2.20 describe experiments to investigate how insulating materials can be charged by friction

When two insulating materials are rubbed together, electrons will pass from one insulator onto the other insulator.

Rub a cloth on a polythene rod. Electrons will move from the duster to the rod. The rod will become negatively charged and the cloth will become equal positively charged. To check, hold the rod and the cloth near a pile of small bits of paper,  the bits of paper will be attracted to the rod/cloth as they are electrically charged.

Alternatively, you could use an acetate rod and cloth, it involves the same process and, therefore, the same outcome will occur. The only difference is that the acetate rod will be positively charged and the cloth will become negatively charged.