As mentioned above, adhesives can be split into two main categories: organically derived and chemically derived. In the past, organic based adhesives took precedent as they were more readily available and safer to use. Fish bones were a popular base for adhesives that were used to glue things like paper etc.
Nowadays – Synthetics are the primary choice. There is a wide range of very safe and easy to use glues available, and there are far less concerns when it comes to application. The main range of synthetics will be described below.
Synthetic adhesives can be broken down into these types:
Elastomers which are naturally elastic are suitable for joining plastics and rubbers – as it makes a very flexible bond.
Thermoplastics are a good solution as they are also very recyclable; when they dry they become very brittle. An example sub-class within thermoplastics are hot melt ‘glues’ these are very flexible and powerful adhesives that you apply using a heated glue gun. It dries in a short period of time and forms a very strong bond. Typically thermoplastics show poor waterproofing.
Thermo setting plastics are those which ‘cure’ and transforms the adhesive into a plastic or a rubber via creating a cross-linked molecular structure. The best example of which, are epoxy resins. These are some of the most expensive, but also strongest adhesives available.
Cynoacrylates are probably the most famous adhesive, marketed into glues such as ‘Superglue’ cyn-acrylates create a very strong, waterproof bond very, very quickly. However in cold conditions the bond can become very brittle and crack very easily.