Meaning
Standardised test methodologies evaluate the resistance of rigid plastics to breakage when subjected to high-rate bending impacts. Specimens tested under ISO 179-1 are struck by a pendulum on their unnotched or notched faces to determine their toughness. This value is used by part designers to ensure material toughness under shock loading.
Specimen Preparation
Machining or injection moulding of specimens must be carried out under controlled cooling rates to avoid internal stress. Failure to conform to ISO 179-1 geometry and notches leads to high scatter in the measured impact strength. Toughness is affected by notch radius.
Impact Behaviour
High impact strength prevents brittle failure of parts in low-temperature environments. Standard testing under ISO 179-1 measures the energy absorbed per unit cross-sectional area of the specimen during fracture. This test defines the boundary where ductile behavior transitions to brittle failure under stress.
Production Evaluation
Sourcing alternative resin requires comparison of datasheet impact values with the actual performance of the moulded part. Since resin suppliers run test bars moulded under optimal conditions, the values held across a production run are often lower due to weld lines and molecular orientation. Periodic impact testing of parts during a production run ensures that processing conditions have not degraded the polymer matrix.
