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Cellulose Film: An Old Dog With New Tricks

What do you do with a packaging material that has been in production for over 70 years but basically remains misunderstood and underused? You take a long hard look at the product, and begin to think outside of the box - or in this case, outside of the packaging.

What do you do with a packaging material that has been in production for over 70 years but basically remains misunderstood and underused? You take a long hard look at the product, and begin to think outside of the box - or in this case, outside of the packaging.

If someone claimed to have discovered a new packaging film that could be produced in almost any color of the rainbow, with natural deadfold characteristics, permeable to moisture but a barrier to bacteria, anti-static, heat-resistant, and easy to tear while being dimensionally stable, most manufacturers would be impressed.

        Unfortunately, no one can make such a claim since Cellophane has been in production since 1933.

        Made from wood pulp from renewable forests, the Cellophane technology has even been used to develop a range of biodegradable and compostable films.
        Over the last couple of years, considerable effort to capitalize on cellulose film's inherent attributes has resulted in developments that are now taking it into a raft of new areas as well as enhancing its packaging performance.

Tight twists

Cellophane has been used to twist-wrap candy for as long as the twist-wrapping packaging method has been around. In fact, it could be argued that without Cellophane, twist-wrapping of candy would never have been devised.

        In this market area, Cellophane is supreme because of its natural deadfold. Put simply, once folded or twisted, Cellophane does not spring back because it lacks the molecular memory of plastic and does not, therefore, fight to return to its previous form.

        A tight twist means waste caused by mis-wraps is reduced to a minimum.

        Other attributes, which are important to this market area, include Cellophane's anti-static properties which mean wrapped sweets glide easily along conveyors - they don't cling together either during handling or once bagged.

        This is driving a resurgence of interest in Cellophane. In recent months, a number of confectionery companies have reversed course, heading back into Cellophane's corner from plastic.

        The US candy market is beginning to re-assess the true cost of its packaging and take into account the hidden assets of Cellophane. While plastic costs less than Cellophane, problems with downtime, static build-up and mis-wraps virtually eliminate any cost savings.

New twists

In the US, many tons of Cellophane are used in condiment sachets because of the film's easy-tear characteristics and high gloss.

        An acrylic-coated Cellophane has been specially developed for this market which combines anti-static properties with quick jaw-release on high-speed form-fill-seal machines.

        Cellophane is also heat-resistant making it an ideal packaging material for the microwave.

        One of the most recent developments in this area is a new film that is both heat resistant and semi-permeable to moisture which prevents a certain degree of steam build up inside the package.

        Ideal for popcorn and pre-cooked pastries and bread-based products, this film is sufficiently resilient to run efficiently on form-fill-seal machinery, and maintains package performance throughout distribution, chill cabinet storage and in the microwave.

Dependable barriers

The barrier properties of material used to wrap food play a vital role in making sure the product reaches the consumer in the best possible condition.

        As well as providing physical protection from dust, dirt and bacteria, Cellophane may also be used to control the movement of gases and moisture into and out of the package.

        Most foods require packaging with a high barrier to oxygen to help reduce oxidative degradation and fat rancidity, as well as protection from external odors and aromas. On the other hand, packaging can impact other requirements such as flavor retention and aroma that need to be securely locked within the package.

        Moisture is a different matter as foods vary greatly in their need to retain or to lose it. At one extreme, high baked cookies are manufactured with low moisture content and need to stay dry to maintain their crispness.

        At the other end of the spectrum, products like pies, doughnuts, soft cheeses and yeast with a high moisture level need to lose water vapor during shelf-life to avoid mold growth.

        Unlike plastics, Cellophane is a natural membrane structure and has an excellent barrier to gases and aromas but a very low barrier to moisture in the uncoated form.

        Tailored semi-permeable Cellophane films, such as those produced by Innovia Films, are especially good for wrapping baked goods, many of which are wrapped while still warm.

        The films offer full product protection on the shelf, in the refrigerator, and in transit with no loss of package integrity or visual appeal.

        Other pastry and bread products are packaged still warm from the oven. Hot packing ensures that microbiological contamination is negligible but it is generally associated with very high moisture content. In hot pies this can be as high as 100% moisture saturation, while bread moisture levels are generally in the region of 30-50% relative humidity in the crust and 96-98% in the crumb.

        For this type of product a breathable film such as Cellophane PS or a coated intermediate semi-permeable film such as Cellophane WS is required. Because of its resistance to heat, Cellophane can be used on pie and pastry products, which are served hot in their packaging.

        Baked goods with a low equilibrium relative humidity (ERH) such as cookies, shortbread, and cheese crackers need a very high moisture barrier film such as PVdC coated Cellophane, or metallized for complete UV protection.

Biodegradable & compostable

One of the most exciting and fundamental developments for over 40 years is that of cellulose-based biodegradable and compostable films.

        These films comprise a transparent cellulose base manufactured from sustainable wood pulp. By adding specially formulated biodegradable and compostable surface layers, the moisture permeability of these films can be controlled to produce material suitable across a whole range of applications from high moisture content fresh produce to more hygroscopic bakery products.

        Biodegradable and compostable cellulose films are stiffer and more oriented than many bio-polymers currently on the market which makes them ideal for use in standard flow-wrap and form-fill-seal equipment for food packaging. Glossy and transparent, they are also static-free for easy handling.

        These films offer many advantages. They are not only biodegradable and compostable for those packer processors keen to use sustainable packaging, but also have a technical performance second to none.

        Everyone is looking for films which will operate at increasingly rapid speeds with no loss of seal integrity and no increase in downtime and handling problems.

        So far, the performance capabilities of these new cellulosic films has been outstanding.

        They are also one of the few materials that have been tested to the specification required for soil, home composting and waste water applications at ambient temperatures, as well as in industrial composting.

        Key application areas are for wrapping fresh produce, especially organic ranges, confectionery twistwrap and personal care products.

        A metallized film has just been introduced to complement the range.

Exciting times in Cellulose films

Of particular interest is the way in which different development areas impact on one another.

        Many of the changes in Cellulose film development right now stem from close examination of the precise nature of the material and its special characteristics.

        When faced with a culture that says "Hey, this isn't any old packaging film, it's a unique, high-tech material which we can utilize in numerous diverse ways," suddenly new developments are being pushed through in more traditional markets. It's a "can do" mentality which will continue to surprise and excite us for years to come.

Cellophane and NatureFlex™ are registered trademarks of Innovia Films Group. This paper looks at the remarkable story of Cellulose film, its heritage and its future.