Dynamic gating of polymers for isotropic properties

摘要

A polymeric article having isotropic properties is fabricated from anisotropic materials by orienting the polymer, as well as any fillers, in different directions at different planes through the polymeric article. In a first embodiment, molten polymer is passed between movable gate members (32 and 34) into cavity (30) of mold (28). The movable gate members (32 and 34) impart a strain on the molten polymer by moving in opposite directions (33 and 35) while the molten polymer is dispensed into the cavity (30). Reciprocating the movable gate members (32 and 34) yields a herringbone pattern. Having at least one movable gate member (38) have comb-like projections (40) can assure the strain is imparted deeper into the thickness of the polymeric article. In a second embodiment, molten polymer is passed through movable gates (96 and 100) on perpendicular sides of a mold cavity (94 and 98) where one movable gate (96) is located towards the top of the mold (84) and the other movable gate (100) is located towards the bottom of the mold (84). The gates (94 and 98) are simultaneously driven in directions (68 and 70) along their respective cavity sides while injecting polymer into the cavity. The finished article has a top layer (56) has polymer oriented (58) in a first direction and a bottom layer (52) with polymer oriented (54) in a perpendicular direction. Polymer is randomly oriented (62) between the top and bottom layer (56 and 52).