Packaging Goes Back to Nature

Remember when consumer pressure forced McDonalds to stop using CFCs in its take-out containers? Scrutiny of packaging and expectations of environmental responsibility hardly eased up since then.

With the ozone hole on the mend, focus has turned to how packaging contributes to fossil fuel, energy, and landfill use. By some estimates, about 200,000 barrels of oil daily go into plastic packaging materials. Plastic houses 53% of all goods. The argument that plastics choke landfills and will never degrade is well known. Recycling is feasible for some plastics, but fewer consumers have access to plastic recycling than to glass and metal services.

Paper and cardboard packaging hold 25% of shipped goods. Both materials are recyclable and biodegradeable, but typical household garbage is still 6.4% paper packaging.

In the last decade, companies with goods to package have developed strategies to ease the impact packaging has on the environment. One corporate example is Hewlett-Packard. The company’s environmental guidelines prohibit the use of heavy metals, PVC, and ozone-depleting materials in its packaging and require that all packaging be recyclable and marked as such.

Many packaging companies have gone in a similar direction. More environmentally friendly technologies that were previously too expensive to develop, like plastics made from corn, are looking more attractive in the face of higher oil prices.

Old news, new packaging
Newspapers are one of the most commonly recycled materials, and the price of baled recycled paper has stayed relatively flat in recent years. EnviroPAK, St. Louis, uses 100% recycled newsprint in its molded-paper-pulp packaging materials. The company claims this saves 41,496 trees, over 16 million gallons of water, and enough energy to power 755 homes annually. While molded paper pulp has been used for over 50 years in egg crates and light-bulb packages, the company has seen a recent surge in interest in more-complex recycled pulp packaging for electronics and other household goods. Molded paper pulp can be recycled, and is biodegradable and compostable.' EnviroPAK makes transfer-molded thin-wall packaging starting with a 4%-solids slurry of pulped recycled newsprint. The slurry is refined and further diluted before wet-forming on a rigid aluminum die covered by preformed stainlesssteel screens. The die mounts to a molding drum that rotates it through the slurry. Vacuum applied through holes in the die attracts the fibers to the screens and removes excess water for recirculation back into the process.' A matching transfer die, without screens, contacts the newly formed part of mechanically interlocked fibers and attracts it with vacuum while a puff of air from the forming die discharges the outpart. At this stage, the product still contains about 75% water and is very delicate. The transfer die moves the part onto a conveyer that carries it through a recirculating hot-air oven that drives off all but roughly 10% of its moisture. After this, the formed pulp is ready for quality inspection, sorting, stacking, counting, wrapping, and shipping. Rejected parts are sent back to the pulper, a closed-loop process that results in zero scrap.

Transfer molding yields products with accurate detail definition and permits deep cavities. This versatility means that designers can make molded-paper-pulp packaging much more complex than a simple egg crate. Thin walls enable designs that stack and nest well.

“Strength comes from the geometry of the design, rather than through thickness of the part”, says Bill Noble, EnviroPAK’s vice president of sales and marketing. Custom-designed molded-pulp packaging can support up to 20 lb without collapse or abrasion. It is chemically and electrically neutral and largely insensitive to changes in temperature and humidity. The material is said to outperform vacuum-formed plastics, corrugated cardboard, and expanded polystyrene (EPS), especially when vibration comes into play.

These qualities have led to its use in packaging electronics, small household appliances, medical products, consumer goods, CDs and DVDs, automotive parts, and food and bottled goods. Packagers can specify end caps, trays, cushions, and clamshell packaging that best fit their product and shipping methods. EnviroPAK produces packaging from 4 5 0.75 in. up to 14 30 4 in.

Although up-front mold costs can run to $15,000, OEMs can cut cargo volume by about 50% for some parts with better stacking and nesting. Likewise, they may see a drop in the cost of warehoused packing material. With the premolded material, packaging takes less time than with die cutting or expand-in-place foam. These factors combine to save companies up to 70% in packaging and shipping by switching to paper pulp from EPS, die-cut corrugated cardboard, and other plastic materials, EnviroPAK claims.

Go biocompostable
Coextruded Plastic Technologies Inc., Edgerton, Wis., offers a few other alternatives to petroleumbased plastics. Most foods are packaged with some kind of Styrofoam, thermoset, or thermoplastic materials. The company claims many of these could be replaced with biocompostable materials that recycle waste and use less energy.

The company’s Go-Green line uses sugar-cane bagasse and polylactic acid (PLA) from the corn sugar dextrose. Both sugar cane and corn are viewed as rapidly renewable resources; they grow from seeds into usable plants in under a year.

Bagasse is the pulp left over after sugar-cane juice is extracted. The cellulose in bagasse can replace wood-derived cellulose in making paper products. To create packaging materials, processors press the pulp into boards and draw the boards into molded packaging. The finished material can be heated to 350°F, microwaved, and frozen down to –13°F.

“Sugar cane sells at a higher price than foamed polystyrene,” said CPT’s President Linda Bracha. “However this doesn’t take ‘cradle-tocradle’ and ‘cradle-to-grave’ considerations into account. If we compare the products’ performance, carbon footprints, and prices, packaging produced from renewable resources offers significant advantages.”

To make PLA, bacteria ferment corn processed into dextrose to produce lactic acid. Chemical catalysts turn lactic acid into lactide which is then polymerized into PLA. Most U.S.-sourced PLA is made from corn, while other countries use soy, sugar cane, and potato starches. PLA-based plastics are made with 65% less energy than petroleum-based plastics, according to one estimate.

Packaging manufacturers receive PLA in resin pellets that they melt and thermoform into containers. CPT’s thermoforming process nests containers to minimize waste and energy input. Packaging made from PLA handles temperatures between 32 and 100°F. Unlike bagasse materials, PLA cannot be frozen or microwaved.

Both materials are biocompostable. Packaging made from bagasse is rated for home or industrial composting. It degrades in 30 to 90 days if broken into small pieces and supplied with appropriate moisture, oxygen, and temperature. PLA is certified for industrial composting; at least 10 days at 140°F are needed for the bacteria to do their work.

The materials are finding their way into food packaging. Because of its temperature stability, consumers will see bagasse used in frozenfood containers meant to be microwaved as well as in meat, seafood, and produce trays. PLA is common in produce trays, cold-drink cups, and food-service trays.

Activating oxygen
Biodegradability is also on the agenda for Oxobioplast Inc., Toronto. The company’s Reverte additive lets plastics manufacturers program the degradation of standard plastic packaging. The manufacturers can look at how long a plastic product must last and tune its degradation timeline accordingly.

“Plastics have always been the last bastion against green packaging,” said Allan Aucoin, vice president for business development at Oxobioplast. “Our additive turns that plastic into biomass in a set amount of time, determined by the customer.”

The additive contains photoactivated metal ions that begin to break apart the polymer chains as the material sees UV light, heat, and oxygen. Part of the additive acts like a sunscreen, delaying the degrader’s activation for six months to five years. Eventually, the protection dissipates and the chain-breaking begins.

The metal ions catalyze oxygen to break apart the polymer chains, leaving carbonyl groups at each new end. The process continues until the chains measure just 4,000 to 10,000 repeat-units long, another three to nine months later.

Landfill operations shred the plastic as it is disposed with other trash. This mechanical breakup, along with the shorter chains, leaves the plastic brittle and susceptible to attack by microorganisms. The additive’s biodegradation enhancers speed the process toward complete degradation. Oxobioplast claims the plastics are reduced to carbon molecules in five years.

Reverte meets EC and FDA food-contact requirements and serves in high and low-density polyethylenes, biaxially oriented polypropylene (BOPP), and chlorinated polypropylene (CPP) for food packaging and shopping bags. Additive levels of about 1% give the desired degradation. Consequently, the difference in cost is nominal and appearance, performance, and processing are unchanged, Aucoin says. Plastic products with the additive can also be recycled using standard procedures.