EPS trays: Learning some clever new tricks

An August 2004 article cited a number of European thermoformers hailing the demise of thermoformed foamed polystyrene packaging in fresh meat packaging. Polypropylene was the stuff of the future for that market, they said. It did not take long for one of Europe''s leading thermoformers to yell, "Poppycock."

Well, no one actually said "Poppycock," but officials at LINPAC Plastics'' film extrusion and tray thermoforming plant in Featherstone, West Yorkshire, England, were quick to counter claims that the material whose processing they have been perfecting at the firm for a little more than 30 years was being replaced by the upstart, PP.

Indeed, these experts say developments just entering the market will more than offset the negative traits ascribed to foamed PS trays. "People moved to PP because they saw them (thermoformed PP trays) as more durable and less costly. But now they are recognizing some of the more subtle features" that are not in PP''s favor, explains Mark Ashcroft, technical manager, citing misting of sealing films, poor tray stability when heated, and slower line speeds during filling.

LINPAC is hardly anti-PP; the firm this year acquired a top PP and A-PET tray thermoformer, Italy''s Infea srl, in Bertinoro. And Ray Newton, general manager at the Featherstone site, notes, "We process practically every polymer available: PS, HIPS, OPS, PP, A-PET, K-Resin and varieties of each of those." But he, Ashcroft and Business Development Manager Trevor Komaromy-who together bring more than 80 years in the thermoforming market to the firm-agree that foamed PS trays'' best days still lie ahead.

Old faithful

Foamed PS is the established material for tray forming; it processes well and accepts PE or PVC overwrap films well. On the downside, it lacks high-temperature stability, which takes away its use in the rapidly expanding microwaveable meals market. When employed in packaging of sensitive foodstuffs it requires a laminated barrier layer, adding to costs and thwarting recyclability.

But maybe most significantly, foamed PS trays are thick-3 mm or so is standard-meaning that they cannot be formed with steep wall angles; the rounded folds on these trays take away from grocers'' shelf space. PP generally tops PS on both points.

"The odds, and trays, are now stacked in our favor"

At least it did. But now, LINPAC says it is entering the market with foamed PS trays that turn these assumptions on their head. For starters, says Ashcroft, "We''ve solved the wall-angle and stacking problem." He explains:

"We''ve taken control of forming every section of the tray" so that thickness of tray bottoms does not necessarily lead to high stacks. "We''re using 50% or so less material than rigid PP trays, plus our trays can also offer high barrier protection and are absorbent (of meat juices that collect in the bottom of trays)." Not surprisingly, LINPAC does not share details on what it has changed in its thermoforming to master this problem.

When stacked, these new trays from LINPAC are only about two-thirds as high as a stack with the same number of standard foamed PS trays. Newton notes these are already in the market, at two of Linpac''s key accounts, and broad marketing of these is commencing now.

The processor not only improved its established tray range but has also expanded the range with new developments. For example, foamed PS trays offer the necessary thickness for a new line of trays called LINfo that contain an anti-theft tag in the tray base, so as not to be visible to consumers. These tags can only be de-activated by a store''s checkout counter; passing them through a store''s EAS gates triggers an alarm. "About 5% of all high-value meat is stolen from stores in Europe," says Komaromy, usually by organized gangs who then re-sell it.

The anti-theft tags add about €50/1000 trays to the cost of the package, but LINPAC argues this is money well-spent. If a store sells one million trays of meat per annum, each costing €10 and with 20% having the LINfo tags, savings are €90,000, assuming just a 1% decrease in theft.

To the microwave

Ashcroft says another novel new package is the LINcool microwaveable foamed PS trays, which the processor thinks will give it a strong foothold in the ready-meal market.

Already, British foodstore chain Tesco is rolling these out in its in-store cafeterias. The insulating properties of foamed PS are key with these trays, keeping consumers'' hands from burning when they remove food from a microwave. Microwaveable PP or crystallized PET trays, with food temperature at 120ºC after heating, have tray temperature of about 80ºC; a temperature higher than 55ºC is uncomfortably hot to touch.

The PS trays only heat to about 38ºC in the same example. Also, the foam trays retain their stiffness even when heated, lowering spillage rates.

Relative tray stiffness for the LINcool trays is greather than 80% at 105ºC compared to about 10% for PP or C-PET ones. Insulation properties of the foam trays also hold true for cold temperatures, giving them much higher pass rates on drop testing done at -30ºC. Ashcroft says the LINcool trays also heat faster in a microwave, saving energy, especially for restaurants, which are re-heating numerous meals per day.

Greater density ahead

Yet another new tray development is the LINform trays, about 50% dense. Most foamed PS trays are only 10% dense, with air comprising the rest of the tray. The greater density gives LINform trays greater rigidity, better gloss, and also allows for much brighter colors of the type many foodstores are now clamoring for to help differentiate their meat brands: green trays for the eco-meats, for example, bright colors for the high-cost ones and black or white trays for the lower-cost brands. Ashcroft says these are formed on the same sort of tooling LINPAC uses for non-foamed (so PP) trays. LINform trays also offer barrier protection.

The LINPAC officials are confident that these new developments will keep foamed PS ahead of PP in meat packaging applications for some time. And there is no problem for food processors to return to the foam fold. "For our customers, it''s no problem to switch back to foamed PS from rigid PP; there is no change to the filling/sealing lines other than a change of the sealing film roll, which anyway has better anti-fog and the added benefit of faster throughput with foamed PS," says Komaromy.

Changes in the meat processing industry, such as automated tray filling equipment, also play to foamed PS''s greater rigidity compared to PP trays, they say. The Linpac crew remains confident that it and its foamed PS trays, having overcome some of foamed PS'' stumbling blocks, will meet the increasingly bespoke needs of customers in the fragmented protein market.

Matthew Defosse [email protected]