I made a J-Head hotend, using PTFE, since I can’t get PEEK in the local market also it is very high in cost. It extruded PLA @180, but after some time the copper part felled down (look like due to melting of PTFE).
Let me know why this happens. is this why the community is using PEEK for this.
Indeed it is. Many people try to replace PEEK which is costly and hard to find in some places - us Russians learn to live without it as well. But you can’t replace PEEK with PTFE - the latter gets soft when heated to our working temperatures. I am still looking for the perfect PEEK-less hotend, and it looks like the highly praised E3D is the best bet - you can try making one yourself if you have the tools. If you don’t want to venture into the all-metal ones you can use PTFE but in a frame - there is an interesting one called Crispy hotend. Another more or less classic design you can find googling for 2beigh3.
And some of us just drill out a piece of 6mm rod, polish the inner surface well and use a drilled 6 mm end cap as nozzle. Works well with ABS, if actively cooled 
@Igor_Larine
Lots of explanation - Thanks for that.