In the new role he will oversee both political lobbying and media relations for the organisation.
The body aims to achieve recognition for its members' contribution to society, and it is an active champion of the chemical industry's stance on chemicals in food and their effects on health.
Gardener joined the association in 1997 after working as a director at lobby shop Market Access.
Previously he advised the Ministry of Defence, and was political correspondence secretary to then prime minister Margaret Thatcher.
He earlier acted as a desk officer for the Conservative Party's research department.
The appointment is one of a number of changes brought about by recently installed CIA director-general Judith Hackitt, aimed at boosting its efforts to restore public faith in the chemical industry.