Pressboard

1. An electrical apparatus comprising a solid insulation material made from a pressboard comprising:

cationic polyvinylamine (PVAm); and

anionic polyacrylamide (PAM);

in a combined amount of between 0.01% and 20% by weight of the pressboard;

wherein the weight ratio of PVAm and PAM is between 1:1 and 2:1.

2. The electrical apparatus comprising a solid insulation material made from a pressboard of claim 1 , wherein the combined amount of PVAm and PAM in the pressboard is between 0.01 and 5 wt %.

3. The electrical apparatus comprising a solid insulation material made from a pressboard of claim 1 , wherein the amount of PVAm in the pressboard is between 0.01 and 5 wt %.

4. The electrical apparatus comprising a solid insulation material made from a pressboard of claim 1 , wherein the amount of PAM in the pressboard is between 0.01 and 5 wt %.

5. The electrical apparatus comprising a solid insulation material made from a pressboard of claim 1 , wherein a cellulose of the pressboard is from sulphite pulp.

6. The electrical apparatus comprising a solid insulation material made from a pressboard of claim 1 , wherein the pressboard is in the form of a spacer, an axial stick or a winding table.

7. The electrical apparatus of claim 1 , wherein the apparatus is a transformer comprising:

a transformer winding; and

an insulation fluid with which the transformer is filled.

8. The transformer of claim 7 , wherein the solid insulation material is in the form of a plurality of spacers integrated with the winding.

9. The transformer of claim 7 , wherein the insulation fluid is a liquid.

10. The transformer of claim 7 , wherein the transformer is a power transformer configured for high voltage operation.

11. The pressboard of claim 1 , wherein a weight ratio of PVAm to PAM is 3:2.

12. The pressboard of claim 1 , wherein the solid insulation material further comprises a sulphite pulp.