I need a mopst efficient way to soften nylon 6/6 without changing any of its
properties. These are small dowels with .0.018" deep grooves around them
and they are supposed to lock into brass tubing with a mating I.D. shoulder.
I'm seriosuly thinking of boiling these dowels to force them into the Brass
jackets. anybody have any other ideas?
... but to soften PA66 is a change of its propereties !?
Soak those dowels in warm or hot water for some time
and use them when they are soft enough for your need.
Afterwards you must somehow dry them in order to get their
"normal" properties back.
John Wizman schrieb:
Could you chill the nylon enough to shrink it the required amount? An
online value for nylon 6,6 is 80 x10^-6 /C. I don't know your starting
diameter, so I don't know how much you would need to chill it to obtain
a 0.018" shrinkage. A 1 in diameter would need a 225 C drop to shrink
the whole 0.018". A 0.25" rod would need 4 times that temperature drop
(not physically possible, and negative temperatures aren't going to
help you either.
Of course, this assumes the coefficient above is correct and constant
at all tempertures. It also assumes that you need to shrink it the
whole 0.018". If you have access to good cooling, you might just want
to try it and skip the theoretical prognostications.
Aspen Research -
"Turning Questions into Answers"
Opinions expressed herein are my own and may not represent those of my
Hi Rolf. Basically that is what I thought. Don't know how easy it is
to deform nylon above Tg. I do know you can actually mold Nomex aramid
powder and Kevlar aramid above Tg's but it takes about 1,000 psi.
Nylon moisture regain and big drop in Tg can cause resin deformation
making the resin unsuitable for some applications like car doors. Our
plastic buddies thought they could get away with it with a low moisture
regain nylon, but it would not work. In 6/6, I recall the moisture
regain be between zero and mayb a 100% humidity of about 5%. Aramids
the Glass Temperature Tg of PA66 is about 60-80 degr.C, depending on your
test method, and its Melting Point Tm is ~255 degr.C. Many PA66 automotive
applications reach end use temperatures of up to 160 degr.C long term and up
to 220 degr.C short term, like air intake manifolds for example! That's why
those type of resin need to be optimized for good long term heat ageing
performance. One of the issues is, that especially between Tg and Tm, PA66
continues to soften significantly, i.e. looses modulus and strength
steadily, until it starts to melt at Tm. Something similar happens as you
expose PA66 to water: due to water pickup Tg starts to decrease down to
below 0 degr.C, when it absorbs up to over 8% water, when soaked in water
and at the same time do both modulus and strength, measured at room
temperature, significantly drop.
Just an example: the flexural modulus of unfilled, natural Zytel*101 (PA66)
changes with water pick up as follows:
2850 MPa dry-as-molded (0,2% moisture content)
1300 MPa at 50% relative humidity (2,5% moisture content)
500 MPa at 100% relative humidity (8,5% moisture content)
So the original question was how to soften PA66. You can do it with water,
but you have to dry out the water afterwards again, in order to regain your
nornal, dryer properties at 50% relative humidity again.
"Frank" schrieb im Newsbeitrag
Yes, but the nylon used in air intake manifolds has a heat stabilizer
It sure isn't simple, but you can soften PA66 with warm acetic acid.
Formic is even better, but you need to be cautious that you don't
dissolve away teh nylon.
My personal opinion is that heating is a useless approach, though the
freezing might work is it is a close fit to begin with. To ask a dumb
question why don't you trim teh dowel down and glue it? Both epoxies
and super gluee work well for plastic to metal bonding.