PP Copolymer against Homopolymer for Cold Chain Drop Impact
Polypropylene impact copolymers containing disperse ethylene propylene rubber phases maintain cold drop impact strength down to minus 40 degrees Celsius where homopolymers shatter.
Astm D5420
Meaning
Standardized procedures for the impact resistance of flat, rigid plastic specimens by means of a falling weight provide a comparative scale for material toughness. Using astm d5420 allows a laboratory to determine the mean failure energy of a polymer by dropping a weight from varying heights. This protocol stops applying to flexible materials, elastomeric membranes or those thinner than the required specification.
Failure Classification
Observation of the impacted surface distinguishes between brittle shattering and ductile tearing. Because astm d5420 relies on a statistical stair-step method, the technician identifies the height at which half of the samples fail. This approach provides a more realistic view of material performance than a single drop.
Brittle failures often indicate a lack of rubber modification or excessive regrind content. In contrast, ductile failure suggests the material can deform and absorb energy effectively without catastrophic breakdown, cracked edges, shattered fragments or surface deformation.
Processing Impact
Molten polymer temperature during the injection of test plaques directly influences the results of the study. If the resin is overheated, degradation can lower the energy absorption measured by astm d5420. Proper cooling rates are also required to avoid internal stresses that might cause premature failure.
Energy Calculation
Potential energy is the product of the mass and the drop height recorded during the test. Calculating the mean energy value provides a metric that appears on material datasheets for resins intended for durable goods. Designers use these figures to choose between different grades of polycarbonate or high-impact polystyrene.