The material. Natural rubber was known to the natives of Peru many centuries ago and is now one of Malaysia’s main exports. It made the fortune of Giles Macintosh who, in 1825, devised the rubber-coated waterproof coat that still bears his name. Latex, the sap of the rubber tree, is cross-linked (vulcanized) by heating with […]
Category: Materials and the Environment: Eco-Informed Material Choice
Phenolics
The material. Bakelite, commercialized in 1909, triggered a revolution in product design. It was stiff, fairly strong, could (to a muted degree) be colored, and, above all, was easy to mold. Earlier products that were handcrafted from woods, metals, or exotics such as ivory, could now be molded quickly and cheaply. At one time the […]
Polyester
The material. Polyesters can be thermosets, thermoplastics, or elastomers. The unsaturated polyester resins are thermosets. Most polyester thermosets are used in glass fiber/polyester composites. They are less stiff and strong than epoxies, but they are considerably cheaper. This record is for thermosetting polyester. It cannot be recycled. Composition (OOC—C6H4—COO—C6H10)n General properties Density 1040 – 1400 […]
Epoxies
The material. Epoxies are thermosetting polymers with excellent mechanical, electrical, and adhesive properties and good resistance to heat and chemical attack. They are used for adhesives (Araldite), surface coatings, and, when filled with other materials such as glass or carbon fibers, as matrix resins in composite materials. Typically, as adhesives, epoxies are used for high-strength […]
Polyhydroxyalkanoates (PHA, PHB)
The material. PHAs are linear polyesters produced in nature by bacterial fermentation of sugar or lipids derived from soybean oil, corn oil, or palm oil. They are fully biodegradable. More than 100 different monomers can be combined within this family to give materials with a wide range of properties, from stiff and brittle thermoplastics to […]
Polylactide (PLA)
The material. Polylactide (PLA) is a biodegradable thermoplastic derived from natural lactic acid from corn, maize, or milk. It resembles clear polystyrene and provides good aesthetics (gloss and clarity), but it is stiff and brittle and needs modification using plasticizers for most practical applications. It can be processed like most thermoplastics into fibers, films, ther […]
Polystyrene (PS)
The material. Polystyrene is an optically clear, cheap, easily molded polymer, familiar as the standard "jewel" CD case. In its simplest form PS is brittle. Its mechanical properties are dramatically improved by blending with polybutadiene but with a loss of optical transparency. High-impact PS (10% polybutadiene) is much stronger, even at low temperatures (meaning strength […]
Polyvinylchloride (tpPVC)
The material. PVC (vinyl) is one of the cheapest, most versatile, and, with polyethylene, the most widely used of polymers and epitomizes their multifaceted character. In its pure form—as a thermoplastic, tpPVC—it is rigid and not very tough; its low price makes it a cost-effective engineering plastic where extremes of service are not encountered. Incorporating […]
Polyethylene terephthalate (PET)
The material. The name polyester derives from a combination of Polymerization and esterification. Saturated polyesters are thermoplastic; examples are PET and PBT, which have good mechanical properties to temperatures as high as 175°C. PET is crystal clear and impervious to water and CO2, but a little oxygen does get through. It is tough, strong, and […]
Polycarbonate (PC)
The material. PC is one of the "engineering" thermoplastics, meaning that they have better mechanical properties than the cheaper "commodity" polymers. The benzene ring and the —OCOO-carbonate group combine in pure PC to give it its unique characteristics of optical transparency and good toughness and rigidity, even at relatively high temperatures. These properties make PC […]