Working with Urea Plastic

[John Warren]

I don't have a laser yet, but am trying to construct a business plan before jumping in. One of the objects I would like to engrave is more readily available in urea plastic than acrylic and I was wondering if anyone had experience with this material in a laser?

I searched the forum, and it seemed to be mixed opinion with little definitive fact on whether or not it released toxic gases when heated/burned.

I'm aware that "urea" is short hand for "urea-formaldehyde" which will release formaldehyde into the air until fully cured (and maybe more when heated/burned?).

I've also seen posts discussing cutting certain plywoods and MDF which contain urea-formaldehyde based glues. From what I've seen, most people seem to think this is okay as long as the ventilation is working properly and you're not breathing the fumes from it.

If that is the case, I would assume the same would be true for cutting/engraving urea-formaldehyde resin - though it may release a higher quantity of those fumes. Obviously, that's just an assumption though, so I was wondering if anyone had direct experience with it.


At the moment, I don't expect to be cutting it so much as engraving and color fillling it. Which leads to my next question for anyone that has direct experience. Aside from fumes, are there any forseeable problems with trying to engrave and colorfill this material?

[Dave Sheldrake]

Don't go there John, urea-formaldehyde resins liberate far more than formaldehyde gas up to and including hydrogen cyanide in some cases.

http://www.sfm.state.or.us/cr2k_subdb/MSDS/UREA_FORMALDEHYDE_RESIN.PDF

cheers

Dave

[Michael Hunter]

Urea-formaldehyde switch plates and panels engrave nicely and you don't need much power to get enough depth to colour-fill in one pass.
Cutting holes for extra indicators etc. is also possible, but the edges come out a bit "burnt" looking (but that doesn't matter too much if the hole is filled by a lamp assembly).

I have found that the surface is often slightly porous (even on high-gloss plates), so either use a wax polish before engraving or engrave through a mask to stop the excess paint discolouring the surface.

For non-critical areas (plant rooms etc.), colouring the engravings with permanent felt-tip markers is a quick and easy alternative to proper paint-filling.



On the safety thing, I take the view that as I happily process tree wood and nylon (both of which release all sorts of nasties when heated to destruction), then a bit of formaldehyde can't be much worse.
Formaldehyde is flammable and I would guess that most is burnt in the engraving process anyway.

That said, I am lucky in that my workshop is a long way from any neighbours and the prevailing wind takes the exhaust away over open fields.
If I was operating in a more built-up area, I would be MUCH more careful!

[John Warren]

Thanks to both for your input, I really appreciate it - though I was hoping there'd be an easy answer that everybody agreed on... ;)


Don't go there John, urea-formaldehyde resins liberate far more than formaldehyde gas up to and including hydrogen cyanide in some cases.

http://www.sfm.state.or.us/cr2k_subdb/MSDS/UREA_FORMALDEHYDE_RESIN.PDF

cheers

Dave

Do you also recommend avoiding plywoods and MDFs that use UF glues? I've seen similar notations on MSDS sheets for those glues.

If properly vented are these gases still likely to cause problems and/or is it something that could be "cleaned" with a carbon filter?




Urea-formaldehyde switch plates and panels engrave nicely and you don't need much power to get enough depth to colour-fill in one pass.
Cutting holes for extra indicators etc. is also possible, but the edges come out a bit "burnt" looking (but that doesn't matter too much if the hole is filled by a lamp assembly).

I have found that the surface is often slightly porous (even on high-gloss plates), so either use a wax polish before engraving or engrave through a mask to stop the excess paint discolouring the surface.

For non-critical areas (plant rooms etc.), colouring the engravings with permanent felt-tip markers is a quick and easy alternative to proper paint-filling.



On the safety thing, I take the view that as I happily process tree wood and nylon (both of which release all sorts of nasties when heated to destruction), then a bit of formaldehyde can't be much worse.
Formaldehyde is flammable and I would guess that most is burnt in the engraving process anyway.

That said, I am lucky in that my workshop is a long way from any neighbours and the prevailing wind takes the exhaust away over open fields.
If I was operating in a more built-up area, I would be MUCH more careful!

I appreciate the input and tips from your experiences working with it. Since it is said to have a low water absorption rate, I would'nt necessarily have expected a porous surface, so that's a nice tip.

I live in the middle of nowhere, so the neighbors aren't so much of a concern - just myself and my family (who I would prefer not to poison), and a bunch of trees...

Do you have any kind of filtration system or do you just exhaust straight outside?

[Dave Sheldrake]

I'll often cut woods that use U-F resin glues but the concentrations are much lower in the outgassing. The only one that would really bother me are the cyanides, they have a cumulative effect due to the bodies lack of ability to process them properly. Getting the msds from the supplier of the specific plastic is usually a good idea and the fire hazard section should give details of what possible problems you could have.

Quite a few nasties can be cut or processed with the right ventilation or for short time periods but long term effects aren't always apparent until it's too late. It's when you come to clean out fan units and piping that problems usually arise. It affects me more than some due to having a big industrial unit and staff so the H&S requirements are a lot stricter (as in they tend to be checked rather than assumed)

In general if it is hazardous I avoid it unless I have the tools or ventilation in place to deal with it.

cheers

Dave

[Michael Hunter]

I just vent outside.

Being a fairly green and safety-concious person, I did consider a filter, but did not proceed with it for the following reasons -

1 High initial cost
2 Time and cost of maintenance
3 Finding an effective and reliable method of testing the filters efficiency
(if it isn't working properly and you don't know, then that seems to me to be worse than no filter at all)

[David Somers]

Michael,

Since acid gas filters are what you are likely to use.....or simply activated charcoal at the least, the normal way to check the degree to which they are spent is weight. A rough estimate would be a 20% weight increase for the media. Check with the supplier though. They can tell you for sure. A looser way to tell is based on time. Most figure a 2 month life for acid gas filters, and a 4 to 6 month life for plain activated charcoal. Obviously this is a really loose guestimate though since that would be affected by the degree of exposure for each media.

There is a special media used to deal with Formaldehyde since there are a current thread or two discussing that chemical.

When I lived in Hawaii we had to deal with Sulphur Dioxide gas in the air. We lived 1.2 miles from the vent of the active volcano there and got quite a bit of it. We filtered the air in our houses and offices using similar materials to what the US Geologic Survey workers used in their offices. The manufacturer of the SO2 absorbant filter media we used recommended a 20% weight increase as the cut off. Replace the media after that. Weight it when installed. Weigh it every month or so after. Replace it when it weighed 20% more.

Hope that helps!

Dave

[Dan Hintz]

3 Finding an effective and reliable method of testing the filters efficiency
(if it isn't working properly and you don't know, then that seems to me to be worse than no filter at all)

When the exhaust starts to stink (for most materials), you know it's no longer working an in need of a recharge. A safer way is to measure the charcoal... when it doubles in weight, it's filled and time to replace. If you're working with particularly nasty stuff, replace when it hits the 75% mark.

[Michael Hunter]

Dan and David

Yes, but how do you know whether your filter is operating efficiently or not?

Weight gain in the filter medium indicates that it has been working, but tells you little about the efficiency.

If the filter was split into two sections (in series with the airflow) then with high weight gain in the first section and low gain in the second, one could reasonably assume that overall the filter was doing a good job - but what if the second section was defective?

Smell is a very poor warning - especially if you are continuously working near the filter output, since the nose desensitises to particular smalls so quickly.

[David Somers]

Michael,

To the best of my knowledge, without some fairly expensive meters, you have to trust the filters and the media are working effectively based on the manufacturers info.

I had used my example of where we lived in HI earlier? In that case I had an SO2 meter with an alarm that lived on one of our main window sills that was normally always open. When SO2 levels increased to a preset point it would sound an audible alarm and we would close all the windows and fire up the filter. I suppose we could have put the filter outside for a bit and measure the ambient air going into the unit with the meter, and then measure it again as it came out and have a decent measurement on the efficiency of it. The meter ran about $400 and lasted 2 years before it would stop working. It needed to be calibrated on a regular basis so it was not maintenance free by any means. And it looked at only one gas...Sulphur Dioxide. In the case of a laser, unless you are running only very specific materials through it the number of gases you might need to monitor could quickly become prohibitively expensive to try and detect with a meter.

In that case, if you were doing this personally I am not sure what choices you have other than to trust to the manufacturer of the filter medias and their recommendations as to the use and depletion of their products. If you are a business then of course the UK equivalent of OSHA and other UK regulators are probably laying other very specific requirements on you about monitoring and filtering the workplace to protect your workers and the environment.

In our home I worked with the manufacturer of the filter and media and we discussed the size and layout of our house and determined what kind of air flow we would need over the filter media to take a given SO2 level in the house air down to a suitable level in a given amount of time, and if we needed multiple filters in various locations to do that. Again, without spending really big bucks to monitor it our only option was to trust to the manufacturer. I know that is not a very good answer, but I am afraid that is all I can give you from my personal experience.

One other thing I might note. Dan mentioned weighing your charcoal for a doubling of weight? I had mentioned a 20% increase in weight? I was referring to the chemical pack that specifically took out SO2 and that was the change the manufacturer recommended changing the media at. There was a charcoal filter in there as well. I looked up some of my old info on it and a doubling of weight was the recommended change point for it. We never reached that weight though even after several years. We had a very good HEPA filter that got hit first protecting the carbon, which in turn protected the SO2 media. We did change the SO2 media about 2 times a year however based on the weight gain. If you have particular gases you are trying to scrub the manufacturer will tell you what the media is capable of removing before it starts to become ineffective. It will vary with each media involved.

Does that help??

Dave

[Michael Hunter]

David

It doesn't help, so much as confirm my reasons for not fitting a filter -

a I'm not going to pay out ££££s for a commercial one.
b If I built my own (from Dan's excellent instructions), I would have great difficulty proving whether it was working well enough to have been worth the effort.

[Glen Monaghan]

I was venting outside before constructing my AC/HEPA filter that recirculates interior air. My outside vent mounted in the window like an air conditioner and, despite the weather stripping, it leaked a little back into the room until I taped everything. That small leak caused (literal) headaches when I cut acrylic and my SO requested that I only cut acrylic when she was away for the day. Now with the AC/HEPA filter dumping exhaust back into the room a few feet away from me, I can cut acrylic with no headaches at all and SWMBO never knows when I'm cutting, or have been cutting, acrylic anymore. It's empirical, but pretty simple proof that it works well enough to have been worth the effort.

[John Warren]

It's empirical, but pretty simple proof that it works well enough to have been worth the effort.

I guess that's the issue summed up right there - what do we see as empirical evidence and what do we count as "worth the effort?" (probably a bit different for each person) Can we satisfy ourselves with the knowledge that we don't see smoke or smell fumes, or are we concerned that there may still be chemicals in the air in a lower concentration than can be detected with a human nose (particularly one that is probably being exposed to those fumes over an extended period of time and getting used to it).

Ultimately it sounds like without spending a ton of money on sensors each person just has to decide what level or risk they are willing to take with that regard and either be satisfied with the evidence that the filter is removing at least most of the chemicals or just keep venting outside.


Are there certain chemicals that we should watch out for which carbon filters are known not to absorb well?

[Dave Sheldrake]

Only really the highly toxics with small DAR's John, I'd avoid working on the toxics unless the output can be verified.For example, the cyanide family can be lethal at concentrations far below the level of human smell detection.

cheers

Dave

[Dan Hintz]

Ultimately it sounds like without spending a ton of money on sensors each person just has to decide what level or risk they are willing to take with that regard and either be satisfied with the evidence that the filter is removing at least most of the chemicals or just keep venting outside.

This has always been the case. I'm comfortable reading the MSDS and determining what, if any, risk exists. If I don't think the filter will work for a particular material, I'll chase down another avenue. For those who cannot understand an MSDS or make a proper decision based upon what it says, they have two options: risk it, or spend money.