On this day in science history: foam rubber was developed

In 1929, foam rubber was developed at the Dunlop Latex Development Laboratories in Birmingham. British scientist E.A. Murphy whipped up the first batch in 1929, using an ordinary kitchen mixer to froth natural latex rubber. His colleagues were unimpressed - until they sat on it. Within five years it was everywhere, on motorcycle seats, on London bus seats, Shakespeare Memorial Theatre seats, and eventually in mattresses.

In 1937 isocyanate based materials were first used for the formation of foam rubbers, after World War II styrene-butadiene rubber replaced many natural types of foam. Foam rubbers have been used commercially for a wide range of applications since around the 1940s. There are two types of foam in use today. One is flexible foam and the other is rigid foam. The flexible version of the foam is used in furniture, car seats, to insulate walls, and even in the very shoes that we wear. The rigid form of foam rubber is used in insulating buildings, appliances like freezers and refrigeration trucks. 

Foam rubber mattress [Public domain], via Wikimedia Commons

So, how is foam rubber manufactured? Rates of polymerization can range from many minutes to just a few seconds. Fast reacting polymers feature short cycle periods and require the use of machinery to thoroughly mix the reacting agents. Slow polymers may be mixed by hand, but require long periods on mixing. As a result industrial application tends to use machinery to mix products. Product processing can range from a variety of techniques including, but not limited to spraying, open pouring, and molding.

• Material preparation - Liquid and solid material generally arrive on location via rail or truck, once unloaded liquid materials are stored in heated tanks. When producing slabstock  typically two or more polymers streams are used.
• Mixing - Open pouring, better known as continuous dispensing is used primarily in the formation of rigid, low density foams. Specific amounts of chemicals are mixed into a mixing head, much like an industrial blender. The foam is poured onto a conveyor belt, where it then cures for cutting.
• Curing and Cutting - After curing on the conveyor belt the foam is then forced through a horizontal band saw. This band saw cuts the pieces in a set size for the application. General contracting uses 4’x12’x2’’.
• Further processing - Once cut and cured the slabstock can either be sold or a lamination process can be applied. This process turns the slabstock into a rigid foam board known as boardstock. Boardstock is used for metal roof insulation, oven insulation, and many other durable goods.

Unfortunately, because of the variety in polyurethane chemistries, it is difficult to recycle foam materials using a single method. Reusing slab stock foams for carpet backing is how the majority of recycling is done. This method involves shredding the scrap and bonding the small flakes together to form sheets. Other methods involve breaking the foam down into granules and dispersing them into a polyol blend to be molded into the same part as the original. The recycling process is still ever developing for foam rubber and the future will hopefully unveil new and easier ways for recycling.

For more information, visit:-

https://todayinsci.com/7/7_03.htm

https://en.wikipedia.org/wiki/Foam_rubber
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On this day in science history: polyethylene was discovered

Polyethylene was first synthesized by the German chemist Hans von Pechmann, who prepared it by accident in 1898 while investigating diazomethane. When his colleagues Eugen Bamberger and Friedrich Tschirner characterized the white, waxy substance that he had created, they recognized that it contained long –CH2– chains and termed it polymethylene.

Polythylene balls, by Lluis tgn (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons

The first industrially practical polyethylene synthesis (diazomethane is a notoriously unstable substance that is generally avoided in industrial application) was discovered in 1933 by Eric Fawcett and Reginald Gibson, again by accident, at the Imperial Chemical Industries (ICI) works in Northwich, England.  Upon applying extremely high pressure (several hundred atmospheres) to a mixture of ethylene and benzaldehyde they again produced a white, waxy material. Because the reaction had been initiated by trace oxygen contamination in their apparatus, the experiment was, at first, difficult to reproduce. It was not until 1935 that another ICI chemist, Michael Perrin, developed this accident into a reproducible high-pressure synthesis for polyethylene that became the basis for industrial LDPE production beginning in 1939. Because polyethylene was found to have very low-loss properties at very high frequency radio waves, commercial distribution in Britain was suspended on the outbreak of World War II, secrecy imposed, and the new process was used to produce insulation for UHF and SHF coaxial cables of radar sets. During World War II, further research was done on the ICI process and in 1944 Bakelite Corporation at Sabine, Texas, and Du Pont at Charleston, West Virginia, began large-scale commercial production under license from ICI.

The breakthrough landmark in the commercial production of polyethylene began with the development of catalyst that promote the polymerization at mild temperatures and pressures. The first of these was a chromium trioxide–based catalyst discovered in 1951 by Robert Banks and J. Paul Hogan at Phillips Petroleum. In 1953 the German chemist Karl Ziegler developed a catalytic system based on titanium halides and organoaluminium compounds that worked at even milder conditions than the Phillips catalyst. The Phillips catalyst is less expensive and easier to work with, however, and both methods are heavily used industrially. By the end of the 1950s both the Phillips- and Ziegler-type catalysts were being used for HDPE production. In the 1970s, the Ziegler system was improved by the incorporation of magnesium chloride. Catalytic systems based on soluble catalysts, the metallocenes, were reported in 1976 by Walter Kaminsky and Hansjörg Sinn. The Ziegler- and metallocene-based catalysts families have proven to be very flexible at copolymerizing ethylene with other olefins and have become the basis for the wide range of polyethylene resins available today, including very low density polyethylene and linear low-density polyethylene. Such resins, in the form of UHMWPE fibers, have (as of 2005) begun to replace aramids in many high-strength applications.

One of the main problems of polyethylene is that without special treatment it's not readily biodegradable, and thus accumulates. In Japan, getting rid of plastics in an environmentally friendly way was the major problem discussed until the Fukushima disaster in 2011. It was listed as a $90 billion market for solutions. Since 2008, Japan has rapidly increased the recycling of plastics, but still has a large amount of plastic wrapping which goes to waste.

In May 2008, Daniel Burd, a 16-year-old Canadian, won the Canada-Wide Science Fair in Ottawa after discovering that Pseudomonas fluorescens, with the help of Sphingomonas, can degrade over 40% of the weight of plastic bags in less than three months.

The thermophilic bacterium Brevibacillus borstelensis (strain 707) was isolated from a soil sample and found to use low-density polyethylene as a sole carbon source when incubated together at 50°C. Biodegradation increased with time exposed to ultraviolet radiation.

In 2010, a Japanese researcher, Akinori Ito, released the prototype of a machine which creates oil from polyethylene using a small, self-contained vapor distillation process.

In 2014, a Chinese researcher discovered that Indian mealmoth larvae could metabolize polyethylene from observing that plastic bags at his home had small holes in them. Deducing that the hungry larvae must have digested the plastic somehow, he and his team analyzed their gut bacteria and found a few that could use plastic as their only carbon source. Not only could the bacteria from the guts of the Plodia interpunctella moth larvae metabolize polyethylene, they degraded it significantly, dropping its tensile strength by 50%, its mass by 10% and the molecular weights of its polymeric chains by 13%.

For more information visit:-

https://todayinsci.com/3/3_27.htm

https://en.wikipedia.org/wiki/Polyethylene

http://www.prlabs.co.uk/lab-supplies.php?N=ethylene-oxide-monitor&Id=41684

On this day in science history: chewing gum was patented

In 1869, William Finley Semple of Mount Vernon, Ohio, was issued the first U.S. patent for chewing gum (No. 98,304), made of "the combination of rubber with other articles adapted to the formation of an acceptable chewing gum", but he never commercially produced gum. That was done by Thomas Adams of Staten Island, N.Y., who knew that chicle, a natural tree gum, could be chewed. His first experiments to vulcanize chicle for use as a rubber substitute were unsuccessful until he boiled a small batch of chicle in his kitchen and created the first chicle-based chewing gum. Testing sales at a local store, he found people liked his gum. In 1871, Adams patented a gum-producing machine so he could increase production.

Chewing gum stick by Lusheeta, via Wikimedia Commons

Humans have used chewing gum in some form for at least 100,000 years. Modern chewing gum today is made from butadiene-based synthetic rubber. Most chewing gums are considered polymers. Longer polymers can produce larger bubbles due to increased intermolecular forces.

Chewing gum in many forms has existed since the Neolithic period. 6,000-year-old chewing gum made from birch bark tar, with tooth imprints, has been found in Kierikki in Finland. The tar from which the gums were made is believed to have antiseptic properties and other medicinal benefits. It is chemically similar to petroleum tar and is in this way different from most other early gums. The Aztecs, as the ancient Mayans before them, used chicle as a base for making a gum-like substance and to stick objects together in everyday use. Forms of chewing gums were also chewed in Ancient Greece. The Ancient Greeks chewed mastic gum, made from the resin of the mastic tree. Mastic gum, like birch bark tar, has antiseptic properties and is believed to have been used to maintain oral health. Both chicle and mastic are tree resins. Many other cultures have chewed gum-like substances made from plants, grasses, and resins.

The American Indians chewed resin made from the sap of spruce trees. The New England settlers picked up this practice, and in 1848, John B. Curtis developed and sold the first commercial chewing gum called The State of Maine Pure Spruce Gum. In this way, the industrializing West, having forgotten about tree gums, rediscovered chewing gum through the First Americans. Around 1850 a gum made from paraffin wax, which is a petroleum product, was developed and soon exceeded the spruce gum in popularity. To sweeten these early gums the chewer would often make use of a plate of powdered sugar, which they would repeatedly dip the gum into to maintain sweetness.

For more information visit:-

http://www.prlabs.co.uk/lab-supplies.php?N=balls-rubber-20mm-&Id=46943

https://en.wikipedia.org/wiki/Chewing_gum

https://todayinsci.com/12/12_28.htm