235
9
Small-Scale Trials
How do we use small-scale equipment to evaluate process options and create proto-
type samples? How do we identify the best process alternatives to commercialize our
new product ideas?
… the seeds for failure are sown very early in the life of a particular
system—during the concept development and design phases.
Professor Robert Bea
In the early 1830s, there was a great surge of interest in creating products
from latex rubber in both the United States and Europe. Rubber was a mira-
cle polymer from South America that outperformed leather, oil-impregnated
fabrics, waxes, and tars in many exible waterproong, gasket, and sealing
applications. New companies were formed and astonishing products were
launched in an effort to be the rst to market. The rubber boom of this period
was very similar to the Internet bubble of the late 1990s, including the result-
ing crash.
Consumers soon discovered that uncured rubber goods had serious aws.
In summer, they became sticky as the latex rst softened and then deteri-
orated into a foul-smelling liquid. Cold weather robbed them of exibility
and caused cracking. The market for rubber products collapsed as custom-
ers became disillusioned. In 1834, the Roxbury India Rubber Company gave
credit for $20,000 worth of defective materials. As 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, was
able obtain raw rubber very cheaply for his experiments. He toiled for years
to overcome rubber’s drawbacks, hoping to develop functional consumer
goods. Goodyear tried to improve latex by blending it with every conceiv-
able additive and evaluating every feasible process path. On several occa-
sions during this decade, he attempted to commercialize a promising recipe,
but met with dismal 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 a stove top and found that, rather than melting, it cured into an
ugly solid plaque. But, curiously, the resulting sample still retained its elastic
properties, even when exposed to extremes of heat and cold. This discovery
was what the industry had been seeking for years. The process became
236 Process Techniques for Engineering High-Performance Materials
known as vulcanization and remains the fundamental technology for cur-
ing both natural and synthetic rubber products.
With his breakthrough, Goodyear hoped to quickly achieve fame and for-
tune, after years of poverty. However, he was constantly disappointed by the
extremely process-dependent nature of vulcanization. Turning the concept
into useful products was very frustrating for him and even more so for his
nancial backers and partners. Today, we know that sulfur atoms cross-link
the isoprene molecules in latex, forming a very stable thermoset elastomer.
To do so, the appropriate amount of sulfur must be uniformly dispersed in
the latex matrix, while the temperature is maintained in a narrow range for
a certain period of time. End-use performance is dependent upon each of
these variables.
Given the process equipment available at the time, this process window
was difcult to achieve and consistently repeat. The products that Goodyear
heated in his oven would slump and fuse before they were fully cured. One
product in a batch might be blistered and charred while others had soft,
tacky spots that were not suitably cross-linked. Techniques were developed
to maintain a uniform heat history from one piece to the next. Numerous
tests were done to nd just the right combination of additives and the appro-
priate compounding techniques. Goodyear struggled to master the process
details with small-scale experimentation before he nally applied for a pat-
ent in 1844.
Once the basic parameters were demonstrated, commercialization fol-
lowed quickly. Goodyear lived to bask in the glory of an admiring public.
However, he was plagued to his death by lawsuits that sprang from sloppy

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