54 is composed of a melt processible thermoplastic elastomer tpe tpes can be molded or extruded on standard plastics processing equipment and are made by copolymerizing two or more monomers using either block or graft polymerization one of the monomers develops a hard or crystalline segment that functions as a thermally stable component that can soften and flow under shear at service temperatures the hard segment provides mechanical strength and toughness the other monomer develops a soft or amorphous segment that provides elasticity through the addition of flame retardants tpes offer greater flame resistance and abrasion resistance than traditional thermoplastics such as polyamides generally the outer layer 54 should not react with the external environment and should be able to withstand various shocks vibrational fatigue and changes in temperature as well as exposure to various corrosive compounds present in motor vehicles furthermore the outer layer 54 should be usable within a temperature range between about 40 u00b0 c and about 150 u00b0 c or preferably within a range of between about 20 u00b0 c and about 120 u00b0 c the filler tube 32 should have a tensile strength of no less than 25 n mm 2 elongation at break of at least 150 and a burst strength at 23 u00b0 c and 120 u00b0 c of.