Standard Test Method for Mechanical Seal Strength Testing for Round Cups and Bowl Containers with Flexible Peelable Lids - PDF

 

ASTM F2824 is the standard test method for mechanical seal strength testing of round cups and bowl containers with flexible peelable lids. Instead of cutting a strip from the seal (as in ASTM F88), the whole lid is peeled off an intact container, so the result reflects the full circular seal: the opening force a consumer feels and how evenly the seal was made. It is used for yogurt and dairy cups, single-serve cups, portion bowls, pharmaceutical and medical cups, and other heat-sealed rigid or semi-rigid containers.

ASTM F2824 Test Setup

• Container held rigidly in a fixture so it cannot rotate or lift during the peel

• Lid tab clamped in a peel grip attached to the load cell of a universal testing machine

• Peel angle set by the fixture, most commonly 45° (90° fixtures are also used); keep the same angle for all comparisons

• Constant crosshead speed, commonly 300 mm/min (12 in/min); use the rate stated in your copy of the standard or your specification

• Low-capacity load cell (typically 50–500 N) so peel forces sit well inside its range

• Optional environmental chamber to test chilled or warm product conditions

ASTM F2824 Procedure

• Condition sealed containers (empty or filled, as specified) at the required temperature

• Mount the container in the fixture with the lid tab facing the grip

• Clamp the tab in the upper grip without slack

• Start the test and peel the lid completely off the container

• Record the force–displacement curve for the whole peel

• Note the failure mode: clean peel, lid tearing, delamination, or seal material transfer

• Test at least 5 containers per condition

Results and Worked Example

Two values are usually reported: the peak (opening) force, which is the first maximum as the seal starts to open, and the average peel force over the rest of the seal.

Example: five cups give peak forces of 14.2, 13.6, 15.1, 14.0 and 13.8 N. Mean peak force = 70.7 / 5 = 14.1 N. Over the steady part of each curve the average peel forces are 8.4, 8.9, 8.6, 8.2 and 8.9 N, so the mean average peel force = 8.6 N. A dip on the curve at the same point on every cup usually means a weak spot in the sealing tool.

Report the container and lid type, sealing conditions, peel angle, speed, peak and average force (mean and standard deviation), and failure mode.

ASTM F2824 vs ASTM F88

ASTM F88/F88M tests a 25 mm (1 in) wide strip cut across a seal, so it measures the seal material itself. ASTM F2824 peels the whole lid from an intact round container, so it measures the package as the user opens it. Many labs run both: F88 for sealing process development and F2824 for finished-package qualification. For burst and leak resistance of the whole package, see ASTM F1140 and ASTM F2054.

ASTM F2824 FAQ

What does ASTM F2824 measure?

The force needed to peel a flexible lid from a round cup or bowl, reported as peak opening force and average peel force for the whole seal.

What peel angle does F2824 use?

The container is held so the lid is peeled at a fixed angle, most commonly 45°. Use the angle in your copy of the standard and keep it constant between tests.

How is F2824 different from F88?

F88 tests a cut 25 mm strip of seal; F2824 peels the complete lid from an intact container.

What equipment do I need?

A universal testing machine with a low-capacity load cell, a container-holding fixture set at the peel angle, and a grip for the lid tab. Confirm the exact speed and angle against your copy of ASTM F2824.