I'm using an extrusion of LDPE, 640i. ID .032" Wall .005". I have a process= where I re-flow the extrusion, using a mandrel,FEP heatshrink and hotair. = I have noticed that my pre reflow process tensile strength is about 2x of w= hat my post reflow process strength is. Also, post process elongation is ab= out 3x what the pre process elongation is. I believe that is telling me tha= t the material is being annealed, and becomes more amorphous during the pr= ocess. =20
The ID and OD do not change significantly during the process step. I used a= thermal couple under the FEP heatshrink to measure the actual temperature = that the material is exposed to during process, and the temperature was 425= F. I tried lowering the temperature to see if that had an effect on the ten= sile strength of the post process material, and there was no difference. St= ill about half of pre process material strength.=20
Can someone explain what is happening? Why does the material loose half of = it's tensile strength, and can I do some post processing to gain the tensil= e strength back? ?( Maybe irradiate the parts to recross link?)
Thanks in advanced.