Polycarbonate’s Rise: How a 1950s Innovation Shaped Modern Materials (Part 11)

During the 1930s, the polymer industry experienced a boom, with PVC, polystyrene, polyethylene, acrylic, and moldable cellulosics moving from laboratory curiosities to commercial products.

By the 1940s, polystyrene’s impact resistance was boosted by blending with butadiene rubber—at the cost of its transparency. Copolymerizing polystyrene with acrylonitrile produced SAN, a clear, heat‑ and chemically‑resistant material. Adding butadiene again yielded ABS, which sacrificed clarity for toughness.

Polycarbonate has become the material of choice wherever transparency, heat resistance, and toughness are required. (Photo: PolyOne)

Early transparent polymers fell into two camps: hard, brittle types like SAN and acrylic, and soft, tough cellulosics. Acrylics, pioneered by chemists such as Otto Rohm, emerged as a safe, weather‑resistant alternative to glass. The 1950s, however, ushered in a breakthrough chemistry that would redefine the field—polycarbonate.

Polycarbonate’s path to market mirrors many other polymers: a protracted development cycle punctuated by false starts and serendipitous discoveries that ultimately converged worldwide. Though its commercial debut is traced to the late 1950s, the first laboratory synthesis dates back to 1898, when German chemist Alfred Einhorn—best known for inventing procaine—reacted hydroquinone with phosgene to create a pre‑polymer. Decades of experimentation, however, yielded no commercial product.

In 1928, Wallace Carothers and his DuPont team produced early polycarbonates while working on polyesters and nylons. Although Carothers’ materials possessed an aliphatic backbone, their thermal, mechanical, and chemical properties were unsatisfactory, leading to shelving of the research.

The turning point came in 1953 when Hermann Schnell’s team at Bayer’s Uerdingen facility synthesized the commercially viable polymer that would later be branded Makrolon. One week later, Dan Fox at General Electric independently discovered the same compound while developing a new wire‑insulating material. Both polymers were chemically identical but differed structurally: Bayer’s Makrolon was linear, GE’s version was branched.

Both variants were clear—initially amber‑tinted until 1971, when impurities were eliminated. Their glass‑transition temperature exceeded any existing transparent polymer by roughly 50 °C (90 °F), and they exhibited unprecedented ductility. Polycarbonate thus expanded the scope of clear, tough materials beyond prior limits.

The simultaneous discoveries prompted legal negotiations, but unlike the lengthy disputes over HDPE and PP, a swift settlement granted Bayer priority and a license to GE. Although GE’s marketing in the 1970s and 1980s made it seem the sole owner, Bayer ultimately held the first rights.

During a 1978 visit to Pittsfield, Massachusetts, I noted the stark contrast between GE’s understated power‑transformer and naval ordnance divisions and the flamboyantly decorated plastics division, a visual cue of where the profits truly lay.

Today, neither Bayer nor GE retains exclusive rights. GE sold its Plastics Division to Saudi Arabia Basic Industries (SABIC) in 2006, and Bayer spun off its polymer interests to Covestro in 2015, reflecting a broader industry shift from rapid growth to mature, capital‑intensive operations.

Production began at Bayer in 1958 and at GE in 1960. Polycarbonate quickly found homes in electronics, construction, food packaging, automotive, aerospace, and medical devices—any application demanding clarity and toughness. Eyewear, windshields, safety shields, and aircraft cockpit canopies became standard PC components. Manufacturing flexibility allowed films, blow‑molded, extruded, injection‑molded, and thermoformed parts.

In 1981, PC entered the data‑storage arena with the first compact discs, soon followed by DVDs. Its high glass‑transition temperature made it ideal for steam sterilization, while its aromatic backbone and amorphous structure suited gamma and e‑beam sterilization. Specialized grades now meet biocompatibility and food‑contact standards; UV‑stabilized grades extend outdoor use, and flame‑retardant grades were first introduced in 1970.

Polycarbonate is frequently blended to enhance performance. Blends with ABS, SAN, ASA, polyesters, and polyurethanes have broadened its application spectrum. Global production reached 10 billion lb in 2016. Copolymers with polyesters push operating temperatures close to 200 °C (392 °F), and incorporating siloxane chemistry improves resistance to hydrolysis and environmental stress‑cracking.

Despite its triumphs, polycarbonate’s journey has not been free of challenges—those we will explore in the next installment.

ABOUT THE AUTHOR: Michael Sepe is an independent materials and processing consultant based in Sedona, Ariz., with clients throughout North America, Europe, and Asia. With over 45 years in the plastics industry, he advises on material selection, design for manufacturability, process optimization, troubleshooting, and failure analysis. Contact: (928) 203‑0408 • mike@thematerialanalyst.com