(styrene-b-isoprene-b-styrene) thermoplastic elastomer was processed via a novel processing technique, dynamic-packing injection molding (DPIM). The shear cessation time is variable during DPIM, and a conventional injection-molded sample (C-sample) was prepared for comparison. For the dynamic-packing injection-molded sample (D-sample) with a short cessation time, a high Youngs modulus was obtained but with no significant enhancement of the break strength relative to the C-sample. However, a significant improvement of the break strength was achieved for the D-sample with longer cessation time. The mechanical performance of both the C-sample and D-samples was interpreted from the contribution of polyisoprene (PI, as the matrix) and polystyrene (PS, as a dispersed phase) segments. It is proposed that a short cessation time (strong shear) can induce the formation of a stretched PI network, while prolonged cessation time (more relaxation) could result in the segregation of PS and PI microdomains and the formation of a perfect parallel orientation of the PS cylinder in a hexagonal lattice.