Developing a bond between adhesives and overlays: proper surface preparation and adhesive use will prevent delamination.

The laminating industry encompasses a broad range of products, which include furniture, cabinets and floor coverings. Adhesives, naturally, play an important role in both structural integrity and aesthetics. Proper surface preparation and selection of the right adhesive will help ensure a long-lasting bond and prevent delamination from occurring.

The Adhesive and Sealant Council estimates the total U.S. market size in 2002 for lamination adhesives used for decorative overlays (excluding saturated papers and edge-banding) at 54 million dry pounds. This figure is predicted to grow 2.5 percent annually over the next five years.

The array of adhesive types is shown in the following table. These figures exclude wood veneer and assembly adhesives, as well as all packaging film-to-film adhesives and similar type adhesives.

Overlay Shipment Figures

The Laminating Materials Assn. estimates that shipments of all decorative overlays and edgebandings that require an adhesive for lamination surpassed 11 billion square feet in 2002; the breakdown of volumes by product group is shown in the accompanying table. The "paper overlays" category includes low basis weight papers and decorative foils. The latter group represents overlays that generally weigh between 40 and 80 grams per square meter, while low basis weight papers generally range between 23 to 35 grams per square meter.

Excluded from the data table are saturated papers that are used for thermofused melamine panels. These overlays do not require an adhesive since the resin compound saturated into the paper acts as the bonding agent by cross-linking with the wood fibers on the surface of the substrate.

Many Factors Determine Adhesive Choice

The right amount of the best adhesive is dependent upon several factors. These include: type and overall condition of laminating equipment (which may include nip roll distance from the adhesive spreader, as well as operating temperature and pressure); whether the adhesive is applied to a web overlay, board core, or both; how the adhesive is applied (i.e., combined wet, semi-wet, or thermal); weight of the adhesive coating; spread roller type; the production line speeds (fpm); drying conditions (type, temperature, and time); ancillary in-line equipment (such as sanders, cutters, and trimmers); and end-use specifications and standards (i.e., how will the end product be used and what environmental conditions will the product be exposed to).

Most adhesive suppliers offer key strengths in specific market niches. Many also conduct testing to ensure the proper adhesive is selected. Larger adhesive companies often have very sophisticated testing labs that can test for industry wide accepted standards. Examples are humidity cycling tests, 180 F heat aging tests, and HPVA type 2 water resistance tests. If industry standards are not well defined, adhesive companies can compare testing results to historical data. By relying on the experience of the adhesive supplier, a company can gain a good perspective on an adhesive's expected performance.

Price is also a consideration. The end-user may need to figure in the price of storage and application equipment to come up with the total cost of using a particular adhesive. Don't forget to include labor and utilities as well. A typical PURHM (polyurethane hotmelt) adhesive can be seven times more expensive per pound than a PVA (polyvinyl acetate), but may save time and money in the long run.

The Lamination Process

In-plant environmental conditions can have an effect on the lamination process. For example, what type of equipment is being used? What are operating temperatures and airflow requirements for proper bonding to occur? Consider the ventilation and dust control situation -- excessive particulates in the air can adversely affect lamination, and ultimately lead to delamination.

Environmental factors also dictate adhesive selection.

Depending upon state and local regulations, adhesives containing high levels of volatile organic compounds may be banned. Regional safety codes may also dictate how adhesives are bandied and disposed of, thus eliminating certain technologies.

Regulations limiting the use of products containing potentially hazardous VOGs may necessitate the use of other products that may seem less ideal. As an example, solvent-based contact cements have been under attack for many years. Fortunately, however, many alternative adhesive formulations have been developed which oftentimes perform better than the incumbents. The adhesive industry is constantly researching ways to "build a better product" that will stay ahead of the environmental curve without compromising performance.

Other Considerations

In addition to environmental considerations, in-use and in-transit conditions also should be considered. Low temperatures can create challenges for certain types of adhesives, such as water-based products. Other products, including those that are polyurethane-based, are more impervious to damage during shipment. In general, freezing should be avoided, as it may affect ultimate performance when the adhesive thaws out. Always check with your supplier before using any products that may have frozen during shipment.

Wide temperature swings inside a production plant should also be considered. For example, typical PVA glues will have a minimum use temperature. If ambient temperatures fall below this point, the adhesive may not perform as well and result in a weaker bond joint. Another example is PURHM formulations. Initial green strength and total process time can be affected if temperatures in the plant fluctuate too much.

Of course, storage and feed equipment must be operated according to manufacturers' guidelines. Tank/tote storage conditions, pumping rates and pressures and application monitoring all need to be considered.

New adhesive trends benefit laminating

There are several new trends in adhesives that are positively impacting the laminating market. According to Chicago Glue Machine, "foaming water-based glues may reduce adhesive usage by 30 to 40 percent, increase operating line speeds, and 'sit up' better on the board, thus resulting in a superior laminated product." These technologies are considered "cost effective for high-production environments with lower coating weights, improved mileage, lower energy costs, and reduced reject rates leading to higher productivity," the company says.

According to Franklin International, fast-setting, water-based adhesives can be processed more quickly through heated roll press systems. The equipment is reasonably priced and process speeds are greatly improved.

In addition, there is a new class of hot press PVA adhesives that permits bonds to be formed, even if the glue is dry before the high pressure laminate is laid up. According to Franklin International, this helps compensate for line stoppages without wasted material. It also permits companies to continue to glue up panels even if the hot press is a bottleneck.

Reactive hotmelt and polyurethane technologies also speed up processing, and are appropriate when gluing difficult or non-porous substrates. Other technologies already on the market include: high solids, web coat, pre-applied and heat- and pressure-activated products.

Lamination Adhesives 2002 for
 Decorative Overlays and Edgebanding

(Million Dry Pounds)


Hotmelts
  Ethylene Vinyl Acetate   8.7
  Polyamide                2.6
  Polyester                0.6
  Polyurethane             1.1

Waterborne
  Polyvinyl Acetate       18.2
  Vinyl Acetate Ethylene  12.2
  Polyurethane             1.8
  Polychloroprene          1.6

Solvent-based
  Polychoroprene           5.8
  Epoxy                    0.7
  Polyurethane             0.7

Total                     54.0

Decorative Overlay Shipments 2002

(Billion Square Feet)


High Pressure Laminate   2.2
Paper Overlays           6.2
Vinyl Films              2.4
Edgebanding (estimate)   0.2

Total                   11.0

RELATED ARTICLE: The Laminating Materials Association (LMA) is a not-for-profit trade group that represents all types of decorative overlays in North America. In addition, the LMA is the representative organization for all edgebanding in the United States and Canada. The products represented by the LMA are applied to a composite wood substrate and used in the production of furniture, store fixtures, cabinets, wall paneling etc.

Starting with only 12 members in 1985, the [MA has grown to nearly 120 member companies in the United States, Austria, Canada, England, Saudi Arabia and Spain. Approximately 40 of these companies are suppliers of decorative overlay materials or edgebanding. The decorative finishing materials represented by the LMA include: decorative foils, heat transfer foils, low basis weight papers, saturated papers (a.k.a. thermofused melamine), vinyl films (includes membrane press vinyls) and edgebanding.

The remaining members in the LMA supply all of the other materials required for laminating., including substrates, adhesives and equipment Some are custom laminators or produce finished goods.

Available Services

Glossary of Terms: This free, pocket-sized booklet provides useful definitions of all the overlays, edgebanding adhesives, substrates and equipment used by laminators.

Voluntary Product Standards: These cover the overlays and three of the edgebanding materials represented by the [MA It also includes standards for profile wrapped materials plus test measures for laminated products.

Statistical Reports: The annual statistical report details four years of historical overlay production. The full report is only available to members of the [MA. However, a brief synopsis of the most current report is available on the LMA'S Web site.

For mare information, contact he [MA at [phone] or visit www.lma.org.

ASC 

The Adhesive and Sealant Council Inc. is a non-profit international trade association incorporated in 1958 for the purpose of providing opportunities for exchange, education, advancement and improvement of all aspects of the adhesive and sealant industry. The mission of the ASC is to serve the needs of the member companies and to effectively create, maintain and enhance a positive image of the adhesive and sealant industry.

Strategic Goals

ASC's strategic goals are to:

* Provide training, information, and interaction for members

* Offer educational programs that communicate the advantages of adhesives and sealants over other types of fasteners 

* Represent the industry in regulatory and government affairs

Membership & Services

Membership is open to all adhesive and sealant manufacturers and industry suppliers. There are approximately 130 member companies currently involved in the ASC. Annual dues are based on a company's North American net sales of products and services to the adhesive and sealant industry.

Member services include: semiannual conventions and expositions; summer leadership conference; technical courses, workshops and regional meetings; peer group meetings for technical, manufacturing, sales/marketing, human resources, senior executives, small businesses, and industry suppliers; regulatory/legislative monitoring and activities at federal and state levels; biennial global industry market report; statistical services; industry- related publications; online technical training program; online career center; and member support programs (energy, freight, HR).

For more information on the organization, contact the ASC at [phone] or visit www.ascouncil.org.

Larry Sloan is the director of marketing and member services for The Adhesive and Sealant Council. For information, contact the ACS at (SO]) 986-9700 or visit www.ascouncil.org.

George Carter is the executive director of the Laminating Materials Assn. Contact the LMA at (201) 6642700 or visit www.lma.org.