I think it should be assumed that dozens of other scientists were working on this.
As best I can tell, Midgley and his team (funded by his boss Charles Kettering as a partnership between General Motors and Frigidaire) were the only ones researching flourocarbons in the late 1920s -- R12 had already been synthesized in the 1890s by a German chemist, but never investigated as a refrigerant. If Midgley is locked up in a mental facility in 1929, Kettering is dead (or bankrupt from the Ethyl Corp. failure), and chemistry department research budgets are about to get zeroed by the Great Depression, it might be another 10 years before anyone discovers them.
And it was sheer luck Plunkett discovered PTFE in 1938 (10 years after Freon became available). Chemists did not expect flourinated polymers like that could exist, and nobody was trying to make them.
So in TTL I think it's plausible nobody discovers them until the Manhattan Project (assuming it still occurs) pours gobs of money and manpower into finding a material that can withstand UF6 vapor. The project may be delayed until they discover it.
Since PTFE is vital to enrichment of weapons-grade uranium, it will definitely be classified. Freons too, since they are a precursor. No doubt the Soviets will discover how to make the materials too, but in TTL nonstick pans and Freon refrigerators probably won't be available to Joe Consumer until the Cold War eases in the 1970s.
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