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How to Define Plastic Film Variability

How do you define plastic film thickness variability?


When purchasing film, a film buyer may ask for plastic film with +/- 10% thickness variability (as an example).  But what does that mean?  How do you measure it and is the method precise and repeatable?

Before October 2017, there was no standard answer, but with the release of ASTM D8136, film buyers and sellers have a standardized method for characterizing film variability.

Different types of plastic film range in thickness variability depending on the process and end use, and there are many different on-line and off-line gauging methods that are used to measure film.  Since there was no standard method in the past, many companies came up with their own methods for defining plastic film variability.  However, this created many problems internally and externally.

Defining Plastic Film Variability

The New Standard For Plastic Film Variability

In the past, many companies would use a contact micrometer and a predetermined amount of points to define the variability.  The number of points measured can vary from company to company, and the reliability and precision of the measurement was often poor.  Some producers tried to use their on-line gauging systems, however, this can be different from line to line, site to site, and company to company.   A simple change to a setting in the gauging sofware

As a result, film buyers could not really use this data to compare suppliers or to really know the variability of the film they were getting.  The variability claim was not that useful.

New ASTM standard D8136 defiles profiling a strip of film as measuring every area on a strip of plastic film.  This means if the measurement footprint is 1/8″ wide, it will take a reading every 1/8th”.   A person will typically take a strip off of the end of the roll, run it through a Profiler, and then use this to characterize the variability of the roll.

A film can be charaterized in both the cross web or down web direction.  Separate profiles will have to be run in each direction to do so.

SolveTech’s proprietary capacitance based technology fully complies with the new standard.  It also has the precision to charaterize the variability of films less than 0.5 mils thick.  This provides usefully data quickly and easily regarding film variability.

Plastic Film Testing
polyester film thickness in west coast

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Products for the Lab

ASTM D6988

The PR2000 Precision Profiler

Profile a strip of film to see the uniformity of the material in the cross web or down web direction.  This unit delivers the highest level of accuracy and repeatability on the market.  You can see how your extrusion is performing in great detail to see the affect of small incremental improvements.  Great for blown film and cast film lines.

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Contact us here, or call 1-302-798-5400 to have a technical discussion regarding plastic film variability.





Defining Plastic Film Variability –  Measure Plastic Film Variability – Standard for Plastic Film Variability

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