Robert W. Gore, 83, who developed Gore-Tex as a lightweight, waterproof, breathable fabric and built one of the region’s largest private companies to sell the material worldwide for use in clothing, medicine, and industry, died Thursday, Sept. 17, after a long illness.

He was chairman emeritus of the Newark, Del.-based W.L. Gore & Associates, a family- and worker-owned company founded by his father, Wilbert L. Gore, which now employs 10,500 worldwide and booked sales of $3.7 billion in 2019.

The company’s core of labs, manufacturing facilities and offices is scattered across the northwest corner of Delaware and neighboring parts of Chester County and Cecil County, Md.

Born in Utah, the oldest of five children, Mr. Gore joined his father’s three-year-old firm in 1961, served as president from 1976 to 2000, and retired from the board, which he had chaired for 30 years, in 2018.

Wilbert L. Gore was an engineer at the DuPont Experimental Station just north of Wilmington who studied polymers. He chafed at the limits placed on corporate researchers, and developed his firm at first to build insulation and other plastic-based materials for the wire and cable industry and the Apollo space program.

He sent Mr. Gore to study chemical engineering at the University of Delaware, where the family later donated funds for Gore Hall, which houses classrooms, and the university science complex. Mr. Gore went on to collect his master’s and Ph.D. degrees in the same discipline at the University of Minnesota.

From his early career, Mr. Gore “appreciated that innovation can arise from many different places," said Jason Field, Gore & Associates’ current CEO. An emphasis on “doing things with your hands, experimenting, testing and observing” marked Mr. Gore’s tenure, along with a focused, disciplined approach to research and development. He was fond of telling customers, “Our products do what we say they will do.”

In 1969, Mr. Gore was researching polymers suitable for thin, pliable, but fluid-resistant pipe-threading tape. Instead of slowly stretching plastics, he experimented with quickly yanking long molecules, and developed one that could stretch more than 10 times its original length, so it could be worked into lightweight formations that trapped air in microporous structures.

The new polymer, expanded polytetrafluoroethylene (ePTFE), formed the basis for breathable but water-repellent Gore-Tex fabrics.

While winter and sports gear marketed to high-end consumers made Gore-Tex a household name, medical and industrial applications occupied many of its engineers. Mr. Gore accumulated nine patents for his work with fluoropolymers.

Mr. Gore is survived by his wife, Jane, and what a company statement called “a large family of children, grandchildren and great-grandchildren,” as well as his four younger siblings. Among Mr. Gore’s stepsons is U.S. Sen. Chris Coons (D., Del).

Memorial services have not been announced.