Polystyrene (IUPAC Poly (1-phenylethane-1 ,2-diyl)), abbreviated following ISO Standard PS, is an aromatic polymer made dariaromatik monomerstyrene, liquid hydrocarbon that is commercially manufactured from petroleum by the chemical industry. Polystyrene is one of the most widely used kinds of plastic.
Polystyrene is a thermoplastic substance, which is in solid (glass) state at room temperature, but flows if heated above the glass transition temperature (for molding or extrusion), and becomes solid again when cooled. Pure solid polystyrene is a plastic, colored hard with limited flexibility. It can be cast into molds with fine detail. Polystyrene can be transparent foam art or can be made to take on various colors.
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). Polystyrene's chemical formula is (C 8 H 8) n, it contains the chemical elements carbon and hydrogen. Because foam art it is an aromatic hydrocarbon, it burns with an orange yellow foam art flame, giving off soot, as opposed to non-aromatic hydrocarbon polymers such as polyethylene, which burn with a yellow flame (often with a blue tinge) and no soot. Complete oxidation of polystyrene produces only carbon dioxide and water vapor. Because of the chemical inertness, the plastic used to make containers for chemicals, solvents, and food.
The addition of styrene polymer results when vinyl benzene (styrene) monomer (containing a double bond between carbon atoms) attach to form a polystyrene chain (with each carbon is attached to two carbon single bond with others and phenyl groups).
Polystyrene is generally flexible and can come in the form of moldable solids or viscous liquids. Tensile force on the plastic is mainly caused by short-range van der Waals attraction between the chains. Because of the long chain hydrocarbon molecules consisting of thousands of atoms, the total attractive force between large molecules. However, when the polymer is heated foam art (or, equivalently, deformed at high speed, due to a combination of viscoelastic and thermal insulation properties), the chain can take a higher level of conformation and the last slide of each other. This intermolecular weakness (versus the high intramolecular strength due to the hydrocarbon backbone) allows the polystyrene chains to slide along one another, rendering foam art the bulk system flexible and elastic. The ability of the system to be easily deformed above the glass transition temperature allows polystyrene (and thermoplastic polymers in general) to be easily softened and molded by the addition of heat.
AD model 3 will show that each of the chiral carbon backbone is located in the center of the tetrahedron, with 4 points to the node bonds company. Say the-CC-bonds rotated so that the backbone chain lies entirely in the area of the diagram. From the flat scheme, it is not clear which of the phenyl (benzene) foam art groups are angled toward us from the plane diagrams, and which are angled foam art 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 a large phenyl groups foam art randomly distributed on both sides of the chain. This random foam art positioning prevents the chains from ever aligning with sufficient regularity to achieve any crystallinity, so the plastic has a very low melting point, ie, T m is much lower than the T RT. But metallocene - polymerization catalysts can produce ordered syndiotactic polystyrene with the phenyl groups on alternating sides. This form is highly crystalline with a T m of 270 C (518 F). Extruded polystyrene is as strong as unalloyed aluminum, but much more flexible and lighter (1.05 g / cm 3 vs. 2.70 g / cm 3 for aluminum). foam art
Thermal conductivity (k)
The coefficient of linear expansion foam art (a)
Polystyrene is formed with a
No comments:
Post a Comment