6 questions about expanded polystyrene

Polystyrene IPA: /ˌpɒliˈstaɪriːn/ is an aromatic polymer made from the aromatic monomer styrene, a liquid hydrocarbon that is commercially manufactured from petroleum by the chemical industry. Polystyrene is a thermoplastic substance, normally existing in solid state at room temperature, but melting if heated (for molding or extrusion), and becoming solid again when cooling off.

Pure solid polystyrene is a colorless, hard plastic with limited flexibility. It can be cast into molds with fine detail. Polystyrene can be transparent or can be made to take on various colors. It is economical and is used for producing plastic model assembly kits, license plate frames, plastic cutlery, CD "jewel" cases, and many other objects where a fairly rigid, economical plastic is desired.
Polystyrene was discovered in 1839 by Eduard Simon, an apothecary in Berlin. From storax, the resin of Liquidambar orientalis, he distilled an oily substance, a monomer which he named styrol. Several days later Simon found that the styrol had thickened, presumably from oxidation, into a jelly he dubbed styrol oxide ("Styroloxyd"). By 1845 English chemist John Blyth and German chemist August Wilhelm von Hofmann showed that the same transformation of styrol took place in the absence of oxygen. They called their substance metastyrol. Analysis later showed that it was chemically identical to Styroloxyd. In 1866 Marcelin Berthelot correctly identified the formation of metastyrol from styrol as a polymerization process. About 80 years went by before it was realized that heating of styrol starts a chain reaction which produces macromolecules, following the thesis of German organic chemist Hermann Staudinger (1881–1965). This eventually led to the substance receiving its present name, polystyrene. The I. G. Farben company began manufacturing polystyrene in Ludwigshafen, Germany, about 1931, hoping it would be a suitable replacement for die cast zinc in many applications. Success was achieved when they developed a reactor vessel that extruded polystyrene through a heated tube and cutter, producing polystyrene in pellet form.
The chemical makeup of polystyrene is a long chain hydrocarbon with every other carbon connected to a Phenyl group (the name given to the aromatic ring benzene, when bonded to complex carbon substituents).

圖片參考：http://upload.wikimedia.org/wikipedia/commons/1/10/Polystyrene_formation.PNG

A 3-D model would show that each of the chiral backbone carbons lies at the center of a tetrahedron, with its 4 bonds pointing toward the vertices. Say the -C-C- bonds are rotated so that the backbone chain lies entirely in the plane of the diagram. From this flat schematic, it is not evident which of the phenyl (benzene) groups are angled toward us from the plane of the diagram, and which ones are angled away. The isomer where all of them are on the same side is called isotactic polystyrene, which is not produced commercially. Ordinary atactic polystyrene has these large phenyl groups randomly distributed on both sides of the chain. This random positioning prevents the chains from ever aligning with sufficient regularity to achieve any crystallinity, so the plastic has no melting temperature, Tm. But metallocene-catalyzed polymerization can produce an ordered syndiotactic polystyrene with the phenyl groups on alternating sides. This form is highly crystalline with a Tm of 270 °C.




Polystyrene

Density
1050 kg/m³

Density of EPS
25-200 kg/m³

Specific Gravity
1.05

Electrical conductivity (s)
10-16 S/m

Thermal conductivity (k)
0.08 W/(m·K)

Young's modulus (E)
3000-3600 MPa

Tensile strength (st)
46–60 MPa

Elongation at break
3–4%

Notch test
2–5 kJ/m²

Glass temperature
95 °C

Melting point[1]
240 °C

Vicat B
90 °C[2]

Heat transfer coefficient (Q)
0.17 W/(m2K)

Linear expansion coefficient (a)
8 10-5 /K

Specific heat (c)
1.3 kJ/(kg·K)

Water absorption (ASTM)
0.03–0.1

Decomposition
X years, still decaying

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