𝐒𝐮𝐧𝐝𝐚𝐲'𝐬 𝐓𝐇𝐎𝐔𝐆𝐇𝐓𝐅𝐔𝐋 𝐏𝐨𝐬𝐭 : 𝐓𝐡𝐞 𝐄𝐯𝐨𝐥𝐮𝐭𝐢𝐨𝐧 𝐨𝐟 𝐑𝐮𝐛𝐛𝐞𝐫: 𝐅𝐫𝐨𝐦 𝐍𝐚𝐭𝐮𝐫𝐚𝐥 𝐋𝐚𝐭𝐞𝐱 𝐭𝐨 𝐕𝐮𝐥𝐜𝐚𝐧𝐢𝐳𝐚𝐭𝐢𝐨𝐧

𝐒𝐮𝐧𝐝𝐚𝐲'𝐬 𝐓𝐇𝐎𝐔𝐆𝐇𝐓𝐅𝐔𝐋 𝐏𝐨𝐬𝐭

𝐓𝐡𝐞 𝐄𝐯𝐨𝐥𝐮𝐭𝐢𝐨𝐧 𝐨𝐟 𝐑𝐮𝐛𝐛𝐞𝐫: 𝐅𝐫𝐨𝐦 𝐍𝐚𝐭𝐮𝐫𝐚𝐥 𝐋𝐚𝐭𝐞𝐱 𝐭𝐨 𝐕𝐮𝐥𝐜𝐚𝐧𝐢𝐳𝐚𝐭𝐢𝐨𝐧

In the early 1830’s, latex rubber was the miracle polymer from South America that outperformed leather, oil impregnated fabrics, waxes and tars in many flexible waterproofing, gasket and sealing applications.  New companies sprang up and products were launched, competing to be the first to market. The rubber boom of this period was very similar to the Internet bubble of the late 1990’s, including the resulting crash.

Un-cured rubber goods had serious flaws. In the heat of summer, they became sticky and some deteriorated into a foul-smelling liquid. Cold weather robbed them of flexibility. The rubber market collapsed in the face of public disillusionment. The Roxbury India Rubber Company gave credit for twenty thousand dollars of defective materials in 1834. Being one of the largest and best capitalized companies, it was barely able to stay in business, unlike most of its competitors.

In the wake of the crash, an impoverished inventor, Charles Goodyear, could obtain raw rubber very cheaply for his experiments. He toiled for years to rehabilitate latex by blending it with every conceivable additive and evaluating numerous processing options. On several occasions, he attempted to commercialize a promising recipe and met with failure as the old problems resurfaced with a change of weather.

In early 1839, Goodyear famously cooked a blend of latex, lead oxide and sulfur on his kitchen stove, curing it into an ugly solid plaque. Curiously, the resulting sample displayed elastic properties, even when exposed to extremes of heat and cold. The vulcanization process remains a fundamental technology for curing both natural and synthetic elastomers to this day.

Goodyear was plagued by the extremely process dependent nature of vulcanization, frustrating his financial backers. Today, we know that sulfur atoms crosslink isoprene molecules, forming a thermoset elastomer. The appropriate amount of sulfur must be uniformly dispersed in the latex matrix, within a certain range temperature for a specific time period. End use performance is dependent upon each of these variables.

The products that Goodyear heated in his oven might slump and fuse before they became fully cured. One item in a batch might blister and char while another displayed soft, tacky spots. Techniques were developed to maintain a uniform heat history from one piece to the next. Goodyear struggled to identify the right combination of additives and the appropriate compounding techniques before he finally applied for a patent in 1844. He lived to bask in glory but was plagued by lawsuits that sprang from sloppy control of intellectual property rights.

source : Tim Oberle