Lammot du Pont Copeland, 78, a past president and board chairman of E.I. du Pont de Nemours & Co., the giant chemical concern, and the great-great-grandson of its founder, died in Mount Cuba, Del., July 1 after a heart attack.

Mr. Copeland was du Pont's president from 1962 to 1967, then served as chairman of the board until retiring in 1971. He began his career with the family company in 1929 as an expediter in its Fairfield, Conn., plant, which made fabrics and finishes.

In 1930, he was laid off for four months before being rehired as a laboratory technician at the Fairfield plant. In 1935, he transferred to Wilmington. He worked in market analysis, and became a director of the company in 1942. He was elected secretary in 1947, and finance committee chairman and corporate vice president in 1954. Five years later, he was named to the company's executive committee.

When he became president, Mr. Copeland had 190,000 common shares of du Pont, and 338,348 shares of Christiana Securities Co., a holding company with 29.2 percent of the outstanding du Pont shares. In 1963, the du Pont company had a net income, after taxes, of more than $472 million, and employed more than 93,000 people, 4,000 of them scientists.

Du Pont was founded in 1802 by Eleuthere Irenee du Pont, a French immigrant who had studied gunpowder-making under Antoine Lavoisier, the father of modern chemistry. Du Pont sold explosives to the U.S. government, and supplied 40 percent of the powder used by the Allied and Associated powers in World War I.

The company in later years perfected the first commercial U.S. synthetic rubber and the first synthetic nitrogen fertilizer. It introduced the world to "dacron," "nylon," and "orlon" fabrics, and made "Lucite," "Freon," and "Teflon," household words.

Perhaps one measure of the company's scope and reach was the 1957 Supreme Court ruling that said du Pont must divest itself of 63 million shares of General Motors common stock it had purchased as an investment between 1917 and 1935. Du Pont had paid about $130 million for the stock. In the mid-1960s when Mr. Copeland finished disposing of it, in the form of dividends to du Pont shareholders, it was worth about $6 billion.

In addition to solving du Pont's General Motors problem without dislocating the stock market, Mr. Copeland, during his presidency, led du Pont's overseas expansion program, helped promote "corfam," a synthetic leather substitute used in footwear, and worked on the development of the antiflu pill "Symmetrel," and the plastic "Surlyn."

Mr. Copeland was a native and resident of Delaware. He was a 1928 graduate of Harvard University, where he earned a bachelor's degree in industrial engineering.

He served as a vice president of the executive committee of the Planned Parenthood Federation, was a trustee of the University of Pennsylvania and member of the Harvard board of overseers, and was a life member of the National Rifle Association. He was a delegate to several Republican national conventions.

He married Pamela Cunningham in 1930. They had three children.