Rotational molders now can use more grades of post-industrial polyethylene in their products, according to researchers from McMaster University and specialty polymers firm Synergy Polymers Inc.
Until now, the finicky rotomolding process primarily has been limited to reprocessed rotomolding grades of PE as feedstock. Limited availability of that material has been a roadblock for some firms seeking government jobs that require higher recycled content.
But the researchers found that rotomolders can use blow molding and film grades of PE, provided they are blended with metallocene-based PE, which serves as an impact modifier.
Researchers blended film and lid resins with polyolefin plastomers and molded the material in a pilot-scale clamshell machine to make battery cases and refuse containers. The combination yielded results with adequate low-temperature-impact strength and ductility, as well as good part appearance, according to researchers.
``I can see there are some people that would see favorable economics by using post-industrial recycled,'' said John Vlachopoulos, professor of chemical engineering at Hamilton, Ontario-based McMaster. ``They're as good as virgin materials. You have to go through the additional step, of course, to do the blending, but we have the technology that we can help companies implement.''
Researchers presented the new ReRun technology June 11 at the Society of Plastics Engineers Rotational Molding Conference in Cleveland. Synergy and McMaster will license the technology and help rotomolders source raw materials. They also will find a local compounder and pulverizer, if necessary.
``We saw a long-term opportunity, thinking that the use of recycled products would grow,'' said Einar Voldner, president of Synergy Polymers in Hornby, Ontario. ``But I think what motivated us more than anything is to give rotomolders ... access to larger amounts of recycled material than would typically be available from within the industry.''
There is not a precise way to pinpoint current available feedstock, but an estimated 10 million pounds of recyclable resin may be available each year from prime rotomolding grades. Each year rotomolders consume about 700 million pounds.
The moment that supply is used up, of course, the rotomolder is at a real disadvantage, Voldner said.
Officials do not know the exact cost of using the post-industrial material, which will vary depending on in-house equipment, including pulverizers and granulators. They said the cost will be higher than traditional recycled materials, but lower than prime resin.
``It solves the environmental problem and provides a good material, good product,'' Vlachopoulos said. ``You get rid of post-industrial waste and you have a lower-cost material base. ... The only complication is that they have to go through blending and modification.''
Steve Copeland, president of specialty resin firm Jerico Plastic Industries Inc. of Wadsworth, Ohio, said the demand for recycled product has risen steadily during the past few years. Copeland also is president of compounding firm Conex Plastic Industries Inc. of Greensboro, Ga.
``Demand of the material we supply has grown every year that we've been in business,'' Copeland said in a July 15 telephone interview. ``This [technology] should improve the availability for feedstocks for people that supply reprocessed materials, which would ultimately benefit the molders, based on what was presented in the paper.''
David Spears, operations director for Charloma Inc. in Cherryvale, Kan., said his company has found a good niche for recycled material in materials-handling, lawn and garden, and liquid waste products.
``We've been able to find enough [recycled] product out there to purchase,'' he said. ``We do buy some reprocessed when our own internal supplies aren't sufficient.''
The firm uses about 40,000 pounds per month of reprocessed rotomolded materials.
``Price is everything,'' he said. ``If you can offer your clients a better price with a material that can still do the job, they're more willing to look at that today than they were in the past.''
The new technology, however, is not for every rotomolder. Kayak and toy producers would not use it, for instance, because they need precise color control, researchers said.