Plastic welding :
In the middle of the 90's a true interest for the use of laser sources in plastic welding emerges. The arrival on the market of new irradiation sources like laser diodes has contributed to the present research works. Their small size, the constant decrease of their prices and above all the new possibilities they offer make them one of the future solutions for the welding of polymers.

Principle :
Laser welding is based upon the behaviour of plastic under irradiation. In near infrared, most plastics are transparent. The laser beam goes through without interaction. The addition of additives or colorants into the plastic can change this transparency.
For polymers, the welding characteristics only depend on the interface temperature, the heating time and the holding pressure. With a laser source the energy supply is always controlled, the welds are perfectly homogeneous and the mechanical resistance usually higher to those obtained with other processes.

	Laser beam	Beam moving
Clamping
			Absorbing polymer
	Heated and welded volume	Transparent polymer

By stacking a transparent material with an absorbing material and irradiating the whole we create a local melting of the absorbing material at the interface. By thermal conduction the transparent material rises in temperature. Interpenetration and tangle of the macromolecular chains will give after cooling a solid bond between both parts.