Regardless of what you call it—cement, adhesive, or glue—if it is not used with discretion, that sticky liquid can do more harm than good when splicing a conveyor belt.
A common belief among many belt splicers and even some belt manufacturers has been, “if a little cement is good, then a lot of cement is better.” However, nothing could be further from the truth. Understanding what rubber cement is—and the role it plays in conveyor belt splicing—is essential.
Rubber cement used in belt splicing typically consists of 10–20% rubber compound dissolved in 80–90% solvent. When the volatile solvent evaporates, or “flashes off,” all that remains is the rubber compound. The primary role of rubber cement in belt splicing is to hold the components of the splice together until they can be secured in the press.
In other words, its purpose is to keep the splice aligned until it is clamped in the platens of the press. Rubber cement does not contribute to how tightly a splice cures. This may be surprising, particularly for those who have been taught that “more cement is better,” when in fact the opposite is true.
Blair Rubber has observed this firsthand. In one experiment, a splice prepared with cement was compared to one assembled without cement. Post-cure testing showed identical adhesion values for both. Fresh tie gum, fresh cover stock, and properly stripped and cleaned belt ends and carcasses are the key factors in achieving a strong, long-lasting splice.
A light application of rubber cement is sufficient. Blair Rubber has identified a series of splice failures with one common factor: excessive cement application. When a coat of cement is too thick, the solvent cannot fully “flash off.” The surface may appear dry, but solvent can remain trapped beneath. If curing occurs with solvent present between the plies, the solvent will expand when heated, potentially causing delamination of the splice components and resulting in splice failure.
To help avoid this issue, dip your brush only about ¼ inch into the cement, tap off any excess, and apply the thinnest possible coat using firm, even brush strokes. Allow sufficient time for the solvent to evaporate. The cement is ready when it is tacky to the touch but leaves no residue on your finger.
Careful application of rubber cement is a simple but crucial step toward reducing the risk of splice failure.