I see hot glue used frequently for various crafts.
But why? There are so many adhesives out there, most of which are used at room temperature. Why fuss with a machine that heats it up and not just squirt some glue out of a bottle (wood glue, Elmer’s Glue, Krazy Glue, etc.)?
Doesn’t hot glue adhere faster? No drying; just cooling.
Hot glue is melty plastic. It starts out solid before you heat it, and it resolidifies shortly after being applied. Room temperature glues are sticky substances that rely on their stickitude to hold things together. Hot glue encases the parts in plastic. Depending on what you’re gluing that can mean a better and more permanent bond.
Apart from its quick setting properties hot melt contains no solvents to destroy your piece or gas out latter.
What does that mean? (really asking)
Pretty sure @RedSky meant “gas out later” ie give off fumes later.
I was not nitpicking the spelling. I do not know what “gas out later” means and why it is bad in this case (people use glue like Elmer’s all the time…not saying it is right for all tasks but I never heard “gas out later” being a worry…but then I know nothing of this which is why I ask).
Ahh, ok. Well I can’t say that I’ve had problems with that issue either but I know that cyanoacrylate glues give off fumes that affect some plastics - though I must say I’d always thought that was something that happened while they were curing rather than later.
As for me I use hot melt glue quite a lot. I rarely use it just as a long term adhesive as such, except for cardboard (for which it excels). I use it more:
as quick dry sealant ie as an “instant set” version of silastic or similar. Like for waterproofing cracks or gaps in something small
as a filler-style material such as if you want to give some general support around electronic components
as a work-aid when you want to hold something in place temporarily while you are working on it. It has the advantages that (a) it sets fast, so you don’t have to wait around mid-project and (b) on most surfaces it doesn’t stick all that well, and can be stripped off easily and without staining, after you’re done.
Well, it’s typically called “outgassing.”
Just about everything evaporates over time, but some things go faster than others. Plastics tend to have a diverse mix of chemicals to give them various properties. If some of these evaporate faster than others (i.e., “outgassing”), it will change the properties of the plastic. Maybe make it brittle, maybe gooey, maybe something else.
Outgassing is especially bad in a vacuum, because it happens faster, and because the gas can deposit on important stuff like camera lenses.
I have had occasional use for, and good results with, PCL (polycaprolactone), which, while not quite at room temperature, melts at 60 °C or so.
In particular, the “cold” glues that come closest to the same structural properties as hot glue are the various rubber cement-like products, and those tend to both outgas a lot and to change their properties a lot when they outgas.
They stink.
I’ve always thought it was called for in many crafts because it set much faster than those others that the OP mentioned so one can keep on crafting instead of waiting a long time for it to dry. It allows one to hold the part in the correct position till it sets. Yes there is quick set epoxies but they are almost a craft in themselves and much more unforgiving which detracts from the crafting efforts.
So it’s not that one can not use glue, it’s just going to take much more time, and perhaps needing some sort of jig to hold the craft till the glue sets.
I’ve been a fan of Hot Glue for 50 years.
But, recently, I’ve found another adhesive that I like even better, for some of the applications that I used to use Hot Glue and Superglues on - UV-hardening resin. I bought 100ml bottles of the resin on Amazon, and an intense LED UV light source on a flexible arm. The resin is super fast for potting, or tacking wires down. It’s not flexible, so I still use Hot Glue, but for many applications the resin is better.
BTW, the glue gun was invented to solve shoe-assembly problems.
My understanding with “Crazy Glue” type adhesives (cyanoacrylics?) is that being very liquid, they can spread out and then they craze creating a bigger unsightly patch on what should be smooth glossy surfaces. Plus if you get them on you, your fingers stick almost instantly. (If you get hot glue on you… you will know!!!)
Elmers glue and such take a while to dry and with anything other than flat surfaces - i.e. beads and plastic shapes, cloth, etc. - they don’t hold well without a huge blob, also unsightly and taking even longer to dry.
Elmer’s glue has its own issues, most notably that it’s water-soluble and it’s not very strong. That’s fine if you’re just gluing paper, which would be damaged by water and isn’t very strong anyway, and it makes cleanup a lot easier. And it also has the strong benefit of being completely non-toxic. But it’s definitely the wrong choice for most craft projects.
Hot glue is pretty forgiving with the materials you use it on, too. Elmers is good at paper to paper. Cyanoacrylate is good with wood and plastics, but not really with metal. Hot glue will give you a moderately strong and flexible hold on any material that isn’t mirror-smooth.
Many strong glues also dry hard and brittle, so if the joint is worked or vibrated the glue can crack.
“Gassing out later” or “outgassing” are both ways you can express the same thing: stuff coming out later, in gas form, as people are saying.
It’s a very big deal in computer hard disk drives, as it messes with the lubrication of the head sliding on or over the disk. I spent years in this industry (and if you have a disk drive you probably have one of my inventions in it).
I bet it matters in art conservation, the field of caring long term for artworks.
For arts and crafts, and most other uses, it probably doesn’t matter unless you dislike a smell.
It matters a great deal in autimobiles. That new car smell is Volative Organic Compounds in the glue and interior materials outgassing. In the past some of them were known carcenigens. And most new cars never have the windows down long enough before they are sold to vent them, so they get trapped inside.