Biodegradable Films Today

PLC Probe

Most of us love our creature comforts, including the many items that use flexible packaging substrates. These include drugs and healthcare products packaged in blister packages, snack foods in flexible packages, and similar items. In fact, consumers want more and more items available in easy-to-use and convenient forms. As a result, increasing amounts of plastic films and foil enter the waste stream, because no easy method is available to recycle, separate, or divert them from disposal in landfills.

Disposal costs for landfills increase regularly, and legislators enact new regulations regarding landfill use. These are often attempts to decrease the amount of plastic films adding to the ever increasing waste stream. Plastic films that are biodegradable offer a practical alternative. Such biodegradable films must continue to offer the benefits of the plastic films they replace in properties such as strength, clarity, flexibility, etc.

What is a biodegradable film? It is one that will decompose in composting conditions. The microorganisms in a compost pile with heat and moisture present actually eat the plastic material and turn it into water and carbon dioxide.

Over the course of time, a plastic film that appeals to the nutritional requirements of the microorganisms goes through their digestive systems. It changes from a solid waste substance to harmless products that enter the ground and atmosphere. The trick to all this is to make a plastic film appropriately biodegradable.

Most of the current technology available today involves adding components such as starch. Two techniques have general use. One is to incorporate starch or a special monomer into the mixture of monomers used to polymerize a film. The other is to compound or formulate starch or another material into a regular plastic film during its processing. Both have had commercial use with various degrees of success, depending on the material being incorporated.

An alternate approach to help solve this problem is to switch to paper instead of plastic. This is the old "paper or plastic" approach that everyone hears in the grocery store when they make a purchase. For many years, the industry touted plastic bags as being more environmentally conscious, because they saved the trees growing in forests. Now the thinking may be changing. Using paper bags instead of plastic bags in the supermarket does indeed deplete the forests, but it also reduces the amount of plastic going into the waste stream that requires decomposition in the land fill.

Other alternatives are possible. One is to have consumers that use plastic bags make compost piles at home, much as they might do with their lawn and garden wastes. This approach probably would not be very popular. Would the decomposition occur in a reasonable time? A modification of this that might be acceptable to consumers would be to manufacture the plastic films used in packaging so they would decompose when placed in water or exposed to sunlight. If the decomposition happened in a reasonably rapid time, the consumer might tolerate this approach.

Some European communities have solved the problem of plastic film disposal by requiring return of packaging material to the manufacturer. This has certain intrinsic disadvantages, including the requirement to accumulate material for return, the cost of the shipping involved, etc.

Perhaps what is necessary is a completely new approach to this problem. Is it possible to make a plastic film from a polymer that would decompose similar to an unzipping of the polymer chain after a certain time or under certain conditions? Could the organisms that do the decomposition of polymers be incorporated into the plastic films in a deactivated state and then undergo activation at a time when it was appropriate?

Finally, everyone hears about "smart" packages now. Is it possible to make a package that is so smart it knows when to biodegrade when necessary? The "smart" mechanism could detect when the package was empty and subsequently begin the degradation process.



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 dbentley@unm.edu.


To read more of David J. Bentley’s PLC Probe columns, visit our PLC Probe Archives.



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