The strongest glues for plastics actually work in two ways, either by forming a bond at the joints or by melding the two plastic surfaces together. Glues that form a bond are known as reactive glues and come in two combinable components that adhere to the two plastic surfaces and form a bond without damaging the plastic. The glues that meld together plastic pieces are known as non-reactive glues. They melt a layer of the plastic's surface to form bonds.
Non-reactive glues, also known as solvent cements, are designed to turn two pieces of plastic at a joint into a single piece of material. The solvent can be applied to one or both of the plastic surfaces. The solvent softens and melts the plastic where applied. Pressure added to the two plastic pieces helps to create a joint that consists of both melted surfaces mixed together.
Reactive glues are created by mixing a catalyst and a base resin to create the adhesive. This mix is then applied to the joint where it hardens, holding the two plastic pieces together. The joint is typically strong and flexible. Reactive glues can also be removed using solvents, enabling the separation of the two plastic surfaces without damaging the plastic in the process.