Testing the Thickness of Plastic Packaging Films

Quick guide to testing the thickness of plastic packaging films

Testing the thickness of plastic packaging films can yield some incredibly useful data about its durability and other essential properties. Dive in to find the answer to one of the most commonly asked questions about testing thickness of plastic packaging films – how do you know what specifications to use for the pressure foot and diameter of the measuring foot of micrometers? 

Whether you’re testing flexible packaging for food, beverages, chemicals or more, a thorough understanding of how to accurately test the thickness of plastic packaging films is essential.

Determining specifications for the pressure foot and diameter of the measuring foot for micrometers

Working out the specifications for the pressure foot and the diameter or the measuring foot for testing the thickness of plastic films requires some prior knowledge.  

ASTM testing methods 

For a start, ASTM recently revised test method F-2251, Standard Test Method for Thickness Measurement of Flexible Packaging Material. 

The new method references ASTM D 6998 “Standard Guide for Determination of Thickness of Plastic Film Test Specimens” as the guide for recommending foot diameter and foot pressure. 

Considering the stiffness and thickness of the film 

Industries such as paper, tissue paper, corrugated board or textiles have well defined specifications listed in the applicable standard. However, plastic film standards such as ASTM D 6988 and ISO 4593 suggest a range for the diameter and foot pressure based on the stiffness and thickness of the material. 

Questions to guide your choices

Is the material considered a thin or deformable film? What are thin films? 

Thin films are ≤ 0.025 mm (0.001 in.). Deformable films are easily compressible and a lower contact foot pressure is recommended. 

If the requirement is to test thin films then a maximum pressure of 70 kPa (10 psi) is suggested. If the material is not classified as a thin film, then a foot pressure range of 160-185 kPa (23-27 PSI) is suggested. 

A pressure foot with a large area is difficult to calibrate and maintain parallelism between the pressure foot and the anvil. Also, a large diameter pressure foot is difficult to keep clean. Any dust or dirt on the film will be measured during the test. During a measurement, dust can adhere to the upper and lower foot and produce a higher reading. This is a very common problem with thickness measurements. 

What diameter pressure foot is recommended for plastic films?  

According to ASTM D 6988, the diameter ranges from 3.2- 12.7 mm (0.125-0.5 inch). ISO 4593 recommends a diameter of 2.5 -10mm (0.098- 0.393 inch).  

What is the recommended pressure for plastic films? 

ASTM D 6988 has a range of 5-70 kPa (0.73-10.1 PSI) for thin films and 160-185 kPa (23-27 PSI) for stiffer films. 

ISO recommends a pressure range of 0.5-1.0 N (51-102 gram) dead weight. 

If you’d like a PDF of this information to keep for your future reference, please download our thickness of plastic packaging films specifications guide.  

Thickness of plastic packing testing options

When you need to test the thickness of plastic, our specialist brand Testing Machines, Inc. has just the test and measurement solutions you need. This includes the Digital Micrometer 49-86 and Digital Micrometer for Corrugated and other Thick Materials 49-87.