Thermal bonding ( also called melt or heat bonding) process, is often applied to low – melting thermoplastic fibres, especially polypropylene and polyethylene . Thermal bonding is achieved by passing the fibrous web between heated metal cylinders, which fuse and bond fibres mainly at their crossing points where the pressure is greatest . (48) But if the melting temperature of the web fibres is high ,bonding additives such as powder can be used to bond the fibres together.
3-Chemical bonding – In the chemical bonding process , which is used the least in geotextiles , a cementing medium such as glue , latex or resin is added to bind the filaments or short fibres together . The impregnated web is then cured and / or calendered. (4)
In this research, both mechanical bonding process ( using needle punching machine) and thermal bonding process ( using heated calendars) were used.A novel technique for web bonding was also used using a woven fabric bonded to the nonwoven web using needle punching technique in order to improve the stability of the produced samples