Speciality chemicals maker A. Schulman is buying privately held Citadel Plastics Holdings for US$800 million to expand its speciality business, the biggest deal for the US company.

Citadel Plastics, owned by private equity firms HGGC and Charlesbank Capital Partners, makes thermoplastic polymers and thermoset plastics. Based in West Chicago, IL, Citadel’s compounds are used for speciality product applications in the automotive, electrical, construction, and appliance markets. Through the addition of Citadel, Schulman says it is able to achieve several critical strategic priorities such as driving profitable top-line growth; expanding its added-value offerings to customers and improving its margins; balancing its current geographic footprint with greater market share in the US.

Citadel operates 21 factories across the world, including ten thermoplastic factories and seven thermoset factories in the US and Canada.

Schulman, which sells products used in the electronics and construction industries, among others, expects the deal to add to its earnings in the first 12 months of ownership. The deal is expected to close in the third quarter of 2015.

Schulman has been on a buying spree over the last two years. While it lost a bid to buy speciality chemicals firm Ferro Corp for US$563 million in 2013, it later went on to purchase a selected majority of the assets of the Specialty Plastics business segment of Ferro for US$91 million in cash. Its other purchases include Perrite Group, a thermoplastics manufacturing business with operations in Malaysia, the UK and France, for approximately US$52 million; Network Polymers, a US niche engineering plastics compounding and distribution business, for US$50 million; Prime Colorants, a manufacturer of custom colours and additive concentrates in Franklin, Tennessee, for approximately US$15.1 million. It also acquired Australian firm Compco Pty, located near Melbourne, for US$6.7 million in cash. Compco is a manufacturer of a variety of plastic compounds and products including masterbatches and custom performance colours.