Meaning
Quality control procedures for evaluating container durability measure the resistance of a finished polymer bottle to sudden kinetic forces. This evaluation, called drop impact testing, involves releasing a filled and sealed container from a specified height onto a rigid surface. It establishes the structural integrity of the bottle design and the impact resistance of the chosen resin.
Mechanical Behavior
Stresses generated upon impact propagate through the bottle walls and concentrate in areas of thin material or poor molecular orientation. The polymer must absorb the kinetic energy through elastic and plastic deformation without catastrophic rupture. During drop impact testing, the base region and the neck finish undergo the highest localized stress concentration.
Biaxial orientation achieved during the blow moulding process significantly increases the toughness of the polymer in these regions.
Testing Protocol
Standard procedures require specific liquid fill volumes and controlled temperatures to simulate real-world transport conditions. Technicians drop the bottles from increasing heights to determine the mean failure limit. This statistical approach helps calculate the probability of breakage in a standard shipping environment.
Failure Identification
Ruptures typically occur along weld lines or in areas where the material exhibits low orientation. Analyzing the fracture surface helps determine whether the failure was ductile or brittle. This feedback allows toolmakers to adjust the gate location or the preform geometry to eliminate structural weak points.
