Glue is a non-metallic substance spread on one or both surfaces of two separate materials to stick them together. Glues are more advantageous over other binding techniques such as sewing, welding, or mechanical fastenings. Some glues are natural, while others are synthetic.
There are different types of glues to choose from when working with plastic and wood. Some are PVA (Polyvinyl Acetate) Glue, Polyurethane Glue, Hot glue, Epoxy Glue, and CA (Cyanoacrylate) Glue. You choose the glue depending on which one you need for your application.
The Discovery of Glue
Humankind has been using glue made from natural sources since ancient times. Six thousand years ago, they made ceremonial and decorative items using glue. There are records 3,500 years old, to show that people used glue to combine papyrus and laminated woodwork.
The use of glue became commonplace across central and southern Europe with the rise of the Greek and Roman Empires. People used them in their daily jobs and construction work. They glued Roman mosaic floors and tiled walls together with substances that kept them intact and strong even to this day.
After that people made glue from plants and heat-treated rubber. Then in Europe people made another glue. They cooked animal hides, connective tissue, and hooves and reduced them to jelly. The process was then to dry the jelly and powder it. They boiled the powder in water to make glue as and when they needed it.
The Revolution of Glue
It was in the 1930s that scientists and chemists cracked open the secrets of plastic, rubber, and synthetic resin glues. People used industrial adhesives extensively during World War II. Later scientists and inventors discovered new compounds like neoprene, epoxies, and acrylonitrile.
The most important development in the history of glues happened during World War II. American chemist Harry Coover Jr created the first cyanoacrylate glue by accident. In the late 1950s working on this family of compounds, he and his employer made the first super glue. This brought about a tremendous change in society.
PVA (Polyvinyl Acetate) Glue
PVA is a glue made by adding vinyl acetate to water with an emulsifying agent. We use polyvinyl acetate glue extensively in woodworking. It is a very versatile glue because you can use it in many different materials like clothing, paper, and wood.
It’s thick, heavy, and opaque but dries clear. Apply it slowly and carefully to avoid splattering. It is long-lasting. You use any type of PVA glue for small projects. For bigger outdoor projects you can use a specific type of water-resistant PVA glue for better and longer bonding.
Pros of PVA Glue
- PVA glue is easy to use as it is a one-step glue
- It dries very quickly. So, you use it for quick projects
- It is relatively cheap
- It is non-toxic
Cons of PVA Glue
- Most polyurethane glues are not waterproof
- You cannot use them in boats and things you leave outdoors
- Takes a long time to dry
- Generally, the drying time is 12-24 hours. Drying time also depends on the temperature and the materials glued
PU (Polyurethane) Glue
PU glue is a liquid glue used for almost any type of bonding. Used to obtain a high level of durability. The high elasticity it offers makes it ideal for static and tactile bonding. Polyurethane glue is available in single and dual-component varieties.
The one-component polyurethane glue used in the woodworking industry is liquid at room temperature. You can bond this glue to various non-wood substrates like rubber, plastic, and metal. To improve the bonding strength it is better to coat the surface of the bonding substrate or layer with a coupling agent.
The two-component polyurethane glue bonds almost all surfaces. It is suitable for wood, plastics, aluminum, synthetic resin, cork, ceramics, porcelain, and metal. The cure time and pot life depend on the temperature of the environment.
You should mix the two-component polyurethane glue according to the instructions. Apply the glue as quickly as possible, because once it has cured, it cannot be liquefied again.
Keep the surface you want to bond, free of grease and dust. For better adhesion roughen the surface with sandpaper. After spreading the glue, fix the two surfaces with clamps until the glue has hardened. This ensures solid and long-lasting binding.
Pros of PU Glue
- It is non-inflammable and has excellent adhesive power
- It is water-resistant and allows sanding and painting once it is completely dry
- Used to fill and even out inconsistencies in surfaces
- It is stronger than water-based glue
- PU glue works fast to form a very strong bond
- Resistant to temperature and chemicals
- Used in varied industries as it has many applications
Cons of PU Glue
- You need to be very fast. It gives you very little time to apply the glue and make the necessary adjustments.
- Exposure to polyurethane glues causes several health issues like allergic reactions, difficulty in breathing, loss of consciousness, and in severe cases even blindness.
Follow the safety tips given below while using PU glue:
- To avoid skin contact with the glue wear nitrile gloves
- To avoid breathing in the vapors, work in a well-ventilated area
- Wear safety glasses to prevent the fumes from getting into your eyes
- Clean drips or spills immediately with warm soapy water or acetone
Hot glue is a very simple way to bond plastic to wood. It is economical and mess-free. Hot glue has a short drying and curing time and forms a very strong and durable bond. It is a good option for big operations as it is non-runny – it is solid.
Use a glue gun to work with this kind of glue. The glue gun heats the glue and loosens its consistency. Used in industries such as automobiles, furniture, electronics, packaging, and appliances.
Pros of Hot Glue
- It is good for both plastic and wood as it works on porous and non-porous surfaces
- It is both solvent and water-resistant
- Long shelf life
- Minimum amount of waste
- Does not contain volatile organic compounds (VOCs)
- Quick drying and curing
- Does not shrink after curing
- Makes tamper-resistant seals
- Can be cost-effective in the long run
Cons of Hot glue
- The use of hot glue on metals is hazardous
- The glue ignites if the metal gets heated and the fire could spread to the rest of the project
- Over time hot glue corrodes metals
The best glue for sticking wood to plastic is Epoxy glue. It works well on plastics such as acrylics and polycarbonates. It creates a very strong bond after hardening. There are two types of Epoxy glues – one-part and two-part glues. The one-part Epoxy glues are rarely used.
The two-part Epoxy glues contain two components- the resin, and the hardener. You need to mix them in equal parts before using them. Then the chemical process of curing begins and bonding takes place.
Epoxy glues also bond materials like metals, tiles, concrete, stone, plastics, ceramics, and wood. This glue is resistant to water, heat, and ultraviolet light.
Pros of Epoxy Glue
- Used on a variety of materials- porous as well as non-porous
- Use Epoxy glue for applications involving wood because of the strong bonding
- Used to fill gaps in wood and repair rotten wood.
- Mends broken household appliances
- Used to glue together broken car parts, lawn chairs, and even PVC (polyvinyl chloride) pipes
- Use it to fill gaps in the cement and also to bond cement.
Cons of Epoxy Glue
- It has a working time of 10 minutes
- Curing takes time – up to two days, depending on the ambient temperature
- You need to clamp down the materials to help with the curing
- More expensive than other wood glues
- Need to add the exact measures of the resin and hardener for the glue to be fully effective
CA (Cyanoacrylate) Glue
Cyanoacrylate glue is also known as super glue. This is a quick-bonding glue. This glue bonds anything from metals to plastics. Made of acrylic resin, it has special bonding conditions. It will bond with a surface only when there is moisture present. Does not stick to a perfectly dry surface.
The molecules in the CA glue react with moisture to form tight chains between the two surfaces in contact. This reaction is instant and generates heat. The bonds formed during curing are extremely strong.
It works very well on wood and a variety of other materials like glass, ceramics, plastics, and abalone. CA glue is also used for fast-setting work, repairs, filling cracks and gouges, and repairing chips in high-tech finishes. It also seals wood to eliminate pin holes. It is used at any temperature both indoors and outdoors.
Pros of CA Glue
- Available in different forms
- There is instant bonding
- Cyanoacrylate glue is a clear, white clear glue, suitable for the finish
- Suitable for gluing stones, rocks, wood, rubber, glass, ceramics, DIY, crafting, woodworking, miniature modeling, woodturning, and pen turning
Cons of CA Glue
- Cyanoacrylate glue‘s tendency to form strong bonds with your skin. This is common because the human skin is constantly perspiring and generates a layer of moisture, thereby creating conditions for the glue to cure
- Short shelf life. You should purchase only when needed.
- Expensive option
- Open time and cure time are very short – under a minute
Keep a bottle of acetone or nail polish remover at hand while using CA glue. Acetone chemically dissolves the strong bonds of the cyanoacrylate glue without harming your skin. It is also used to eliminate glue residue from any surface.
Glues are very material-specific. Different glues bond different materials. Wood glues are different from ceramic or metal glues. The preferred glues to stick plastic and wood are epoxy glue and cyanoacrylate glue because of their versatile nature and strong bonding.