Applications of laser welding for the joint of plastic materials

A pulsed infrared laser source, like the Nd:YAG, welds the irradiated plastic materials by means of a thermal process that gives a direct chemical bond between two layers in close contact each other. The intense photon radiation, of the order of 1010 W/cm2, is capable to modify the polymeric materials inducing a melting process that seals two sheets at their interface. The sealing action occurs between the polymeric layers if one of them, placed in second plane, can absorb the laser light while the other, placed in first plane, is radiation transparent. The polymer filler presence (like carbon nano-structures, iron oxide, silicate,...) is required in order to absorb the laser light and to obtain the joint at the interface with other polymers through an accurate control the filler concentration. The penetration depth of the laser light and the mechanical resistance can be regulated by the absorption power of the polymeric layer. With this aim, the filler amount must be accurately chosen in order to produce a strong joint. In this work we investigated the applications of Nd:YAG laser welding for the polyethylene biomedical joint devices. In particular, we examined the possibility to define the optimal depth of the sealing action by regulating the filler type and amount in different joint geometries.