Do you have a question about batch inclusion bags? Ask Professor J.D. Lomel, and your question will be answered on this page or in a private e-mail message. Read below to see the Professor's answers to other questions. Check here often to see answers to new questions. Submit your question now.

Ralph Bright, Customer Service Manager at Buckeye Rubber asks:

I hear people talking about the "melting point" and "softening point" of plastic bags. Is there a difference, and if so, how does this effect the batch inclusion bags I use?

Professor J.D. Lomel says:

The melting point is the temperature where all the crystallinity in the bags and film is destroyed. When this happens, the bag will completely disperse into the rubber. The softening point describes a temperature where the bag will begin to experience noticeable changes in physical properties. The bags weaken and become soft and stretchy, but will not completely melt and disperse into the rubber. You may notice this when using low melting bags in the summertime if the temperatures in the plant are very high. The softening point may also be referred to as the Vicat temperature and is usually 15 to 20 degrees C lower than the melting point.

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Joe Tomsic from Polymer Southeast asks:

I understand that the melting point of the bag is very important when choosing a batch inclusion film. What is the best way to determine the melting point?

Professor J.D. Lomel says:

Several methods can be used for testing the melting point of a film. The method that most accurately and precisely determines the melting point is called a Differential Scanning Calorimeter or DSC. To run this test, a small piece of plastic is heated in the DSC unit at a constant rate. As an ingredient in the film melts, it releases energy creating a peak on the graph. The temperature is measured at the peak to determine the melting point.

A DSC is the best test because it requires no human interpretation or manipulation as is often needed with oven or melt point meter tests. The main advantage of the DSC is that it gives a complete and objective melting profile of all the ingredients in the film. Besides the actual melting point, a DSC can show the presence of a small level of high melting contamination that other test methods would miss. The J. Drasner & Co. runs DSC tests on retains of all films produced allowing us to check the quality of the bags and to supply meaningful certificates of analysis and Cpk data.

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