- December 31, 2004, David J. Bentley, Jr., Contributing Editor
An important concept for chemistry students to grasp is solubility. Teachers sometimes jest with their students by asking them about a universal solvent. What is the one material that will dissolve everything? Some students take longer than others to ascertain that a universal solvent is not possible, because no container could hold it.
In a similar vein, new employees in the adhesive industry often receive a challenge to find a universal adhesive. What is the one material that will adhere to everything? Astute individuals rapidly will reason this also is impossible, because removing a universal adhesive from its container would be impossible.
Let us take this concept of universality one step further. Is there a universal film for flexible packaging? All converters and package designers know the answer to this question is a resounding no.
PE film has certain attributes, but it also has limitations such as heat resistance. PP film offers some benefits over PE, but it does not have good barrier properties. Polyester film has excellent strength characteristics, but it has no heat sealability. Statements of this type could be made for any other film.
These and similar reasons are the rationale for the existence of a wide variety of combinations of plastic materials achieved through the lamination or coextrusion process.
Composites made by laminating or coextruding also do not provide a universal flexible packaging material. Snack packages require a specific composite to provide sealability and retention of freshness. Boilable pouches require a different composite to attain the heat and chemical resistance required in this application. Active packages may need the ability to breathe. These are the reasons for the existence of a myriad of composites for flexible packaging.
Nevertheless, a universal composite for flexible packaging may be possible. Admittedly, any plastic now available will not form a film that would find universal use in flexible packaging. A composite material made through coextrusion, however, might be able to function as a universal packaging material. How could this be possible?
The first step would involve entering into a computer program all the properties needed in flexible packages, from the simplest to the most complex. This would include everything: strength, barrier properties, clarity, heat sealability, printability, and all the other characteristics known to the packaging world. In other words, this list would cover all the possible properties anyone could imagine a universal film would require.
The next step would be to enter the properties of all known plastics into the same computer program and ask the computer to select the proper combination of plastics that would meet all the requested needs of the universal composite.
Since we live in the real world, we also would need to impose on the results the computer would generate restrictions on such practical things as cost, thickness, etc.
After considerable cogitation, the computer program would grind to a halt with its answer. Considering the complexity of the problem, the answer probably will not be simple.
It undoubtedly will involve a number of different polymers, each used at a particular thickness in the total coextruded composite. Yes, the proposed material will offer excessive benefits for low-performance packages. That will not matter, though, because the economies of scale required to make it for the entire field of flexible packaging will mean it can be cost-efficient.
Elimination of some middle men also will help the cost picture. The new process simply will coextrude polymers into a film and then convert that into a flexible package.
Is the preceding impractical? Be careful how you answer this question. Realize we now live in the year 2005. Those who say the suggestions above are totally ridiculous are living physically in 2005 but not mentally. They lack imagination and creativity. Those who answer yes are forward thinkers who realize almost nothing is impossible today due to the many technological advances now available in many fields of science and technology. They are the people for whom this new year of 2005 and the future will be times of great success.
David J. Bentley Jr. is a recognized industry expert in polymers, laminations, and coatings with more than 30 years of experience in R&D and technical service. Contact him at firstname.lastname@example.org.