The quality of a polymer melt is heavily influenced by the shear rate applied during processing. Shear rate refers to the speed at which layers of the polymer flow past one another, and it plays a pivotal role in shaping the final properties of the formed part. At low shear rates, the polymer chains have adequate duration to relax and align slowly, which can lead to non-uniform motion and poor homogeneity. This often results in notable flaws like sharkskin or melt fracture, notably in long-chain thermoplastics.

As the shear rate increases, the polymer chains begin to follow the flow of the flow, تولید کننده گرانول بازیافتی which can enhance the uniformity of the melt and reduce viscosity. This non-Newtonian response is beneficial in many processing applications because it enables smoother material movement through dies and molds without requiring excessive pressure. However, if the shear rate becomes overly intense, the polymer chains can be strained beyond capacity or even broken down. This leads to molecular weight reduction, which weakens the mechanical properties of the final product.

Excessive shear can also generate localized heat due to viscous dissipation, causing heat-induced breakdown in thermally unstable resins. This can result in discoloration, odor, or the generation of volatile byproducts that undermine product integrity. In addition, high shear rates may cause non-uniform velocity profiles, leading to built-up tension that appear as warping or loss of tolerances after cooling.

To achieve ideal processing conditions, processors must carefully balance the shear rate with the polymer’s flow characteristics, melt temperature, and equipment design. Using the optimal screw geometry, barrel temperature profiles, and die design helps ensure a stable and controlled shear rate throughout the process. Tracking and regulating shear rate ensures that the polymer melt remains predictable, even, and intact, ultimately producing parts with uniform quality and flawless appearance.