PVC and IPVC wire

Better Hookup Wire

Easy to strip hookup wire which doesn’t shrink back during soldering.

Copyright © 2011 by Stephen H. Lafferty. All rights reserved.

Long ago, I never had any trouble with insulation shrink back when soldering hookup wire. Several years ago, I needed to replenish my stock and also decided to splurge on getting a good selection of colors. (So many times, I had wished for purple to signify the –15V line.)

Much to my dismay, I discovered that some of the modern hookup wire had a problem with shrink back. As seen with the orange PVC wire above, you start with the insulation close to the connection, (upper) and after soldering, you end up with it as seen in the lower picture.

Researching the Problem

After searching the Web, posting questions on forums and asking around, I found that not all vinyl hookup wire has a real problem with this. A buddy says that the hookup wire he buys at RadioShack is fine. I tested the various rolls which I have and found some good ones. Looking at technical documents on the Web, I learned that shrink back is dependent on controlling the relative feed rates of insulation and wire in the manufacturing process. If the metal gets ahead of the insulation, so the plastic is stretched, it leaves a stress in the material which is released when stripped and soldered. Hence, the insulation shrinks back.

Finding Solutions

The problem was that I needed to order some new hookup wire and there was no way to tell if prospective products would have the issue or not. I couldn’t find meaningful claims or specs that would reassure me. Some people on the forums advocated using wire with Teflon (DuPont’s brand name for PTFE) insulation. While expensive, that would certainly cure the shrink back problem. The downside is that PTFE is difficult to strip. I recalled having trouble with that long ago, when my brother gave me some. Looking around the Web, I found descriptions of slow and tedious procedures for properly stripping PTFE. Geez. All I wanted was to have something like the vinyl wire I had always used.

After additional Web research, I finally discovered Irradiated PVC (IPVC) wire insulation. This is regular PVC wire which has been passed under a powerful electron beam. It cross-links the polymers, making the plastic much more resistant to heat. It also makes it tougher and more resistant to plasticizer loss (which ages many plastics). The only concern I had was the fact that it makes the wire stiffer. Would that make it hard to route in tight corners? I’m pleased to report that it turned out to be a non-issue. The IPVC does not seem at all stiff to me and there is certainly no problem bending the #22 and #18 sizes which I tested. As expected, IPVC is at least as easy to strip as regular PVC wire.

Buying IPVC Wire

Of course, the IPVC is harder to find and more expensive than regular PVC wire but it isn’t usually as expensive as PTFE. The key words to look for are:

  • UL1429 (for 150VDC)
  • UL1430 (300VDC)
  • UL1431 (600VDC)

The 300VDC rating is typical for ordinary hookup wire. However, I was planning a tube analyzer (VTA) project which would need the 600V rating. Also, while I normally use solid hookup wire, the VTA has over 60-wires going to the main PCB. Concern about being able to flip the board over led to stranded wire for flexibility. So the numbers listed may be limited to stranded wire. I was able to find UL1429 and UL1431 at McMaster-Carr. They have 1429 in many colors but 1431 is only carried in black and white:
http://www.mcmaster.com/#9615t712/=cx1et0

I ordered UL1431 from them. #22 presently costs $14.06/100ft or
$52.65/500ft. #18 goes for $23.29/100ft or $87.20/500ft.

I also found IPVC on eBay. There I bought 650ft of brown #22 UL1430 for $30 plus shipping.

Testing the IPVC

As mentioned, I was pleased to find that the stiffness is no problem. The wire from mcmaster.com was specified as white but I notice that it is actually off-white (a bit pinkish), which I ascribe to the irradiation process. In the picture above, the brown wire on the right is the IPVC. As you can see, it really nails the shrink back issue, showing no sign of shrinkage or even melting at the point of soldering.burn test low

Carrying things one step further, I applied a 700F soldering iron to the #22 wires for 5-seconds. At
right
, the brown IPVC shows very little indentation. The orange PVC below it though, has been penetrated to the metal. When you are soldering in close quarters, it is all too easy to brush up against a wire. With regular PVC that usually leaves an unsightly gash. IPVC would barely show a mark from a brief stroke.

Conclusions

It seems clear that IPVC insulation is preferable insulation for hookup wire. It is available in afforable lengths, for certain colors, voltages and strandings. Alas, I have not found it yet in affordable lengths with a #22 solid conductor, 300V rating and in a variety of colors. When that becomes available, I will be ready to replace my reels of common hookup wire!

 

Reader Comments


Posted by Steve L. April 30, 2017 - 10:49 am
Hi Lloyd, Sorry that you weren't able to find what you wanted. (The Rolling Stones had a song about that :) Best wishes with your project.

Posted by Lloyd B April 28, 2017 - 04:50 pm
Hi Steve

No reply from Flex Wires to my email so eventually I phoned them. Bill, in sales there, was very helpful but had to direct me to Allied Wire and Cable in Pennsylvania as Flex sells 10,000-foot drums. Unfortunately I'd already checked Allied: it sells XLPVC on-line, but only one size and rating in solid core. Worse from my PoV, its checkout only accepts US shipping addresses. I think I've exhausted the possibilities for now. Will check out Keynar - thanks for the suggestion - and others such as PTFE, or may simply have to use ordinary PVC and be very careful.

Posted by Steve L. April 25, 2017 - 06:30 am
Yeah, I much prefer solid-strand hookup wire too, though after being forced to use stranded in a recent project, I have to admit some softening on that position. (Had 60+ wires going to a PCB which needed to be able to flip over for servicing, so flexibility was essential.) You might want to consider Kynar, as mentioned in the November, 2011 comments below. I only found it up to 20AWG but that was long ago and I didn't search widely. Don't know about 600V in that though. Hope you find what you need.

Posted by Lloyd B April 25, 2017 - 02:27 am
Hi again Steve. Yes, that looks like a good product and I was't aware of it - thanks. Raychem's TE Connectivity seems to be the mfr.: tinyurl.com/mxbq5eh No solid-core and limited colours, so I'll keep chasing the XLPVC for what I need and let you know how I get on.

Posted by Steve L. April 24, 2017 - 07:33 pm
Hi Lloyd, I appreciate the kind words. Recently, I discovered a great, new-type wire and will be adding an addendum to the "Better Hookup Wire" article as soon as I get time. Depending on your requirements, it may be superior to IPVC. The product is Raychem's type 400R wire: I needed 600V wire for my application but the diameter of the #22, 600V version is just 49mils, versus about 100mils for the IPVC I had been using. (It seems about the same diameter as PVC 300V wire.) The dielectric constant is just 2.3, versus 3.5 to 8 (5 typ) for PVC. That's good for reducing parasitic capacitance. It's rated to 125C. My 5-sec test of 750F soldering iron against the insulation showed almost no effect! Whereas PVC melts "to the bone" and IPVC shows slight surface charring. Unlike PTFE, it's easy to strip and doesn't outgas corrosive fluorine. Best of all, (as quality hookup wire goes at Mouser) it's CHEAP. I paid $8.80 for 100ft. They cut it to the length you order and I didn't see a minimum but I try not to pester them with nuisance orders.

I was looking for stranded wire and don't know about availability of a solid version. As a starting point, you can see what I found (in various AWG values) at Mouser by searching there on 400R0111. The primary insulation used is irradiated polyolefin and it also has a 3-mil coating of irradiated fluoropolymer. (PTFE is one of many fluoropolymers.) I speculate that the coating is the reason that the soldering iron test came through so impressively. The only downside I've noticed is quite minor: it seems slightly stiffer than PVC but I don't think I would have noticed if I hadn't already researched the insulation characteristics.

Hope you find what you're looking for. Please post here if you find something nice. Thanks, Steve

Posted by Lloyd B April 24, 2017 - 06:08 pm
I'm late to the party Steve, but this page was really helpful - thanks! I've been hunting out sources of irradiated PVC and at present the only one I can find that does it in solid-core, in the gauges and voltage ratings I need - 18, 20 and 22AWG in 300V and 600V - is Flex Wires in CA. They make those in a range of colours, also a range of temperature ratings including 105degC. I've asked about distributors as I doubt their minimum put-up is small enough for the likes of me: no longer than 100' and I'd prefer 25' in some cases. I'll post here if I get a reply from them.


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