Splay

Visual Defect

Silver streaks result from the light scattering off the tiny bubbles that have been smeared across the surface of the part. This cosmetic issue is highly visible on dark-colored or polished components, which makes them unacceptable for aesthetic applications. These streaks are often accompanied by a rough surface texture along the flow lines.

Rheological Disruption

Water vapor present in the polymer melt reduces the localized viscosity and creates microscopic pockets of gas that disrupt the smooth flow of the plastic. This gas phase does not mix with the liquid polymer, which causes phase separation as the material enters the thin sections of the mold. The pressure drops as the gate is passed, which triggers the expansion of these trapped gas bubbles.

Corrective Measure

Eliminating this cosmetic defect requires thorough drying of the polymer resin before it is fed into the injection unit. Operators should also verify the operation of the desiccant dryer and ensure the hopper temperature remains at the specified level. Reducing the injection speed or the melt temperature can also help minimize the formation of these streaks by lowering the shear stress on the polymer, which helps ensure that the finished parts meet both cosmetic and structural quality requirements.