Why is rubber a good insulator?

[Kriske]

Good night/evening/afternoon/morning, forum members.

I was wondering what makes rubber a good insulator. I understand less dense materials make better insulators, as insulators absorb/trap heat. But I want to know why rubber is a good insulator.
For example, wood makes a good insulator due to the air pockets in it's biological structure.
What can be said about rubber? What can be said about rubber's structure that makes it a good insulator?

 

[Deleted member 26818]

Is rubber a good insulator, or is it just when it's vulcanised?
To be honest I thought good insulators are that just because they are non conductive.

 

[Kriske]

Is rubber a good insulator, or is it just when it's vulcanised?
To be honest I thought good insulators are that just because they are non conductive.

Well insulators are what they are because they don't conduct electricity. But I'd hope to explain more. Such as the case with wood and it's air pockets.

 

[Deleted member 26818]

Not sure that the air pockets in wood have an effect on electrical conductivity?
Basically, a conductor is a material which has loose atoms which are available to flow via electricity.
An insulator is a material with densely packed atoms which will not flow.

 

[dmxtothemax]

I was wondering what makes rubber a good insulator. I understand less dense materials make better insulators, as insulators absorb/trap heat. But I want to know why rubber is a good insulator.
For example, wood makes a good insulator due to the air pockets in it's biological structure.
What can be said about rubber? What can be said about rubber's structure that makes it a good insulator?

Rubber is a good insulator because it is easily moulded, lasts well outdoors.
if it gets wet enough it can break down but they just have to make it a little thicker.

 

[Lucien Nunes]

Various factors make a 'good' insulator:
High resistivity - there are few naturally occurring charge carriers (e.g. electrons or ions) able to move under the influence of an electric field to form a current.
High breakdown voltage - a high voltage per unit length is required to liberate electrons from atoms to create extra charge carriers.
Useful physical properties - for commercial applications, an insulating material that can be manufactured and applied easily that will withstand the conditions it is subjected to.

Rubbers are mainly polymers of isoprene that offer the above advantages. When the isoprene molecules polymerise, the arrangement of strong intermolecular bonds uses up some of the internal pi bonds in the molecules, leads to a large bandgap that prevents electrons being liberated from the valence band. Physically, rubbers were some of the first good insulators that could be moulded to shape and extruded.

 

[Taylortwocities]

The science of insulators is well explained in Wikipedia
Insulator (electricity) - Wikipedia, the free encyclopedia - https://en.wikipedia.org/wiki/Insulator_(electricity)

 

[Kriske]

I was wondering what makes rubber a good insulator. I understand less dense materials make better insulators, as insulators absorb/trap heat. But I want to know why rubber is a good insulator.
For example, wood makes a good insulator due to the air pockets in it's biological structure.
What can be said about rubber? What can be said about rubber's structure that makes it a good insulator?

Rubber is a good insulator because it is easily moulded, lasts well outdoors.
if it gets wet enough it can break down but they just have to make it a little thicker.

Various factors make a 'good' insulator:
High resistivity - there are few naturally occurring charge carriers (e.g. electrons or ions) able to move under the influence of an electric field to form a current.
High breakdown voltage - a high voltage per unit length is required to liberate electrons from atoms to create extra charge carriers.
Useful physical properties - for commercial applications, an insulating material that can be manufactured and applied easily that will withstand the conditions it is subjected to.

Rubbers are mainly polymers of isoprene that offer the above advantages. When the isoprene molecules polymerise, the arrangement of strong intermolecular bonds uses up some of the internal pi bonds in the molecules, leads to a large bandgap that prevents electrons being liberated from the valence band. Physically, rubbers were some of the first good insulators that could be moulded to shape and extruded.

The science of insulators is well explained in Wikipedia
Insulator (electricity) - Wikipedia, the free encyclopedia - https://en.wikipedia.org/wiki/Insulator_(electricity)

I thank you all for taking the time out to better explain insulators to me, especially at this late hour, where some of you have already left. But I thank you again for your help!

 

[Silly Sausage]

For example, wood makes a good insulator due to the air pockets in it's biological structure.

The last things you want in an insulator are voids.
You get microscopic arcing which eventually breakdown the insulator.

 

[Marvo]

Are you confusing thermal insulation with electrical insulation perhaps?

 

[7029 dave]

vulcanised Indian rubber just falls apart over time.

 

[Deleted member 26818]

Yep, my tyres fall apart all the time.

 

[7029 dave]

Yep, my tyres fall apart all the time.

Are you saying it doesn't then Spin.?

 

[Darkwood]

Im with Marvo here, what exactly are we discussing here? Thermal or Electrical insulation as they are two very different properties and not always common together in a product , reading the thread the OP suggests thermal insulation but discussions of electrical insulation properties are mentioned too.. @Kriske Can you expand a little here as there seems to be confusion in the thread as to what we are actually dicussing

 

[Silly Sausage]

Thermal insulation - Wikipedia, the free encyclopedia - https://en.wikipedia.org/wiki/Thermal_insulation#Insulation

See the 2nd paragraph on cylinders.
Well, I never knew that, interesting!

 

[David M]

Not sure that the air pockets in wood have an effect on electrical conductivity?
Basically, a conductor is a material which has loose atoms which are available to flow via electricity.
An insulator is a material with densely packed atoms which will not flow.

Not quite but you are on the right track.
In Layman's terms - electrical current conducting materials have electrons that easily move from atom to atom. Where as electrical insulating materials have atoms that tend to hang on to their electrons.

 

[Lucien Nunes]

Re. thermal insulation, you can see the effect of critical radius at work with cables, e.g. when comparing CCC for singles and sheathed multicores with the same core. Depending on dimensions, adding a thicker sheath to the cable, which looks like it will tend to impair heat dissipation and therefore reduce CCC for a given conductor and ambient temp, actually increases the CCC because the increased convective surface area outweighs the thermal insulation of the sheath.

Returning to electrical insulators with cellular structure / air pockets, while Archy is quite right about void discharges etc on power cables, sometimes air / gasfilled voids are good things. Airspaced coaxial cable and the foamed dielectric on satellite and high performance data cables is used because the air / gas fill making up much of the volume has a lower dielectric constant and lower losses than solid plastics, leading to lower high frequency loss.

 

[Darkwood]

Check this out, this is a thermal insulator that could have revolutionised the world but the inventor took it to his grave, it featured on TV a few times and amazed anyone who tested it.

Starlite - Wikipedia, the free encyclopedia - https://en.wikipedia.org/wiki/Starlite

 

[Silly Sausage]

sometimes air / gasfilled voids are good things. Airspaced coaxial cable and the foamed dielectric on satellite and high performance data cables is used because the air / gas fill making up much of the volume has a lower dielectric constant and lower losses than solid plastics, leading to lower high frequency loss.

Ah, all very well, but they're operating at much lower voltages than power cables.
Different kettles of fish, surely?

Any road, when's your museum opening up to us unwashed masses?

 

[Silly Sausage]

Check this out, this is a thermal insulator that could have revolutionised the world but the inventor took it to his grave, it featured on TV a few times and amazed anyone who tested it.

Starlite - Wikipedia, the free encyclopedia - https://en.wikipedia.org/wiki/Starlite

The stuff he took to his grave because no one would buy it?
Check out your thermal conductivity tables for the perfect thermal insulator!