Understanding Bond Strength & Tack in Lamination Adhesives
In the technical world of lamination, the terms 'tack' and 'bond strength' are often used to describe an adhesive's performance. While they are related, they represent two distinct and equally critical properties that determine the success of a lamination process. A nuanced understanding of both is essential for selecting the right adhesive and optimizing production lines for quality and efficiency. Simply put, tack is the initial stickiness that holds substrates together on the machine, while bond strength is the ultimate, permanent adhesion that ensures the product's long-term durability. Misunderstanding this difference can lead to poor material selection, production inefficiencies, and costly product failures in the field.
Tack, often referred to as 'initial tack,' 'wet grab,' or 'green strength,' is the property of an adhesive that allows it to form an immediate bond upon contact with a substrate with minimal pressure. This initial stickiness is crucial for high-speed lamination machines where substrates are brought together for only a fraction of a second in the nip roller. High initial tack ensures that the layers are held together firmly as they move through the machine, preventing common defects like tunneling, wrinkling, or immediate delamination before the adhesive has had time to fully cure. An adhesive with poor tack may allow the layers to shift or separate, leading to significant material waste and production downtime. It's the property that gets you off the machine successfully.
Final bond strength, on the other hand, refers to the ultimate strength of the adhesive bond after it has fully cured and set. This is the measure of the force required to separate the two laminated substrates and is the ultimate indicator of the lamination's durability and longevity. This property is measured through various standardized tests, such as peel tests (measuring the force needed to pull layers apart at a specific angle and speed) and shear tests (measuring resistance to forces sliding in parallel). The required bond strength depends entirely on the end-use application—a flexible food pouch requires high bond strength to withstand handling and product weight, while a protective film might need a lower, controlled bond strength to allow for clean removal by the end-user. This is the property that ensures the product performs as intended throughout its lifecycle.
A successful lamination requires a carefully engineered balance of both properties. An adhesive might have excellent final bond strength, but if its initial tack is insufficient for the machine speed, it is unusable. Conversely, an adhesive with great tack but poor final bond strength will lead to field failures and damage a brand's reputation. At Kubron's in-house QC laboratories, we conduct rigorous testing to ensure our products, like the Aquatack Plus PF, deliver the optimal balance. By simulating real-world application conditions and analyzing peel strength, shear resistance, and environmental stress durability, we engineer adhesives that provide both the immediate tack for high-speed efficiency and the long-term, durable bond strength for ultimate product integrity. This ensures our customers receive a solution, not just a product.