[vdblnkr34 (OP)]

Hi. I want to make my own custom balloon. Which plastic film I can buy, so it will be tough enough to be used for a long time?

[evan_au]

It's not likely to survive the first bad landing...

It is important to know how the balloon will be filled:
- high-temperature performance is importance for a hot-air balloon, but unimportant for other types
- An Aluminium coating helps with helium leakage, but not important for other types of balloon

Cost is also an important criterion...

[paul cotter]

Polyoxymethyene (acetal, delrin?) is one of the stronger plastics but I don't know if it is suitable for a balloon. strength and flexibility would be of equal importance. Another important parameter would be uv stability if outdoor use is planned: many plastics undergo serious degradation on exposure to uv and become brittle.

[Bored chemist]

They make balloons out of mylar for a reason.

[vdblnkr34 (OP)]

its definitely for outdoor. Is there any light cloth there can be used to hold helium. Regular plastic bags may be. Radio says it takes 100 years to decompose.

[Petrochemicals]

Latex rubber.

[evan_au]

Is there any light cloth there can be used to hold helium

Cloth is a woven material, which means it has numerous gaps between all the fibers.
- Cloth would not be good for holding Helium.
- You need large areas made from a single sheet of non-porous plastic, with any joints being carefully sealed along the entire length.

[vhfpmr]

Latex rubber.

Latex is porous.

[Petrochemicals]

Latex rubber.

Latex is porous.

Weather balloons seem to function OK, do they add a pore sealing agent?

[SeanB]

Weather balloons are single use, and only have to hold up for at most a day aloft before they burst.

[alancalverd]

Mylar seems to work for small helium balloons.

Large (man-carrying) hydrogen balloons rely on the surface/volume relationship to make the loss of (cheap) hydrogen tolerable  through rubberised ripstop nylon.

Hot air balloons also use ripstop nylon, with a polyester coating (lighter than rubber, and tolerates 100 degree contents).

The most intriguing balloon story https://en.wikipedia.org/wiki/East_German_balloon_escape used polyester taffeta (wedding dress fabric) although umbrella fabric would have been preferable but was considered too expensive.

[Petrochemicals]

Large (man-carrying) hydrogen balloons rely on the surface/volume relationship to make the loss of (cheap) hydrogen tolerable  through rubberised ripstop nylon.

Did they not switch to helium after a disaster of some sort?

[SeanB]

Helium was the gas of choice, but it was replaced with hydrogen more as a stop gap measure when the USA started limiting it's export to Germany, as hydrogen is very cheap to make, compared to refining thousands of litres of liquified natural gas, to get the naturally collected helium there from the decay of radioactives in the planet core. Helium is used more for the lack of care you can have with handling, the larger lifting capability of hydrogen, despite the benefit, is more than overshadowed by the need for very special handling, especially with the wide explosive limit in air, 5% to 95% being explosive. Small leaks are very quickly explosive in any area, so you need special handling to make sure there are no sparks or hot surfaces nearby, plus gas monitors.

Biggest disadvantage of having hydrogen fuelled vehicles, in that simply parking in an enclosed space, that is well closed, overnight, can have an explosive level present, needing only a spark of turning a light switch on to ignite it. Hydrogen is well known for considering most materials you think of as gas tight, like steel, as merely a very high pressure drop filter, and even more so for plastics, though there at least it does not make them brittle from creating metal hydrides.

[evan_au]

Hydrogen's wide explosive limit in air, 5% to 95%

So I guess that combining a hydrogen balloon with a propane burner for extra lift is not recommended, then?

[alancalverd]

Large (man-carrying) hydrogen balloons rely on the surface/volume relationship to make the loss of (cheap) hydrogen tolerable  through rubberised ripstop nylon.

Did they not switch to helium after a disaster of some sort?

Interestingly, the Hindenburg disaster was caused by the flammable envelope destroying the rigid structure. Most of the hydrogen simply escaped upwards,  causing very little damage.

There are plenty of hydrogen balloons flying for sport these days.   

[alancalverd]

Hydrogen's wide explosive limit in air, 5% to 95%

So I guess that combining a hydrogen balloon with a propane burner for extra lift is not recommended, then?

Solar-heated helium is very effective!

And it is worth remembering that for about 150 years, most western houses and businesses were lit and heated by 50% hydrogen supplied through pipes. Amazing how we survived.

[SeanB]

Hydrogen's wide explosive limit in air, 5% to 95%

So I guess that combining a hydrogen balloon with a propane burner for extra lift is not recommended, then?

Solar-heated helium is very effective!

And it is worth remembering that for about 150 years, most western houses and businesses were lit and heated by 50% hydrogen supplied through pipes. Amazing how we survived.

The other half was carbon monoxide as well, doubly as dangerous as the chance of dying from poisoning was greater than the chance of it exploding, all you needed was a leak.

[alancalverd]

The reason for changing to methane  in the 1960s was the CO, not the H2 content! There have been just as many gas explosions with CH4 as there ever were with H2 + CO, and if the boiler isn't properly ventilated, you still get cases of CO poisoning from the incomplete combustion of CH4. Overall, I think pure hydrogen might actually kill fewer people.

[SeanB]

I would say the bigger reason was that North Sea gas was there in abundance, and it was cheaper for the energy suppliers to move it into the existing network, instead of having to mine coal, transport it to a coking furnace, and turn it into town gas in a reformer. All they had to do with natural gas was simply scrub it to clean it, add in mercaptan as an odourant to show leaks, and then plumb it into the existing gas mains. Scrubbing and the pumping was a lot cheaper to do, and also a lot less machinery to maintain, along with needing a lot fewer people as well. The gas was essentially free to them, as the oil paid for all the infrastructure needed, and they otherwise would have this by product that was there in massive volume, and which cost them money to burn off. So instead they figured out good uses for it, and it still is there, even after most of the oil is not economical to extract.

Yes the risk with natural gas is still the same for explosion, though it is higher as the gas tends to accumulate at low points, and is very explosive then, but the CO poisoning risk is lower, as now it is only there with incomplete combustion, instead of as being an inherent part of the gas itself. Hydrogen though has big issues with sealing, as the common methods used with gas, neoprene rubber seals, plastic hose, thin wall steel pipes, are going to have a greater amount of leakage from them, plus the added disadvantage of hydrogen burning in open air has a flame that is only visible in the ultraviolet, with no visible flame, and anything you add is not going to leak out at the same rate, or out through things porous to hydrogen. You use helium to detect leaks in piping, and it will show up leaks of less than a gram per year in refrigeration pipes and fixtures, which are normally hermetic. Hydrogen the same, and the same detectors will pick it up, making it hard to contain. You need metal to metal compression seals all round, or use seals made from PTFE and a labyrinth seal, and even those still will have leakage. Flexible pipes will also have a fatigue life as well, along with all components subject to the pressurised gas. Filling a hydrogen fuelled vehicle will not be a 3 minute stop and go, more like a half hour, with leak testing being done before, during and after filling to catch any failing seals, plus a limited life for the filling equipment as well.

[Petrochemicals]

Large (man-carrying) hydrogen balloons rely on the surface/volume relationship to make the loss of (cheap) hydrogen tolerable  through rubberised ripstop nylon.

Did they not switch to helium after a disaster of some sort?

Interestingly, the Hindenburg disaster was caused by the flammable envelope destroying the rigid structure. Most of the hydrogen simply escaped upwards,  causing very little damage.

There are plenty of hydrogen balloons flying for sport these days.   

Hydrogen's wide explosive limit in air, 5% to 95%

So I guess that combining a hydrogen balloon with a propane burner for extra lift is not recommended, then?

Solar-heated helium is very effective!

And it is worth remembering that for about 150 years, most western houses and businesses were lit and heated by 50% hydrogen supplied through pipes. Amazing how we survived.

You must  be posh! oil lamps and coal for the majority, peat if it was convenient.