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Joining ends of PVC cord


#1

Hi - I need to join 2 ends of 2mm PVC cord to form a circle. The
problem is it is going to be constantly under tension when worn -
like a slightly stretchable elastic band. So far the most secure
method I’ve been able to devise is making a small sleeve for the 2
ends out of silver tubing & supergluing them inside. Once dry, I’ve
put 2 rivets of 5mm wire through each end of the tubing/cord to
further secure it. Does anyone have any other ideas & which sort of
epoxy would you use for maximum durability?

Many thanks
Deborah Miller


#2

Hi Deborah, you could try this:

take a short - say 4 - 5 mm length of .8mm or less wire (silver or
copper).

Now drill a 2.5mm into each end of the cord with the appropriate
size drill, making sure the holes are central, dab a drop of
superglue on one end of the wire and insert into one hole, repeat the
process with the other end of the wire, pushing the two ends firmly
together. Wipe off any excess glue with acetone et voila - a closed
circle.

Using soft silver or copper wire means you can ensure the circle is
smooth.

I use a variant of this, gluing only one end of the wire, to give an
’invisible’ join for a necklace. It is surprisingly secure because
the PVC grips the unglued end.

You don’t say how big the circle is, or how much tension it will be
under, so I hope this helps.

Jane Walker


#3

Are you sure it is PVC? The black rubbery chord we get here is called
neoprene and I find that superglue has an affinity to it and bonds
very well. I tried making a small band with some scrap neoprene by
butting the ends together and glueing with a spot of superglue. When
cured the band easily withstood a 25% stretch. Try it on your rubber.

Also try making a scarfe joint, cut each end to a long taper so that
the glue bonds a larger area. A scarfe join may not work as well as a
butt join because the glue line will be stretched, whereas with a
butt join the glue line remains more static.

Your method of using a sleeve and pins is probably the best for this
difficult material. Do some experiments and compare the % of stretch
before breaking. Even if the butt joint wins, it is not very
reassuring to a customer. The sleeve and pins joint at least shows
that you have done the most possible to make a secure join.

Cheers, Alastair


#4

Deborah; Although I never new such a thing exised if it is pvc try
pvc cement used to join pvc pipe. It actually melts the pvc to form a
bond, you can get it at any hardware store.

Dave Owen


#5
Are you sure it is PVC? The black rubbery chord we get here is called
neoprene and I find that superglue has an affinity to it and bonds

I agree it is very unlikely that you are using PVC. see:

http://www.marcorubber.com/cord.htm

You have to know the material to be sure of the adhesive, but super
glue is a common one.

jesse


#6
It actually melts the pvc to form a bond, you can get it at any
hardware store. 

wouldn’t that make the joint really brittle and subject to cracking
with wear and tear?

Amery Carriere Designs
Romantic Jewelry with an Edge
www.amerycarriere.com


#7

Thank you for the responses. I shall certainly try Jane’s suggestion
of gluing an inner core with wire. The circles I am seeking to make
are only approximately the size of a dime. My previous failures
included trying the superglue / skarfe method (then whipping it with
waxed twine as if finishing a rope join) but the cord snapped at the
weaker part & the PVC cement which was horribly messy & I couldn’t
get a neat joint. As for whether it is PVC, that it what it is
described as. (This is an English site so we may be entering the
realm of 2 nations divided by a common language!) Here’s the link
for those that are curious:-

http://www.empirebeads.co.uk/stringing-supplies/thread-cord/pvc-cord/

Life would be simpler if I only needed black O rings but the colours
available in this cord are so much nicer! Any further suggestions
gratefully received.

Deborah Miller


#8

Hi Deborah,

Looking at the product link you provided, PVC sounds correct. PVC is
a thermoplastic, it should melt and solidify without changing it’s
properties. This may not be true if the chord is stretchy as it could
then have something else mixed with the PVC. Anyway, it might be
possible to melt each end and press together for a welded join. The
heat source can be a clean hot piece of metal to press the ends
against, or briefly melt each end in a clean flame and immediately
press together.

Just Googled it to check that it is a thermoplastic, and see many
references to nasty chemicals in PVC, so experiment with welding it
in a well ventilated area!

Good luck, Alastair


#9

Deborah,

One Orchidian has already suggested superglue for joining neoprene
cord, explaining how a scarfed joint will improve the strength by
increasing the bond area. Any solid cord of material that is
superglue-receptive will benefit from an internal pin, included in
the joint. Not only does it increase the grip area, but stretching
the cord reduces the cord diameter, compressing the cord down onto
the pin even tighter. Use a textured pin. Shaped joining pins are
used for industrial round belt jointing, but only as small as 5mm
diameter. Take a peek, just for the idea, at

and scroll thru to see the double-mushroom pins they use. A tad gross
for jewelry!

But you can get urethane (polyurethane) in many colors, down to
quite small diameters, in the form of tubing - rather than industrial
belting. One of hundreds of suppliers is Ark-Plas (we use them)

http://www.ark-plas.com/products/product.asp?classID=6

and this opens up quite a few possibilities:

  1. Tubing is more flexible than solid cord,

  2. Tubing lets you have optical effects if it’s in a transparent
    color,

  3. You can include all kinds of pretty things inside the tubing,

  4. Tubing can be mushroom-pin joined and you can make your own pins,
    miniatures of the examples I pointed you to at poly-products "heavy"
    industrial site,

  5. Both tubing and solid cord of polyurethane, depending on grade,
    can be melt-bonded very durably - but I am a real fan of internal pin
    jointing of this tubing.

If you work through the industrial links above (and many others
readily Googled) you may find more colors, more diameters, more
jointing methods than you expected.

Mark Bingham
http://fourth-axis.com


#10

The best epoxy for joining rubber cord into an endcap is JB Weld.
I’ve used it for 9 years and not one return due to failure. I torch
the end cap to remove it from the cord. It’s available at any
hardware store.

Cheers,
Reba