We delivered another strong quarter in Q3 with sales increasing approximately 16% organically and adjusted EBITDA margin expanding 250 basis points.
As reported, sales of $283.1 million in the third quarter increased 5.5% year over year.
As Eric noted, organic sales for the quarter increased about 16% compared to the third quarter of 2020.
Gross profit margin of 38.7% increased 350 basis points versus the prior-year period.
Adjusted EBITDA of $51.5 million increased 22.3% over the prior-year period as a result of operating leverage on organic sales growth.
Adjusted EBITDA margin of 18.2% expanded approximately 250 basis points compared to the third quarter of 2020.
Corporate expenses of $11.6 million in the third quarter were essentially flat from a year ago.
Adjusted diluted earnings per share of $1.40 increased 39% compared to the prior-year period.
Amortization of acquisition-related intangible assets in the third quarter was $11.2 million compared to $9 million in the prior year, reflecting the addition of Alluxa.
As a reminder, our estimated normalized tax rate used in determining adjusted earnings per share is 30%.
Sealing Technologies sales of $146.9 million decreased 6.9% due to the impact of divestitures in 2020.
Excluding the impact of foreign exchange translation and divested businesses, sales increased 15.7%, driven by strong demand in the petrochemical, heavy-duty truck, food and pharma, and general industrial markets, partially offset by tepid aerospace and power generation markets.
For the third quarter, adjusted segment EBITDA increased 7.8% to $34.5 million, and adjusted segment EBITDA margin expanded 320 basis points to 23.5%.
Excluding the impact of favorable foreign exchange translation and divestitures, adjusted segment EBITDA increased 26.5% compared to the prior-year period.
Third quarter sales of $64.3 million increased 44.2%, driven by continued strong demand in the semiconductor market and the addition of Alluxa.
Excluding the impact of the foreign exchange translation and the Alluxa acquisition, sales increased 23.6% versus the prior-year period.
For the third quarter, adjusted segment EBITDA increased 44.8% to $19.4 million and adjusted segment EBITDA margin of 30.2% was relatively flat compared to a year ago.
Excluding the impact of Alluxa and foreign exchange translation, adjusted segment EBITDA increased 8.2%, reflecting transactional foreign exchange headwinds and start-up costs of the new facility in Taiwan to support strong lean tech growth.
Sequentially, adjusted EBITDA margins improved 380 basis points in the quarter.
In Engineered Materials, third quarter sales of $73.8 million increased 9% compared to the prior year, driven primarily by sales in general industrial markets, partially offset by sales in power generation, oil and gas and automotive markets.
Excluding the impact of foreign exchange translation and last year's divestiture of GGB's Bushing Block business, sales for the quarter increased 11%.
Third quarter adjusted segment EBITDA increased 11.4% over the prior-year period to $8.8 million and adjusted segment EBITDA margin was relatively flat year over year.
We ended the quarter with cash of $330 million and full availability of our $400 million revolver, less $12 million in outstanding letters of credit.
At the end of September, our net debt to adjusted EBITDA was approximately 0.8 times, a sequential decline from the 1.1 times reported at the end of the second quarter.
Free cash flow for the first nine months of 2021 was $84 million, up from $37 million in the prior year, driven primarily by higher operating profits, offset by working capital investments supporting higher sales.
And during the third quarter, we paid a $0.27 per share quarterly dividend.
For the first nine months of the year, dividend payments totaled $16.8 million, a 3.7% increase versus the prior year.
First, we increased our environmental reserve for the Passaic River site by $4.5 million in response to estimated remedial costs and ongoing settlement negotiations with the United States EPA, bringing our total reserve for this legacy environmental liabilities of $5.4 million at the end of the third quarter.
Second, subsequent to quarter end, we received a tax refund from the Internal Revenue Service for $26 million in conjunction with several years of audits proceeding in the 2017 completion of the ACRP process.
And finally, as previously noted, we signed an agreement to sell CPI for a price of $195 million with estimated after-tax proceeds of approximately $175 million in conjunction with the sale, which is expected to close by the end of the first quarter of next year.
In light of the divestiture of our Polymer Components business, we are adjusting our sales guidance to be in the range of $1.085 to $1.12 billion and our 2021 adjusted EBITDA range to $202 million to $208 million.
We expected adjusted -- or we expect adjusted diluted earnings per share from continuing operations to be in the range of $5.35 to $5.55, and up slightly at the midpoint from the range of $5.16 to $5.50 provided last quarter.
Our guidance assumes depreciation and amortization expense, excluding amortization of acquisition, acquisition-related intangible assets in the range of $28 million to $30 million and net interest expense of $13 million to $15 million.
The company is expected to generate sales and EBITDA in 2021 of approximately $190 million and $70 million, respectively.
Finally, we look for EBITDA margins and cash flow return on investment greater than 20%.
The combination of NxEdge with the existing AST businesses would result in aftermarket recurring revenue increasing from 35% to 44% of 2020 pro forma ASD sales.
Looking at Slides 20 and 21.
TSMC, Intel, and Samsung have all announced major expansions in the U.S.-focused on leading-edge chip nodes sub-14 nanometer.
Under the terms of the agreement announced today, EnPro will acquire NxEdge from Tribe Capital for $850 million in cash, subject to limited closing adjustments, including working capital.
As Eric mentioned, NxEdge expects to generate sales and adjusted EBITDA in 2021 of approximately $190 million and $70 million, respectively.
At current interest rates, we expect NxEdge to contribute approximately $1.70 in adjusted diluted earnings per share in 2022, which represents approximately 30% above the midpoint of our 2021 guidance range.
Of note, 2021 pro forma adjusted EBITDA margins are 700 basis points above 2019 margins.
And with 240 basis points of that improvement attributable to the impact of this year's completed and announced transactions.
Upon completion of the NxEdge acquisition, we anticipate net leverage of approximately 3.7 times adjusted EBITDA.
Proceeds from the sale of CPI will lower our leverage ratio to about 3.3 times.
This is the right deal at the right time, with the right company, with the right leadership for EnPro in a growing market that expects to exceed $1 trillion by 2030.

Summary:
As reported, sales of $283.1 million in the third quarter increased 5.5% year over year.
Adjusted diluted earnings per share of $1.40 increased 39% compared to the prior-year period.