Water-based Adhesives
Water-based adhesives are composed of a combination of water, polymers, and additives. These adhesives cure when the water evaporates.
Water-based adhesives are generally formulated from natural polymer, from vegetable sources such as starches and dextrins, protein sources like casein, fish, soybean, milk albumen and animal sources or soluble synthetic polymers, including polyvinyl alcohol,
cellulose ethers, methylcellulose, carboxymethylcellulose, and polyvinylpyrrolidone.
The most important range of water-based adhesives are usually based on polyvinyl acetate, which is used as an emulsion that needs stabilizing.
The main stabilizer is approximately 5% polyvinyl alcohol. This is specially prepared by the hydrolysis of the acetate and retains around 20% of residual acetate groups to provide a molecular weight which is relatively low.
Types of Water-based Adhesives
Most water-based adhesives are originally synthetic, based on polymers such as PVOH, EVA, and PVAC. There are also vegetable sources such as starch and sugar. Four main types of water-based adhesives are as follows:
Polymer Adhesives: The main components in resin water-based adhesives are vinyl acetate, ethylene vinyl acetate, and acrylic resin emulsion polymers. In order to produce these kinds of water-based adhesives, water is mixed with the polymers, polyvinyl acetate and ethylene vinyl acetate to produce a bright white liquid mixture.
Once the adhesive has been applied and allowed to dry, however, it produces a clear, pliable bond that is also used for paper, wood and plastic.
Natural Rubber/ Latex Adhesives: Latex glues are made of emulsified elastomers, or rubbers. Like polymer adhesives, latex adhesives must be applied to the substrate surface and allowed to dry into either a solid bond, or a more crude, flexible bond, depending on the formulation.
The drying time of latex adhesives can vary depending on the type and formulation of the adhesive, but generally, they dry relatively quickly. These types of water- based adhesives are mainly used for bonding stamps, fabric, leather, and wood.
Latex adhesives have a limited shelf life and can degrade over time, especially if they are
exposed to high temperatures or moisture.
Dextrin Adhesives: Dextrin adhesives are usually typically brown in color and are one of the more popular water-based adhesives types. These adhesives contain a starch base and result in a more clean finish.
For that reason, they are commonly used for in the paper industry for such applications as bookbinding. These adhesives are known for being quite durable when used with material
such as paper, however, their vegetable base make them more susceptible to breakdown when exposed to water.
Casein-based Adhesives: Protein adhesives are derived from either animal organs that are processed specifically to produce hot glue, or from proteins found in animal milk, which is used to make casein glue. Casein-based adhesives can be extremely water resistant. Hence, they are ideally suited for the beverage industry for the labeling of bottles.
Water-based adhesives can also be categorized by the way in which they form bonds, which is wet bonding and dry bonding. Wet bonding water-based adhesives cure through evaporation, and include both dispersion and emulsion systems.
In this bonding process the waterbased adhesive is applied either to one adherent or both of them. As curing occurs as a result of evaporation, it is very important that at least one of the adherents is porous, absorbing the water and allowing it to leave the waterborne adhesive system faster.
However, as they are generally more robust and provide better heat resistance, dry bonding adhesives are employed more widely than the wet bonding systems.
Areas of Application
Water-based adhesives are used in virtually any industry, such as in the packaging industry, cardboard processing, woodworking, lamination, panel construction and bookbinding.
Glues are used in the process at many factories, often this is a hot melt or a water-based glue. Eve though there are various types of glue, water-based glues and hot melts are usually used in industrial production processes due to their high efficiency and low costs.
Water-based adhesives are also still widely used in manual applications, such as wallpaper, floor and construction applications.
Advantages of Water-based Adhesives
Water-based adhesives offer several advantages over other types of adhesives, such as solvent-based adhesives or hot melt adhesives. Some of the advantages of water-based
adhesives include:
1)Environmental Friendliness: Water-based adhesives are non-toxic, non-flammable, and emit very little volatile organic compounds (VOCs), making them safer and more
environmentally friendly than other types of adhesives.
2)Easy Clean-up: Water-based adhesives can be easily cleaned up with water, which makes them more convenient to use than solvent-based adhesives.
3)Good Adhesion: Water-based adhesives have excellent adhesion properties and can bond well with a variety of substrates, including paper, cardboard, fabric, and wood.
4)High Solid Content: Water-based adhesives can have a high solid content, which means that 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: Applying water-based adhesives does not require as many safety measures as systems that contain solvents, which can improve efficiency.
Overall, water-based adhesives are a safe, effective, and environmentally friendly option for bonding a variety of materials.
Prepared by: Murat Soygür
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
