𝐒𝐮𝐧𝐝𝐚𝐲'𝐬 𝐓𝐇𝐎𝐔𝐆𝐇𝐓𝐅𝐔𝐋 𝐏𝐨𝐬𝐭 : 𝐇𝐨𝐰 𝐁𝐞𝐥𝐥 𝐋𝐚𝐛𝐬 𝐌𝐚𝐝𝐞 𝐏𝐥𝐚𝐬𝐭𝐢𝐜 𝐋𝐚𝐬𝐭: 𝐓𝐡𝐞 𝐒𝐭𝐨𝐫𝐲 𝐨𝐟 𝐖. 𝐋𝐢𝐧𝐜𝐨𝐥𝐧 𝐇𝐚𝐰𝐤𝐢𝐧𝐬

 𝐒𝐮𝐧𝐝𝐚𝐲'𝐬 𝐓𝐇𝐎𝐔𝐆𝐇𝐓𝐅𝐔𝐋 𝐏𝐨𝐬𝐭

𝐇𝐨𝐰 𝐁𝐞𝐥𝐥 𝐋𝐚𝐛𝐬 𝐌𝐚𝐝𝐞 𝐏𝐥𝐚𝐬𝐭𝐢𝐜 𝐋𝐚𝐬𝐭: 𝐓𝐡𝐞 𝐒𝐭𝐨𝐫𝐲 𝐨𝐟 𝐖. 𝐋𝐢𝐧𝐜𝐨𝐥𝐧 𝐇𝐚𝐰𝐤𝐢𝐧𝐬

Contrary to popular opinion, plastics do not survive forever in the environment. Pure Low-Density Polyethylene (LDPE) is susceptible to oxidation over time, which results in brittleness, loss of strength and discoloration. In the 1950’s, this was a big problem for plastic-coated telephone wires.

Traditionally, phone lines were coated with lead to insulate and protect them. However, lead is heavy, expensive, and persistently toxic in the environment. In the 1940’s a process for jacketing electrical wires with polyethylene was developed for military purposes, such as airborne radar equipment. This innovation found many civilian applications after the war.

Telephone wiring was expected to last for decades. Instead, the phone company (there was only one US phone company at the time – AT&T) discovered that poly insulation tended to deteriorate in less than a year when exposed to direct sunlight. Their research center, Bell Labs, was tasked with solving the problem.

Working on this assignment was W. Lincoln Hawkins, a chemical engineer and the lab’s first African American researcher. He was partnered with organic chemist Vincent Lanza. They correctly diagnosed the root cause of the problem as oxidative degradation. The typical antioxidant additives of that period became ineffective when blended into LDPE along with the carbon black that was commonly used to block the UV radiation.

The task of testing the fitness-for-use of alternative solutions would have been time consuming if the team simply hung the samples outside in the sun. Instead, they developed an accelerated aging test. Known antioxidant materials were compounded into small samples of LDPE. These polymer blends were subjected to a pure oxygen atmosphere in sealed containers at elevated temperatures. By monitoring the oxygen uptake of experimental samples, Hawkins and Lanza could quickly evaluate the relative effectiveness of each one and the appropriate loading level. By 1956, additives such as benzyl phenyl sulfide and dibenzyl sulfide were identified as the most effective solutions to protect wire insulation.

The company commercialized plastic cable insulation that survived a wide temperature range and protected the copper wires from environmental corrosion. The new coating greatly reduced the costs of installing and operating phone networks while eliminating toxic lead. It facilitated the extension of phone lines into rural areas.

Hawkins went on to have a long and distinguished career at Bell Labs, publishing three books, fifty-six scientific papers, and being awarded eighteen U.S. patents. Lanza left AT&T in 1959 to do pioneering work on polyethylene crosslinking at Raychem, eventually becoming the VP of R&D.

source : Tim Oberle