Triboelectricity refers to the static electricity generated when two insulating materials brush against each other. Electrons are stripped from one material by the other material. The material which loses electrons becomes positively charged while the material which picks up electrons becomes negatively charged.
The Triboelectric series is a list of materials arranged in a manner which tells us which materials have a tendency to gain positive charge and to loose negative charge. If a material lower in the series is rubbed with a material higher in the series, the lower material will become negatively charged while the higher material will become positively charged. For instance, based on the series below, if glass and nylon are rubbed, glass acquires a positive charge while nylong becomes negative.
If the distance in the series between the two materials is more, the the voltage produced will be more. This will be valid only if the materials are clean and dry. If the materials are dirty, the voltage will not be generated.
Triboelectric series is as follows
Polyethylene (scotch tape)
Polypropylene Vinyl (PVC)