Meaning
Polymer chain scission occurring within a base resin matrix under high shear or heat loads reduces the molecular weight of the masterbatch vehicle. Carrier resin degradation permanently alters the rheological profile of the concentrate, forcing the downstream injection moulding process to deviate from standard viscosity targets. This chemical breakdown creates a drop in mechanical integrity within the final part, often resulting in brittle zones or surface fractures when the base polymer chemistry loses its intended structural coherence.
Viscosity Shift
Differential flow behavior occurs when the modified carrier exhibits a lower melt flow index than the specification sheet suggests. A processor detects this drift through changes in injection pressure profiles or irregular filling patterns inside the mould cavity. Variations in temperature set points cannot correct the discrepancy because the shift originates from a permanent loss of polymer chain length rather than a temporary thermal effect.
Molecular Fracture
High intensity mixing during production exerts forces on the concentrated additives that exceed the stability threshold of the resin structure. This stress triggers a cascade of bond ruptures, converting uniform pellets into a mixture of high and low viscosity fractions that prevents consistent dispersion.
Thermal Sensitivity
Accelerated oxidation rates define the boundary where the material ceases to function as a stable delivery system for dyes or functional additives. Heat history remains the primary determinant of this state, as prolonged exposure to molten temperatures within the barrel eventually exhausts the oxidative stability of the resin. Once the chain architecture undergoes this terminal reduction, no mechanical adjustment can return the material to its original specification.
