Water-Based Adhesives

Water-based adhesives consist of a combination of water, polymers and additives. These adhesives cure through water evaporation. Water-based adhesives are typically formulated from natural polymers derived from plant sources such as starches and dextrins, protein sources such as casein, fish, soy beans, milk albumin, or soluble synthetic polymers including polyvinyl alcohol, cellulose ethers, methylcellulose, carboxymethylcellulose and polyvinylpyrrolidone. The most important types of water-based adhesives are polyvinyl acetate-based adhesives, which are typically used as an emulsion and generally require stabilization. The main stabilizer is approximately 5% polyvinyl alcohol. This is specifically prepared through acetate hydrolysis and contains approximately 20% of residual acetate groups to provide a relatively low molecular weight.

Types of Water-Based Adhesives

The majority of water-based adhesives are synthetic in origin and are based on polymers such as PVOH, EVA and PVAC. There are also natural, plant-based sources such as starch and sugar. The four main types of water-based adhesives are as follows: Polymer Adhesives: The main components of resin water-based adhesives are vinyl acetate, ethylene vinyl acetate and acrylic resin emulsion polymers. To produce this type of water-based adhesive, polyvinyl acetate and ethylene vinyl acetate polymers are mixed with water to obtain a bright white liquid mixture. After the adhesive is applied and allowed to dry, it forms a transparent, flexible bond that is also used for paper, wood and plastic. Natural Rubber/Latex Adhesives: Latex adhesives are made from emulsified elastomers or rubbers. Like polymer adhesives, latex adhesives must be applied to the substrate surface and allowed to dry as a solid bond or a harder, flexible bond depending on the formulation. The drying time of latex adhesives can vary depending on the type and formulation of the adhesive, but they generally dry relatively quickly. This type of water-based adhesive is primarily used for bonding materials such as stamps, fabrics, leather and wood. Latex adhesives have a limited shelf life and can deteriorate over time, especially when exposed to high temperatures and moisture. Dextrin Adhesives: Dextrin adhesives are typically brown in colour and are among the most popular types of water-based adhesives. These adhesives contain a starch base and provide a cleaner surface. For this reason, they are commonly used in the paper industry for applications such as bookbinding. Dextrin adhesives are known for being quite durable when used with materials such as paper, but their plant-based nature makes them more susceptible to brittleness when exposed to water. Casein-Based Adhesives: Protein adhesives are derived from animal organs specially processed to produce hot adhesives or from proteins found in animal milk used to make casein adhesive. Casein-based adhesives can be extremely water-resistant. These adhesives are ideal for labelling bottles in the beverage industry. Water-based adhesives can also be categorized as wet-tack and dry-tack based on how they form bonds. Wet-tack water-based adhesives harden through evaporation and include both dispersion and emulsion systems. In this adhesive process, the water-based adhesive is applied to one bonding surface or to both. Since curing occurs as a result of evaporation, it is essential that at least one of the surfaces is porous and absorbs water to allow water to separate from the adhesive more quickly. However, dry-tack adhesives are more commonly used than wet-tack systems because they are generally more robust and provide better heat resistance.

Areas of Application

Water-based adhesives are used in almost every sector including packaging, carton processing, woodworking, lamination, panel manufacturing and bookbinding. Many factories benefit from adhesives in this process, typically hotmelt or water-based adhesives. Although there are various types of adhesives, in industrial production processes water-based adhesives and hotmelts are generally used due to their high efficiency and low cost. Water-based adhesives are still widely used in manual applications such as wallpaper, flooring and construction applications.

Advantages of Water-Based Adhesives

Water-based adhesives offer various advantages over other adhesive types such as solvent-based adhesives and hotmelt adhesives. Some of the advantages of water-based adhesives are: 1) Environmental Friendliness: Water-based adhesives are non-toxic, non-flammable and emit very low volatile organic compounds (VOCs), making them safer and more environmentally friendly than other adhesive types. 2) Easy Cleaning: Water-based adhesives are easily cleaned with water, making them more convenient to use compared to solvent-based adhesives. 3) Strong Bonding Properties: Water-based adhesives have excellent bonding properties and bond well with various substrates including paper, cardboard, fabric and wood. 4) High Solids Content: Water-based adhesives can have high solids content, meaning they can provide a strong bond while using less adhesive. 5) Versatility: Water-based adhesives can be formulated to meet specific performance requirements such as flexibility, heat resistance and water resistance. 6) High Efficiency: The application of water-based adhesives does not require as much safety precaution as solvent-containing systems, which can increase efficiency. Overall, water-based adhesives are a safe, effective and environmentally friendly option for bonding various materials.   Sources: https://www.sciencedirect.com/topics/engineering/water-based-adhesive https://www.adhesivesandcoatings.com/adhesives/about-adhesives/water-based-adhesives-and-sealants/ https://www.simalfa.com/lp/water-based-adhesives https://adhesive.intercol.eu/en/welke-watergebaseerde-lijmenzijn-er/index.html http://adhesive.intercol.eu/en/producten-2/koudlijmen/dextrine-lijmen/index.html