What determines how much electrical charge an object can hold? Does increase voltage force more electrical charge to be store in an object (Van de Graaff generator), since electric field increase as voltage increase. I don't think it is about relative permittivity in dielectric material because it just creates a bipolar.
[Physics] What determines how much electrical charge an object can hold
chargeelectricityelectrostatics
Related Solutions
In theory, if you had a sphere encased in a great dielectric than maybe you could charge it up to the breakdown limit of the dielectric. However, for a VdG generator, you need access to the sphere for the support and charging system, which then becomes the breakdown path.
As noted by @UncleAl, real accelerators use high pressure gas (not always SF6 since is expensive and a greenhouse gas), with the pressure and gap determined by the Paschen curves.
Another benefit of gas insulation is that it self heals after a spark, which your solid dielectric would not do, so you would need to replace the mica every time it sparked.
So there exists a power supply that provides the positive charge and removes the electrons. The comb is for distributing the charges.( Depending on the materials used one could accumulate negative charges and remove the positive ones)
The Concentration of Charge
It is important to realize that the charge on the roller is much more concentrated than the charge on the belt. Because of this concentration of charge, the roller's electric field is much stronger than the belt's at the location of the roller and lower brush assembly. The strong negative charge from the roller now begins to do two things:
It repels the electrons near the tips of the lower brush assembly. Metals are good conductors because they are basically positive atoms surrounded by easily movable electrons. The brush assembly now has wire tips that are positively charged because the electrons have moved away from the tips, toward the connection at the motor housing.
It begins to strip nearby air molecules of their electrons. When an atom is stripped of its electrons, it is said to be plasma, the fourth state of matter. So we have free electrons and positively charged atoms of air existing between the roller and the brush. The electrons repel from the roller and attract to the electronless brush tips while the positive atoms attract to the negatively charged roller.
The positively charged atomic nuclei from the air molecules try to move toward the negatively charged roller, but the belt is in the way. So now the belt gets "coated" with the positive charge, which it then carries away from the roller.
One should not confuse high voltage with high power. The video shows that it is not dangerous to be charged by a Van de Graaff generator.
Best Answer
It should be associated with the work function, which is the minimum thermodynamic work (i.e. energy) needed to remove an electron from a solid to a point in the vacuum immediately outside the solid surface, and different materials have different work functions.
Consider a very simple case, that a spherical electrical object exists in vacuum.
Considering that we move an electron from the object to the infinitely distance, if the energy of the system decrease, then it shows the electrical object is unstable. Hence, the maximum electric charge that an object can hold should make the energy unchanged in the process of removing electron.
If its radius is $R$, the work function is $W$, the maximum electric charge that it can hold is $Q$, then $$\frac{1}{4 \pi \epsilon_0} \frac{Qe}{R}=W$$ the left side is the change of electrical energy.
As for the object with other shape, you have to change the form of expression in the left side.