HGGC-backed Citadel Plastics Holdings Inc. is buying the Composites Group from Highlander Partners LP for an undisclosed amount.

The Composites Group, headquartered in Highland Heights, Ohio, manufactures engineered composite compounds, including high-performance fiberglass and carbon-fiber compounds, for the aerospace, automotive, defense, electrical, energy, heavy machinery and recreation markets.

The buyer, headquartered in West Chicago, Illinois, makes thermoplastics and engineered composite products for the automotive, electrical, construction, heating and air conditioning, home and garden, appliance and energy markets. Citadel says the deal improves its positioning and should allow it to gain customers in current and new end markets. The deal was announced Oct. 13.

Citadel has made other add-on acquisitions, including the December purchase of Lucent Polymers Inc. 

The company is backed by Palo Alto, California-based private equity firm HGGC and Boston-based Charlesbank Capital Partners.

HGGC's recent transactions include an investment in insurance company Pearl Holding Group, and VTLS Inc., a library automation group. HGGC's Gary Crittenden is the chairman of Citadel. 

In September, Charlesbank bought HDT Global, which makes shelters, generators, heaters and other technology products from Metalmark Capital. The firm closed a $1.75 billion fund in July. 

Seller Highlander Partners is a private equity firm headquartered in Dallas that invests in light manufacturing, materials, food products, business and industrial services companies.

Kirkland & Ellis LLP served as Citadel's legal counsel. William Blair & Co. LLC provided financial advice to the Composites Group, while Andrews Kurth LLP provided legal advice.