There are a huge variety of adhesives and glues available, in this guide we'll concentrate on the most commonly used glues for paper and packaging and hopefully it will be a springboard for your own investigation into the glues you'll consider using. Check out the sustainable adhesive options at the bottom and the introduction to no-glue alternatives.
Essentially we can subdivide glues into synthetic and naturally derived, and into reactive and non-reactive. For more details of the history and different properties of glues check this link.
The main environmental impacts from glues are the:
- solvent and gas emissions derived from the production and curing process
- biodegradability of the disposed product
- renewability of the material the glue was manufactured from
PVA is a white glue which is an emulsion of polyvinyl acetate in water. This synthetic polymer sticks porous materials like paper and wood as the water evaporates leaving behind the PVA polymer. It forms transparent films that are resistant to organic solvents, oil and grease and impermeable to most natural gases. PVA can be made a neutral pH to increase the lifespan of books and papers. PVA is nontoxic to humans however it does release toxic fumes if burned. PVA is biodegradable. PVA glue is a synthetic polymer manufactured from products generated by the petrochemical industry.
Clear glue in a tube that has a strong solvent smell (ie. Multipurpose, UHU or GOOP) you don't have to mix it with anything. You may find them marketed as different products to bond different materials however they are all essentially the same although some may be thinner for precise application, thicker for non-drip/vertical application, or with added UV resistance and added colour.
They bond to metals, glass, some rubber and plastics, ceramics, paper, wood, leather, vinyl, canvas, masonry, concrete. They dry clear and are waterproof, acid free and slightly flexible.
Synthetic Resin glues give off solvents as they are curing and are irritating to eyes and skin. These glues are toxic to aquatic organisms and may cause long-term adverse effects in the aquatic environment. All of these products are made from petrochemicals.
These glues require two parts to be mixed together, an epoxide resin and a hardener.
They can be used on paper, card, wood, metal, glass, stone, and some plastics. Epoxy adhesives are better in heat and chemical resistance than other common adhesives.
They can be made flexible or rigid, transparent or coloured, and have various setting times.
The main hazard is allergic reaction to the hardener and can cause occupational asthma. Some chemical compounds in the epoxy resin can cause cancer and developmental disorders in animals and humans as they are endocrine disruptors.
Almost all of these products are made from petrochemicals however some manufacturers have made epoxy that includes natural wood resins.
Latex-based adhesives are used to glue fabric, carpets and flexible porous objects. They can also be used as removable adhesives on non-porous surfaces. Latex glues are formed from natural latex (rubber trees) or synthetic latex. They are mixed in a solvent to keep them fluid, this is generally acetone, hexane or heptane. There is also a type of latex-based glue that is water-based (Copydex in the UK). These solvents evaporate leaving behind the rubber.
Latex-based glues do not work well in very cold conditions and can cause discolouration to light fabrics and paper. Natural latex glue is generally not as durable as other adhesives however it is very flexible. Natural latex is biodegradable and is naturally resistant to mold, mildew and bacteria. Some people have an allergic reaction to natural latex. Synthetic latex is created from oil-derivatives of the petrochemical industry, it forms a stronger bond and is hypoallergenic.
The solvents in these glues are produced from the petrochemical industry and can be hazardous if inhaled, they are also highly flammable. These solvents can damage some plastics and other polished surfaces.
Superglue, cyanoacrylate or CA glue is a fast bonding adhesive that forms strong but brittle bonds. It bonds skin and other organic and porous materials very well and is water resistant. These glues contain solvents such as methyl alcohol to keep them in a liquid form. The fumes can irritate eyes, nose and throat and skin. CA glue is made from formaldehyde plus products from the petrochemical industry.
PVC plastic cement is used to bond PVC plastic together. It doesn't bond any other type of material or plastic. Essentially it provides a chemical weld between the two PVC plastic surfaces. This works because the cement is actually a solvent that dissolves the PVC surfaces that it is in contact with. As the solvent evaporates the PVC plastic hardens and both surfaces are bonded together. The main hazard is inhalation of the vapour as it evaporates. The solvent is a product of the petrochemical industry.
Animal product based glue or horse glue is not commonly used except for speciality trades such as musical instrument repair and traditional cabinet carpentry. It is brittle and requires heating before application. It is biodegradable and from a renewable source.
Another alternative to "cold glue" is heat-seal adhesives. These are thermoplastics that are coated onto the surfaces and then activated by heat and pressure. These adhesives don't change chemically but bond together due to heat. Heat-seal adhesives can be solvent or water-based that are applied as liquid coatings. Some heat-sealing adhesives can also be applied as a hot melt coating via gravure, slotted die, or extrusion processes. The heat-seal process can be run on high speed production lines and is common for packaging. An example of a heat-seal adhesive is Vinyl Acetate Acrylic Copolymer in a water based solution - a product of the petrochemical industry.
The most sustainable options for adhesives involve using water-based emulsions or aqueous, latex-based or starch-based glues. These are usually solvent-free alternatives. Solvent-less adhesives have been shown to emit 75% less CO2 and use 80% less energy than solvent-based adhesives.
Various adhesive manufacturers make sustainable options for both cold-seal and heat-seal adhesives.
The most ecological and sustainable designs are those that use no glue at all! There is a lot of great design work happening for packaging that redesigns the need for glue. When was the last time you found your pizza box was glued together? This also saves on production costs. Stay tuned to this blog for examples of designs that have out-designed the glue!
If you're interested in the sustainable options for paper, recycled paper or ink then check out the other quick guides in this series.