Water-based adhesives are versatile, and they provide advanced bonding to meet demanding applications in a wide variety of end-use markets. As a leader in developing adhesive solutions across industries, Henkel is one of the most trusted of all water-based adhesive manufacturers. The products in our AQUENCE® range of water-based adhesives are coater-ready, while superior finishes allow our customers to maintain product quality and improve total cost of ownership.
Henkel water-based adhesives are used to create a variety of products including books, home appliances, medical tape, and packaging. Our adhesives are selected because they solve many of the problems faced by manufacturers including label flagging and adhesive transfer. Manufacturers can choose from adhesives based on different polymers to find the solution that perfectly suits their products.
Water-based adhesives are developed using a combination of water, polymers, and additives. They are ideal for porous or non-porous substrates. These adhesives may be formulated as solutions and are activated as the water evaporates or is absorbed by the substrate. There are several different chemistries, using both natural-based and synthetic-based materials. These include:
- VAM-based emulsions (VAE or PVA emulsions)
- Acrylic-based emulsions
- Natural-based or bio-based adhesives
- Natural rubber adhesives
- Liquid polyurethane – structural engineering and food packaging/flexible laminates (LIOFOL)
- Additives for water-based adhesive applications
There are two primary types of VAM-based emulsions. The first is polyvinyl acetate (PVA) adhesives. They are aliphatic, rubbery synthetic polymers and are considered a type of thermoplastic. PVAs are designed for use on porous materials, particularly paper, wood, tissue, non-wovens, cloth, and some stone materials. Paper applications, such as corrugated board, bookbinding, envelopes and labelling are the most common uses.
The second is vinyl acetate ethylene (VAE) adhesives. They offer considerable performance advantages over PVA adhesives. VAE adhesives offer comparable machining properties to PVAs with improved adhesion to non-porous surfaces. VAE adhesives have better flexibility and water resistance, with superior bonding properties.
Flexible packaging is the biggest application type for VAE adhesives. Another large category is laminating applications due to their flexibility, moisture resistance, and superior substrate adhesion. VAEs are widely used in furniture, bookbinding, and textile applications. VAEs are also popular in the fabrication of non-woven products, such as personal hygiene applications.
Acrylic-based emulsion adhesives are made by homogeneously emulsifying vinyl acetate, EVA, or acrylic synthetic resin polymers in water. These adhesives provide a balance between:
- Peel – the strength between the adhesive and the substrate, increasing over time during the curing process
- Shear – the ability for the product to adhere to itself
- Tack – the speed at which the adhesive bonds immediately to the substrate
Many acrylic polymers are cross-linked, which improves the weather- and ageing resistance, as well as preventing breakdown by other solvents. Some common acrylic adhesives include pressure-sensitive adhesives and paper-laminating adhesives. Acrylic-based emulsion adhesive is commonly used to manufacture packaging, particularly paperboard boxes.
Natural-based polymers are developed from organic materials. Some of the most popular are derived from vegetable sources, such as starches and dextrins, or protein sources, such as soya beans, casein, and milk albumen. Natural-based adhesives with caseins have relatively long drying times, form very strong bonds, and are resistant to water. Dextrins are commonly used in the paper industry and are very durable with specific materials. However, they are susceptible to breakdown when exposed to water.
Natural-based or bio-based adhesives are supplied in two forms – liquid solutions or dry powders – both are mixed with water prior to application. Adhesive strength results when water evaporates or is absorbed into the substrate. Common applications involve a permeable substrate; however, there are other methods involving dry time before the adhesive can be activated, with a "quick tack" joining two non-permeable substrates. Many natural-based adhesives are perishable and extended storage is not possible.
High-quality water-based adhesives are extremely quick and easy to apply. They can be applied via rollers, spray guns, and using immersion processes. Water-based adhesives do not adversely impact rollers and other equipment as they dry. Water-based adhesives are also easier to remove from equipment, further minimising the risk of blockages. Water-based adhesives are delivered in bulk containers, such as:
- Drums
- Totes
- Tankers
Depending on the product, there are different concentration levels. This requires some effort to dilute the products to meet the application needs. In some cases, two-part systems are used. These require additional effort to mix the adhesive for each application.
Water-based adhesives also have different viscosities – defined by application. They range from flowing like water up to more viscous options similar to black treacle. Viscosity is measured by centipoise (cPs) – essentially this is the thickness of a water-based adhesive. The higher the cPs, the thicker the substance. Water is measured at 1 cPs, castor oil is 1000 cPs, and peanut butter is 250,000 cPs.
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