A relative newcomer to the edgebanding adhesive market, PUR (polyurethane) adhesives have found a wider acceptance in Europe than in this country.
Containing no solvents and requiring no mixing because they come in cartridge form, sealed PUR hotmelts are stable solids at room temperature and are applied at temperatures near 225F, according to Rolf Zollinger, president of A.T.C.O Inc.
PUR adhesives also chemically crosslink with the substrate after curing, forming a temperature- and waterproof bond.
"In moisture exposure tests conducted at the Vocational College for Wood Processing Technology of Rosenheim, Germany, both PVC and solid wood edges bonded with PUR were immersed in water for one full day without any signs of glue failure," said Baltayan.
The new closed edgebanding system, which replaces the roller and open glue pot with adjustable slot-nozzle technology, includes a Nordson MC Series applicator for PUR processing, an EB60V adjustable edgebanding slot gun for applying the material and a PLC interface to the company's IDM Activa edge bander from SCM Group USA.
Unlike traditional edgebanders that incorporate open glue pots and rollers, the PUR glue supplied by Kleiberit Adhesives USA is metered, providing adhesive control through fixed pressure dispensing.
According to Busener, the Nordson sys tem solves problems commonly associated with applying PUR adhesives with systems using glue rollers and open pots.
"I'm getting a better bond with the PUR and better appearance because there's no excess adhesive being used."
The application of PUR hotmelts in the wood-working industry usually is carried out with cartridge-holding guns.
PUR hotmelts can also be applied by slot die coat, extrusion or swirl spray, and are dispensed from drum, pail or 2-kilogram "unloaders" for flat and intricate substrates.
PUR hotmelts are widely used today in profile wrapping applications for furniture, picture frame, door and window profiles, kitchen counter top lamination production, postforming applications, desk and table top lamination applications, prefabricated wall and divider lamination, door lamination applications, and wall panel lamination in the RV industry.
PUR hotmelts are prevalent in the automotive, transportation, bookbinding, door assembly, and woodworking industries bonding substrates such as wood and wood products, steel, aluminum, ABS, polycarbonate, polystyrene, vinyls, HPL and fiberglass.