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It’s fast approaching that time of year where we in the PU industry all shut up shop for the Holidays.  Everyone gets a much deserved rest and a little quality time with our families (or telly).  

However, problems often rear their ugly head when we return. Especially if we haven’t properly prepared for the shut down.

The Nightmare

Back from a merry time and a few pounds heavier, you open up shop to find a mess of problems. None of your machines will start, a full drum of Isocyanate has turned solid and you’ve got customers expecting you to send out a shipment by the end of the week.

Not a good start to the new year…  If only you’d known how to prepare for closing!

With a few quick tips from our MD, we can all help prevent this nightmare from happening.


Prevention is Better Than Cure

Your materials are probably the weakest link when planning for a holiday closure, as many of the materials involved in PU manufacturing are susceptible to cold weather.

For example, once some Isocyanate gets too cold it may never be quite the same again, and if your material isn’t at its best, neither will the products you produce.

Isocyanates can crystallise or even solidify – a bit like honey – if the temperature is allowed to drop too low for too long. When that happens, the only way to revive it is to cook it at 70 C for about 24 hours.

The problem with that is once its been heated to that temperature, undesirable reactions tend to occur resulting in solid particles forming. This interferes with processability.

So, the general consensus is that prevention is better than cure.

A good rule of thumb for preventing all this is not to let your material drop below the minimum temperature specified on your suppliers technical data sheet, normally above 15 degrees C. Keep it nice and warm while it’s not being used.

Autorim Injection Moulding Machine Screen. Displaying Isocyanate Polyol Temperatures and other Specs.

Stopping Isocyanate from ‘Freezing’

The number one iso-killer in this weather is concrete floors. I’m sure you’ve felt a concrete floor in winter before, it generously shares it’s coldness with you, and isocyanate drums aren’t immune to this either.

The concrete will send up all its cold into the drum and get straight to work at ruining your Iso.  If you’re really unlucky, you’ll come back to a half sludge, half solid drum.

If you do nothing else before Christmas, get your drums off the concrete floor! 

We recommend storing them on a wooden pallet or rack.  The air will take longer to crystallise the Iso than concrete would.

You’d also benefit from keeping the workshop warm in your absence. Though many don’t like the idea of heating a building with no one in it, we’d argue that it’s better than your material being put out of commission.

You might even consider wrapping it up in some warm winter clothes…

There are several ways to keep your materials warm – band heaters, thermal jackets, warm rooms are all ways of keeping the heat in and the cold out.

Weigh up your options, and determine the best way for you to keep your material warm this winter.

What About Machinery?

Foam Machine tanks can suffer the same problem as drums, as Tony Arnold, our Managing Director, recalls;

“When I was on technical service, the first day back after Christmas was all people ringing up saying the machines wouldn’t start.  And the reason they wouldn’t start was all because the cold had affected the isocyanate.  It’d freeze and the pistons wouldn’t move and tanks were half full of sludge.” 

AutoRim Machine Pump

The best practice to prevent this is to ethier leave the machines running, or have someone go in and run them for 30 minutes or so every couple of days.

As for preparation, (for low pressure machines) we recommend taking the mixing head off, giving it all a good clean and applying plenty of lubricant.  

 “…So the trick is to cover everything with vaseline and keep ‘em warm.” – Tony Arnold, Managing Director, Complexia Ltd

Use either Vaseum or Lithium based grease, to keep everything lubricated over the break.  These types of grease are best because they won’t react with Isocyanate.

You want to stop any moisture from getting to the Iso, or else they’ll react and cause all that sticking and jamming tony described earlier.

Unfortunately, humidity is more or less a given during the winter months.  

Good luck and Merry Christmas from everyone at Complexia.