F. Goodwill and Intangible Assets

The carrying amount of goodwill attributable to each reportable segment with goodwill balances and the changes in those balances during the nine month period ended June 30, 2018 are as follows:

	Reinforcement Materials			Performance Chemicals			Purification Solutions			Total
	(In millions)
Balance at September 30, 2017	$	53		$	9		$	92		$	154
Goodwill acquired⁽¹⁾		—			33			—			33
Impairment charge⁽²⁾		—			—			(92	)		(92	)
Foreign currency impact		(2	)		(1	)		—			(3	)
Balance at June 30, 2018	$	51		$	41		$	—		$	92

⁽¹⁾	Consists of goodwill acquired in the acquisition of Tech Blend as described in Note C.

⁽²⁾

Refer to Note E for details on the Purification Solutions goodwill impairment test and the resulting impairment charge recorded in the second fiscal quarter of 2018. Based on the Company’s most recent annual goodwill impairment test performed as of May 31, 2018, the fair values of the Reinforcement Materials, Fumed Metal Oxides, and Specialty Compounds reporting units were substantially in excess of their carrying values.

The following table provides information regarding the Company’s intangible assets:

	June 30, 2018							September 30, 2017
	Gross Carrying Value		Accumulated Amortization			Net Intangible Assets		Gross Carrying Value		Accumulated Amortization			Net Intangible Assets
	(In millions)
Intangible assets with finite lives⁽¹⁾
Developed technologies	$	50	$	(1	)	$	49	$	49	$	(7	)	$	42
Trademarks		8		—			8		16		(1	)		15
Customer relationships		49		(10	)		39		94		(14	)		80
Total intangible assets	$	107	$	(11	)	$	96	$	159	$	(22	)	$	137

⁽¹⁾	Refer to Note E for intangible assets impairment charges recorded in the second fiscal quarter of 2018.

Intangible assets are amortized over their estimated useful lives, which range between twelve and twenty-five years, with a weighted average amortization period of approximately nineteen years. Amortization expense for the three month periods ended June 30, 2018 and 2017 was $1 million and $2 million, respectively, and is included in Cost of sales and Selling and administrative expenses in the Consolidated Statements of Operations. Amortization expense for both nine month periods ended June 30, 2018 and 2017 was $6 million and is included in Cost of sales and Selling and administrative expenses in the Consolidated Statements of Operations. Total amortization expense is estimated to be approximately $6 million each year for the next five fiscal years.