[Manufacturer Research Update] Sticky Subject

Can’t get that bait station to stay in one place? It’s not a figment of your imagination — it’s a real problem. The chemistry of most plastic bait stations makes it difficult to get glue or other adhesives to stick to them. Of course, this makes it difficult to secure the station to other surfaces like concrete pavers so they can be anchored and made tamper resistant.

The author recently explored this problem in an effort to provide information that will help pest control professionals. His findings are straightforward, but insightful. For this project, adhesion is defined as the bond of an adhesive to a surface. In this case there are two dissimilar surfaces involved, plastic and concrete. Cohesion is the internal strength of an adhesive. All tests were conducted using Liphatech’s Aegis-RP bait station.

A STANDARDIZED TEST. The adhesive was applied in a simple T-shaped pattern. Another pattern, three 2-inch diameter circles of adhesive applied around holes drilled in the bottom of the station to form rivet-like heads, also was tested. Neither method performed well, regardless of the adhesive issued. Applying adhesive in a 3⁄8-inch to ½-inch bead in an oval T-shaped pattern performed the best in the testing (see photos). About 2 ounces of adhesive were applied per station.

Adhesives used in the test included:

• PL Polyurethane Premium Construction Adhesive, which includes a mixture of hydrotreated naptha, diphenylmethane diisocyanate, talc, silicon dioxide and polymeric MDI isocyanate and is recommended for adhesion to wood, metal, masonry, drywall and plastics.
• PL Plus Super Duty Construction Adhesive, which includes a mixture of petroleum solvent, resin, clay, limestone, toluene, acetone and methyl acetate, and is recommended for adhesion to wood, metal and masonry.
• PL 200 Construction Adhesive, which includes a mixture of petroleum naptha, rubber, resin, kaolin, calcium carbonate and xylene, and is recommended for adhesion to wood, metal studs, drywall to drywall and drywall to concrete.
• PL 400 Construction Adhesive, which includes a mixture of naptha, toluene, ethanol, resin, clay and calcium carbonate, and is recommended for adhesion to wood, metal and masonry.
• PL 500 Outdoor Project Adhesive, which includes a mixture of toluene, solvent naptha, ethanol, resin, clay and calcium carbonate, and is recommended for adhesion to wood.
• Liquid Nails Heavy Duty Construction Adhesive, which includes a mixture of cyclohexane, limestone, kaolin, titanium oxide, hepane, cristobalite, quartz, benzene, dimethyl polymer, solvent naptha, petroleum distillates, petroleum naptha, hydrotreated naptha, benzene and ethenyl polymer, and is recommended for adhesion to wood, metal studs, drywall and brick veneer (specifically not for plastics).

Adhesive holding power was determined by securing the concrete paver in place and using a winch to pull on the bait station while measuring the force necessary to break the station free from the concrete. (Table 1 shows holding power in pounds.) The stations were cured indoors at about 70°F using PL 200 Construction Adhesive. Note the importance of proper curing to the holding power of the adhesive. (See table 2.)

For the test comparing the holding power of all six products, the adhesive was allowed to cure for three days, as advised by label directions. Then the stations were used in ways that simulated real-world handling and conditions, which included being loaded and unloaded from a vehicle, being stacked in a warehouse for a week and being weathered outdoors for two months. During this time, the samples were subjected to temperatures ranging from 75°F to -5°F, as well as sun, rain, snow and ice.

After the initial testing phase using the adhesives and measuring holding power, the author wanted to explore simple ways that pest management professionals in the field can improve adhesion. The key word is simplicity. We wanted to develop some techniques pest control professionals can realistically take in the field to improve adhesion quickly and easily. (See table 3.)

In addition to learning the holding power of various adhesives and the tips that make adhesion even stronger, these additional findings were reported:

• It takes a week or more for the adhesive bond to reach full strength.
• The bond deteriorates with age and exposure to weather.
• Sanding and cleaning the plastic increased the holding power and slowed the deterioration of the bond significantly.
• Price is not an accurate indicator of holding power.
• There is no difference in the holding power comparing gray and black stations.
• At various stages of the curing process the adhesive may create a bulge in the bottom of the bait station.
• Although PL 500 Outdoor Project Adhesive does not list plastic as a recommended use, it had the strongest bond.

SUMMARY. Based on a recent visit to a hardware store, PL 200 Construction Adhesive is priced from $1.30 to $3 for a 10.2-ounce tube. That works out to a modest cost of 25 to 60 cents per station.
In the end, simply sanding the bottom of the plastic bait station improved adhesion markedly, regardless of the adhesive used. Maintaining bait station security, including adhesion to various surfaces, is key in ensuring effective, efficient rodent abatement. So don’t forget the sandpaper (or acetone) when you plan to use adhesives.

Ted Bruesch is Liphatech national technical support manager.

Author’s notes: PL, PL 200, PL 400 and PL 500 are registered trademarks of the Henkel Corporation. Liquid Nails is a registered trademark of Liquid Nails.

Liphatech offers a comprehensive line of rodenticides, including Generation, BlueMax, Maki and Rozol rodenticides and the Aegis line of bait stations. For information, call 888/331-7900 or visit www.liphatech.com.