The material. Polyethylene, (—CH2—)n, first synthesized in 1933, looks like the simplest of molecules, but the number of ways in which the—CH2 units can be linked is large. It is the first of the polyolefins, the bulk thermoplastic polymers that account for a dominant fraction of all polymer consumption. Polyethylene is inert, and extremely resistant […]
Category: Materials and the Environment: Eco-Informed Material Choice
Polypropylene (PP)
The material. Polypropylene, or PP, first produced commercially in 1958, is the younger brother of polyethylene, a very similar molecule with similar price, processing methods, and application. Like PE it is produced in very large quantities (more than 30 million tons per year in 2000), growing at nearly 10% per year, and like PE its […]
Polyamides (Nylons, PA)
The material. Back in 1945, the war in Europe just ended, the two most prized luxuries were cigarettes and stockings made of nylon. Nylon (PA) can be drawn to fibers as fine as silk and was widely used as a substitute for it. Today, newer fibers have eroded its dominance in garment design, but nylon-fiber […]
Acrylonitrile butadiene styrene (ABS)
The material. Acrylonitrile butadiene styrene, or ABS, is tough, resilient, and easily molded. It is usually opaque, although some grades can now be transparent, and it can be given vivid colors. ABS-PVC alloys are tougher than standard ABS and, in self-extinguishing grades, are used for the casings of power tools. Composition (CH2-CH-C6H4L General properties Density […]
Polymers
Polymers are the chemist’s contribution to the materials world. The fact that most are derived from oil (a nonrenewable resource) and the difficulty of disposing of them at the end of their life (they don’t easily degrade) has led to a view that polymers are environmental villains. There is some truth in this, but the […]
Cast iron, ductile (nodular)
The material. The foundations of modern industrial society are set, so to speak, in cast iron: it is the material that made the Industrial Revolution possible. Today it holds a second honor: that of being the cheapest of all engineering metals. Cast iron contains at least 2% carbon; most have 3-4%—and from 1-3% silicon. The […]
Stainless steel
The material. Stainless steels are alloys of iron with chromium, nickel, and often four or five other elements. The alloying transmutes plain carbon steel that rusts and is prone to brittleness below room temperature into a material that does neither. Indeed, most stainless steels resist corrosion in most normal environments, and those that are austenitic […]
Low alloy steel
The material. Addition of manganese (Mn), nickel (Ni), molybdenum (Mo), or chromium (Cr) to steel lowers the critical quench rate and comes to create martensite, allowing thick sections to be hardened and then tempered. Adding some vanadium, V, as well creates a dispersion of carbides, giving strength while retaining toughness and ductility. Chrome-molybdenum steels such […]
Low carbon steel
The material. Think of steel and you think of railroads, oil rigs, tankers, and skyscrapers. And what you are thinking of is not just steel, it is carbon steel. That is the metal that made them possible; nothing else is at the same time so strong, so tough, so easily formed, and so cheap. Carbon […]
Nickel-based superalloys
The material. With a name like superalloy there has to be something special here. There is. Superalloy is a name applied to nickel-based, iron-based, and cobalt-based alloys that combine exceptional high-temperature strength with excellent corrosion and oxidation resistance. Without them, jet engines would not be practical: they can carry load continuously at temperatures up to […]