Method for the thermal bonding of contacting pieces of a thermoplastic material

The improved method for thermal bonding of contacting pieces of a thermoplastic material to form a bonded porous mass by the ignition of a combustible gas around the contacting pieces forming an unbonded porous mass so as to bond the pieces together which comprises:

• (a) providing contacting pieces of a thermoplastic material in a confined space having a variable volume with an initiator means for igniting the combustible gas externally of the confined space, with an explosion diffuser providing a tortuous gas flow path adjacent the porous mass between the initiator means and the porous mass and with a combustible gas around the pieces which form an unbonded porous mass, said volume being reducible to compact the pieces in the unbonded porous mass;
• (b) igniting the combustible gas within the unbonded porous mass by activating the initiator means which ignites the combustible gas externally of the confined space and diffuses the ignited gas through the tortuous flow path of the diffuser element so as to transiently heat the pieces sufficiently to cause them to interbond without damage from the ignited combustible gas when they are brought into contact with each other by compacting the unbonded porous mass;
• and
• (c) compacting the pieces while they are heated by reducing the volume of the confined space so as to cause contact of the heated surfaces and to cause bonding and formation of the bonded porous mass.