PET Drying Windows and the Hydrolysis a Moulder Absorbs
Excess residual moisture causes instant ester chain hydrolysis in molten PET, dropping intrinsic viscosity and destroying mechanical part strength.
Notched Charpy Impact
Meaning
Pendulum impact test procedures quantify total mechanical energy absorbed during high-velocity sample fracture under triaxial stress states. Measuring notched charpy impact strength provides design engineers with a standardized metric for evaluating notch sensitivity and impact toughness in rigid plastics. Quality assurance laboratories perform this test on injection molded test specimens to verify material toughness against specification limits.
The standard test methodology ceases to differentiate material performance when flexible specimens bend without fracturing completely.
Specimen Preparation
Machining precise V-shaped notches into injection molded test bars creates standardized stress concentrations that dictate fracture initiation. Performing a notched charpy impact evaluation requires controlling notch radius geometry to within tight dimensional tolerances. Cutter wear during notch machining introduces microscopic surface flaws that alter measured impact energy values artificially.
Injection moulding parameters influence internal molecular orientation, directly affecting impact test repeatability.
Fracture Energy
Absorbed energy calculations account for pendulum potential energy prior to release and residual kinetic energy after specimen fracture. Reporting notched charpy impact values in kilojoules per square meter allows material specifiers to compare impact resistance across competing resin grades. Glass fiber reinforcement increases overall impact resistance while altering notch sensitivity in engineering thermoplastics.
Virgin resins display higher impact energy absorption than thermally degraded regrind blends.
Ductile Transition
Testing across varied temperatures identifies brittle transition zones. Low temperatures decrease impact energy absorption sharply.