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Gluing Pallets?
Adhesive manufacturer to reformulate existing wood glue product and to conduct additional tests to etermins its feasiblilty for pallet assembly.

Date Posted: 12/1/1998

An adhesive manufacturer is planning to reformulate one of its existing products and to conduct additional tests in order to determine if it may be suitable for assembling wood pallets.

Franklin International, located in Columbus, Oh., has been a manufacturer of adhesives and sealants for more than 60 years. A privately-held, family-owned business, Franklin makes the Titebond® brand of wood glues and adhesives.

The company plans to partner with several pallet manufacturers in the Midwest to test the reformulated product.

Franklin’s decision followed a research project recently conducted at Virginia Tech into the potential use of adhesives for assembling wood pallet components.

The company plans to make modifications to the physical properties of a brand of adhesive that Franklin already sells in such markets as residential wood manufacturing, millwork, and cabinetry.

"We are going to identify any application hurdles that remain and move forward with reformulating," said Matt McGreevy, Franklin vice president. "It’s a very exciting project."

"We’re confident in our ability to reformulate it very quickly," McGreevy added. "We will have lots more to talk about in just a few months," he predicted.

McGreevy was equally confident that pallet assembly machinery can be adapted easily to using adhesives. "Adhesives are used all the time in high-speed assembly processes," he noted, "whether they are applied by hand or automated systems. It’s just a matter of matching up the right equipment. The technology is abundantly available."

Franklin has been in contact with several Midwest pallet businesses and also at least one pallet customer to test the reformulated product. The user company is particularly interested in reducing losses of damaged goods from problems associated with metal fasteners used for pallet assembly — such as product snagging on nails.

McGreevy described Franklin as a "medium-sized player" in the adhesive industry. "We place a lot of emphasis on our ability to solve problems that require some technical level of expertise and a systems approach," he said. "That’s one of the reasons why I think this one is right up our alley."

Assembling pallets with adhesives, provided the pallets perform well and can be manufactured in large quantities, would be a breakthrough development in the pallet industry.

The use of adhesives for wooden pallet assembly, which has been investigated before, has the potential to help the industry overcome drawbacks that some users associate with wooden pallets. For examples, nails may cause splitting of pallet components, and exposed fasteners can snag and damage product. Fasteners also are a factor in repairing and disassembling pallets, and typically they must be removed when wooden pallets are ground into certain wood fiber products, such as ground coverings for playgrounds and bedding for animals.

The research at Virginia Tech’s pallet and container laboratory, conducted earlier this year and sponsored by the National Wooden Pallet and Container Association, screened a number of commercially available adhesives to determine their effectiveness in bonding green and air-dried rough sawn wood pallet parts.

Nineteen adhesives were tested. They were analyzed for:

  • ability to fill gaps for bonding rough sawn and warped surfaces

  • resistance to weather exposure after assembly

  • low sensitivity to fluctuations in wood surface moisture content at time of assembly

  • good substrate penetration at relatively low clamping pressures

  • low emission of volatiles

  • easy clean-up and disposal of unused adhesive

  • rapid cure and short "closed" assembly time

  • long pot life

  • low cure temperature

  • low cost

  • resilience to impact loading

  • resistance to creep and relaxation

The adhesives were compared to the fastening performance of a helically threaded, 11-gauge, 2.25-inch, stiff stock, two-nail connection. Eight of the 19 adhesives had shear strength equal to or better than the nailed connections in air dried components. (In tests of shear strength, two wooden parts that are fastened at a joint are pushed toward each other so they become nearly parallel.) Only one of the 19 adhesives was satisfactory for green pallet components.

Cross-linked polyvinyl acetates in air-dried connections were equivalent to nailed connections while a Hot Melt Urethane Isocyanate was stronger in both green and air-dried pallet parts.

The NWPCA’s research steering committee plans to work with adhesive manufacturers to reduce the closed assembly times required. For air-dried pallet part assembly, reactive hot melts are candidates for future testing of creep response because of their relatively short closed assembly time and ease of handling.

Initially, most of the tests proved fruitless and the study actually had concluded when a representative of Franklin visited the pallet lab and expressed interest in the project. The lab agreed to provide the company with specimen parts for further tests.

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